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Syndromes of production in intercropping impact yield gains

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Intercropping, the simultaneous production of multiple crops on the same field, provides opportunities for the sustainable intensification of agriculture if it can provide a greater yield per unit land and fertilizer than sole crops. The worldwide absolute yield gain of intercropping as compared with sole crops has not been analysed. We therefore performed a global meta-analysis to quantify the effect of intercropping on the yield gain, exploring the effects of crop species combinations, temporal and spatial arrangements, and fertilizer input. We found that the absolute yield gains, compared with monocultures, were the greatest for mixtures of maize with short-grain cereals or legumes that had substantial temporal niche differentiation from maize, when grown with high nutrient inputs, and using multirow strips of each species. This approach, commonly practised in China, provided yield gains that were (in an absolute sense) about four times as large as those in another, low-input intercropping strategy, commonly practised outside China. The alternative intercropping strategy consisted of growing mixtures of short-stature crop species, often as full mixtures, with the same growing period and with low to moderate nutrient inputs. Both the low- and high-yield intercropping strategies saved 16–29% of the land and 19–36% of the fertilizer compared with monocultures grown under the same management as the intercrop. The two syndromes of production in intercropping uncovered by this meta-analysis show that intercropping offers opportunities for the sustainable intensification of both high- and low-input agriculture.
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https://doi.org/10.1038/s41477-020-0680-9
1College of Resources and Environmental Science, National Academy of Agriculture Green Development, China Agricultural University, Beijing, China.
2Soil Biology Group, Wageningen University, Wageningen, The Netherlands. 3Centre for Crop Systems Analysis, Wageningen University, Wageningen, The
Netherlands. 4College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot, China. e-mail: zhangfs@cau.edu.cn;
wopke.vanderwerf@wur.nl
With the ongoing increase in the global population and
demand for food, improving crop productivity is a press-
ing challenge1. Intensive agriculture provides high yields
but comes with serious environmental impacts24. Intercropping
(that is, the mixed cultivation of crop species on the same field5,6)
is a sustainable way to develop productive agriculture68: it offers
ecological mechanisms for weed suppression9, pest and disease con-
trol10,11, efficient use of light12 and water1315, conservation of soil
resources1618, and yield increase1921. The most obvious advantage of
intercropping is land sparing, which is usually quantified by the land
equivalent ratio (LER). The LER is defined as the ratio of the area
under sole cropping to the area under intercropping needed to give
the same yields22. An LER greater than one means that intercropping
saves land. Previous meta-analyses have shown that the LER of inter-
cropping averages 1.22 ± 0.02 (ref. 23) or 1.30 ± 0.01 (ref. 8), depend-
ing on the studies selected for meta-analysis. However, the LER is a
dimensionless indicator of relative yields in intercropping compared
with monocultures. It does not provide information on the absolute
yield increase per unit area achieved by intercropping.
The absolute yield gain of species mixtures can be assessed by
the net effect (NE) of species mixtures on the yield per unit area24.
The NE is defined as the difference in yield or biomass between the
mixture and the average of the sole crops24. The information pro-
vided by the NE and the LER is complementary. Both metrics are
relevant for assessing the benefit of intercropping. The LER evalu-
ates the comparative land use efficiency of intercropping, while the
NE indicates how much more yield is produced per unit area than
expected on the basis of sole crop yields and species proportions.
The relative yield can be high at low-yield levels, but the NE is not
likely to be substantial at low-yield levels. When issues of global
food security are at stake, it is important to not focus solely on the
land use efficiency (LER) but to also pay attention to the NE (that is,
the absolute yield gain). The absolute yield gain of intercropping at
a global scale is unknown.
Intercropping is an ancient cropping system, practised all around
the world25,26 (Supplementary Fig. 1). Various crop combinations
have been recognized and utilized in Africa, Asia, Europe and the
Americas for centuries and are still prevalent27. Crop species may be
grown simultaneously or partly so, and in no distinct row arrange-
ment (mixed) or in alternate rows or strips on the same field25
(Fig. 1). In strip intercropping, the strips are wide enough to per-
mit independent cultivation but narrow enough to allow beneficial
interspecific interactions6 (Fig. 1a,b,e–g).
Maize (Zea mays) is a frequently used species in intercropping.
This high-yielding C4 species can be sown in strips of several rows,
alternating with several rows of a C3 species (for example, a small
grain such as wheat (Triticum aestivum)28 or a legume such as soy-
bean (Glycine max)29). Maize has a late and long growing season and
is usually harvested after a C3 species in a system known as relay
strip intercropping25,26,30 (Fig. 1b).
Maize and other cereals can also be sown in alternate rows or
mixed in a more or less random pattern with other small grains
or legumes (Fig. 1c,d). Alternate-row and mixed intercropping
are popular in organic farming with low input in Europe16,31,32.
Here, mixtures of a legume and a C3 cereal species are the most
popular combination (Fig. 1h–j). These intercropping systems have
low nitrogen (N) fertilizer input but realize an acceptable pro-
tein content in the cereal grain due to N2 fixation by the legumes.
