Article

Nutrient Stocks, Nutrient Cycling, and Soil Changes in Cocoa Ecosystems: A Review

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Abstract

It is generally assumed that agricultural systems with perennial crops are more sustainable than systems with annual crops. Soil erosion is negligible and perennial crops have more closed nutrient cycling. Moreover, inorganic fertilizers are used more commonly in cash crops such as perennial crops so that soil fertility decline and nutrient mining are less likely to occur. In the past decades, considerable research has been devoted to the quantification of nutrient stocks and nutrient cycling in agro-ecosystems. This article reviews the main stocks and flows of nutrients in cocoa ecosystems for several cocoa-growing regions in the tropics. Most of the nitrogen is found in the topsoils, and less than 10% of the total N stock is in the cocoa and shade trees. Nitrogen in the annual litter fall is about 20 to 45% of the total N in the vegetation and 2 to 3% of the total N in the soil. The accumulation of potassium is low in cocoa ecosystems, and in most systems the total amount in the biomass is equivalent to the available P content in the topsoil. Phosphorus in the annual litter fall is about 10 to 30% of the total P in the vegetation and 10 to 40% of the available P in the soil. Potassium is a major nutrient in mature cocoa. Stocks of exchangeable K in the topsoil vary from 100 to 550 kg ha−1, and high K levels in the soil correspond to high K levels in the vegetation and litter. Partial nutrient balances were calculated that compares the losses, addition, and transfer of N, P, and K. The nutrient balance is negative in the absence of inorganic fertilizers, especially for K. Rainwash and litter fall are key components in the cycling of nutrients of cocoa ecosystems. The amount of nutrients transferred by rainwash is less than 8 kg ha−1 for N and P but varies from 38 to more than 100 kg ha−1 year−1 for K. Most soils under cocoa had a lower fertility when compared to primary forest, although soil chemical properties seem to settle at equilibrium levels. This review shows that large amounts of nutrients in cocoa ecosystems are transferred each year and that such nutrient cycling is essential for maintaining cocoa production.

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... The regional differences are thus also related to climatic and geological conditions and cultural circumstances. Studies of above-and belowground C storage and turnover in afforestation systems have thus faced and continue to face the problem of heterogeneity and defining reference stages (Ekanade et al., 1991;Hartemink, 2005). Biomass production of AFS is also depending on the availability of plant nutrients such as nitrogen (N) and phosphorus (P). ...
... Measured nutrient contents in the biomass of erythrina species are sometimes quite significantly higher than those of cacao (Beer et al., 1990;Isaac et al., 2007;Schneidewind et al., 2019). Hartemink (2005) In addition, the pruning residues of the erythrina and cacao trees were not distributed in the area, but were placed in the area under the cacao crown. So that a general horizontal exchange of nutrients takes place system-wide. ...
... With more than 4 Mg N ha -1 in the upper 25 cm, even in conv MCS, the nitrogen stocks in this study are far above those from Ghana reported by . However, the values in the AFS in this study are still in the lower third of the values for cacao AFS described by Hartemink (2005). This may be due to the fact that the systems were, relatively young (6 years). ...
Thesis
There is hardly any place left on earth that can be considered untouched nature. Humans penetrate into all areas of this earth, and may it be through greenhouse gas emissions or other types of air and environmental pollution. Deforestation and the conversion of land to agriculture are processes that accompany the spread of humans on this earth, and which shape the landscapes. In this context, tropical forests are nowadays in the focus of forest clearing and land use change. To maintain or restore the ecosystem functions and biodiversity of tropical forests, alternative agricultural land uses are needed. In order to test alternative production systems, the Research Institute of Organic Agriculture (FiBL) launched the research project "Comparison of cropping systems in the tropics" (https://systems-comparison.fibl.org/). In Alto Beni (Bolivia), five different cacao production systems are being tested in a long-term trial with regard to their economic, ecological and social impacts. The farming systems range from monocultures to simple agroforestry systems, each under conventional and organic management, to highly complex successional, multistrata agroforestry systems. The plots were established in 2008, in a completely randomized block design, with four replications. The general objective of this dissertation is to compare, within the long-term experiment in Bolivia, the different cacao cropping systems in terms of their capacity to store and convert carbon, and to draw conclusions on the availability of nutrients through microbial activity. It was hypothesized that (1) AFS store more above and below ground biomass, in the form of carbon, over time, and that (2) both biological management and AFS result in higher biological activity. To verify this, (1) the different aboveground biomass pools were studied, (2) the biomass obtained from pruning was measured, (3) the annual leaf fall was recorded, (4) the decomposition of leaf litter within one year was analyzed, and (5) the root growth was estimated. The work performed showed that total aboveground biomass is greater in AFS than in monocultures. However, in the monocultures, the biomass of cacao trees is larger than in the other cropping systems. The total aboveground biomass in AFS is only about one-third of the biomass stored in trees in the surrounding forests. In managed AFS, the biomass produced by pruning can be twice that of natural leaf fall, and is thus an important source of carbon and nitrogen. The half-life of litter decomposition in the different systems did not differ, despite different microclimates and higher microbial activity in the organically managed plots. Nitrogen-rich leaves of legumes were decomposed faster than lignin-rich cacao leaves. Soil quality is improved 6 years after installation, in the organically managed plots compared to the conventional plots, as evidenced by higher carbon and nitrogen levels, as well as higher microbial activity. Fine root growth is also greater in AFS and biologically managed plots than in the monocultures. The different studies show that AFS have a pronounced advantage over monocultures in terms of biomass accumulation, even if they do not reach the level of primary or secondary forests. The work shows that there is a strong linkage of the different carbon pools in AFS. More aboveground biomass and fast-growing legumes allow regular pruning, which stimulates carbon and nitrogen cycling. Accumulated litter is decomposed by microorganisms, leading to better soil conditions and nutrient availability. Therefore, it can be concluded from the present work that AFS cannot per se prevent the clearing of rainforests for agricultural land. However, AFS, unlike monocultures, have a better ecological balance, with more biomass and better soils. The more stable and sustainable AFS are therefore preferable from an ecological perspective to monocultures which are designed for short-term profit.
... However, these may be immobilized in the coarse parts or excluded from cycling in the short term (Fontes et al. 2014). Thus, soil fertility and functioning are maintained mostly owing to litters, which is crucial in the low fertility-tropical soils, particularly under low-fertilization small-holder cocoa farms (Hartemink 2005;Ofori-Frimpong et al. 2007;Naik et al. 2018). Importantly, the litter layer serves as a habitat and source of energy to soil fauna thereby promoting biodiversity (Bisseleua et al. 2009) and activity of soil microorganisms which underpins plant productivity (Barrios et al. 2018). ...
... Importantly, the litter layer serves as a habitat and source of energy to soil fauna thereby promoting biodiversity (Bisseleua et al. 2009) and activity of soil microorganisms which underpins plant productivity (Barrios et al. 2018). In West Africa, research works that have focused on cocoa leaf litterfall and decomposition are related only to shaded-cocoa plantations where litterfall consists of mixed leaf litters, with shade tree's leaf litter sometimes being greater than that of cocoa (Hartemink 2005). The share of the shade tree leaf litter may amount to 60-70% of the total (Ofori-Frimpong et al. 2007;Saj et al. 2021). ...
... Yet, this microbial-mediated process is responsible for most nutrient transformations in soil, regenerating minerals that may limit plant productivity (Delgado-Baquerizo et al. 2016). Because cocoa leaf litterfall may hold 10 to 45% of the total macronutrient stock (Hartemink 2005) and up to 17% of the total carbon stock (N'Gbala et al. 2017) in the cocoa vegetation, addressing the mineralization of that biomass pool is essential to the agroecosystem functioning. To date, unfortunately, very few studies have investigated the impacts of cocoa on the soil microbial activities in Africa (Sauvadet et al. 2020). ...
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Nutrient cycling has been widely studied in tree plantations. However, studies on the observed negative changes relative to natural vegetations and how these could be capitalized toward setting up ecofriendly agroecosystems are rare. This study was conducted in Central-West Côte d'Ivoire to establish the changes in carbon and macronutrient cycling occurring in full-sun cocoa (Theobroma cacao L.) and Teak (Tectona grandis) relative to primary forest and subsequently make cocoa agroforestry-based recommendations. Leaf litterfall and associated carbon and macronutrient inputs, rates of leaf litter decomposition, and macronutrient release were assessed. In addition, soil (0-10 cm depth) chemical and microbial parameters were evaluated. Litterfall yields were 10.6 ± 2.0, 9.3 ± 0.8, and 10.1 ± 0.4 Mg dry mass ha −1 year −1 in forest, cocoa, and teak, respectively. Compared to the forest, the cocoa plantation supplied lower inputs of C (−736 kg ha −1 year −1 or −15.5%) and N (−75 kg ha −1 year −1 or −27%), similar P, but greater K. Similar quantities of C and N were recorded in the teak plantations and the forest. However, the teak plantation supplied lower K but higher P inputs than the forest. Cocoa leaf litters decomposed at the same rate as those of the forest (k = 0.3 month −1) but faster than the teak's, the initial leaf litter N:P ratio being the most influencing factor. Except for P, the macronutrient release from cocoa and forest litters exhibited similar patterns and rates, which were significantly different from those observed in the teak leaf litter. Soil C mineralization rate and mineral N concentration drastically declined in both tree plantations, the greatest gap occurring in cocoa (C min : −40%, mineral N:-54.2%) due to lower litter Ca input and soil acidity. Teak appears to be a good candidate for shade as it may compensate for the deficit in litter C (and N, to a lesser extent) supply exhibited by cocoa relative to the forest. The trends in microbial activity underscore the need to grow cocoa in association with trees that provide quality litter materials, for improved cocoa nutrient availability and faster C storage in soil. In line with this, some suggestions were made and discussed. This study can be used in support of developing an efficient cocoa agroforestry system in West Africa.
... In many parts of the world, cocoa is produced under natural or planted shade tree. Shade trees compete for growth resources but may also ameliorate adverse climate conditions; reduce soil erosion, pests, and diseases; and increase nutrient use efficiency in cocoa (Beer et al., 1998;Hartemink, 2005). Litterfall is significantly low in nutrient concentration when compared to the fresh leaves as nutrients are reabsorbed before the leaves fall. ...
... Average concentration of N in the soil ranges from 0.61 to 0.67% while its quantity in the above-ground biomass is 0.31 to 0.35% respectively (Table 1-3). Nitrogen in the annual litterfall is about 20 to 45% of the total N in the vegetation and 2 to 3% of the total N in the soil (Hartemink, 2005). Therefore, results across the tables show that litter has great capability to replenish some of the lost essential nutrients (P, Mg 2+ , Ca 2+ ) and Mn) conveniently back into the soil in cocoa ecosystem. ...
... This show that nutrient with higher concentration in the litterfall is able to supplement loss nutrient from the soil. Large amounts of nutrients are returned to the soil with the litterfall (Hartemink, 2005). Nutrient concentrations in the litterfalls are lower than fresh leaves as nutrients are reabsorbed before the leaves fall. ...
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Survival of cocoa in tropical rainforest is saddled with the sequential circulation and concentration of nutrient between the above and below-ground biomass. Prominent among the above-ground biomass is litter of which the accumulated nutrient in leaves return into the soil. Ability of cocoa tree to remain productive for quiet a number of years without the application of chemical fertilizer lies on the role of litterfall in returning nutrient already uptaken back to the soil. This paper assessed the aboveground biomass potential in soil fertility under cocoa plantations. A community from Idanre, Owo and Odigbo were purposively selected where matured cocoa farms within age 45 and 50 years were chosen. Leave litters and soil samples (topsoil and subsoil) were collected from each of the 25m by 25m quadrat. Both samples were subjected to physico-chemical analyses, using routine laboratory techniques. ANOVA result shows significant variation within the study area and Student t-test indicates significant difference between the above and belowground biomass. It was observed that the ability of litter to replenish lost nutrient from the soil is high when its nutrient content is considered in terms of P, Mg 2+ , Ca 2+ and Mn in aged cocoa plantations. The study recommends seasonal relocation of pod deposit, periodic application of micronutrient via agrochemical and spreading of podhusk across the farms as well as adoption of pod husk fertilizer; to complement the effort of litter.
... Another approach considers the stock of nutrients present in soil, pondering the values according to the reference volume and soil bulk density (a. o. [3]). The estimates can be referred to the topsoil only or extended to different depths (a. ...
... The resulting soil has a silty clay texture along the entire profile, is very poor in organic matter, strongly calcareous, without skeleton, and show two main horizons. The first, which derives from the deep ploughing (Ap), is about 600 mm deep, compact, with a poorly developed angular and prismatic polyhedral structure, of coarse size, very firm consistency, and a bulk density of 1.45 g cm 3 . The Ap overlays the Cg horizon, poorly pedogenized, hydromorphic, unstructured, and extremely firm, but with fissures and cracks that cross the horizon, and a bulk density of 1.75 g cm 3 . ...
... The first, which derives from the deep ploughing (Ap), is about 600 mm deep, compact, with a poorly developed angular and prismatic polyhedral structure, of coarse size, very firm consistency, and a bulk density of 1.45 g cm 3 . The Ap overlays the Cg horizon, poorly pedogenized, hydromorphic, unstructured, and extremely firm, but with fissures and cracks that cross the horizon, and a bulk density of 1.75 g cm 3 . The average quantity of roots is low throughout the whole profile, but in the first horizon the roots of the vines develop mainly in a sub-horizontal way and are in quantity less than 10 every 100 cm 2 , in the Cg they are only occasional and follow the cracks vertically up to about 1500 mm in depth. ...
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The estimate of soil fertility, namely, water and nutrient availability, and biological activity , is usually made considering soil as being uniform in the reference layer. The potential fertility is thus estimated for homogeneous soil volumes. However, both the soil profile and its horizons are often not homogeneous for many characteristics and properties. The soil rooting volume, in particular , can be limited by the presence of obstacles, such as bedrock, cemented layers, and stones, but also by soil masses, or clods, that are so dense that cannot be penetrated by roots. Clods can not only occur at the soil surface, but also throughout the soil profile and within a horizon. The presence of clods is usually only considered for the soil surface, and always overlooked in the estimation of soil fertility. In this work, an innovative method, which considers the presence of clods in the soil volume for estimating the potential soil rooting capacity, is explained, and used to estimate the available water holding capacity according to soil rootability. Correcting the values of water holding capacity according to the potential soil rooting volume increases its correlation with plant phenology and the agronomic result. The method could be also applied for a better estimate of the stock of available nutrients and considered in precision farming.
