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Biomass production and Partitioning pattern of Yam (Dioscorea rotundata).

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... The HI was calculated using observed data (range: 0.91-0.98), with the mean value of 0.95 used for the HI (Srivastava and Gaiser, 2008) (Dagbenonbakin, 2005). The values concerning fractions of root weight at emergence and maturity were set according to the findings of Srivastava and Gaiser (2008). ...
... with the mean value of 0.95 used for the HI (Srivastava and Gaiser, 2008) (Dagbenonbakin, 2005). The values concerning fractions of root weight at emergence and maturity were set according to the findings of Srivastava and Gaiser (2008). Values for the rate of decline in WA per unit increase in vapor pressure deficit (WAVP); the threshold for sensitivity of leaf conductance to vapor pressure deficit (VPTH); the rate of decline of leaf conductance with increasing vapor pressure deficit (VPD2); maximum stomatal conductance (GSI), and fraction of water in yield (WCY), were the same as used by EPIC for Cassava. ...
... America, the Caribbean, Pacific Islands and Southeast Asia (Onyeka et al., 2006). Although, there has been a decline in yam production relative to cassava and rice in Africa, yam is a preferred staple food and, considering projected population increases, total production is likely to increase in the future (Srivastava and Gaiser, 2008). ...
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Declining productivity in the Republic of Benin (West Africa) highlighted the need for a study to determine both the effect of fertilization on yam (Dioscorea spp.) yield and biomass production, as well as the best agronomic management options available for stabilizing yam productivity, via the modeling of yam growth and development. This study addressed the above issues by conducting plot experiments in the Benin Republic, which analyzed the effect of mineral fertilizer, manure and crop residue application on total biomass production, tuber yield and dry matter partitioning pattern, in two species of yam (Dioscorea alata var. Florido and Dioscorea rotundata var. Kokoro). Significant positive effects of mineral fertilizer were observed on yam total biomass production and tuber yield, but the magnitude of its effect were dependent on the species of yam. Crops receiving crop residues and manure also registered increases in yield, but were not significantly different from the yield under unfertilized conditions. Regarding partitioning pattern of dry matter to different plant organs, no significant difference was observed between control and fertilized treatments. An attempt has been made to simulate the effect of fertilization and fallow availability on yam (Dioscorea alata var. Florido) production by using the Environmental Policy Integrated Climate (EPIC) model. A new crop parameter file for Dioscorea alata was developed. The model accurately simulated the effect of fertilizer on the yam yield as indicated by a relatively low mean relative error (MR) ranging from 4.3 to 9.7 %. Different scenarios of fallow availability (Scenario S1 [100 % of the bush savannah is available as fallow land], Scenario S2 [50% of the bush savannah is available as fallow land] and Scenario S3 [25% of the bush savannah is available as fallow land]) were explored in the Upper Ouémé basin of Benin Republic (West Africa) by incorporating the EPIC model into the spatial decision support system (SDSS) PEDRO (Protection du sol Et Durabilité des Ressources agricoles dans le bassin versant de l'Ouémé). The best agreement between simulated and observed crop yields was found under the assumption that 50% of the bush savannah is available as fallow land under the prevailing cropping patterns. The results show the capacity of the EPIC model in connection with the SDSS PEDRO to capture both the biomass production and sensitivity of regional yields of yam to fallowing. They further reveal how a crop model can be used to analyze fallow practices at the regional scale. However, the models accuracy is most likely to be improved by a more detailed modeling of the phenological development of yam. In order to increase yam productivity and maintain soil fertility in the Upper Ouémé basin, fallowing the crop land is not a viable option due to increased demographic pressures. Mineral fertilizer application appears to be essential, but its high cost and accessibility restraints, limit its use by the farmers. The solution lies in providing mineral fertilizers to the farmers at subsidized rates. Additionally, nitrogen fixing crops could partially provide the N inputs needed, if included within crop rotations.
... The HI was calculated using observed data (range: 0.91-0.98), with the mean value of 0.95 used for the HI (Srivastava and Gaiser, 2008) (Dagbenonbakin, 2005). The values concerning fractions of root weight at emergence and maturity were set according to the findings of Srivastava and Gaiser (2008). ...
