Cereal–legume intercropping is promoted within semi-arid regions as an adaptation strategy to water scarcity and drought for low-input systems. Our objectives were firstly to evaluate the crop model APSIM for pearl millet (Pennisetum glaucum (L.))—cowpea (Vigna unguiculata (L.) Walp) intercropping—and secondly to investigate the hypothesis that intercropping provides complimentary yield under drought conditions. The APSIM model was evaluated against data from a two year on station field experiment during the dry season of a semi-arid environment in Patancheru, India, with severe, partial and no water deficit stress (well-watered); densities of 17 and 33 plants per m⁻², and intercrop and sole crop production of pearl millet and cowpea. Overall, APSIM captured the dynamics of grain yields, indicated by the Willmott Index of Agreement (IA: 1 optimal, 0 the worst) 0.91 from 36 data points (n), total biomass (IA: 0.90, n = 144), leaf area index (LAI, IA = 0.77, n = 66), plant height (IA 0.96, n = 104 pearl millet) and cowpea (IA 0.81, n = 102), as well as soil water (IA 0.73, n = 126). Model accuracy was reasonable in absolute terms (RMSE pearl millet 469 kg/ha and cowpea 322 kg/ha). However, due to low observed values (observed mean yield pearl millet 1,280 kg/ha and cowpea 555 kg/ha), the relative error was high, a known aspect for simulation accuracy in low-yielding environments. The simulation experiment compared the effect of intercropping pearl millet and cowpea versus sole cropping under different plant densities and water supplies. A key finding was that intercropping pearl millet and cowpea resulted in similar total yields to the sole pearl millet. Both sole and intercrop systems responded strongly to increasing water supply, except sole cropped cowpea, which performed relatively better under low water supply. High plant density had a consistent effect, leading to lower yields under low water supply. Higher yields were achieved under high density, but only when water supply was high: absolute highest total intercrop yields were 4,000 (high density) and 3,500 kg/ha (low density). This confirms the suitability of the common practice among farmers who use the low planting density under water scarce conditions. Overall, this study confirms that intercropping is no silver bullet, i.e. not per se a way to achieve high yield production or reduce risk under drought. It does, however, provide an opportunity to diversify food production by additionally integrating protein rich crops, such as cowpea.

中文翻译：

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Can intercropping be an adaptation to drought? A model-based analysis for pearl millet–cowpea,间作可以适应干旱吗？基于模型的珍珠粟-豇豆分析

Cereal–legume intercropping is promoted within semi-arid regions as an adaptation strategy to water scarcity and drought for low-input systems. Our objectives were firstly to evaluate the crop model APSIM for pearl millet (Pennisetum glaucum (L.))—cowpea (Vigna unguiculata (L.) Walp) intercropping—and secondly to investigate the hypothesis that intercropping provides complimentary yield under drought conditions. The APSIM model was evaluated against data from a two year on station field experiment during the dry season of a semi-arid environment in Patancheru, India, with severe, partial and no water deficit stress (well-watered); densities of 17 and 33 plants per m⁻², and intercrop and sole crop production of pearl millet and cowpea. Overall, APSIM captured the dynamics of grain yields, indicated by the Willmott Index of Agreement (IA: 1 optimal, 0 the worst) 0.91 from 36 data points (n), total biomass (IA: 0.90, n = 144), leaf area index (LAI, IA = 0.77, n = 66), plant height (IA 0.96, n = 104 pearl millet) and cowpea (IA 0.81, n = 102), as well as soil water (IA 0.73, n = 126). Model accuracy was reasonable in absolute terms (RMSE pearl millet 469 kg/ha and cowpea 322 kg/ha). However, due to low observed values (observed mean yield pearl millet 1,280 kg/ha and cowpea 555 kg/ha), the relative error was high, a known aspect for simulation accuracy in low-yielding environments. The simulation experiment compared the effect of intercropping pearl millet and cowpea versus sole cropping under different plant densities and water supplies. A key finding was that intercropping pearl millet and cowpea resulted in similar total yields to the sole pearl millet. Both sole and intercrop systems responded strongly to increasing water supply, except sole cropped cowpea, which performed relatively better under low water supply. High plant density had a consistent effect, leading to lower yields under low water supply. Higher yields were achieved under high density, but only when water supply was high: absolute highest total intercrop yields were 4,000 (high density) and 3,500 kg/ha (low density). This confirms the suitability of the common practice among farmers who use the low planting density under water scarce conditions. Overall, this study confirms that intercropping is no silver bullet, i.e. not per se a way to achieve high yield production or reduce risk under drought. It does, however, provide an opportunity to diversify food production by additionally integrating protein rich crops, such as cowpea.,在半干旱地区推广谷物-豆类间作，作为低投入系统对缺水和干旱的适应策略。我们的目标首先是评估珍珠粟 ( Pennisetum glaucum (L.)) - 豇豆 ( Vigna unguiculata (L.) Walp) 间作的作物模型 APSIM，其次是研究间作在干旱条件下提供互补产量的假设。在印度帕坦切鲁（Patancheru）半干旱环境的旱季，对 APSIM 模型进行了为期两年的现场试验数据评估，该环境具有严重、部分和无缺水压力（浇水充足）；每平方米 17 和 33 株植物的密度^-2，以及珍珠粟和豇豆的间作和单一作物生产。总体而言，APSIM 捕获了谷物产量的动态，由 36 个数据点 (n) 的 Willmott 协议指数（IA：1 最佳，0 最差）、总生物量（IA：0.90，n  = 144）、叶面积表示为 0.91指数（LAI，IA = 0.77，n  = 66），株高（IA 0.96，n  = 104 珍珠粟）和豇豆（IA 0.81，n  = 102），以及土壤水分（IA 0.73，n = 126)。模型精度在绝对值上是合理的（RMSE 珍珠粟 469 公斤/公顷和豇豆 322 公斤/公顷）。然而，由于观测值较低（观测到的平均产量珍珠粟 1,280 千克/公顷和豇豆 555 千克/公顷），相对误差很高，这是低产环境中模拟准确性的一个已知方面。模拟试验比较了不同种植密度和供水条件下珍珠粟和豇豆间作与单作的效果。一个重要的发现是，间作珍珠粟和豇豆的总产量与唯一的珍珠粟相似。单作和间作系统都对增加供水反应强烈，但单作豇豆除外，后者在低供水情况下表现相对较好。高植物密度具有一致的效果，导致低水供应下的产量降低。在高密度下实现了更高的产量，但只有在供水量高的情况下：绝对最高的间作总产量为 4,000（高密度）和 3,500 公斤/公顷（低密度）。这证实了在缺水条件下使用低种植密度的农民普遍做法的适用性。总体而言，这项研究证实间作不是灵丹妙药，即本身不是实现高产生产或降低干旱风险的方法。然而，它确实提供了一个机会，通过额外整合富含蛋白质的作物，如豇豆，使粮食生产多样化。这证实了在缺水条件下使用低种植密度的农民普遍做法的适用性。总体而言，这项研究证实间作不是灵丹妙药，即本身不是实现高产生产或降低干旱风险的方法。然而，它确实提供了一个机会，通过额外整合富含蛋白质的作物，如豇豆，使粮食生产多样化。这证实了在缺水条件下使用低种植密度的农民普遍做法的适用性。总体而言，这项研究证实间作不是灵丹妙药，即本身不是实现高产生产或降低干旱风险的方法。然而，它确实提供了一个机会，通过额外整合富含蛋白质的作物，如豇豆，使粮食生产多样化。