... The transfer of energy and nutrients between the biological and non-biological components of an ecosystem is crucial for its existence and resilience (Hartemink, 2005;Owusu-Sekyere et al., 2006;Fontes et al., 2014). Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity in all ecosystems (Hartemink, 2005;Ofori-Frimpong et al., 2007;Becker et al., 2015). ...
... The transfer of energy and nutrients between the biological and non-biological components of an ecosystem is crucial for its existence and resilience (Hartemink, 2005;Owusu-Sekyere et al., 2006;Fontes et al., 2014). Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity in all ecosystems (Hartemink, 2005;Ofori-Frimpong et al., 2007;Becker et al., 2015). Plant litter acts as an input-output system for organic matter and humus, thus it influences the soil quality of an ecosystem (Hartemink, 2005;Fontes et al., 2014). ...
... Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity in all ecosystems (Hartemink, 2005;Ofori-Frimpong et al., 2007;Becker et al., 2015). Plant litter acts as an input-output system for organic matter and humus, thus it influences the soil quality of an ecosystem (Hartemink, 2005;Fontes et al., 2014). Litterfall and its attendant processes such as decomposition and nutrient mineralization are key components of the plant-soil system (Kumar, 2008;Becker et al., 2015). ...
Thesis
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This research was undertaken to evaluate the potential of organic and conventional cocoa agroforestry systems in different productive stages (Young, ≤ 15 years; Mature, 16 to 30 years; Old, ≥ 31 years) to contribute to sustainable land management through tree biodiversity conservation, carbon sequestration and nutrient recycling. It also assessed the influence of organic and conventional management of cocoa agroforestry systems on soil physico-chemical properties, cocoa pod production and crop (Musa spp.) yield. The study was conducted in the Moist Semi-deciduous Forest Zone of the Eastern Region of Ghana. Cocoa systems under organic management consistently maintained greater shade tree species diversity compared to those under conventional management. Shade tree species richness was higher on organic farms (5.10 ± 0.38) than conventional farms (3.48 ± 0.39). On organic farms, density of food and fruits shade trees (per ha) was three-fold (Org. 341 ± 38 vs. Con. 106 ± 18) when compared to conventional farms. Organically managed cocoa agroforestry systems demonstrated a greater potential to sequester and store carbon in the aboveground (39.6 Mg C ha-1), belowground (10.3 Mg C ha-1) and soil (0-30 cm depth, 59.7 Mg C ha-1) pools compared to conventionally managed cocoa systems (22.1 Mg C ha-1, 7.1 Mg C ha-1, 49.7 Mg C ha-1, respectively). The rate of total carbon storage (vegetation plus soils) ranged from 3.4 Mg C ha-1 yr-1 (young cocoa systems) to 9.0 Mg C ha-1 yr-1 (old cocoa systems) in the organic systems and 1.1 Mg C ha-1 yr-1 (young cocoa systems) to 4.9 Mg C ha-1 yr-1 (old cocoa systems) on conventional farms. Annual litterfall (Org. 12.4 Mg ha-1 yr-1 vs. Con. 12.7 Mg ha-1 yr-1) and nutrient deposition through litterfall were similar on both organic and conventional cocoa farms. The contribution of shade tree species to nutrient return via litterfall was more pronounced in organic systems than conventional systems. Organic cocoa farms had a greater rate of leaf litter decomposition (k = 1.9) than conventional cocoa systems (k = 1.3). Similarly, the rate of macro- and micro-nutrient mineralization was consistently greater on cocoa farms under organic management compared to those under conventional management. The time required for 99% mineralization of nutrients (t99) in leaf litter ranged from 1.30 (Fe) to 2.22 years (Ca) on organic cocoa farms versus 1.84 (K) to 3.22 years (Ca) on conventional cocoa farms. Organic management enhanced the physico-chemical properties of soils compared to conventional management; soil moisture content and electrical conductivity were consistently greater on organic cocoa systems than conventional cocoa systems. Similarly, organic farms had significantly higher stocks of P (51.0 kg ha-1), Mn (310 kg ha-1) and Cu (0.4 kg ha-1) at the 0-30 cm depth compared to conventional farms (28.1 kg ha-1, 165 kg ha-1 and 0.1 kg ha-1, respectively). Annual cocoa pod production per tree was similar for both organic and conventional farms (10 pods per tree for both farm types). However, the overall cocoa pod production was greater on conventional farms (12,433 ha-1 yr-1) than organic farms (9,560 ha-1 yr-1) due to greater cocoa tree density (Org. 1012 ± 40 stems ha-1 vs. Con. 1203 ± 40 stems ha-1). The annual production of banana (Musa sapientum L. f. thomsonii King ex Baker) and plantain (Musa paradisiaca L.) was significantly greater in organic cocoa systems (186.3 kg ha-1 yr-1) than conventional systems (31.6 kg ha-1 yr-1). The results emphasize the potential of smallholder organic cocoa systems to ensure environmental sustainability and long-term cocoa productivity. The adoption of organic management in smallholder cocoa systems is therefore recommended.
... The transfer of energy and nutrients between the biological and non-biological components of an ecosystem is crucial for its existence and resilience (Hartemink, 2005;Owusu-Sekyere et al., 2006;Fontes et al., 2014). Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity in all ecosystems (Hartemink, 2005;Ofori-Frimpong et al., 2007;Becker et al., 2015). ...
... The transfer of energy and nutrients between the biological and non-biological components of an ecosystem is crucial for its existence and resilience (Hartemink, 2005;Owusu-Sekyere et al., 2006;Fontes et al., 2014). Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity in all ecosystems (Hartemink, 2005;Ofori-Frimpong et al., 2007;Becker et al., 2015). Plant litter acts as an input-output system for organic matter and humus, thus it influences the soil quality of an ecosystem (Hartemink, 2005;Fontes et al., 2014). ...
... Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity in all ecosystems (Hartemink, 2005;Ofori-Frimpong et al., 2007;Becker et al., 2015). Plant litter acts as an input-output system for organic matter and humus, thus it influences the soil quality of an ecosystem (Hartemink, 2005;Fontes et al., 2014). Litterfall and its attendant processes such as decomposition and nutrient mineralization are key components of the plant-soil system (Kumar, 2008;Becker et al., 2015). ...
... Litter in general and leaf litter in particular is a central nutrient resource and litterfall is a critical link between plants and soils for the return and recycling of organic matter and nutrients (Hartemink 2005;Triadiati et al. 2011;van Vliet et al. 2015;Naik et al. 2018) and maintenance of soil fertility and ultimately contributes to the regulation of primary productivity in an ecosystem (Mamani-Pati et al. 2012;Fontes et al. 2014). Decomposition is a complex process that reduces dead organic matter or litter into mineral nutrients, water and carbon dioxide (Dawoe et al. 2010;Kaba 2017). ...
... The subsequent release of nutrients in the residual material after the period of immobilisation may be attributed to microbial oxidation of recalcitrant litter components and physical-biological fragmentation (Gupta et al. 2017;Naik et al. 2018). Different species have different nutrient release patterns, which are attributable to an interaction between litter quality and seasonal environmental factors (Hartemink 2005;Wang et al. 2014;Yang and Zhu 2014;Gupta et al. 2017;Lori et al. 2017). Furthermore, litter chemistry changes over time as decomposition progresses (Fig. 4), thus continuously affecting the rate of substrate decomposition and nutrient mineralisation (Kumar 2008;Domínguez et al. 2014;Lori et al. 2017). ...
Article
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Purpose Although litter decomposition and nutrient release patterns have been studied in cocoa agroforestry systems in general, studies focusing on organic and conventional cocoa systems are lacking which is critical as organic farms are particularly dependent on nutrient returns from decomposing litter. Materials and methods Dynamics in leaf litter decomposition and the mineralisation of macro- and micro-nutrients in organic and conventional cocoa agroforestry systems were studied using the litterbag technique for 12 months. Results The average monthly mass loss was more than two times higher on organic farms (9.2–14.4 g month⁻¹) compared to conventional farms (4.2–7.3 g month⁻¹) in the first five months. The annual rate of decomposition (k) was higher on organic farms (1.9) compared to conventional systems (1.4). The time required for 50% (t50) and 99% (t99) decomposition of leaf litter was both lower on organic farms (t50 = 0.4 years, t99 = 2.6 years) than conventional farms (t50 = 0.5 years, t99 = 3.5 years). The estimated k values for macro- and micro-nutrients on organic cocoa systems ranged from 2.3 for calcium to 4.5 for potassium compared to 1.6 (Ca) to 2.8 (K) on conventional farms. The k values of all nutrients (except nitrogen and phosphorus) were significantly greater on organic farms than conventional systems. The estimated k values for both litter decomposition and nutrient mineralisation correlated with soil pH and moisture content, but not initial litter chemistry. Conclusions Organic management of smallholder cocoa agroforestry systems enhanced leaf litter decomposition and nutrient mineralisation through improved soil conditions. Thus, organic management of cocoa agroforestry systems may contribute to sustainable cocoa production in smallholder systems through enhanced nutrient return from litter decomposition.
... Typically, cocoa trees planted on a freshly cleared forest initially benefit from high fertility due to high organic matter levels and well-developed soil structure. However, the subsequent removal of the harvested pods and beans can reduce nutrient levels (Boyer, 1973;Fassbender et al., 1988;Hartemink, 2005;Thong & Ng, 1978;van Vliet et al., 2015), and soil fertility declines if they are not replenished with organic or mineral/inorganic fertilizers (Aikpokpodion, 2010;Hartemink, 2005). Degradation can also occur due to the acidification of the soil from the use of acidifying fertilizers, like urea, organic matter decay, the removal and leaching of basic cations (Goulding, 2016), and an increased availability of toxic elements (Lal et al., 1989). ...
... Typically, cocoa trees planted on a freshly cleared forest initially benefit from high fertility due to high organic matter levels and well-developed soil structure. However, the subsequent removal of the harvested pods and beans can reduce nutrient levels (Boyer, 1973;Fassbender et al., 1988;Hartemink, 2005;Thong & Ng, 1978;van Vliet et al., 2015), and soil fertility declines if they are not replenished with organic or mineral/inorganic fertilizers (Aikpokpodion, 2010;Hartemink, 2005). Degradation can also occur due to the acidification of the soil from the use of acidifying fertilizers, like urea, organic matter decay, the removal and leaching of basic cations (Goulding, 2016), and an increased availability of toxic elements (Lal et al., 1989). ...
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In Indonesia, management practices that reduce soil fertility could be limiting cocoa (Theobroma cacao L.) production. To address this, we investigated the effects of fertilizers and organic amendments comprising different combinations of NPK urea, dolomite, and manure-based compost on soil properties and cocoa productivity. We extended an existing field experiment in South Sulawesi, Indonesia, to assess these treatments' effects on cocoa trees from the age of 2.9 years to 7.4 years. The treatments were first applied 5 months after planting and subsequently twice a year. Soil analyses were performed before planting, after 3 years, and finally after 7 years. Productivity was assessed yearly between the age of 3.5 and 7.4 years. The highest yields were obtained from the plots receiving compost, although the yield benefits diminished over time. Inorganic fertilizer alone doubled the yield compared to the control, while the yields with compost and compost fertilizer were three times that of the control. With dolomite alone, the yield cumulated over 4 years was 41% higher than the control. The positive effect of compost on cocoa yields can potentially be attributed to (1) physical changes increasing soil water availability, (2) the chemical improvement of nutrient availability, and (3) biologically, by promoting the activity of beneficial organisms. The application of dolomite increased soil pH, Ca, and Mg contents. Soil organic carbon greatly declined in the composted treatments, even though 10 kg of compost was applied per tree per year, probably because of the low C:N ratio of the compost. Future studies should assess different fertilizer formulations and combinations with organic inputs and explore the mechanisms by which compost promotes cocoa productivity.
... These depths are described as topsoil and subsoil respectively. Sampling was carried out in these depths because the feeding roots of cocoa are usually found in this zone (Hartemink, 2005;Aikpokpodion, 2010). The soil samples were mixed thoroughly and taken to the laboratory for analysis. ...
... The SOC content under cocoa farm in this study ranged from 1.74 to 3.77% (0.21 to 0.45 kg) and 1.21 to 2.68% (0.15 to 0.32 kg) in forest soil (Table 1). The fertility of soils under cocoa was lower when compared to the primary forests (Hartemink, 2005). Litterfall in cocoa ecosystem is made up of litter from cocoa and associated shade trees which include branches, twigs, leaves, fruits, and flowers. ...
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The emission of greenhouse gases into the earth’s atmosphere has been credited as the major cause of climate change which is being experienced all over the world. Climate change mitigation is one of the strategies that have been suggested as a way of stabilising the concentration of greenhouse gases in the atmosphere. This study assessed the capacity of agroforestry of cocoa trees in reducing atmospheric carbon dioxide. The carbon content in the cocoa plant variables made up of bean, litter, leaf and podhusk were determined in the laboratory through standard procedure. The laboratory results were subjected to descriptive and inferential statistical techniques. The study showed the magnitude order of carbon storage in cocoa agroforestry as cocoa bean (2.86 kg) > pod husk (2.73 kg) > cocoa litter (2.65kg) > cocoa leaves (2.62 kg) > soil (1.14 kg)..The ability of cocoa and forest soils to retain nitrogen, leaf and litterfall to stock more carbon proved that cocoa agroforestry has a higher potential of mitigating climate change in the tropical region. The study recommended the adoption of agroforestry systems which are capable of sequestering carbon as a means of addressing the challenge of climate change.