Syndromes of production in intercropping impact
yield gains
Chunjie Li 1,2,3, Ellis Hoffland 2, Thomas W. Kuyper 2, Yang Yu3, Chaochun Zhang 1,
Haigang Li 1,4, Fusuo Zhang 1 ✉ and Wopke vander Werf 3 ✉
Intercropping, the simultaneous production of multiple crops on the same field, provides opportunities for the sustainable
intensification of agriculture if it can provide a greater yield per unit land and fertilizer than sole crops. The worldwide absolute
yield gain of intercropping as compared with sole crops has not been analysed. We therefore performed a global meta-analysis
to quantify the effect of intercropping on the yield gain, exploring the effects of crop species combinations, temporal and spa-
tial arrangements, and fertilizer input. We found that the absolute yield gains, compared with monocultures, were the great-
est for mixtures of maize with short-grain cereals or legumes that had substantial temporal niche differentiation from maize,
when grown with high nutrient inputs, and using multirow strips of each species. This approach, commonly practised in China,
provided yield gains that were (in an absolute sense) about four times as large as those in another, low-input intercrop-
ping strategy, commonly practised outside China. The alternative intercropping strategy consisted of growing mixtures of
short-stature crop species, often as full mixtures, with the same growing period and with low to moderate nutrient inputs. Both
the low- and high-yield intercropping strategies saved 16–29% of the land and 19–36% of the fertilizer compared with mono-
cultures grown under the same management as the intercrop. The two syndromes of production in intercropping uncovered by
this meta-analysis show that intercropping offers opportunities for the sustainable intensification of both high- and low-input
agriculture.
NATURE PLANTS | VOL 6 | JUNE 2020 | 653–660 | www.nature.com/natureplants 653
Content courtesy of Springer Nature, terms of use apply. Rights reserved
... Intercropping is the cultivation of more than one species in the same field at the same time for a significant period of time, but without necessarily sowing or harvesting the two species at the same time (Willey, 1979). Intercropping may be an efficient means to deliver sustainable and productive agriculture (Lithourgidis et al., 2011;Li et al., 2020a;Tilman, 2020;Yang et al., 2021) by enhancing land productivity, and simultaneously enabling a reduction in external inputs such as fertilizer (Bedoussac et al., 2015;Li et al., 2020b). ...
... There is thus a body of knowledge on growth responses in relay intercropping and the importance of the competition-recovery production principle in the yield advantage of late maturing species, such as maize. Maize can potentially be intercropped with many crop species, differing in intercropping advantage (Li et al., 2020b). Thus, it is necessary to determine how the traits of the companion species influence the competition-recovery in maize-based intercropping. ...
... In our study, the yield achieved in intercropping was significantly higher at high than at low nitrogen application rate, while the advantage of intercropping, characterized by LER values greater than one, was greater at a low than at high nitrogen application rate. It has been suggested that intercropping is more suitable in low-N input situations (Fujita et al., 1992;Jensen, 1996;Bulson et al., 1997), but it has also been noted that an intercropping yield advantage in an absolute sense increased at higher rates of nitrogen input (Li et al., 2020b). Additionally, at a given nitrogen rate, the intercropping yield advantage depends on species combination and temporal niche differentiation (Dong et al., 2018). ...
Article
Context: Maize (Zea mays L.)-based intercropping-growing maize with at least one species in the same field for a significant period-is a common practice in China. Intercropping may allow ecological intensification of maize production by achieving higher yields and higher resource-use efficiency than sole maize. Such advantages strongly depend on interactions between species and nitrogen availability. Unfortunately, there is a shortage of experiments combining both species choice and nitrogen management. Research question: It remains unclear how growth characteristics of the companion species, and notably its temporal complementarity with maize, and nitrogen fertilizer affect the performance of maize-based inter-cropping. Therefore, this work aims to explore the importance of the recovery response in relation to the duration of co-growth and that of maize recovery in interaction with nitrogen availability on the yield advantage of maize-based intercropping. Methods: A two-year field experiment was conducted in Gansu Province (China) to quantitatively determine the effect of different companion species and nitrogen fertilizer rates on yields, relative yields and land equivalent ratios (LER). Experimental treatments included two nitrogen input rates (120 and 240 kg N ha − 1), and six companion species in a substitutive design: wheat (Triticum aestivum L.), linseed (Linum usitatissimum L.), cabbage (Brassica oleracea L.), garlic (Allium sativum L.), pea (Pisum sativum L.) and soybean (Glycine max L.). Results: Yields of intercropped maize were higher at 240 kg N ha − 1 than at 120 kg N ha − 1. Averaged over nitrogen inputs, the yield of maize intercropped with pea, cabbage, garlic, wheat, linseed and soybean was 71%, 72%, 78%, 53%, 50% and 58% of that of sole maize. LERs were greater than one for all species combinations, except for soybean/maize. LERs and overyielding of maize were higher at 120 kg N ha − 1 than at 240 kg N ha − 1. Overyielding of maize was negatively correlated to species co-growth duration and positively correlated to temporal niche differentiation, with the highest overyielding of maize with garlic corresponding to the shortest co-growth period. Conclusions: Overyielding was significantly increased with the duration of the recovery period of maize (after harvest of the companion species), while it was negatively correlated with the duration of the co-growth period. Our results suggest that the competition-recovery principle contributed greatly to yield advantage in maize-based intercropping. Implications: Our results should be considered in designing maize-based intercropping by choosing species and dates of sowing and harvesting for maximizing yield benefits.