... with the mean value of 0.95 used for the HI (Srivastava and Gaiser, 2008) (Dagbenonbakin, 2005). The values concerning fractions of root weight at emergence and maturity were set according to the findings of Srivastava and Gaiser (2008). Values for the rate of decline in WA per unit increase in vapor pressure deficit (WAVP); the threshold for sensitivity of leaf conductance to vapor pressure deficit (VPTH); the rate of decline of leaf conductance with increasing vapor pressure deficit (VPD2); maximum stomatal conductance (GSI), and fraction of water in yield (WCY), were the same as used by EPIC for Cassava. ...
... America, the Caribbean, Pacific Islands and Southeast Asia (Onyeka et al., 2006). Although, there has been a decline in yam production relative to cassava and rice in Africa, yam is a preferred staple food and, considering projected population increases, total production is likely to increase in the future (Srivastava and Gaiser, 2008). ...
... Yam is the third most important tropical root crop after cassava (Manihot esculenta Crantz.) and sweet potato (Ipomoea batatas L. Lam.) in West Africa, Central America, the Caribbean, Pacific Islands and Southeast Asia. Although, there has been a decline in yam production relative to cassava and rice in Africa, yam is such a preferred staple food that, bearing in mind population increases, demand will remain and the absolute production will rather increase (Srivastava and Gaiser, 2008). Thus, the ability to meet the future demand may hinge upon proper assessment of medium-and long-term yam production vulnerability to climate change and the measures taken to adapt accordingly. ...
... In this study, a calibrated EPIC model (version 3060) for yam (Dioscorea alata) for the study region (Srivastava and Gaiser, 2010) has been used for simulating the effect of climate change on its production. The harvest index value used for yam in this study was measured in field experiments conducted in the studied region (Srivastava and Gaiser, 2008). EPIC (version 3060) has the capacity to simulate the CO 2 -fertilization effect on RUE and evapotranspiration (ET) to account for increased photosynthesis and reduced ET in plants due to reduced stomatal conductance under conditions of elevated CO 2 concentrations (Stöckle et al., 1992a,b), thereby improving water use efficiency (Chavas et al., 2009). ...
Article
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This study elucidates the effects of the projected climate variables and CO2 on yam yield in relation to three major soils in the Upper Ouémé basin (Benin Republic) on yam (Dioscorea alata) yield. The impact of the SRES climate scenarios A1B and B1 based on the output of the GCM ECHAM5 downscaled with the REMO model and the A1B scenario output of the GCM HADC3Q0 downscaled with the RCMs SMHIRCA and HADRM3P were analyzed. The A1B scenario, as expected with highest increase in temperature and extreme decline in rainfall, exhibited a decrease of 33% in yield until 2050 under ambient CO2 concentration (350 ppmv), while under B1 around 27% decline was registered. Whereas, decline under A1B emission scenario of SMHIRCA and HADRM3P accounted 19% and 18%, respectively. The soil type “Ferruginous soils improverished without concretions” (S1) was most sensitive to climate change registering a decline of 48% in yam yield in the decade 2041–2050 followed by “Ferralitic soils” (S2) and “Raw mineral soils” (S3) showing a decline of 36% and 33%, respectively under A1B scenario derived from REMO model. Analysis of the growth constraints suggest that besides water stress, the indirect effect of reduced rainfall on the release of nitrogen from soil organic matter and hence nitrogen deficiency in the yam crop was the major constraint in the S1soil type.
... Physiological growth analysis is a way to assess what events occurs during plant growth and eventually it is important in the prediction of yield of crop (Hokmalipour and Darbandi, 2011). Biomass partitioning is important for crop production and plants usually divert accumulated biomass to other plant parts to ensure and maintain a high production capacity (Srivastava and Gaiser, 2008). The data of different blocks of Hamirpur shows that during SW monsoon (June-September), 696.0-1283.2 ...