... kg N ha − 1 and 27.2-77.2 kg K ha −1 for 1000 kg of cocoa beans harvested (Hartemink 2005), poor management of the husks can cause fairly large losses from the plantations. The fresh cocoa husks weigh 10 times more than the dry beans they contain (Khanahmadi et al. 2016;Mansur et al. 2014). ...
... To what extent does husk management contribute to K recycling and cocoa nutrition? For current regional mean cocoa bean yields of 400 kg ha −1 in west Africa, about 17-31 kg K ha −1 can be expected in cocoa pod husks (Hartemink 2005). These are modest amounts in relation to crop requirements (up to 300 kg K ha −1 , Von Uexküll and Cohen 1980) and husk recycling alone is insufficient to meet the K needs of cocoa, highlighting the importance of K fertilizer additions. ...
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Aim Recycling of cocoa pod husks has potential to contribute to mineral nutrition of cocoa. Yet little is known of the nutrient content and nutrient release patterns from the husks. The potassium (K) rich husks are usually left in heaps in cocoa plantations in Africa. We aimed to understand and quantify release patterns of K and other nutrients from husks under varying rainfall regimes and assessed the effects of partial decomposition and inundation on nutrient leaching rates. Methods We incubated chunks of cocoa pod husks to assess decomposition rates and we measured nutrient leaching rates from two sets of husk chunks: one set was placed in tubes that were submitted to simulated scheduled rainfall events while the second set was continuously inundated in beakers. Results Decomposition of husks followed a second-order exponential curve (k: 0.09 day ⁻¹ ; ageing constant: 0.43). Nutrient losses recorded within 25 days were larger and more variable for K (33%) than for other macronutrients released in this order: Mg > Ca ≈ P > N (less than 15%). Potassium leaching was mainly driven by rainfall frequency ( P < 0.05) and reinforced by intense rainfall, especially at lower frequency. Under water-saturated conditions, 11% of K was leached out within 48 h from fresh husks compared with 92% from partially decayed husks. Conclusion Some initial decomposition of cocoa pod husks is required to expose K to intense leaching. As decomposition progresses, abundant K losses are to be expected under frequent and/or intense rainfall events.
... Potassium is the most abundant cation in plant cells [21,64]. Typically, nutrient content in crop residues is influenced by nutrient and water management, soil characteristics, cropspecific nutrient demands, and phenological stage at harvest as plant K dynamics change over the season [31,36,65,66]. A substantial fraction of annual K uptake can accumulate in tree fruits during development. ...
... For instance, Muhammad et al. (2015) found that around 91% of whole plant K accumulation in almonds was allocated to fruit tissues [26]. Additionally, nutrient concentrations can vary substantially across regions as shown in cacao husk [65,67]. Post-harvest processing can influence residue K concentrations; for example, composting can substantially increase K content [68]. ...
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Ecosystem-based approaches to nutrient management are needed to satisfy crop nutrient requirements while minimizing environmental impacts of fertilizer use. Applying crop residues as soil amendments can provide essential crop nutrient inputs from organic sources while improving nutrient retention, soil health, water conservation, and crop performance. Tree crop hulls, husks, and shells have been found to contain high concentrations of potassium across species including almond, cacao, coffee, pecan, and hazelnut. The objective of this review is to characterize organic sources of potassium focusing on lignocellulosic pericarps and discuss reported effects of surface application on potassium cycling, water dynamics, soil functionality, and crop yield. Research indicates potassium ions solubilize readily from plant material into soil solution due to potassium’s high mobility as a predominately unbound monatomic cation in plant tissues. Studies evaluating tree crop nutshells, field crop residues, and forest ecosystem litter layers indicate this process of potassium release is driven primarily by water and is not strongly limited by decomposition. Research suggests orchard floor management practices can be tailored to maximize the soil and plant benefits provided by this practice. Contextual factors influencing practice adoption and areas for future study are discussed.
... The amount of light falling on a cacao tree is known to affect its growth and yield, and moderate shade tends to reduce water and nutrient stress [6,12,27]. Optimum growth of young cacao plants was achieved at 20 to 30% of full sunlight [1,28,29]. However, maximum yield of adult plants requires limited shade or full sun especially in areas of ecosystems with heavy cloud cover [8]. ...
... Soils in the cacao growing regions of the world are often acidic, infertile and invariably deficient in nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn) and iron (Fe), and that leads to severe essential nutrients deficiencies in cacao [11,12,29,[48][49][50][51][52]. Increasing atmospheric [CO2] coupled with low soil fertility and low irradiance subject cacao to severe nutrient stress and results in decline of yield potentials. Cacao has considerable genetic variation in morphological and physiological traits [4,[53][54][55]. ...
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Cacao (Theobroma cacao L.) was grown as an understory tree in agroforestry systems where it received inadequate to adequate levels of photosynthetic photon flux density (PPFD). As atmospheric carbon dioxide steadily increased, it was unclear what impact this would have on cacao growth and development at low PPFD. This research evaluated the effects of ambient and elevated levels carbon dioxide under inadequate to adequate levels of PPFD on growth, physiological and nutrient use efficiency traits of seven genetically contrasting juvenile cacao genotypes. Growth parameters (total and root dry weight, root length, stem height, leaf area, relative growth rate and net assimilation rates increased, and specific leaf area decreased significantly in response to increasing carbon dioxide and PPFD. Increasing carbon dioxide and PPFD levels significantly increased net photosynthesis and water-use efficiency traits but significantly reduced stomatal conductance and transpiration. With few exceptions, increasing carbon dioxide and PPFD reduced macro-micro nutrient concentrations but increased uptake, influx, transport and nutrient use efficiency in all cacao genotypes. Irrespective of levels of carbon dioxide and PPFD, intraspecific differences were observed for growth, physiology and nutrient use efficiency of cacao genotypes.
... The amounts of cocoa Agroforestry Residues in Ghana and most West Africa countries is between 5 and 10 t/ha/year of dry matter. This residue contains significant amount of nutrients which can be made available for cocoa uptake after decomposition (Hartemink, 2005;Dawoe et al., 2010;Fontes et al., 2014). It is therefore not surprising that for the majority of cocoa farmers, fertility of soils under cocoa plantations is maintained through the recycling of nutrients through residue decomposition (Lal, 2008;ISSER, 2004;Dawoe et al., 2010). ...
... The majority of cocoa farmers in the study area practice cocoa agroforestry system, where multipurpose shade trees are integrated into their cocoa farms (Kaba and Abunyewa, 2019). Thus, such soil fertility management practice could further improve when Nfixing legume trees are intercropped with cocoa due to the extra amount of fixed N and other nutrients present in their biomass (Hartemink, 2005;Anhar, 2005;Isaac et al., 2007b). ...
Article
Climate change and environmental degradation have contributed in compromising the soil nutrient integrity of cocoa farmlands, yet sustainable nutrient recycling innovation in cocoa waste management has received less research attention. Utilizing experimentation methodology in an agroforestry system composed of cocoa (Theobroma cacao L.) and a Nitrogen-fixing Gliricidia sepium (Jacq. Kunth ex Walp.), the study examines how the soil nutritional level of farmland can be enhanced. The study confirms the proposition that the rate of decomposition and nutrients release from an innovative mixed waste sample (60% cocoa waste and 40% gliricidia waste in this case) is significantly higher in comparison with the traditional cocoa waste only sample. The results further established that innovative mixed waste sample had a faster decomposition rate (no biomass left at 216 days after laying) as compared to traditional cocoa waste which fully decomposed at 277 days after laying. A difference of 51 days after laying justifies the waste mixture decomposition as a sustainable nutrient recycling innovation within cocoa agroforestry waste management context. These results have implications for agroforestry waste management, soil nutrient recycling and cocoa industry performance.
... Natural forest converted into agricultural land use coffee multistrata plantation caused carbon stock decrement 262 ton ha -1 decreased into 82 ton ha -1 and coffee monoculture plantation caused carbon stock decrement into 52 ton ha -1 [1]. Cacao (Theobroma cacao L) is the agriculture commodity in the tropical country [2]. Cacao is one of the agricultural broadly commodity developed in Indonesia has an opportunity in carbon stock. ...
Thesis
This study aims to determine cacao carbon stock based on the conditions of cacao farmers plantation at Tomoni Beringin Jaya Village East Luwu South Sulawesi. Carbon stock estimated aboveground biomass and belowground biomass using allometric methodology, were carried out at cacao field farmer with sampling intensity 30% cacao field at 5 year (n = 214), 10 year (n=229) and 15 years (n=329), soil sampling disturb (measure soil organic carbon), un disturb (measure bulk soil bulk density) and soil bulk density at depth 0-10 cm and 10-20 cm. Carbon stock cacao aboveground biomass at the age of 5 years (M45) was 1.89 ton C ha-1 and belowground biomass was 0.56 ton C ha-1 with proportion 77.19%:22.81%. Carbon stock cacao aboveground biomass at the age of 10 year (BR25) was 3.66 ton C ha-1 and belowground biomass 1.01 ton C ha-1 with a proportion 78.37%:21.63%. Carbon stock cacao aboveground biomass at 15 year (BR25) was 4.58 ton C ha-1 and belowground biomass of 1.21 ton C ha-1 with a proportion 79.07%:20.93%. Cacao carbon stock at 5 year, 10 year, and 15 year respectively increased, nevertheless mean annual carbon stock cacao decreased in 5 years cacao aboveground biomass was 0.37 ton C ha-1 and belowground biomass 0.11 tonCa-1. Carbon stock cacao 10 year aboveground biomass 0.36 ton C ha-1 and belowground biomass 0.10 ton C ha-1. Carbon stock cacao 15 year aboveground biomass 0.30 ton C ha-1 and belowground biomass 0.08 ton C ha-1. Soil organic carbon showed dynamic under different year cacao plantation. Soil organic carbon in cacao plantation age 5 year was 0.031 tonCha-1 , cacao plantation age 10 year was 0.034 ton C ha-1, and cacao plantation age 15 year was 0.043 ton C ha-1 .
... Lower yields in cacao grown under shade are mostly related to climatic conditions such as reduced light intensity, precipitation, temperature [20] [22] [23] [29] and therefore under such management systems it is advantageous to adopt cacao genotypes that can maintain desired productivity even under reduced light intensity. Optimum cacao growth is achieved at 20% to 30% of full sunlight [1] [30] usually with adequate soil nutrient availability [31]. Under shaded plantations in Bahia Brazil, light intensity at noon above the cacao canopy ranged between 30 and 100% of the full sunlight and 4% -10% at the ground level [32]. ...
... (Table 3). At the soil sampling time (2017), two composite soil samples were collected from two soil depths (surface depth, i.e., 0-15 cm, and subsurface depth, i.e., 15-30 cm), critical for cacao nutrition [18,19], where approximately 80% of cacao tree lateral roots are found [20]. e soil samples were taken from the base of four cacao trees per plot and bulked into polyethylene bags as a composite sample for each depth. ...
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Sustainable cacao cultivation in Ghana has been seriously hampered by high seedling mortality due to the low soil fertility of lands used for the establishment of new cacao farms. Alleviating the low soil fertility to enhance sustainable cacao cultivation requires the use of fertilizers. A study was therefore conducted at the Cocoa Research Institute of Ghana to determine the effect of integrated application of poultry manure (PM) and sulphate of ammonia (SOA) fertilizers on survival, growth, and nutrient uptake by cacao seedlings under marginal field conditions. A randomized complete block design with four replications was used to evaluate the effects of six treatments. Traits assessed were percentage survival, height, trunk cross-sectional area (TCSA), and nutrient uptake. Results from the study showed no significant differences in soil N and K among the treatments. PM-amended plots had significantly higher soil P than nonamended control and SOA alone. Seedling survival rate ranged from 73.3 to 89.3% with a higher proportion of surviving plants in PM amended soils. The application of PM alone and its combination with SOA improved growth. Cacao trees of T4 (75% recommended dosage of SOA + PM) had the largest TCSA increment, which was significantly different from the other soil treatments. Leaf nutrient concentrations in cacao of T4 were higher than the other soil treatments. It was therefore concluded that T4 could be used during cacao establishment in marginal areas for improved plant survival and growth.
... This last point is of special interest for tropical ecosystems whose soils are highly weathered and often poor, making litter one of the main resources of nutrient return (Lian and Zhang 1998;Martius et al. 2004;van Vliet et al. 2015). According to Hartemink (2005), litterfall variations in cAFS are the result of a combination of rainfall dynamics and levels as well as associated tree species, density and age. While information on cAFS are increasingly available around the world, little data is published on the mass flow of litterfall, its composition and seasonal variations in these systems (see Kumar, 2007;Dawoe et al. 2010). ...
... This last point is of special interest for tropical ecosystems whose soils are highly weathered and often poor, making litter one of the main resources of nutrient return (Lian and Zhang 1998;Martius et al. 2004;van Vliet et al. 2015). According to Hartemink (2005), litterfall variations in cAFS are the result of a combination of rainfall dynamics and levels as well as associated tree species, density and age. While information on cAFS are increasingly available around the world, little data is published on the mass flow of litterfall, its composition and seasonal variations in these systems (see Kumar, 2007;Dawoe et al. 2010). ...
Article
Nutrient cycling in cocoa agroforestry systems (cAFS) is complex and poorly understood. To better understand the mass flow of carbon and nutrients into the soil subsystem under various contexts we quantified the mass flow of litterfall, its composition and seasonal variations in different agroforestry systems in Bokito (Central Cameroon). We studied litterfall dynamics and in situ leaf-litter cycling of cAFS established on past forest lands (F-cAFS) and savannah (S-cAFS). We also studied the decomposition of cocoa and associated tree leaf-litter in litterbags. Local secondary semi-deciduous forests were included as control. Annual litterfall in full-grown cAFS ([ 15 years old) was high (9.4 Mg ha-1 y-1) and represented ca. 67% of litterfall in control forests. In full-grown cAFS, associated tree leaf-litter contributed to litterfall the most and ranged between 60 and 70% of the total amount recorded (6.3 Mg ha-1 y-1). The quantities and dynamics of the litter components monitored were similar in full-grown Sand F-cAFS. The microclimate was best buffered in forests and least buffered in young S-cAFS but could not be linked to leaf-litter decomposition. Forest leaf litterfall was higher and tended to cycle faster than total leaf-litter of cAFS, whose decomposition appeared limited by cocoa leaf-litter quality. Our study underlines (i) the critical contribution of associated trees to the nutrient cycle of agroecosys-tems established on poor soils and, (ii) the ability of farmers to channel associated tree communities towards similar functioning despite different past land-uses.