... Loss of crop species diversity may make global food production less sustainable and less stable (4,5) and increase the need for crop protection against pests, diseases, and weeds due to lower resilience (6)(7)(8)(9). Intercropping, i.e., the mixed cultivation of two (or more) crop species on the same field (10,11), is a crop diversification strategy which allows lowering inputs while achieving higher crop yields than expected based on the sole crop yields of the constituent species (12,13). Due to its contribution to efficient use of resources and diversification of crop species, intercropping provides a compelling opportunity for the sustainable intensification of agriculture. ...
... An LER larger than one means that intercropping is more efficient in land use than sole cropping. Based on the values of LER estimated from large databases, previous meta-analyses have shown that intercropping saves on average 18 to 23% of the required land compared with production of the same species in sole crops (13,(19)(20)(21). That means intercropping allows to obtain the same crop outputs on a smaller land area. ...
... Contrary to the LER, which is a sum of dimensionless ratios, the net effect of intercropping is expressed in terms of a yield difference per unit area (16). Using global data on crop yields in intercropping, Li et al. (13) showed that intercropping produces 1.5 t grain yield per hectare more than expected on the basis of the sole crop yields, confirming that on average intercrops outperform the mean of the component sole crops. Here, following Cardinale et al. (19), we will express the net effect as a yield ratio (total yield observed)/(total yield expected) to make it more easily comparable to the LER (Table 1 and Box 1). ...
Article
Crop diversification has been put forward as a way to reduce the environmental impact of agriculture without penalizing its productivity. In this context, intercropping, the planned combination of two or more crop species in one field, is a promising practice. On an average, intercropping saves land compared with the component sole crops, but it remains unclear whether intercropping produces a higher yield than the most productive single crop per unit area, i.e., whether intercropping achieves transgressive overyielding. Here, we quantified the performance of intercropping for the production of grain, calories, and protein in a global meta-analysis of several production indices. The results show that intercrops outperform sole crops when the objective is to achieve a diversity of crop products on a given land area. However, when intercropping is evaluated for its ability to produce raw products without concern for diversity, intercrops on average generate a small loss in grain or calorie yield compared with the most productive sole crop (-4%) but achieve similar or higher protein yield, especially with maize/legume combinations grown at moderate N supply. Overall, although intercropping does not achieve transgressive overyielding on average, our results show that intercropping performs well in producing a diverse set of crop products and performs almost similar to the most productive component sole crop to produce raw products, while improving crop resilience, enhancing ecosystem services, and improving nutrient use efficiency. Our study, therefore, confirms the great interest of intercropping for the development of a more sustainable agricultural production, supporting diversified diets.
... The most obvious way to improve the LUE is adoption of components of CRIWM such as intercropping which was proved to suppress weeds and increase land equivalent ratio (LER) which is the ratio of the area under sole cropping to the area under intercropping needed to give the same yields. The intercropping strategies saved 16-29% of the land as compared to mono-cultures grown under the same management as the intercrop (Li et al. 2020). The choice of legume for intercropping with cereals determines the productivity of intercropping systems by ensuring compatibility in utilizing growth resources (Iqbal et al. 2019). ...
... It is possible to increase in irrigated area by saving water through best weed management and utilize saved water for bringing more area under irrigation . Intercropping is a sustainable way to offers ecological mechanisms for weed suppression, efficient use of water and increase crop productivity (Rao and Shetty 1983a;Li et al. 2020). ...
... Light interception pattern and leaf area index (LAI) observations revealed that inclusion of smother crop viz, cowpea and mungbean resulted In quicker and earlier attenuation of maximum LAI and percentage of light by crops (Rao and Shetty 1981). Intercropping is a sustainable way for weed suppression, efficient use of light and crop productivity improvement (Li et al. 2020) ...
Article
Full-text available
The global agricultural production must increase by around 70% to meet the food and nutrition demands of 9.9 billion people, by 2050. It was predicted that 670 million people will still be undernourished in 2030. Hence, feasible and cost-effective strategies in the global agri-food system need to be implemented for meeting nutrition security. Weed management played a key role in achieving global food and nutrition security, till to date. In this paper the role of weed management in meeting food and nutrition security is revisited in view of the changed scenario of prevailing unintended ecological imbalance, climate change, water overuse and waste, soil degradation, loss of natural resource quality, and declines in biodiversity, increased herbicide use, and chemical runoff that are decreasing crop growth yields and raising reasonable concerns about the sustainability of the current agricultural methods in meeting the future food and nutrition security. The future role of weed management is discussed in terms of: reducing the continued losses caused by weeds and improving crops productivity and production by reducing yield gap; improving resources (land, water, light, nutrients); improving farmers income; advancement of farmers livelihood; combating climate change and balancing biodiversity. The possible role of climate resilient integrated weed management in playing the intended roles in agri-food system is discussed. In order to play much more sustainable role, the weed management, as an integral part of agricultural production, needs to move away from its mono-disciplinary perspective at targeting weeds to multidisciplinary and multifaceted technological solution to serve as a component of overall technological solutions to improve agricultural production for achieving ever increasing food and nutritional security challenges.