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A field experiment was conducted during kharif season 2016 at farmer's fields in district Hamirpur. The experiment included 8 treatment combinations was conducted in random block design with three replications. The experiment was carried out during June to September in Bhoranj, Nadaun and Taunidevi blocks with th st th different dates of sowing viz. Gwardu (L) 30 May, Dhamrol (L) 31 May, Mann treti (L) 30 June and 1 2 3 th Jhandvi (L) 6 June of district Hamirpur. Location (L) i.e. Mann treti in Nadaun block was found to be the 4 3 2 best location. Higher crop growth rate (42.5 g/m /day) and plant height (202.3 cm) were recorded in Nadaun block at Mann treti (Location L) with 500-800 mm rainfall. The Farmers practice (FP) showed significantly 3 2 2 higher plant height (216.7 cm), leaf area index (1.91), crop growth rate (46.5 g/m /day) and relative growth rate (0.0069 g/g/day). Farmer's practice proved to be better than zero budget natural farming at all the three locations.
... Dioscorea spp. is the third most important tuber crop after cassava and sweet potato in West Africa, Central America, the Caribbean, Pacific Islands and Southeast Asia [6]. According to [7], yam (6%), is included among the top five food crop species contributing 99% of the world production, and ranks number four in the world after potatoes (46%), cassava (28%), cassava (28%) 18%), followed by types of taro (1%). ...
... De nombreux travaux de recherche relatifs à l'utilisation des fumures minérales et organiques, à l'agroforesterie, aux plantes de couverture et aux rotations culturales ont été réalisés ces dernières années au Bénin, en Afrique de l'Ouest et dans les régions tropicales. Ainsi, des essais de fertilisation minérale sur la croissance et l'élaboration du rendement des variétés d'igname de Dioscorea alata, de même que la fertilisation organique et minérale sur les variétés du complexe Dioscorea cayenensis-rotundata, ont été menés par Dumont et al. (1997), Strivastava et Gaiser (2008), Ettien et al. (2009), Aziadekey et al. (2014) et Cornet (2015. L'intérêt des légumineuses herbacées et de l'agroforesterie pour une production durable d'igname en Afrique de l'Ouest a fait également objet d'études ces dernières décennies (Kouame, 2003 ;Maliki et al., 2012). ...
Article
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This paper presents a literature review about botany, ecology, cropping systems, processing, constraints and prospects of sustainable yam production in tropical regions of Africa. Yam is a taxon of mainly tropical species requiring high temperatures. Germination is optimal between 25 and 30 °C, whereas temperatures below 15 °C or above 35 °C delay it. Yam is successfully cultivated in areas with rainfall ranging from 1000 to 1800 mm; however, it is possible to cultivate yam with a rainfall of only 600 mm, but yield remains low. To reach vegetative growth and good tuber formation, yam prefers sandy-loamy or loamy soils, with hydraulic conductivity of 15 cm/h, apparent soil density between 1.1 and 1.6 g.cm 3 and light and deep soils (> 0.6 m), well drained, rich in organic matter, nitrogen, potash, magnesium and calcium. A soil pH from 5 to 7 is suitable for a good yam production. Beyond the edaphic and climatic factors, cultivation practices, including cultivar, plantation density, date of planting, management of weeds, diseases and pests, cropping history of plots and farmers’soil management practices, affect yam productivity. Farmers base the choice of yam varieties mainly on culinary quality of tubers, productivity, commercial value, propagation, quality of chips, tuber formation precocity, conservation, facility of culture, roles as food and for ritual ceremonies.
... De nombreux travaux de recherche relatifs à l'utilisation des fumures minérales et organiques, à l'agroforesterie, aux plantes de couverture et aux rotations culturales ont été réalisés ces dernières années au Bénin, en Afrique de l'Ouest et dans les régions tropicales. Ainsi, des essais de fertilisation minérale sur la croissance et l'élaboration du rendement des variétés d'igname de Dioscorea alata, de même que la fertilisation organique et minérale sur les variétés du complexe Dioscorea cayenensis-rotundata, ont été menés par Dumont et al. (1997), Strivastava et Gaiser (2008), Ettien et al. (2009), Aziadekey et al. (2014) et Cornet (2015. L'intérêt des légumineuses herbacées et de l'agroforesterie pour une production durable d'igname en Afrique de l'Ouest a fait également objet d'études ces dernières décennies (Kouame, 2003 ;Maliki et al., 2012). ...