... This last point is of special interest for tropical ecosystems whose soils are highly weathered and often poor, making litter one of the main resources of nutrient return (Lian and Zhang 1998;Martius et al. 2004;van Vliet et al. 2015). According to Hartemink (2005), litterfall variations in cAFS are the result of a combination of rainfall dynamics and levels as well as associated tree species, density and age. While information on cAFS are increasingly available around the world, little data is published on the mass flow of litterfall, its composition and seasonal variations in these systems (see Kumar, 2007;Dawoe et al. 2010). ...
Article
Full-text available
Nutrient cycling in cocoa agroforestry systems (cAFS) is complex and poorly understood. To better understand the mass flow of carbon and nutrients into the soil sub-system under various contexts we quantified the mass flow of litterfall, its composition and seasonal variations in different agroforestry systems in Bokito (Central Cameroon). We studied litterfall dynamics and in situ leaf-litter cycling of cAFS established on past forest lands (F-cAFS) and savannah (S-cAFS). We also studied the decomposition of cocoa and associated tree leaf-litter in litterbags. Local secondary semi-deciduous forests were included as control. Annual litterfall in full-grown cAFS (> 15 years old) was high (9.4 Mg ha⁻¹ y⁻¹) and represented ca. 67% of litterfall in control forests. In full-grown cAFS, associated tree leaf-litter contributed to litterfall the most and ranged between 60 and 70% of the total amount recorded (6.3 Mg ha⁻¹ y⁻¹). The quantities and dynamics of the litter components monitored were similar in full-grown S- and F-cAFS. The microclimate was best buffered in forests and least buffered in young S-cAFS but could not be linked to leaf-litter decomposition. Forest leaf litterfall was higher and tended to cycle faster than total leaf-litter of cAFS, whose decomposition appeared limited by cocoa leaf-litter quality. Our study underlines (i) the critical contribution of associated trees to the nutrient cycle of agroecosystems established on poor soils and, (ii) the ability of farmers to channel associated tree communities towards similar functioning despite different past land-uses.
... Al evaluar los diferentes tratamientos, se encontró que al compararse con el tratamiento de la persona productora (convencional) todos presentaron un mejor aporte de nutrientes y su valoración, en términos económicos, fue superior en un 70% para el caso T3-ecocacao; 52% para T4-químico+orgánico y en un 50% para T2-químico (Tabla 3). Si bien, las concentraciones de los nutrientes en las hojas que caen en forma de hojarasca son muy bajas, relacionado con el hecho de que muchas veces estos nutrientes se vuelven a absorver antes de que las hojas caigan, (Hartemink 2005), son un aporte para la nutrición del cultivo de cacao y permiten a la persona productora la reducción en alguna medida en la utilización de agroinsumos. ...
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Introducción. El sistema productivo cacaotero contribuye con la sustentabilidad del manejo de suelos a través del reciclaje de nutrientes, junto con la producción de hojarasca. Objetivo. Estimar el aporte de biomasa y nutrientes en plantaciones de cacao bajo efectos de fertilización química y orgánica. Materiales y métodos. En el SAF con cacao-CCN-51 (Theobroma cacao L.) asociado a matarratón (Gliricia sepium L.) en Rionegro (Santander), se evaluó el efecto de 4 fuentes de fertilización sobre la producción de hojarasca (kg.ha-1 MS) y el aporte de nutrientes esenciales N, P, K, Ca, Mg (kg.ha-1). Se empleó un diseño de bloques completos al azar con 3 repeticiones, con los siguientes tratamien- tos: T1-Convencional, T2-Químico, T3-Ecocacao y T4-Orgánico+químico. La fertilización se realizó durante 3 años. El aporte de hojarasca y nutrientes se evaluó durante el último año (2012), mediante trampas colectoras muestreadas mensualmente y analizadas en 2 épocas del año: bajas precipitaciones (BP: enero-febrero) y altas precipitaciones (AP: julio-diciembre). El aporte de nutrientes se calculó mediante el contenido de N, P, K, Ca, Mg determinado en laboratorio a partir de la hojarasca recolectada. Resultados. Los mayores aportes de hojarasca se presentaron en época de altas precipitaciones para el T3-ecocacao y T2-químico con 567,2 y 541,33 kg.ha-1 MS, respectivamente. La variación estacional por época del año tuvo efecto significativo sobre el aporte de P, K, Ca y Mg presente en hojarasca de cacao. Se observó que en el 80% de los casos el mayor aporte de nutrientes fue en época de BP. El T3-ecocacao se destacó por su aporte de los nutrientes N, Ca y Mg (8,11-7,74 y 1,02 kg.ha-1. año-1, respectivamente). Conclusión. En Rionegro-Santander el mayor aporte de hojarasca lo realizó el T3-Ecocacao con 992,11 kg.ha-1.año-1 MS que representó un valor monetario (como equivalente en fertilizante comercial) superior al 70% con respecto a T1-convencional.
... Al evaluar los diferentes tratamientos, se encontró que al compararse con el tratamiento de la persona productora (convencional) todos presentaron un mejor aporte de nutrientes y su valoración, en términos económicos, fue superior en un 70% para el caso T3-ecocacao; 52% para T4-químico+orgánico y en un 50% para T2-químico (Tabla 3). Si bien, las concentraciones de los nutrientes en las hojas que caen en forma de hojarasca son muy bajas, relacionado con el hecho de que muchas veces estos nutrientes se vuelven a absorver antes de que las hojas caigan, (Hartemink 2005), son un aporte para la nutrición del cultivo de cacao y permiten a la persona productora la reducción en alguna medida en la utilización de agroinsumos. ...
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Litter production and nutrient contribution in cocoa under different fertilization schemes, Rionegro-Santander. Introduction. The cocoa production system contributes to the sustainability of soil management, through the recycling of nutrients along with leaf litter production. Objective. To estimate the contribution of biomass and nutrients in cocoa plantations under the effects of chemical and organic fertilization. Materials and methods. In SAF with cocoa-CCN-51 (Theobroma cacao L.) associated to matarratón (Gliricia sepium L.) in Rionegro (Santander), it was evaluated the effect of 4 fertilization sources on the production of leaf litter (kg.ha-1 MS) and contribution of essential nutrients N, P, K, Ca, Mg (kg.ha-1). A complete randomized block design with 3 repetitions was used with these treatments: T1-Conventional, T2-Chemical, T3-Ecocacao and T4-rganic+Chemical. Fertilization was carried out during 3 years. The contribution of leaf litter and nutrients was evaluated the last year (2012), through collecting traps sampled monthly and analyzed in 2 times of the year: low rainfall (BP: January-February) and high rainfall (AP: July-December). The contribution of nutrients was calculated through the content of N, P, K, Ca, Mg determined in thelaboratory with the leaf litter production per ha. Results. The highest contribution of leaf litterwas occurred in the period of high rainfall for the treatments T3-Ecocacao and T2-Chemical with 567,2 and 541,33 kg.ha-1. MS, respectively. The seasonal variation by time of year had influenced signifivatively the contribution of N,P, K, Ca and Mg present in cocoa leaf litter. It was observed that in 80% of the cases a greater contribution of nutrients occurred in B.P season. The T3-ecocoa stood out for its contribution of N, Ca and Mg nutrients (8,11-7,74 and 1,02 kg.ha-1.year-1 respectively). Conclusion. In Rionegro- Santander, the greatest contribution of leaf litter was carried out by the T3-Ecocacao with 992.11kg.ha-1.year-1 MS, that represented a 70% higher monetary value (in terms of commercial fertilizer cost) with respect to T1-conventional.
... Wang et al. (2012), expresan que se pueden alcanzar mejores ajustes para estimar COS a temperaturas entre 375 y 550 °C durante 12h, pero estos estudios se restringen a los suelos de regiones semiáridas de China solo en suelo de regiones semiáridas China. Aunque no se realizó pruebas para determinar si los suelos son calcáreos, la información recaba de los suelos ecuatoriano indican que no son del tipo calcáreo (Moreno et al., 2016), aunque algunos suelos en estudio tuvieron un pH mayor a 8 (Tabla 1), por el nivel alto de Ca el cual es aporte de la hojarasca del cacao (Hartemink, 2005). ...
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The Loss On Ignition (LOI) method is used to estimate the soil organic matter (SOM) but has its advantages and limitations compared to other methods that calculate it from organic carbon (OC). The objective of the work was to calibrate the LOI method for use in alluvial soils cultivated with cocoa (Theobroma cacao L.). Thirty soil samples were extracted from 0 to 30 cm depth, and the following were determined SOM by LOI at 350, 430 and 600°C for 2h. These samples were contrasted with the dry combustion (DC) and Walkley and Black (WB) methods for OC determinations. The values obtained by LOI increased from 3,46% <4,95%<7,66%, when the temperature increased, being lower than those obtained with DC (1,85%) and WB (1,96%). The best linear adjustment obtained between LOI and DC was, at 430°C with an explanation coefficient (R2) equal to 0.83. Although the LOI method at 430°C was the best fi t to be used in the SOM calculation, more repetitions should be done for a better calibration model.
... Farmers perceived trees to be very important in adding up to organic matter. Trees of about 6 to 8 in number are found on farms of about 0.8 ha, and these serve as shade against intense sunshine, regulation of soil moisture, and production of litter (Hartemink, 2005;Afrifa and Acquaye, 2010;Blaser et al., 2017;Wartenberg et al., 2018). Soil moisture also creates a conducive atmosphere for micro and macrofauna to help in the decomposition of litter into humus and improving organic carbon in the soil (Jobbágy and Jackson, 2000;Lal, 2004). ...
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Farmers can play an important role in climate change mitigation through sustainable soil management practices. Semi-structured interviews were conducted in the Atwima Nwabiagya municipality of Ashanti region, Ghana, to explore farmers' knowledge and perceptions of their soils, soil fertility, applied management practices, and climate change on soil organic carbon. The interviews included topics related to farmers' access to training and its impact in adopting and changes in management strategies. Summary for interviews was prepared based on notes and recordings and analyzed with the Qualitative Content Analysis (QCAmap) software using emergent codes. Results show that farmers had a lot of knowledge on soil organic matter (SOM) and how it affects climate and the relationship between SOM and soil fertility. They also acknowledged that their management practices affect quantities of SOM in topsoil and subsoil and soil fertility. The adoption of current and new management practices including, the use of organic and inorganic fertilizers, manure, mulching, and shade management, is a reflection of their newly acquired knowledge and understanding of fertility sustaining processes. The study highlights the relationship between farmers' training and changes in their adopted practices and how management practices affect SOC influencing climate change and soil fertility.
...  Contribuyen a mantener la fertilidad del suelo mediante la disponibilidad significativa de materia orgánica y el reciclaje de nutrientes (Hartemink, 2005;Rojas M. et al., 2017). Esta contribución a la fertilidad del suelo se considera muy importante, ya que, en los cultivos de cacao tradicionales, la fertilización es una práctica agronómica poco frecuente. ...
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El modelo productivo que se ofrece en el presente documento resulta importante dado el panorama descrito hasta aquí. El documento muestra la actualidad del sector cacaotero en Santander y brinda información sobre la oferta tecnológica que AGROSAVIA y otros actores han desarrollado para el departamento. El fin de esta oferta tecnológica es resolver las brechas tecnológicas y dar apoyo a los servicios de capacitación y asistencia técnica de las entidades que atienden a los productores, en aspectos sensibles de la productividad como obtención de material vegetal de calidad, manejo de enfermedades y plagas, establecimiento de plantaciones, procesos de beneficios y transformación del producto
... There are many studies reviewing various aspects of intercropping, including yield stability [24][25][26], water and nutrient utilization [27][28][29][30][31], biodiversity [32][33][34][35][36][37][38][39], allelopathy [17,[40][41][42][43][44], agroforestry [29,[45][46][47][48][49][50][51], or species-dependent intercropping such as cereal-legume or maize-based intercropping [7,31,52,53]. However, no study has investigated the overall research tends and features of intercropping. ...
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Intercropping has been practiced worldwide in both traditional and sustainable agriculture to feed the growing population. This study aims to analyze the research status and evolution of intercropping, to identify the influential authors, research centers, and articles, and to reveal the main research topics between 1992 and 2020 based on the Web of Science Core Collection database. The results show that the volume of publications in this field has increased rapidly over the past three decades. The analysis identifies the top three authors (i.e., Meine Van Noordwijk, Wenyu Yang, and Teja Tscharntke), top three contributing organizations (i.e., the World Agroforestry Center (ICRAF), the Chinese Academy of Science, and the INRA), and three most productive countries (i.e., the USA, India, and China). Co-occurrence analysis demonstrates that studies on intercropping can be divided into four clusters as centered by keywords of intercropping/maize, biodiversity/conservation, agroforestry, and carbon, respectively. Lal 2004 is the most influential study with the greatest number of citations and Agroforestry Systems is the most utilized journal. Perspectives on future studies were also given. This study helps researchers to clarify the current research status in the field of intercropping and put forward its future research.
... For each farm, two (2) composites made up of topsoil and subsoil was taken for further analysis. Altogether were six (6) composites samples for laboratory analysis The sampling was limited to this area due to the fact that the most feeding roots of cocoa are concentrated in that depth (Thong and Ng, 1978;Wood and Lass, 1985;De Oliveira andValle, 1990 andHartemink, 2005;Aikpokpodion 2010). Soil particles were airdried, mixed up together, sieved with 2.0mm sieve and analyzed using standard laboratory techniques at Step-B Central Research Laboratory, Federal University of Technology, Akure. ...