... Intercropping is the planned cultivation of multiple crop species in one field for at least part of their growing periods (Willey, 1990). It provides a suitable cropping model for sustainable intensification (Brooker et al., 2015) because of improved use efficiency of land (Li et al., 2020b;Yu et al., 2015), light (Gou et al., 2017;Liu et al., 2017;Raza et al., 2019;Tsubo et al., 2001), water (Morris and Garrity, 1993;Tan et al., 2020;Yin et al., 2020), and nutrients (Darch et al., 2018;Guiducci et al., 2018;Tang et al., 2021;Xu et al., 2020). Furthermore, intercropping can lead to higher organic soil carbon and nitrogen content Wang et al., 2014), better pest and disease control (Boudreau, 2013;Risch, 1983;Tooker and Frank, 2012;Trenbath, 1993;Zhang et al., 2019), and better weed suppression (Corre-Hellou et al., 2011;Gu et al., 2021Gu et al., , 2022Liebman and Dyck, 1993). ...
... Intercropping is usually considered advantageous at low levels of resource availability (Brooker et al., 2015;Franco et al., 2015;Jensen et al., 2020) because complementarity is dominant with constrained resources, while competition prevails with ample resources (He et al., 2013;Justes et al., 2021). Nevertheless, meta-analyses indicate that yield advantages in intercropping increase with nitrogen (N) input in high-input agriculture (Li et al., 2020b;Yu et al., 2015). In high-input systems in China, bi-specific intercrops (one component species of which is often maize, Zea mays L.) are planted in alternating narrow strips of a few crop rows whereby the combined species are sown and harvested in a relay succession. ...
... In high-input systems in China, bi-specific intercrops (one component species of which is often maize, Zea mays L.) are planted in alternating narrow strips of a few crop rows whereby the combined species are sown and harvested in a relay succession. The yield increase is related to the difference in growing periods, which decreases interspecific competition for light and other resources, while the extended total growth duration increases the aggregate resource capture of the system as a whole (Gou et al., 2017;Li et al., 2020b;Yu et al., 2015;Zhang et al., 2008a). Policymakers are interested in increasing sustainability of farming, but they want to maintain as much as possible high levels of productivity, to ensure food security and healthy diets (Lankoski and Thiem, 2020). ...
Article
Full-text available
Combinability of species in intercrops depends on the production conditions and there is limited information on the potential of intercropping under conventional (i.e., non-organic) management in Western Europe. Here we determined productivity of four crop species (maize, Zea mays L.; wheat, Triticum aestivum L.; faba bean, Vicia faba L.; pea, Pisum sativum L.) in six different bi-specific mixture compositions. Species were spring-sown and fertilized in their strips according to common practice for monocrops. Strips were 1.5 m wide enabling strong interspecific interactions. Intercrops with maize, a species sown and harvested later than the other three species, had land equivalent ratio (LER) values that were in four out of six cases significantly greater than one, from 1.14 ± 0.04 to 1.22 ± 0.05 in 2018, and from 0.98 ± 0.06 to 1.15 ± 0.01 in 2019. Simultaneous intercrops comprising two of the other three species had LER values that tended to be lower than one, even though many LERs were not significantly different from one: from 0.94 ± 0.02 to 0.95 ± 0.04 in 2018, and from 0.80 ± 0.08 to 0.93 ± 0.04 in 2019. The yield gain (net intercropping effect; NE) in relay intercrops with maize ranged from 1.33 ± 0.59 to 2.01 ± 0.54 Mg ha⁻¹ in 2018, and from 0.29 ± 0.41 to 1.04 ± 0.14 Mg ha⁻¹ in 2019. The NE of simultaneous intercrops ranged from −0.43 ± 0.13 to −0.27 ± 0.22 Mg ha⁻¹ in 2018, and from −1.17 ± 0.49 to −0.36 ± 0.22 Mg ha⁻¹ in 2019. Results indicate that temporal complementarity between species drove the LER (or NE) in these experiments. On the other hand, values of the LER (or NE) were similar in species combinations with or without legumes, suggesting no major role for complementarity for nitrogen capture under the conditions of the study. Faba bean was the most competitive species and reached high partial LER and NE values in intercrops at the expense of the companion species. Competition from faba bean reduced the grain yield of wheat and pea more than it increased faba bean grain yield, resulting in negative net effects. Results suggest that relay strip intercropping can improve land use efficiency and total grain yield in conventional farming in Western Europe if species have temporal complementarity.
... In this research, the co-effects of complementarity and select effect affected the productivity advantage of MSI. The LER M had a significant positive correlation with crop yield (p < 0.001), indicating that intercropping system land productivity was improved mainly due to the increased yield of intercropped maize [47], while intercropped maize yield had a significant positive correlation with complementarity and select effect (p < 0.001), indicating that the higher the complementarity effect and select effect, the greater the effect of increased maize yield. Complementarity effects were higher than select effects; in addition, intercropped soybean yields also had a significant positive correlation with the compensatory effect (p < 0.01), indicating that the intercropping advantage was mainly derived from complementarity effect [27], which was due to the competitive strength and broad-row light transmission of intercropped maize, which further strengthened after intercropped soybean harvest and improved the spatial ecological niche of the crops [48]. ...