Article
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Cette revue de littérature couvre la botanique, la domestication, l’écologie, les systèmes de culture, la transformation ainsi que les contraintes et perspectives pour une production durable des ignames en Afrique tropicale. L’igname est un taxon d’espèces essentiellement tropicales qui nécessitent des températures élevées. Ainsi, la germination est optimale entre 25 et 30 °C, alors que des températures inférieures à 15 °C ou supérieures à 35 °C la retardent. La culture de l’igname se pratique avec succès dans des zones où la pluviométrie varie entre 1000 et 1800 mm ; toutefois, il est possible de cultiver l’igname avec une pluviométrie de 600 mm mais le rendement reste faible. L’igname, pour la croissance végétative et une bonne tubérisation, préfère des sols limono-sableux ou sablo limoneux, ayant une conductivité hydraulique de 15 cm/h, une densité apparente comprise entre 1,1 et 1,6 g.cm ⁻³ et surtout légers, profonds (> 0,6 m), bien drainés, riches en matière organique, en azote, en potasse, en magnésium et en calcium ; un pH compris entre 5 et 7 est aussi propice à une bonne culture d’igname. Au-delà des paramètres édaphiques et des facteurs climatiques, les pratiques culturales, notamment le type de cultivar, la densité de plantation, la date de plantation, les adventices, les maladies et ravageurs, sans occulter l’histoire des parcelles et les pratiques paysannes de gestion du sol, ont un effet sur la productivité des ignames. Les facteurs déterminant le choix des variétés d’igname cultivées par les producteurs sont principalement : la qualité culinaire des tubercules, la productivité, la valeur commerciale, la facilité de multiplication, la qualité des cossettes, la précocité de tubérisation, la conservation, la facilité de culture, le rôle dans l’alimentation et l’importance pour les cérémonies rituelles.
... In Africa, yam is used as the main staple food and source of income for subsistence farmers. Yam is also the third most important tuber plant after cassava and sweet potatoes in West Africa, Central America, the Caribbean, the Pacific Islands and Southeast Asia [6]. ...
Article
Under the present climate conditions, physical water scarcity does not appear to be a major limiting factor for food and livelihood security in Benin. Rather, the fast demographic growth arising from high fertility rates and immigration causes a high pressure on natural resources such as soils, forests, water as well as on biodiversity, and challenges the assurance of food security and economic development. The projected climate warming and drying trend occurs in addition to these developments. In parts of the sub-humid tree savannah of Central Benin, particularly in the Haute Vallée de l'Ouémé (HVO), farmland expanded considerably at the expense of natural forests during the IMPETUS project period 2000-2009. In the HVO, some of the highest population growth rates in Benin in excess of 5% p.a. also occurred due to immigration mainly from the Atakora mountain area in northwest Benin. The increasing population and the prevailing extensive, labor-intensive cropping and animal husbandry systems were the major drivers of the rapid land use change that was monitored by IMPETUS in the HVO. Migrants were strongly involved in the process of agricultural colonization. In some villages in the HVO, rural migrants without secure land rights already constitute the majority of the population.
Article
Globally, yam (Dioscorea spp.) is the fifth most important root crop after sweet potatoes (Ipomoea batatas L.) and the second most important crop in Africa in terms of production after cassava (Manihot esculenta L.) and has long been vital to food security in Sub-Saharan Africa (SSA). Climate change is expected to have its most severe impact on crops in food insecure regions, yet very little is known about impact of climate change on yam productivity. Therefore, we are trying estimating the effect of climate change on the yam (variety: Discovery popularly known as Florido) yield and evaluating different adaptation strategies to mitigate its effect. Three regional climate models REgional MOdel (REMO), Swedish Meteorological and Hydrological Institute Regional Climate Model (SMHIRCA) and Hadley Regional Model (HADRM3P) were coupled to a crop growth simulation model namely Environmental Policy Integrated Climate (EPIC) version 3060 to simulate current and future yam yields in the Upper Ouémé basin (Benin Republic). For the future, substantial yield decreases were estimated varying according to the climate scenario. We explored the advantages of specific adaptation strategies suggesting that changing sowing date may be ineffective in counteracting adverse climatic effects. Late maturing cultivars could be effective in offsetting the adverse impacts. Whereas, by coupling irrigation and fertilizer application with late maturing cultivars, highest increase in the yam productivity could be realized which accounted up to 49% depending upon the projection of the scenarios analyzed.
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