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The mainstay agro-based economic activity in southwest Nigeria, especially among the peasant farmers is cocoa (Theobroma cacao) production. Cocoa could be broadly divided into indigenous and hybrid in terms of varieties. Indigenous type had been cultivated over the decades but for more than two decades ago now, the grown of hybrid has been rapidly predominated. From the previous studies, comparative analysis of the soil nutrient degradation between cocoa varieties are not available particularly those that differentiate hybrid from indigenous. This paper examines the difference between both varieties in terms of nutrient concentration in leaf, bean and pod husk in relation to their impacts on soil nutrient degradation. Multiple regression analysis shows that cocoa outputs immensely contributed to the soil nutrient degradation under hybrid than indigenous varieties in old cocoa plantations. Finding shows that pod husk and cocoa bean are the main determinants of soil nutrient degradation in both varieties. To ameliorate the problem of soil nutrient degradation to the nearest minimum, the study recommends seasonal application of chemical or pod husk fertilizers to complement the impact of litterfall.
... In many parts of the world, cocoa is produced under natural or planted shade tree. Shade trees compete for growth resources but may also ameliorate adverse climate conditions; reduce soil erosion, pests, and diseases; and increase nutrient use efficiency in cocoa (Beer et al., 1998 andHartemink, 2005).Litterfall significantly low in nutrient concentration when compared to the fresh leaves as nutrients are reabsorbed before the leaves fall.However, nutrient concentration in litterfall is the function of season, species, soil fertility and surface configuration. The amount of nutrients annually transferred depends on the amount of litterfall and the nutrient concentration in the litterfall. ...
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Nutrient accumulation in leaves return to the soil through litterfall and this is the most important component of the forest ecosystem because; it is a major pathway of nutrient and energy transfer. Ability of cocoa tree to remains productive for number of the years without the application of chemical fertilizer lies in the impact of litterfall. This study examines the nutrient variability status of litterfall and fresh leaf under indigenous and hybrid cocoa plantation. Results showed that average storage of essential nutrient slightly varied from indigenous to hybrid. Correlation analysis result indicates that there is higher relationship between litterfall (r = 0.98) than fresh leaf (r = 0.74) in both species while ANOVA result indicates similarity in the nutrient storage and return rate. Nevertheless, the quantity of essential nutrients released into the soil via indigenous litter exceeds that of hybrid. Thus, macronutrient returns via litterfall in indigenous cocoa plantation follows the order of: N<Mg<K<P, hybrid: N<Mg<P<K and micronutrient: Cu<Fe<Zn<Mn for both species. It was observed that low return of the essential nutrients in hybrid was as a result of the quantityseasonally stocked in pod husks and beans removed through yield harvest, as well as immobilized nutrient in the tree parts. The study recommends interplanting of both species and periodic application of pod husk fertilizer; to complement the effort of litterfall, especially in hybrid cocoa plantation.
... Cocoa producers in Latin America either drop out the CPH in stripping sites after harvest or are composted in designed places as a strategy to fertilize the soils (Salazar et al. 2018). The use of tons of CPH produced in the form of compost through the decomposition of harvested residues provides nutrient supply opportunities on cacao ecosystems (Hartemink 2005). However, any treatment without reduction of Cd, can increase its content in soils, as noted by Ramtahal et al. (2018). ...
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Is it possible to use the same cocoa pod husk product as an amendment to fertilizer and remediate the soil under the cocoa crop?. Purpose: The role of cocoa pod husk waste in soil cadmium contamination has been largely overlooked. Hence, this study aims to provide a strategy for the management of cocoa pod husk waste when representing a pollution menace for cocoa plantations. Method: Cocoa pod husks waste was subjected to composting and pyrolysis for decreasing the heavy metal content. Biochar and compost were characterized using SEM-EDS, and FTIR-ATR. Macro and micronutrients (Mg, K, Zn, Fe, Cu, Zn, Mn, and Na), and Cd were measured by atomic absorption spectroscopy (AAS). Sorption experiments and soil incubation experiments for two months were also carried out looking for an application of CPH materials in Cd sorption and remediation. Results: Pyrolysis showed more effectiveness for Cd reduction in cocoa pod husk waste (90%) than composting (66%), 700 °C was the optimal temperature. Equilibrium isotherm experiments showed maximum Cd adsorption of 21.58 mg g-1 for Bc700 in solution. Biochar showed a small reduction of available Cd in naturally contaminated soil. Both materials have the potential to be used as organic fertilizer because of their high nutrient contents. Conclusion: Biochar is an alternative to compost for the management of post-harvest cocoa wastes contaminated with Cd.
... Nutrient cycling in rainforest ecosystem is closed and can be illustrated in terms of input and output systems (Hartemink 2005). This due to the influence of nutrient returns through litter decomposition and reabsoption, through fall, stemflow and root turnover. ...
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Apart from pests and diseases, a vital issue in the early mature of cocoa crop in Nigeria is soil nutrient degradation in relation to the ageing of the farms and annual mining of nutrients via yield harvests. Indigenous production of cocoa in southwest Nigeria has been on without fertilizer applications. This is the basis for the reduction average lifespan and productive years of the plantation. The aim of this study was to quantify the rates of soil nutrient losses via cycling channels in old cocoa farm using cocoa beans, leaves, litters, and pod husks in south western Nigeria forest belt. Old cocoa farms with an average age of 55 years were selected from Idanre, where nutrients in soil cultivated to cocoa and plant variables were experimentally evaluated. Identified variables were randomly sampled and the composite samples were subjected to laboratory analysis. Results through routine laboratory techniques were subjected to descriptive analysis. Using average and percentage, the results show that inputs from litter falls account for about 29%, pod husks (24%), leaves (28%), beans (13%) and soil (6%) approximately. Soil nutrient balance equation indicates that an average of 1.32% nutrient amounts to loss via annual cycle and the order of nutrient concentrations in old cocoa ecosystem is therefore considered as litter > leaves > podhusks > beans > soil. Results also showed that nutrient cycling in old cocoa farm was high while the loss was low. The study hereby recommends land evaluation, annual relocation and seasonal spreading of pod husks across the farm for redistribution of nutrients to compliment nutrients return through litter fall instead of its usual concentrations where not useful for plant development.
... • Según el manejo de la sombra, influencian positiva o negativamente la dinámica de la población de plagas y la incidencia de enfermedades tanto en el cacao como en las especies acompañantes (Schroth et al., 2000). • Contribuyen a mantener la fertilidad del suelo mediante la disponibilidad significativa de materia orgánica y el ciclaje de nutrientes (Hartemink, 2005;Rojas et al., 2017). Esta contribución a la fertilidad del suelo se considera muy importante, ya que, en los cultivos de cacao tradicionales, la fertilización es una práctica agronómica poco frecuente. ...
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Santander es el primer productor de cacao en Colombia y con un rendimiento promedio de 600 kg/ha de cacao seco, superior a otros departamentos. Sin embargo, esos indicadores de productividad no le garantizan una rentabilidad, ni la sostenibilidad que permita que la producción de cacao sea aspiracional para todos los jóvenes rurales que emigran a la ciudad en búsqueda de alternativas productivas, ya que no hay una mejora en su calidad de vida. Estamos seguros de que productores juiciosos, dedicados y que aplican la tecnología disponible para el sector cacaotero tienen rendimientos superiores a los 1.500 kg/ha de cacao seco que hacen rentable el sistema productivo. Todo se hace utilizando las técnicas y los conocimientos adecuados que han aprendido a través de la experiencia y de las capacitaciones con las diferentes instituciones del sector, como Fedecacao y agrosavia. Por ello, este modelo productivo les ofrece la oferta tecnológica disponible que se requiere para generar un cambio en el manejo de las plantaciones y dar respuesta a los desafíos que afronta la cacaocultura a nivel mundial. En los once capítulos de este documento podrá encontrar información útil para el manejo de cacaos finos de sabor y aroma bajo sistema agroforestal (SAF).
... It might also be related to the fact that cocoa system in the present study is older ( observed that litterfall production showed a significant increase over time after forest conversion and ranged from 5.0 to 10.4 Mg DM ha − 1 yr − 1 on the same sites. A number of other studies (e.g., Owusu-Sekyere et al., 2006;Opakunle 1989;Isaac et al., 2005;Hartemink 2005) have all observed that litterfall contributes significantly to nutrient cycling and carbon sequestration in forests and tree-based cropping systems like shade cocoa systems. The report of Dawoe (2009) in the same study area did not observe significant differences in total SOC stocks between forest and different aged cocoa systems where mean SOC stocks ranged from 49.0 to 67.4 Mg ha − 1 (0-60 cm) for a 3-year-old cocoa farm and secondary forest system respectively. ...
... It might also be related to the fact that cocoa system in the present study is older ( observed that litterfall production showed a significant increase over time after forest conversion and ranged from 5.0 to 10.4 Mg DM ha − 1 yr − 1 on the same sites. A number of other studies (e.g., Owusu-Sekyere et al., 2006;Opakunle 1989;Isaac et al., 2005;Hartemink 2005) have all observed that litterfall contributes significantly to nutrient cycling and carbon sequestration in forests and tree-based cropping systems like shade cocoa systems. The report of Dawoe (2009) in the same study area did not observe significant differences in total SOC stocks between forest and different aged cocoa systems where mean SOC stocks ranged from 49.0 to 67.4 Mg ha − 1 (0-60 cm) for a 3-year-old cocoa farm and secondary forest system respectively. ...
Article
Landuse conversion is the highest contributor to atmospheric CO2 in the tropics. While forest conversion to agriculture results in the depletion of soil organic carbon (SOC), cocoa agroforestry may improve SOC stocks. The aim of our study was to explore the effects of topography and landuse change from forest to cocoa agroforestry on the quantity, quality, and distribution of SOC stocks. A total of 324 soil samples from the upper 0–145 cm were collected from catenas with 3 replicates along 3 hillslope positions: upper hillslope/summit position, middle hillslope/backslope position and lower hillslopes/foot- or toeslope positions. SOC stocks were highest in the upper hillslope positions at the 0–30 and 0–60 cm depths and varied from 42.85 ± 10.91 to 44.04 ± 13.70 Mg C ha⁻¹ (0–30 cm depth) and 57.66 ± 18.80 to 60.32 ± 16.36 Mg C ha⁻¹ (0–60 cm depth) for land use types. Hillslope position (upper, middle or lower) significantly affected humic substances with the topsoil having more humified organic materials in the upper compared to other hillslope positions. Forest conversion to shaded-cocoa had a strong impact on the quality of humic substances. Cocoa agroforestry systems had significantly lower E4:E6 ratios with more labile carbon at the lower slope positions compared to similar positions in forest systems. The most labile and readily available organic molecules (fulvic acids) are under forest systems whereas higher proportion of stabilized less soluble organic molecules (lower E4:E6 ratio) are found in cocoa soils in the form of humic acids. Slope position impacted E4:E6 ratios with lower degree of humification of organic materials in lower hillslope positions across the two landuses. A positive correlation was observed between humic substances and clay content. Our study contributes to the understanding of the influence of topography on SOC quantity and quality in forest and cocoa systems in Ghana.
... Most of P in cocoa ecosystem was found in vegetation, and leaf litter from vegetation have little effect on P displacement. According to Hartemink (2005), fertilization of inorganic fertilizers of less than 1,430 kg.ha 1 in a cocoatree agroforestry pattern changes P balance in soil. However, P fertilizer has no significant effects on P content in organic matter. ...
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Shade trees are used in agroforestry pattern for production and service aspects. Cocoa-tree agroforestry pattern is expected to improve atmospheric and rhizosphere zone in cacao plantations. However, the information related to this is still quite limited. This study was conducted using a nested design, with types of shade trees as nest. Shade trees used were Falcataria moluccana, Cocos nucifera, and Cassia spectabilis, and without shade was used as control. Variables observed were light, air temperature, humidity, soil temperature, soil texture, bulk density, permeability, and moisture content. Soil chemical properties were also observed, including organic C, pH, total N, P, K, Ca, Mg, B and content of available P, K, Ca, Mg, and B. The results showed that cacao agroforestry pattern using F. moluccana and C. spectabilis was able to improve the microclimate characteristics and soil fertility. However, F. moluccana showed lower soil fertility than C. spectabilis. F. moluccana and C. spectabilis shade trees were able to optimize light plants from 33 % to 34 %, and from 38 % to 39 %, respectively. F. moluccana could provide optimal air and soil temperature of 30 ⁰C to 32 ⁰C and 27 ⁰C, respectively. Meanwhile, C. spectabilis could provide optimal air and soil temperature of 29 ⁰C to 31⁰C and 26 ⁰C to 27 ⁰C, consecutively. Cocoa-tree agroforestry pattern using C. Spectabilis shade trees could optimize soil moisture content, pH, total N, and P, and availabilities of K, Ca, Mg, and B in soil.
... The influence of agricultural land use on soil conditions and capacities can be positive or negative (Ahukaemere et al., 2012;Lal, 2015). For instance, continuous mining of soil nutrients through annual cocoa pod harvesting from the same land can result in soil quality degradation and depletion of soil nutrients if not sustainably managed or replenished (Hartemink, 2005;Lal, 2015). Declining soil quality retards the functions and provisioning of soil ecosystem services (SES) such as freshwater purification and storage, energy supply, carbon sequestration, biodiversity pool and biomass stocks like timber, food, tree and cash crops (Bouma, 2019;Koch et al., 2013). ...
Article
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Improving agricultural soil conditions is essential for attaining global soil security against land degradation. This requires the use of complex geospatial farm soil information, the absence of which hinders sustainable cocoa (Theobroma cacao L.) soil management in West Africa. This study seeks to create geospatial visibility (awareness) on the conditions and capabilities of cocoa soils. Specifically, to examine the geospatial distribution of soil organic carbon (OC), clay, pH, iron (Fe) and aluminium (Al) in the entire cocoa-growing Districts of Ghana. A visual analysis of geographically referenced secondary data from farm soil survey conducted by the National Cocoa Rehabilitation Programme (NCRP) of Ghana Cocoa Board (COCOBOD) was made. The data were collected based on stratified random sampling of soils at 20 cm depth in 739 newly established cocoa farms, covering 60 Districts. R-GIS enabled descriptive analysis that showed District level mean and standard deviation of these soil properties in colour-graduated thematic maps. Generally, Cocoa District soils were low with 0.42 g kg⁻¹ OC, 5.3 pH, 0.09 cmolc kg⁻¹ Fe with Al in excess of 7.48 cmolc kg⁻¹. Soil clay capability was 22.2%. Combined with a dearth of awareness, policy and economic incentives to improve these conditions, imply cocoa soil security is very low as well. The geovisual maps provide spatially explicit soil information for managing and monitoring cocoa soil security, specifically, Al, OC and pH at Districts. Farmers, agricultural extension workers, soil scientists, agronomists, policymakers like COCOBOD and development practitioners can use these findings as a guide for restoring cocoa soils.