... In this research, the co-effects of complementarity and select effect affected the productivity advantage of MSI. The LERM had a significant positive correlation with crop yield (p < 0.001), indicating that intercropping system land productivity was improved mainly due to the increased yield of intercropped maize [47], while intercropped maize yield had a significant positive correlation with complementarity and select effect (p < 0.001), indicating that the higher the complementarity effect and select effect, the greater the effect of increased maize yield. Complementarity effects were higher than select represent N, P, and K nutrient aggressivity and partial land equivalent ratio for intercropped maize, respectively. ...
Article
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Intercropping plays an indispensable role in sustainable agriculture. The response of bandwidth row ratio configuration to crop interspecific relationships and land productivity in the maize–soybean intercropping system (MSI) is still unclear. A 2-year field experiment was conducted with sole maize (SM) and sole soybean (SS), two different bandwidths (2.4 m (B1), 2.8 m (B2)), two different maize and soybean row ratios (2:3 (R1), and 2:4 (R2)) for MSI. The results showed that intercropping had advantages for land productivity compared with sole planting. Intercropping cropping had significant differences on crop yield under different intercropping treatments. The 2-yr average land equivalent ratio (LER, 1.59) and group yield under the intercropping patterns of B1R2 were significantly higher than other intercropping treatments (p < 0.05). With a bandwidth of 2.4 m and planting four rows of intercropped soybean, the total LER and group yield increased by 7.57% and 10.42%, respectively, compared to planting three rows of soybean. Intercropped maize was the dominant species and also had a higher nutrient aggressivity than intercropped soybean. The complementarity effect was higher than the select effect in the MSI system, and intercropping advantage was mainly derived from the complementarity effect, which was significantly correlated with intercropped maize yield. Nitrogen and phosphorus nutrient aggressivity in intercropped maize showed significant correlations with group yield and intercropped maize yield. In conclusion, bandwidth 2.4 m, row ratio 2:4 was a reasonable planting pattern because of its superior land productivity, crop nutrients uptake advantage, and harmonious interspecific relationship, which could provide a reference for MSI promotion and application research.
... Crop mixtures are two or more different crop species or different cultivars of the same crop species grown simultaneously in the same field in alternate rows or mixture with no distinct row arrangement [10] . Of the different kinds of crop diversification in agroecosystems, intercropping, which grows at least two crops simultaneously at the same field, has attracted considerable interest because of its great potential to increase biodiversity and use resources, when more attention is given to sustainable agriculture development [11] . ...
... Nitrate is a problematic contaminant in agricultural regions and nitrous oxide (N 2 O) is a greenhouse gas, and both are derived mainly from excess fertilizer N use [46,47] . Intercropping reduces the inputs of nitrogen fertilizers through the efficient use of resources [11] and further reduces ammonia volatilization and NO and N 2 O emissions ( Fig. 1(b)). A meta-analysis shows that 376 of 409 values of fertilizer nitrogen equivalent ratio (FNER) were > 1 (92%), indicating that intercropping achieved not only high yields but also high nitrogen use efficiency [48] . ...
... The premise that mixtures are more productive than pure stands is based on the assumption that mixed species would explore different niches and capture more resources (Vandermeer, 1992). This complementarity for resources acquisition and yield advantage was repeatedly reported in earlier studies on semi-natural systems and food crops (Tilman et al., 1996(Tilman et al., , 2006Knops and Tilman, 1999;Fornara and Tilman, 2008;Cong et al., 2014Cong et al., , 2015Yu et al., 2015;Li et al., 2020;Xu et al., 2020). However, for cover crops, it is more evident that the most productive species in a pure stand would dominate the mixture when mixed with a less productive species, which is known as the selection effect (Loreau and Hector, 2001;Elhakeem et al., 2019). ...
Article
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Agricultural soils are at risk of nitrogen (N) leaching especially during the fallow period in autumn and winter. Cover crops are grown to capture soil mineral N that otherwise would leach to the groundwater. They can serve as green manure providing mineral N to the cash crop in spring. We investigated whether mixing species of cover crops can enhance N capture and therefore reduce N leaching more effectively than pure stands in autumn without increasing the risk of N leaching in spring. We hypothesised that mixed species with complementary traits will capture more N and accumulate more biomass. It was also expected that residues from cover crops with higher biomass and lower C:N ratio would mineralise faster and subsequently increase N leaching in spring. In a 4-year field experiment, cover crops were grown between August and February in a rotation with different cash crops. We used eight cover crop treatments, including three pure stands: radish (Raphanus sativus), vetch (Vicia sativa) and oats (Avena strigosa), all possible 2- and 3-species mixtures and a fallow (no cover crop). Treatment effects on leaching losses were estimated by analysing N concentrations in samples of leached pore water below the rooting zone and by modelling the volume of water leached per plot. Most N leaching occurred in autumn and winter while the amount of N leached in spring was negligible due to the lower precipitation. N leaching in autumn correlated negatively with cover crop biomass, N uptake and root length density. Radish and oats were the most productive species and dominated mixtures. Compared to the fallow, radish and mixtures that contained radish reduced N leaching by 49–73% and were characterized by quick soil cover, high N uptake and low to moderate C:N ratio. Subsequently, residues from radish and mixtures containing radish mineralized quickly, resulting in an increase in soil mineral N in spring by 70–110% as compared to fallow. This mineral N did not leach in spring and was available to the subsequent cash crop. This study demonstrates the importance of species selection in cover crop mixtures and recommends the use of radish-based mixtures if the purpose is to reduce N leaching in autumn and provide mineral N in spring.