... In general, the magnitude of crop yield responses to changes in climate has been found to be influenced by soil characteristics, as the water and nutrient holding capacity of soils enables crops to either sustain or reduce growth during periods of adverse conditions (Folberth et al., 2016;Mäkinen et al., 2017). In West Africa, soils under cocoa farms are rather infertile, (van Vliet and Giller, 2017), exacerbated by continued nutrient mining after forest clearing (Hartemink, 2005). On nutrient limited soils, yields are not only low on average, but have also been reported to be relatively constant from year to year, thus insensitive to changes in climate (Descheemaeker et al., 2020;Masikati et al., 2019). ...
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ABSTRACT CONTEXT: Cocoa (Theobroma cacao L.) is one of the world’s most important agricultural commodity crops with the largest share of global production concentrated in West Africa. Current on-farm yields in this region are low and are expected to decrease in response to climate change, through warming and shifts in rainfall. Interventions intended to improve yields and climate adaptation require an understanding of the main drivers of yields across farms. OBJECTIVE: In this regard, we quantified the extent to which environmental (i.e., climate and soil) conditions drive cocoa yields and how this differs for farms achieving on average low- and high mean production levels based on an unprecedented dataset of 3827 cocoa farms spanning the environmental gradients of Ghana. We further quantified the relative importance of management practices based on a subset of 134 farms for which management information was available. METHODS: We modelled on-farm annual cocoa yield as a function of environmental variables for the large dataset and cocoa yield per tree as a function of environmental and management variables for the subset farms using mixed-effects models. Differences in effects on yield between farms with low and high mean production levels were evaluated using quantile mixed-effects models. RESULTS AND CONCLUSIONS: There was considerable variability in yields across farms, ranging from ~100 to >1000 kg ha−1 (mean = 554 kg ha−1). Mixed-effects models showed that the fixed effects (i.e., environmental variables) only explained 7% of the variability in yields whilst fixed and random effects together explained 80%, suggesting that farm-to-farm variation played a large role. Explained variation in cocoa yields per tree of 134 farms in the subset increased from 10% to 25% when including management variables in addition to environ- mental variables. In both models, climate-related factors had a larger effect on yields than edaphic factors, with radiation of the main dry season and that of the previous year having the strongest effects on on-farm- and tree yields, respectively. The quantile regression analyses showed that productivity in high-yielding farms (90th percentile) was more strongly driven by environmental factors than in low-yielding farms (10th percentile). In conclusion, agronomic management is the dominant determinant of on-farm cocoa yields in Ghana, more so than environmental conditions. Furthermore, high-yielding cocoa farms are more sensitive to environmental conditions than low-yielding ones. SIGNIFICANCE: Our findings suggests that good agricultural practices need to be in place before investing in additional climate adaptation practices.
... Though yields have increased slightly over the past 60 years (Kozicka et al. 2018), yield gaps remain significant at up to 82% of yield potential (Aneani and Ofori-Frimpong 2013), and cacao growers remain faced with numerous challenges to sustainable production as well as increasing global demand. Pests and diseases (Bailey and Meinhardt 2016), insufficient soil nutrients (Hartemink 2005;Snoeck and Dubos 2018), pollination limitation (Groeneveld et al. 2010), and the impacts of a changing climate (Lahive et al. 2019) all reduce productivity far below the genetic potential of T. cacao. Yield stability is also remarkably low in cacao, with highly variable yields across years and even between adjacent trees (Jones and Maliphant 1958). ...
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Crop root-associated microbiomes have been heralded for their potential to improve plant health and productivity. Optimizing beneficial interactions with rhizosphere microorganisms has been proposed to reduce reliance on external inputs, increase pathogen resistance, and alleviate abiotic stresses. Producers of Theobroma cacao, the economically important tropical perennial whose pods are used to produce chocolate, are faced with numerous challenges to sustainable production and rising demand. Cacao further provides an interesting case study to complement the extensive plant microbiome research on annual crops in temperate regions. However, current knowledge of the cacao root-associated microbiome is limited. Characterizing the factors that influence the composition and functions of microbial communities associated with cacao roots is a key first step to developing microbiome-targeted interventions for improved agricultural sustainability in cacao agroecosystems. These rhizosphere engineering approaches can be understood within the framework of provisioning, regulating, and supporting ecosystem services. Here we review the potential of cacao root-associated microbiomes to solve current challenges to production by increasing provisioning of ecosystem services. The major points are the following: (1) We describe factors affecting the cacao root-associated microbiome by expanding the traditional model of genotype-by-environment (G × E) interactions to include agricultural management (G × E × M) and discuss the unique aspects of this model in cacao agroforestry systems. (2) We then highlight how specific breeding targets and management practices can be optimized to enhance the ecosystem services mediated by the cacao root-associated microbiome. Such optimizations of ecosystem services will alleviate the reliance on external inputs and, eventually, contribute to more sustainable cacao production systems.
... 31: Thong and Ng (1978). 32: Hartemink (2005 (2018). The values of the fruit, wood, leaf and fruit biomass are multiplied with 1.1 and 0.9 to assess their sensitivity. ...
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The current expansion of cacao cultivation in the Republic of Côte d’Ivoire is associated with deforestation, forest degradation, biodiversity loss and high greenhouse gas (GHG) emissions. Global concerns about emissions that are associated with tropical commodity production are increasing. Consequently, there is a need to change the present cacao-growing practice into a more climate-friendly cultivation system. A more climate-friendly system causes lower GHG emissions, stores a high amount of carbon in its standing biomass and produces high cacao yields. GHG emissions and carbon stocks associated with the present cacao production, as assessed in 509 farmers’ fields, were estimated by using the Perennial GHG model and the Cool Farm Tool. On average, the production of 1 kg cacao beans is associated with an emission of 1.47 kg CO2e. Deforestation contributed largely to GHG emissions, while tree biomass and residue management contributed mainly to carbon storage. The collected data combined with the model simulations revealed that it is feasible to produce relatively high yields while at the same time storing a high amount of carbon in the standing biomass and causing low GHG emissions. The climate-friendliness of cacao production is strongly related to farm management, especially the number of shade trees and management of residues. Calculated emissions related to good agricultural practices were 2.29 kg CO2e per kg cacao beans. The higher emissions due to the use of more agro-inputs and other residue management practices such as recommended burning of residues for sanitary reasons were not compensated for by higher yields. This indicates a need to revisit recommended practices with respect to climate change mitigation objectives.
... The continuous crop removal through harvested beans results in the loss of nutrients from the soils (Ahenkorah et al. 1987;Appiah et al. 1997) leading to nutrient imbalances (Stoorvogel and Smaling 1990). Low soil fertility has been identified as one of the major causes of decline in yield of cocoa (Hartemink 2005). The cocoa trees have very high nutrient requirement for growth and yield, increasing very rapidly in the first 5 years and then reaching a plateau after that with subsequent increases depending mainly on export of nutrients in increased yield (Ling 1984). ...
... Natural forest converted into agricultural land use coffee multistrata plantation caused carbon stock decrement 262 ton ha -1 decreased into 82 ton ha -1 and coffee monoculture plantation caused carbon stock decrement into 52 ton ha -1 [1]. Cocoa (Theobroma cocoa L) is the agriculture commodity in the tropical country [2]. Cocoa is one of the agricultural broadly commodity developed in Indonesia has an opportunity in carbon stock. ...
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This study aimed to determine cocoa carbon stocks based on the conditions of cocoa plantations in Tomoni Beringin Jaya Village, East Luwu, South Sulawesi, Indonesia. Carbon stocks were estimated from aboveground and belowground biomass using an allometric methodology. Sample sites were cocoa plantations; sampling intensity was 30% of the land planted with cocoa for 5 years (n = 214), 10 years (n=229) and 15 years (n=329), soil sampling disturb (measure soil organic carbon), un disturb (measure bulk soil bulk density) and soil bulk density at depth 0-10 cm and 10-20 cm. Carbon stock cocoa aboveground biomass at the age of 5 years (M45) was 1.89 ton C ha ⁻¹ and belowground biomass was 0.56 ton C ha ⁻¹ with proportion 77.19%:22.81%. Carbon stock cocoa aboveground biomass at the age of 10 year (BR25) was 3.66 ton C ha ⁻¹ and belowground biomass 1.01 ton C ha ⁻¹ with a proportion 78.37%:21.63%. Carbon stock cocoa aboveground biomass at 15 year (BR25) was 4.58 ton C ha ⁻¹ and belowground biomass of 1.21 ton C ha ⁻¹ with a proportion 79.07%:20.93%. Cocoa carbon stock at 5 year, 10 year, and 15 year respectively increased, nevertheless mean annual carbon stock cocoa decreased in 5 years cocoa aboveground biomass was 0.37 ton C ha ⁻¹ and belowground biomass 0.11 tonCa ⁻¹ . Carbon stock cocoa 10 year aboveground biomass 0.36 ton C ha ⁻¹ and belowground biomass 0.10 ton C ha ⁻¹ . Carbon stock cocoa 15 year aboveground biomass 0.30 ton C ha ⁻¹ and belowground biomass 0.08 ton C ha ⁻¹ . Soil organic carbon showed dynamic under different year cocoa plantation. Soil organic carbon in cocoa plantation age 5 year was 0.031 tonCha ⁻¹ , cocoa plantation age 10 year was 0.034 ton C ha ⁻ 1, and cocoa plantation age 15 year was 0.043 ton C ha ⁻¹ .
... It is also plausible that the water accumulating in the depressions facilitated the leaching of the lime below the root zone making it ineffective. Other studies have shown that most of the functional roots of cocoa remain within the top 20 cm within the enriched top soil layer (Hartemink 2005;Toxopeus 2008). ...
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Although mitigation approaches have been developed to reduce Cd in cocoa beans the efficacy of the approaches have been inadequate to make them economically viable. A field study was conducted in a cocoa farm in Biche, Trinidad using two soil amendments, lime and biochar, at recommended rates using three methods of application, soil surface application with incorporation (SA), soil injection (SI) or deep placement using an auger (AA) along with a control. The objective was to determine the application method that would be most efficacious with respect to rapidity of effect, magnitude of reduction and persistency of effect on leaf Cd. The experiment was arranged in randomized complete block design with three replications with 15 trees per replication. Phytoavailable soil Cd, soil pH, CEC and total leaf Cd concentration were monitored monthly on three guarded trees per plot over a one-year period. The results showed that both lime and biochar were effective in reducing leaf cadmium levels albeit at different levels. The efficacy of SI was significantly better than SA in terms of rapidity of the effect on leaf Cd in comparison to the control (40% compared to 30%) as well as the effect was more persistent in SI. With biochar, again the SI was significantly better than SA with regards to reducing leaf Cd levels in comparison to the control (35% compared to 20%) but the time taken to action and the persistency were lower compared to lime application. AA did not significantly reduce Cd level in the leaf with lime or biochar application.
... However, it should be noted that the quantity of leaf litter produced from G. sepium is lower than that produced from T. cacao. Usually, G. sepium produces 100-500 kg litter/ ha (Fontes et al., 2014;Villanueva-López et al., 2015), whereas T. cacao can produce up to 5000 kg litter/ha and litter production from some shade tree species has been estimated to be around 10,000 kg litter/ha (Beer, 1988;Hartemink, 2005;Fontes et al., 2014). To the best of our knowledge, no information regarding C. indicum litter production exists. ...
Article
Mineral nutrient fluxes derived from litterfall are key components of nutrient biogeochemical cycles in both natural and agroforesty systems. Cocoa production systems are generally nutrient depleted and may benefit from on external nutrient application to maintain primary productivity. However, in developing countries the main source of nutrients is often nutrient recycling through decomposing leaf litter, and in this regard shade-tree species play an important role in cocoa agroforestry. This study aimed to investigate the nutrient inputs of litter from two shade-tree species (Canarium indium and Gliricidia sepium) and cocoa trees (Theobroma cacao) after 15 months of decomposition in a cocoa plantation. Litter from G. sepium lost more mass (59%) than T. cacao (37%) and C. indium (10%), and showed a higher average concentration of total nitrogen (TN), boron (B), iron (Fe) and phosphorus (P) after 15 months of field incubation than that of C. indium. It also showed a low C:N ratio and N release, which suggest N mineralisation. All litter species showed high C:P ratio and negative P release, which suggests P immobilisation. Litter from G. sepium and T. cacao showed a rapid K release after 1 month of decomposition. The differing mass loss rates and litter nutrient concentrations of the three species could benefit T. cacao by providing asynchronous nutrient inputs and improve long-term sustainability of mixed-species plantations.
... The order of the primary macronutrient concentrations and returns to the soil through litterfall as observed in the isolated tree is N > K > P while that of the secondary macronutrient is Mg > Ca (an indication of the ranges of nutrient elements in concentrations and returns via litterfall). These results are close to those of [29], working on nutrient stocks, nutrient cycling, and soil changes in cocoa agroforestry. It could therefore be deduced that nutrient concentration in the litterfall of some trees is higher compared to other tree species, consequently some trees have a high fertility potential compared to others. ...
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Investigations to assess farmer’s perceptions on the fertilizing potential of associated trees species in cocoa agroforest of degraded forest ecology were carried out in southern Cameroon. The perception of the farmers was based on the ability of the trees to maintain or improve soil fertility of their farms. The verification of these perceptions was done through an evaluation of litter fall biomass nutrient content (N, P, K, Ca and Mg) of selected trees. The top 5 associates trees ranked by farmers was: Milicia excelsa, Ceiba pentandra, Ficus mucuso, Asltonia boonei, Terminalia superba. The chemical analysis of the leaf litter from the different tree species revealed a significant different between their chemical components. N appeared to have the highest concentrations varying from 2.82 to 5.57% with a mean value of 4.25 ± 1.065%, P had the lowest concentrations typically around 0.001%. The top 5 tree species based on the chemical analysis ranking were: C. pentandra, M. excelsa, Eribroma oblungum, Alstonia boonei, Zanthoxylum heitzi. Farmer’s perceptions thou holistic, are not completely different from scientific finding. Therefore, they should be taken in consideration in management plans for cocoa- based systems in order to enhance their ecological and economic performance.
... Potassium is a major nutrient in mature cacao (Hartemink, 2005). Potassium levels vary with the location, with Sites 2 and 4 having very high exchangeable potassium content, Sites 5 and 8 having optimum levels, and Sites 3 and 1, 6 and 7 (the latter being alluvial soils) having deficient levels. ...
Article
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The study was conducted to understand the physico-chemical characteristics of the soils under cacao production system in Davao de Oro, Philippines. Eight (8) cacao farms were selected for detailed field characterization and sampling of soils for various nutrient analyses. Fertility status of each selected farm was determined by comparing the fertility properties of each soil with the critical nutrient level requirement for cacao. Results showed that most of the soils have a dark brown soil color in the upper horizons, and dark, yellowishbrown in the lower horizons. They range from moderately deep to very deep soil profile (19 to 150 cm), with very friable to extremely firm when moist, slightly sticky to very sticky, and slightly plastic to very plastic when soil consistence is wet. Lower elevations had shallow solum with high water table, resulting in the development of mottles and redoximorphic properties. The amount of clay ranged from 9 to 37%, with 18 to 40% for silt, and 30 to 68% for sand. Most of the cacao farms were intercropped with coconut, durian, lanzones, rubber, and banana. Most of the soils are moderate to slightly acidic, with pH values < 6.5 and CEC ranging from 10 to 34 meq/100g. Moreover, most of the areas have low organic matter (1.66%) except for the areas which continually applied organic matter during fertilization (4.60%). The amount of nitrogen (N) is optimum; however, phosphorus (P) was generally deficient in the soils of most cacao farms surveyed, while amount of potassium (K) ranges from 41.30 to 375.60 mg/kg.
Article
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Litterfall is a critical link between vegetation and soils by which nutrients are returned to the soils, thus the amount and pattern of litterfall regulates nutrient cycling, soil fertility and primary productivity for most terrestrial ecosystems. We quantified, analyzed and compared macro- and micro-nutrients return through litterfall in organic and conventional cocoa agroforestry systems in Suhum, Ghana. We further assessed the contribution of shade tree species to litterfall and nutrient dynamics. The annual pattern of litterfall was affected by seasonality, with a major peak in the dry season and minor peaks during the rainy season. In terms of annual fractional litterfall, mean leaf litter from shade tree species was significantly higher (50 %) in organic systems (5.0 ± 0.5 Mg ha⁻¹ yr⁻¹) compared to conventional systems (3.3 ± 0.6 Mg ha⁻¹ yr⁻¹). Whereas cocoa leaves (45.0 %) were the predominant fraction of annual litterfall from conventional farms, both shade leaves (40.0 %) and cocoa leaves (39.4 %) dominated litterfall from organic farms. The return of primary macro-nutrients (P and K), secondary macro-nutrients (Ca, Mg and S) and micro-nutrients (Mn, B, Cu, Zn and Mo) via litterfall varied significantly with season, and annual return of nutrients were similar in organic and conventional cocoa systems. Shade tree leaf litter accounted for 30–47 % of annual macro- and micro-nutrient return (except Ni and Zn) in organic cocoa systems versus 20–35 % in conventional cocoa systems. The results emphasize the complementary role of the different shade tree species which compose organic and conventional cocoa systems in nutrient recycling. We conclude that organic management of cocoa agroforestry systems ensure nutrients return similar to those receiving synthetic fertilizer inputs, highlighting its potential to support cocoa production.
Article
Soil characteristics over time have been fundamentally influenced by farming practice especially where small and medium-scale farming and fallow system are predominant in the tropics. To provide a solution to the problem of soil nutrient degradation calls for scientific soil fertility assessment to complement local system. Determining the best of these methods calls for comparative study between the indigenous and scientific methods of soil assessment. It was also observed that using modern methods of soil assessment alone may not provide a realistic solution to the soil management problem. This study recommends periodic soil assessment and mapping for sustainable food production.
Thesis
Ecosystem functioning depends on a variety of factors and disturbances. Human disturbances provoke large changes in ecosystem functioning that often lead to land-use change. In the tropical regions of West and Central Africa cocoa cultivation is a main cash crop that leads to land-use change of tropical forests. Cocoa-AFS, which ecosystem multifunctionality is greater than that of monoculture systems, are still widely spread over this region and mainly cultivated by smallholder farmers. Previous research in Central Cameroon showed, beside the installation of cAFS in forest, the possibilities of afforestation of savannah land with economically valuable cAFS. However, not much is known on the impact of the past land-use on the cAFS performance and on the duration of the effect.
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Nutrient stability in old cocoa farm requires sequence interaction and flow between soil and plant. Also, nutrient status in grown crop and other above-ground biomass depends wholly on the available nutrient in the soil. The study examined the nutrient status in soil-plant chemical properties in old cocoa farms of about 55 years of age. Laboratory results on soil and plants variables were subjected to multivariate analysis; multiple regressions, Student T-test, and Analysis of Variance. Result shows high efficiency of litterfall in Idanre and Odigbo. However, fresh leaf required high nutrient for development in Owo and Odigbo compared to Idanre while possibility of rapid soil nutrient degradation seemed to be prevalent in Owo compared to other location due to nutrients stocked in bean and podhusk. The study hereby recommends spatial integration of shade trees, seasonal spreading of accumulated podhusk to compliment litter nutrient input, and replacement of unproductive cocoa tree stands on annual basis.
Article
Cocoa ( Theobroma cacao ) farmers in Sulawesi, Indonesia typically use subsidised, ammonium-based rice fertilisers that in combination with poor agricultural practices have resulted in soil acidification, loss of organic matter, aluminium toxicity and lower soil fertility. As a result, these soils are only marginally appropriate for replanting cocoa to boost production. A field experiment was performed to test alternative soil amendments for successful replanting of cocoa on these deficient soils. In a trial with a randomised block design, 6-month old seedlings, top-grafted with the local MCC02 clone, were planted under light Gliricidia sepium shade and after 3 months treated quarterly with two options of mineral fertilisers: either a customised fertiliser, consisting of Nitrabor (a combination of calcium nitrate and boron), dolomite, rock phosphate and KCl or a NPK/urea mix used by farmers, each supplied with or without ‘micronutrient’ rock salt, organic fertiliser and beneficial microorganisms or their culture medium, a mixture of chitin and amino acids (a total of 20 treatments). Over a 4-year period, the marginal mean rates of stem diameter increment and flowering score were higher in customised fertiliser than NPK/urea treatments. The average growth rate was highest in the first year and was increased by supplying organic fertiliser. A significant correlation ( r = 0.22, p < 0.05) occurred between growth and available P, but concentrations of available P were higher in the NPK/urea plots, which also had lower mean growth rates. Combined supply of organic fertiliser and microbes increased available P, as well as growth rates, in both the customised and NPK/urea treatments. In contrast, NPK/urea-treated plots without these amendments demonstrated very low growth rates. The customised formulation was more effective with or without added organic fertiliser or inoculated microbes. Micronutrient supply stimulated flowering. Growth rates in trees supplied with NPK/urea were also promoted by micronutrients. Leaf flush production occurred in regular cycles and was unaffected by the nutrient amendments. After 3 years, the customised and organic fertiliser application increased soil pH and exchangeable Ca and Mg concentrations, although they remained below recommended levels for cocoa production. These treatments had little impact on soil C content (about 1.3%) which was also deficient. Exchangeable Al and total Zn concentrations were higher in soils amended with NPK/urea. The results of the trial provide evidence that utilisation of organic fertiliser in combination with customised nitrate-based formulations improves cocoa establishment, growth and soil properties and should be recommended as a replacement for the NPK/urea fertilisers traditionally used by farmers.
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Predictive models were developed for Cordia alliodora branch and Theobroma cacao branch or leaf biomass,based on branch basal areas (r2 0.79) but the model of C. alliodora leaf biomass, although significant, was of very low accuracy (r2 = 0.09) due to annual leaf fall. At age 10 years, shade tree stem biomass accounted for 80% of the total above-ground biomass of either tree. However, between the ages of 6 and 10 years, the biomass increment of T. cacao branches (3–4t.ha–1.a–1) was similar to that of the shade tree stems. During the same period, the net primary productivity was 35 and 28 t.ha–1.a–1, for the Erythrina poepigiana and and C. alliodora systems, respectively.Cocoa production under either of the shade trees C. alliodora or E. poeppigiana was 1000 kg.ha–1.a–1 (oven-dry; ages 6–10 yr). During the same period, C. alliodora timber production was 9 m3.ha–1.a–1 whilst the leguminous shade tree E. poeppigiana does not produce timber. Litterfall over the same 5 years, including crop and/or shade tree pruning residues, averages 11 and 23 t.ha–1.a–1, respectively. The main difference was due to E. poeppigiana pruning residues (10t.ha–1.a–1).Soil organic material reserves (0–45 cm) increased over 10 years from 198 to 240 t.ha–1 in the E. poeppigiana plots and from 168–184 t.ha–1 in the C. alliodora plots. These values, together with the productivity indices presented, provide evidence that the systems are sustainable.For economic reasons, the use of C. alliodora is recommended under the experimental conditions. however, on less fertile soils without fertilization, the greater biomass and hence nutrient return to the soil surface under E. poeppigiana, might make this the preferable shade tree.
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The hydrological balances for the agroforestry systems of Theobroma cacao with Cordia alliodora or Erythrina poeppigiana were calculated using measurements taken over four years (1983–1987) of the following parameters: climatic (precipitation, evaporation); edaphological (texture, soil moisture tension, hydraulic conductivity, variations in soil moisture content). Water fluxes (interception, simulation of transpiration and percolation) were estimated from one year of measurements (1986–1987). Weekly samples of percolated water were taken from March 1986 – March 1987 using lysimetric capsules at 100 cm soil depth. N, P, K, Ca and Mg concentrations were determined to calculate the annual leaching losses. Nutrient concentration values were extrapolated for the whole 4 years observation period, in order to calculate leaching losses for the whole study period. Precipitation samples were also taken to determine the corresponding annual nutrient inputs.
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Shade trees reduce the stress of coffee (Coffea spp.) and cacao (Theobroma cacao) by ameliorating adverse climatic conditions and nutritional imbalances, but they may also compete for growth resources. For example, shade trees buffer high and low temperature extremes by as much as 5 °C and can produce up to 14 Mg ha−1 yr−1 of litterfall and pruning residues, containing up to 340 kg N ha−1 yr−1. However, N2 fixation by leguminous shade trees grown at a density of 100 to 300 trees ha−1 may not exceed 60 kg N ha−1 yr−1. Shade tree selection and management are potentially important tools for integrated pest management because increased shade may increase the incidence of some commercially important pests and diseases (such as Phythphora palmivora and Mycena citricolor) and decrease the incidence of others (such as Colletotrichum gloeosporioides and Cercospora coffeicola). In Central America, merchantable timber production from commercially important shade tree species, such as Cordia alliodora, is in the range of 4−6 m3 ha−1 yr−1. The relative importance and overall effect of the different interactions between shade trees and coffee/cacao are dependent upon site conditions (soil/climate), component selection (species/varieties/provenances), belowground and aboveground characteristics of the trees and crops, and management practices. On optimal sites, coffee can be grown without shade using high agrochemical inputs. However, economic evaluations, which include off-site impacts such as ground water contamination, are needed to judge the desirability of this approach. Moreover, standard silvicultural practices for closed plantations need to be adapted for open-grown trees within coffee/cacao plantations.
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This paper reviews the research themes and methodologies used by CATIE in agroforestry research with shade trees over coffee (Coffea arabica) and cacao (Theobroma cacao) during the past 20 years. Initially research focused on characterization and production studies (of crop and timber including border areas) of traditional systems using temporary and permanent sample plots on private farms. The assessment area of traditional shade-coffee (or cacao) systems should be the whole plot, including the border areas, and not some subjectively selected central area which supposedly represents unit area productivity. Uncontrolled crop, tree, and management heterogeneity limited extrapolation of early on-farm research results to other farmers' fields. Replicated case studies of best bet technologies (traditional or experimental) on different farms are often preferable to the use of formal experimental designs. On-station research included the use of systematic spacing designs to test extreme shade tree density treatments of coffee. Most nutrient cycling studies were also carried out on-station, using service and timber shade species over coffee and cacao to evaluate the ability of these agroforestry systems to maintain nutrient reserves and diversify production. Plot size (even 36 × 36 m) was limiting for long term research because of inter-plot interference, both below- and above ground, when using fast growing, tall timber trees as shade. These experiences suggest a minimum plot size of 2,500 m2. Individual tree designs and tree-crop interface studies (e.g. regression analysis of data taken along transects) are promising experimental/sampling approaches that need further development. The principal research thrusts proposed for the next five years are bio-physical process research on coffee responses to shade and competition with trees (growth, carbon allocation, phenology, disease-pest tolerance, yields and coffee quality effects) and socioeconomic analyses of both traditional and new or improved shade – coffee combinations vs. monocultures.