... Continuous monoculture adopted in the cultivation of Cucumis sativus, an important horticultural crop, has caused problems such as yield reduction and quality deterioration [32,33]. Intercropping has proved to be a sustainable way to solve these problems [34]. The morphological plasticity is very important for the utilization of limited resources in the presence of neighbors in the intercropping systems. ...
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Plants exhibit various behaviors of growth and allocation that play an important role in plant performance and social interaction as they grow together. However, it is unclear how Cucumis sativus plants respond to different neighbors. Here, we performed 5 neighbor combinations with C. sativus as the focal species. The selected materials of C. sativus responded to neighbors and exhibited different behavior strategies in a species-specific manner. All competition treatments reduced the growth of C. sativus seedlings to a certain extent, but only the Eruca sativa neighbor treatment reached a significant level in total root length and shoot biomass. Compared with growing under solitary conditions, focal plants avoided, tended to and did not change their allocation to their nearby plants. The larger the biomass of their neighbors, the stronger the inhibition of the focal plants. In addition, no significant correlations between growth and allocation variables were found, suggesting that growth and allocation are two important aspects of C. sativus behavioral strategies. Our findings provide reference and support for agricultural production of C. sativus, but further research and practice are still needed.
... Intercropping is a cropping system where two or more annual crops are grown in the same field in the same season [1]. Compared with monoculture, intercropping has yielded advantages due to the effective use of radiation, heat, water, and nutrients, leading to increased land productivity [2]. ...
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Wheat/maize intercropping has been widely practiced in northwestern China. It is crucial to optimize the canopy structure and geometric configurations to enhance the performance of the system. This research determined the responses of intercrops to the different canopy structures created by the different wheat/maize intercropping systems. Field experiments were carried out in 2012, 2013, and 2014 at Wuwei, Gansu. Three intercropping patterns—six rows of wheat alternated with two rows of maize (6W2M), six rows of wheat alternated with three rows of maize (6W3M), and six rows of wheat alternated with four rows of maize (6W4M)—were compared with sole wheat and sole maize. The results showed that maize plant heights differed between the inner rows and the border rows, and the difference was greater for the 6W3M system than for the 6W4M system. The three intercropping systems had an average land-use equivalent ratio (LER, calculated based on grain yield) of 1.25, indicating an increase in land-use efficiency by 25% compared to the corresponding sole crops. The shape of maize strips in 6W3M optimized the canopy structure and increased the productivity of wheat and maize. The wheat in 6W3M had significantly more grain yield compared with the sole wheat and the 6W2M due to the maize belt shape, which resulted in the soil evaporation negatively affecting the intercropped wheat grain yield of the 6W3M. Similarly, the maize belt shape facilitated the light penetration and enhanced the reproductive growth by increasing the two cobs per plant rate (TCR) of the maize. The highest TCR of the 6W3M produced a higher maize grain yield than the 6W2M and sole maize in the three growing seasons. The maize belt width in the strip intercropping system had a significant effect on the grain yield of both wheat and maize, which reduced water evaporation, harmonized light distribution, and increased productivity.
Article
Context Plants can modify their morphological or physiological traits in response to nutrient availability and to the presence and identity of neighboring individuals. However, few studies have addressed the effects of changes in above- and below-ground functional traits for the productivity advantage in intercropping. Hypothesis We hypothesized that the plasticity of above- and below-ground functional traits of crops in response to nutrients availability and interspecific interactions affects biomass of both crop species and whole intercropping systems. Methods A 2-year field experiment was performed with two N levels (with and without), two P levels (with and without) and five cropping systems (i.e. sole maize, peanut and soybean, and maize/peanut and maize/soybean intercropping). We measured thirteen above- and below-ground functional traits related to light interception and use efficiency, root length and distribution at the grain filling stage of maize, and final biomass at harvest. Results Maize/peanut and maize/soybean intercrops has productivity advantages compared to monoculture, and this was mainly in terms of increases in maize biomass. Compared with monoculture, intercropping increased maize biomass more than it decreased soybean (24 %) or peanut (49 %) biomass. Maize had a yield advantage through greater leaf area, root length and root biomass density when intercropped. Intercropped soybean resisted suppression by maize through increased height and specific leaf area, but intercropped soybean had decreased specific leaf N and biomass. Branch number, leaf area, specific leaf nitrogen and root biomass density of peanut were all suppressed by maize, which caused a large decrease in peanut biomass when intercropped. Conclusions and significance Our study provides evidence that changes in above- and below-ground functional traits in response to nutrients availability and interspecific interactions are key to explaining patterns of transgressive overyielding. Our findings can help to better understand the underlying mechanisms that regulate productivity advantages in species mixtures, and have implications for the sustainable management of species-diverse food-production systems.