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One of the environmental consequences of slash-and-burn farming is the loss of forest system carbon which in turn contributes to atmospheric change and impacts upon global climates. International attention has become focused upon the development of alternatives to slash-and-burn agriculture to alleviate poverty, protect biodiversity and reduce climate change. Before alternative land use systems can be evaluated in terms of carbon sequestration, baseline measurements of carbon dynamics resulting from current practices are required. We have characterized the carbon stocks in six slash-and-burn chronosequences in the humid forest zone of Cameroon. Each chronosequence consisted of original forest, two year-old cropland, a cacao plantation, bush fallow, tree fallow and secondary forest. Four, nine and seventeen years, respectively, had passed since the original forest was cleared for the latter three land uses. At each of 36 site × land use combinations, tree, understorey, litter, root and soil (0–50 cm) carbon were measured in five 100 m2 quadrates. The original forest contained 308 t C ha−1 and lost 220 t C ha−1 upon conversion to agriculture. The most vulnerable carbon pool was the above ground tree biomass and the most stable was soil organic matter. Carbon reaccumulated in the recovering fallows at a rate of 9.4 t C ha−1 yr−1 (r = 0.83). When these results were extrapolated using a geographic information system, deforestation rates in Southern Cameroon were estimated to be 1,355 km−2 yr−1 between 1973 and 1988 resulting in annual forest system carbon losses of 13.5 million t C. During the course of this study, three alternatives to slash-and-burn were identified: commercial cassava cultivation, improved forest conversion, and stratified agroforestry. These alternative land uses have the potential to reduce C losses over current practices by 10, 55 and 75 t C ha−1, respectively, and also differ greatly in their potential to alleviate rural poverty, protect biodiversity and deflect additional deforestation.
Book
Agroforestry refers to land use systems in which trees or shrubs are grown in association with agricultural crops, or pastures and livestock. From its inception, it has contained a strong element of soil management. Well-designed and managed agroforestry systems have the potential to control runoff and erosion, maintain soil organic matter and physical properties and promote nutrient cycling. By these means agroforestry can make a suitable contribution to sustainable land use. This new edition summarises the present state of knowledge and research of agronomy systems: the plant-soil processes; soil conservation and erosion control; soil management and nutrient cycling. It is essential reading for all concerned with agroforestry whether as students, research scientists or for practical purposes of development.
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Soils of the tropics (and elsewhere) divide into two major types, variable-charge and permanent-charge, with differences that affect nutrient cycling processes. Differences in soil structure affect nutrient retention capacity. In soils with a bi-phasic water flow regime, water flows mainly along preferred paths, through macropores and between aggregates, largely bypassing the soil matrix. Such soils thus resist leaching. In weathered tropical soils, stable aggregation is caused in large party by low electric charge on clay particle surfaces. Thus, as weathering decreases a soil's ablity to retain ions on exchange sites, it may increase its ability to resist leaching. -from Author
Chapter
This chapter discusses a number of factors influencing the throughfall and stemflow quality and their variation. The effect of the canopy in altering the precipitation quality is also discussed. The annual nutrient return to the forest soil for the elements K, Na, and S is predominantly via throughfall and stemflow and little because of litterfall. Stemflow transfers only 5–20% of the total in precipitation-borne solutes, yet it is the major nutrient input to restricted areas of the forest floor. Because throughfall and stemflow are associated with precipitation events, the transport of nutrients contained in throughfall and stemflow depends on the magnitude, timing, and form of the precipitation. Thus, a reliable estimate of throughfall nutrient flux demands a good forest hydrological budget. The quantity and distribution of throughfall and stemflow depends on microscale features of canopy structure, such as crown density, closeness of the foliar elements, distance from the nearest bole, or open spaces in the canopy.
Chapter
This chapter describes the agronomic potential and ecological consequences of conversion of tropical rainforest. Tropical rainforest refers to the climax vegetation of the lowland humid tropics where there is either a short period of water deficit or none at all. Tropical rainforest is confined to the equatorial region and is a very diverse and complex ecosystem. Soil is an integral element of the rainforest ecosystem and is as much influenced by the vegetation as the vegetation itself is influenced by the soil. Soils supporting tropical rainforests are usually old, highly weathered, and excessively leached. Estimates of forest conversion in the Brazilian Amazon, in tropical Africa, and in the tropics are presented. Possible local effects of deforestation on biophysical environments are explained. Major effects are on microclimate, water and energy balance, nutrient capital with disruption in pathways of various nutrient elements, soil, flora and fauna composition and activity. Deforestation for intensive land use is an important factor in forest conversion. Methods of deforestation vary widely depending on the intended cropping systems, and soil and crop management methods. It is suggested that forest conversion for plantation crops should also be preferably done by manual, and slash and burn methods.
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Mature tropical rain forest is in a state of dynamic equilibrium with its soil, micro-and macro-climate. Data collected in the cocoa producing areas of SW Nigeria show that when this forest is removed and replaced by field or tree crops, the balance between vegetation and soil breaks down, and this leads to instability and a considerable deterioration in soil quality. An index of soil deterioration was derived and showed the following percentage declines for field and tree crops respectively: bulk density, 28% and 31%; total porosity, 12% and 18%; pH, 16% and 13%; organic matter, 29% and 26%; nitrate nitrogen, 35% and 27%; available phosphorus, 19% and 19%; calcium, 24% and 41%; sodium, 50%, 50%; potassium, 27%, 43%; magnesium, 36%, 47%; cation exchange capacity, 36%, 34%; base saturation, 5.4%, 8.7%. This study is one of the first attempts to assess soil deterioration on peasant farmers' cocoa plots.
Article
Understanding soil erosion processes is essential in appreciating the extent and causes of soil erosion and in planning soil conservation. A comprehensive study was conducted on steep slopes on the east coast of Peninsular Malaysia where the rainfall pattern is monsoonal. Rates of rainfall and runoff, and soil loss, were accurately measured from four large plots of 1000 m2 and a bare plot of 20 m2. Instruments used include Parshall flumes, height recorders, a pluviometer and a runoff tipping bucket recording on a datalogger, with the associated computer hardware and software for data processing and analysis. Because of the slope of the land (about 18%) and the existence of large well-defined flow pathways, soil was largely eroded through the processes of entrainment and reentrainment. Soil loss and runoff were particularly high where the pathways were very pronounced. Other factors influencing soil erosion were disturbance to the soil surface, which produced easily entrainable material, and percent contact cover. The parameter β, calculated for a large number of events, was found to vary according to the availability of entrainable material. There was a gradual general decrease of β with time although most values were in the range 0.37 to 0.25. Suspended load was commonly more than 50% of total soil loss. Consequently, high chemical enrichment ratios were obtained. This has important implications on the reduction of soil quality through nutrient and organic matter losses.
Article
The changes that take place in topsoil properties after the tropical rain forest has been replaced by fallow (resulting from food crops cultivation) and tree crops are considered in a part of southwestern Nigeria known for the cultivation of food crops, cocoa and kola on separate plots. The study clearly shows that water holding capacity, organic matter content, total nitrogen, calcium, magnesium and cation exchange capacity (C.E.C.) under fallow, cocoa and kola differ significantly from those under forest. These results indicate that once the tropical rainforest is removed the soil-vegetation system is disrupted significanctly. The study also shows that water holding capacity, calcium, potassium and C.E.C. are significantly different between fallow and the tree crops while no soil property differs significantly between cocoa and kola. These results serve to show that under fallow soil appears better protected than under cocoa and kola while the latter tree crops could be deemed to be similar in their absorption pattern of soil nutrients. The reasons for these significant differences are discussed.
Article
A cacao (Theobroma cacao) plantation under shade trees was studied in northern Venezuela in order to estimate nitrogen stores in the soil and plantation trees and nitrogen fluxes associated with litterfall, decomposition and harvest. The cacao plants contained 302 kg N ha−1, of which woody above-ground parts made up 50%. Fine roots and leaves containedca. 60 kg N ha−1. Litter on the soil surface was sampled quarterly and found to contain from 24 kg N ha−1 in November to 50 kg N ha−1 in May, with an annual average of 37 kg N ha−1. Shade tree leaves made up 61% of the total nitrogen in the litter on the soil. Mineral soil stores of total nitrogen were 35×103 kg N ha−1, 40% of which was found in the first 20 cm depth.
Article
Coffee and cacao are two of the most important perennial agricultural crops in Latin America. Plantations of these crops occur in all Latin American countries except for those in the southern cone of South America. In addition, Brazil is the largest coffee exporter in the world.
Article
The authors' study examined the environmental impacts of cocoa and rubber cultivation on soil and water in six Nigerian states where their production is intensive. Primary data were collected by the administration of questionnaires to 180 farmers selected through a multistage random sampling process. These data were subjected to gross margin and cost-benefit analyses. Soil and water samples collected from the study locations were also subjected to chemical assays. The study found that cocoa cultivation remained an attractive economic venture at the current lending rate of 35%, but that rubber cultivation did not. It also found that nutrients and metal pollution levels were very low on cocoa and rubber farms. However, it was concluded that this result was obtained as a consequence of farmers' low levels of use of agrochemicals. A warning was issued to the effect that attempts to make agrochemicals more available and accessible to farmers in future might portend negative environmental impacts that must be prepared for.
Article
The pattern of change of soil nutrient status under cocoa plantations, aged between one and 55 years, owned and managed by peasant farmers in southwestern Nigeria, was investigated. The mean values of the measured soil properties were significantly lower under cocoa than those under forest. The pattern of change of these properties over time under cocoa, however, demonstrated a small initial rise followed by a decline to about the tenth year. This was followed by an increase in their values reaching a peak about the twenty-fifth year. Consistent decreases in their values then followed. In order to maintain the nutrient status of the soil beyond the twenty- fifth year it would be necessary for farmers either to apply chemical fertilisers, or to use organic manure as a mulch in the practice of cocoa plantation management. It is also possible that appropriate agroforestry systems may be devised to achieve the same objective.
Article
Rainwater and throughfall water were evaluated nutrient sources for a cacao (Theobroma cacao L.) ecosystem in Ilhéus, Bahia, Brazil. Rainwater was collected for 35 months in an open area. Throughfall was collected on shaded and unshaded cacao plots. The shade trees were Erythrina and some species of Ficus. In evaluating the results, the agricultural year was subdivided into winter (April–September) and summer (October–March). It was found that the concentrations of N, P, K, Ca and Mg, in both rainwater and throughfall varied between and for periods within years. The nutrient concentrations in the throughfall also varied with the presence or absence of shade trees in the cacao plantation. The rainwater contributions of N, Ca, Mg, K, and P reached averages of 43, 21, 9, 9 and nearly 1 kg ha−1 year−1, respectively. The averages of annual throughfall recycling to the soil in the unshaded and shaded plots, respectively, were 141 and 47 kg K ha−1, 28.4 and 21 kg Ca ha−1, 21 and 12.2 kg Mg Ha−1, and 13 and 8 kg P ha−1. The throughfall K and P appears to be rapidly absorbed by the cacao roots, whilst most of the Mg, Ca, and N are retained in the soil. The throughfall and leaf fall constitute the most important nutrient recycling processes in the cacao ecosystem, which appears to be self-sufficient in terms of its nutrient requirements.
Article
The cultural features, management practice, environmental sustainability, and economic profitability of smallholder cacao (Theobroma cacao) production in West and Central Africa are reviewed. The aim is to highlight factors affecting the cacao production and marketing sector and to propose appropriate strategies to ensure sustainable and profitable cacao production in the region. The cacao cultivation system causes minimum damage to soil resources. In terms of carbon sequestration and below-and above-ground bio-diversity, the cacao agroforest is superior to the alternative food crop production land use. The food crop production system is based on the practice of slash-and-burn farming, which, due to population pressure and reduced fallow cycle, is no longer sustainable. Economic profitability analysis of this system in Cameroon showed that, at current prices, even with no value assigned to the tree species, the sector could still be profitable. Based on the current review and our knowledge of West and Central Africa, there is an urgent need to: (a) rationalize and optimize arrangement of the various components in cacao agroforest, (b) domesticate high value and shade tolerant indigenous species such as Gnetum africanum and integrate into the system in order to enhance the system's diversity and profitability, (c) develop shade-tolerant and disease-resistant cacao varieties, (d) integrate small-stock production into the system, and (e) develop an enabling policy environment addressing cacao marketing, plant protection, land tenure and transformation of non-cacao primary products from the cacao agroforests.
Article
A cacao (Theobroma cacao) plantation under shade trees was studied in northern Venezuela in order to estimate nitrogen stores in the soil and plantation trees and nitrogen fluxes associated with litterfall, decomposition and harvest. The cacao plants contained 302 kg N ha−1, of which woody above-ground parts made up 50%. Fine roots and leaves containedca. 60 kg N ha−1. Litter on the soil surface was sampled quarterly and found to contain from 24 kg N ha−1 in November to 50 kg N ha−1 in May, with an annual average of 37 kg N ha−1. Shade tree leaves made up 61% of the total nitrogen in the litter on the soil. Mineral soil stores of total nitrogen were 35×103 kg N ha−1, 40% of which was found in the first 20 cm depth. Litterfall rates were studied monthly for a year; 20.9×103 kg dry litter ha−1 fell during the year, the major contribution (50%) from shade-tree leaves. The rate of nitrogen transfer with litterfall was 321 kg N ha−1 yr−1. Decomposition rates (k) for shade-tree leaves, cacao leaves, twigs, and flowers and fruits were 7.7, 9.5, 7.5 and 19.7 respectively. In litterbag decomposition experiments, a small increase in per cent N was observed as decomposition progressed for all fractions. Rainfall collected during October and November contained nitrogen predominantly as NH4, a fraction of which was retained by the canopy. Nitrogen output by harvest wasca. 45 kg N ha−1 yr−1, with some 20 kg N ha−1 yr−1 returned to the field with pod shells after processing. The net harvest output can be amply compensated for by inputs of nitrogen in shade-tree leaf litter alone. Much of this shade-tree nitrogen may be from deeper soil horizons than those exploited by cacao and possibly from biological N2-fixation by the shade trees.
Article
Models for cycles for organic matter and nutrients element (N, P, K, Ca and Mg) are presented for the agroforestry systems of cacao (Theobroma cacao) withCordia alliodora orErythrina poeppigiana in Turrialba, Costa Rica. For the models, system reserves (soil, humus, vegetation divided into leaves, branches, stems, fine roots, fruits) and transference between compartments (production and decomposition of litter residues) inputs (fertilizer, rainfall) and outputs (harvests) of the system are considered. The implications of the models are discussed in detail. Aspects of net primary production in the systems studied are considered. N fixation is calculated on the basis of balances. Analysis of soil water showed high variations that coincided with rainfall patterns and pruning of theE. poeppigiana.