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Strip intercropping increases land use efficiency but the effect on water use efficiency is less well-known. Here we develop a modelling method to simulate the growth of an intercrop taking into account the acquisition of light and water by the component species in order to calculate the efficacy of light and water acquisition in an intercropping system as compared to sole crops. The model is parameterized, calibrated and validated using data on wheat-maize intercropping in Gansu province, Northwest China. Observed above-ground biomass was 1630 g m⁻² for sole wheat and 1334 g m⁻² for intercropped wheat while it was 3023 g m⁻² for sole maize and 2259 g m⁻² for intercropped maize. The average water use was 405 mm in sole wheat, 595 mm in sole maize and 711 mm in wheat-maize intercropping. Based on observed yields, the land equivalent ratio (LER) was 1.59 and the water equivalent ratio (WER) was 1.14, where LER and WER express the relative amounts of land and water needed to achieve the yields obtained in a unit area of intercrop using sole crops. These results indicate that relay strip intercropping of wheat and maize achieves an increase of land use efficiency of 59% and of water use efficiency of 14%. Overall the intercrop model gave satisfactory predictions, with coefficients of efficiency (CE) in validation of 0.86–0.97, 0.90–0.95, 0.85–0.91 and 0.98 for biomass of sole wheat, sole maize, intercropped wheat, and intercropped maize, respectively. Overall CE of water use was 0.95. Simulated LER and WER were similar to observed LER and WER. The results show that intercropping could be used to obtain more yield on less land with less water. Policies that limit water use per unit land and prohibit the use of intercropping on the basis of its high water use per unit area may therefore be counter-productive. The model for intercrop growth and development under water limitation may be used for exploring production possibilities under land and water constraints.
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Intercropping is known to increase the efficiency of land use, but no meta-analysis has so far been made on the yield gain of intercropping compared to sole cropping in terms of absolute yield per unit area. Yield gain could potentially be related to a relaxation of competition, due to complementarity or facilitation, and/or to the competitive dominance of the higher yielding species. The contributions of competitive relaxation and dominance were here estimated using the concepts of complementarity effect (CE) and selection effect (SE), respectively. We compiled a dataset on intercropping of grain-producing crops from China, a hotspot of strip intercropping in the world. We quantified the yield gain and its components and analysed the contribution to yield gain of species traits (C3, C4, legume, non-legume), complementarity in time and nutrient input. Total yield in intercrops exceeded the expected yield, estimated on the basis of sole crop yields, by 2.14 ± 0.16 Mg ha −1 (mean ± standard error). Ninety percent of this yield gain was due to a positive CE while the remaining 10 % was due to SE. The net yield gain increased with temporal niche differentiation (TND) which is the proportion of the total growing period of the crop mixture during which species grow alone. The mechanism underlying yield gain shifted from competitive dominance of the higher yielding species when there was more overlap in growth period between the two species, to competitive relaxation when there was less overlap, while competitive relaxation remained the major component of the yield gain. The yield gain was substantially greater in intercrops with maize than in intercrops without maize, but there was no difference in yield gain between systems with and without legumes. The yield gain increased with nitrogen (N) input in maize/C3-cereal inter-crops but not in cereal/legume intercrops, illustrating the ability of legumes to compensate for low N input, and highlighting the need for N input for high productivity in intercropping systems without legumes. Yield gain did not respond to phosphorus (P) input. We conclude that competitive relaxation is the main contributing factor to yield gain in the investigated Chinese intercropping systems, which were mostly relay strip intercropping systems. The underlying drivers of yield gain were related to presence of maize and species complementarity in time, but we did not find strong evidence for the selection effect.
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Growing mixtures of annual arable crop species or genotypes is a promising way to improve crop production without increasing agricultural inputs. To design optimal crop mixtures, choices of species, genotypes, sowing proportion, plant arrangement, and sowing date need to be made but field experiments alone are not sufficient to explore such a large range of factors. Crop modeling allows to study, understand, and ultimately design cropping systems and is an established method for sole crops. Recently, modeling started to be applied to annual crop mixtures as well. Here, we review to what extent crop simulation models and individual-based models are suitable to capture and predict the specificities of annual crop mixtures. We argued that (1) the crop mixture spatio-temporal heterogeneity (influencing the occurrence of ecological processes) determines the choice of the model-ing approach (plant or crop centered). (2) Only few crop models (adapted from sole crop models) and individual-based models currently exist to simulate annual crop mixtures. Crop models are mainly used to address issues related to both crop mixtures management and the integration of crop mixtures into larger scales such as the rotation. In contrast, individual-based models are mainly used to identify plant traits involved in crop mixture performance and to quantify the relative contribution of the different ecological processes (niche complementarity, facilitation, competition, plasticity) to crop mixture functioning. This review highlights that modeling of annual crop mixtures is in its infancy and gives to model users some important keys to choose the model based on the questions they want to answer, with awareness of the strengths and weaknesses of each of the modeling approaches.
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p>Intercropping entails the concurrent production of two or more crop species in the same field. This traditional farming method generally results in a highly efficient use of land, but whether it also contributes to a higher technical efficiency remains unclear. Technical efficiency refers to the efficiency with which a given set of natural resources and other inputs can be used to produce crops. In this study, we examined the contribution of maize-based relay-strip intercropping to the technical efficiency of smallholder farming in northwest China. Data on the inputs and crop production of 231 farms were collected for the 2013 agricultural season using a farm survey held in Gaotai County, Gansu Province, China. Controlling for other factors, we found that the technical efficiency scores of these farms were positively affected by the proportion of land assigned to intercropping. This finding indicates that the potential negative effects of intercropping on the use efficiency of labour and other resources are more than offset by its higher land-use efficiency when compared with monocropping.</p
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Traditional maize (Zea mays L.) and soybean (Glycine max (L) Merrill) intercropping practice cannot be adapted to modern agriculture due to low light use efficiency, radiation use efficiency, low comparative profits of soybeans and incompatibility with mechanization. However, a new type of maize and soybean intercropping system (MSIS) with high land equivalent ratio (LER) provides substantial benefits for small-land hold farmers worldwide. Our research team has done a wide range of research to suggest the appropriate planting geometry that ensures high yield and LER as high as 2.36, nutrient acquisition and mechanical operations in MSISs. Increase in the distance between soybean and maize rows and decrease in the spacing of maize narrow rows is useful for the high light interception for the short soybean in MSISs. This review concludes that MSIS has multifold and convincing results of LER and compatible with mechanization, while those practiced other than China still require technolo-gical advancements, agronomic measures and compatible mechanization to further explore its adaptability.
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Due to an unfortunate turn of events, the names of the authors appeared incorrectly in the original publication as given names and family names have been reversed. The correct representation of the authors’ names is listed above and below and should be treated as definitive.
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Lentil has been overlooked by organic farmers in Europe mainly because of low and unstable yields, notably due to lodging and bruchid beetles. Our study aimed to evaluate the efficiency of lentil-spring wheat intercrops to lower these reducing factors and increase yield and gross margin. A 2-year field experiment was carried out in southwestern France in 2015 and 2016 under organic farming rules. Four lentil and two wheat cultivars were grown as sole crops and intercrops. The “yield gap” concept was adapted to include grain losses due to mechanical harvest and insufficient quality. Mean total intercrop grain yield before mechanical harvest was higher than mean sole crop (1.91 ± 0.47 vs. 1.57 ± 0.29 t ha−1, respectively), with a lower mean yield of lentil in intercrop than in sole crop (1.06 ± 0.28 vs. 1.61 ± 0.54 t ha−1). This led to a lower mean gross margin of intercrop than that of sole cropped lentil (1772 ± 507 vs. 2371 ± 756 € ha−1), before mechanical harvest. The percentage of bruchid-damaged grain did not differ significantly between intercrop and sole crop (41%). However, lentil lodging was lower in intercrop than in sole crop (15 vs. 40%), which strongly increased lentil mechanical harvest efficiency (75 vs. 50%). This led to a similar mechanically harvested yield of lentil in intercrop and sole crop (0.80 t ha−1). Consequently, mean marketable gross margin of intercrops was higher than that of sole cropped lentil (949 ± 404 vs. 688 ± 393 € ha−1), due to the addition of marketable wheat yield. We thus demonstrated for the first time the interest of extending the yield gap concept to consider all grain losses that influence profitability, including those linked to mechanical harvest efficiency and insufficient grain quality. Furthermore, this is a first demonstration of the higher profitability of organic lentil-wheat intercrops compared to sole crops despite the additional costs associated with grain sorting.
Book
The practice of growing two or more crops together is widespread throughout the tropics and is becoming increasingly practised in temperate agriculture. The benefits of nutrient exchange, reduced weed competition and pathogen control can generate substantial improvements in growth and yield. In this book John Vandermeer, a leading worker on the subject, shows how classical ecological principles, especially those relating to competition and population ecology, can be applied to intercropping. Despite the large amount of research activity directed towards the subject over the last 20 years, the practice of intercropping has, until now, received very little serious academic attention. The Ecology of Intercropping is unique in approaching the question of intercropping from a theoretical point of view. In addition the details of the approach will take as their starting point well-accepted ecological theory. Using this basis the author shows how the approach can be used to design and evaluate intercropping systems to improve agricultural yields.
Preprint
Growing mixtures of annual arable crop species or genotypes is a promising way to improve crop production without increasing agricultural inputs. To design optimal crop mixtures, choices of species, genotypes, sowing proportion, plant arrangement, and sowing date need to be made but field experiments alone are not sufficient to explore such a large range of factors. Crop modeling allows to study, understand and ultimately design cropping systems and is an established method for sole crops. Recently, modeling started to be applied to annual crop mixtures as well. Here, we review to what extent crop simulation models and individual-based models are suitable to capture and predict the specificities of annual crop mixtures. We argued that: 1) The crop mixture spatio-temporal heterogeneity (influencing the occurrence of ecological processes) determines the choice of the modeling approach (plant or crop centered). 2) Only few crop models (adapted from sole crop models) and individual-based models currently exist to simulate annual crop mixtures. 3) Crop models are mainly used to address issues related to crop mixtures management and to the integration of crop mixtures into larger scales such as the rotation, whereas individual-based models are mainly used to identify plant traits involved in crop mixture performance and to quantify the relative contribution of the different ecological processes (niche complementarity, facilitation, competition, plasticity) to crop mixture functioning. This review highlights that modeling of annual crop mixtures is in its infancy and gives to model users some important keys to choose the model based on the questions they want to answer, with awareness of the strengths and weaknesses of each of the modeling approaches.