Irrigated lowland systems contribute most to rice production in sub-Saharan Africa and play a critical role in meeting the increasing rice demand. However, in dry areas of West Africa, negative effects associated with climate change and widespread water scarcity hamper efforts to increase the productivity of irrigated rice. Quantifying rice yields and water productivity and identifying the drivers for the prevailing variability can aid in the targeting and dissemination of appropriate soil, water, and crop management practices. The main objectives of this research were: (i) to quantify the rice yield gap in representative irrigated systems in dry areas of West Africa, both in wet and dry seasons, and identify factors that can contribute to narrowing the gap, and (ii) to assess the trade-offs or synergies between productivity and resource (water and fertiliser) use efficiency. We monitored 203 and 192 smallholder farmers’ fields in the wet and dry seasons, respectively, in four contrasting irrigation schemes in Burkina Faso from 2018 to 2020 and assessed key performance indicators (grain yield, water productivity, and nutrient use efficiency). We calculated rice yield gaps (difference between exploitable and actual farmer yields) and identified the drivers of variability of yield and water productivity using machine learning and Shapley Additive exPlanations (SHAP) feature importance. Indicators of productivity and sustainability differed between irrigation schemes and seasons. Rice yield was higher in wet (5.3 Mg ha) than in dry seasons (3.7 Mg ha), while the variability was higher in the dry (CV = 46%) than in the wet seasons (CV = 29%). Also, the yield gap was slightly higher in the dry (36%) than in the wet seasons (31%). While differences in the number of seedlings per hill and the source of seeds were the key drivers of yield variability in wet-season rice, the split of N fertilizer applications, bird control, and the soil dryness index were the most important in dry-season rice. Furthermore, within seasons, high-yielding fields had higher water productivity, and N, P, and K use efficiencies. These findings suggest that rice yields can be increased without trade-offs with water productivity and nutrient use efficiencies. This is the first study highlighting the season-specificity of determinants of variability of yield and water productivity in irrigated rice in West Africa. Improved water and fertilizer management can contribute to achieving the dual goal of narrowing the yield gap and improving water productivity, while increasing nutrient use efficiency, particularly in the dry season.

中文翻译：

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提高西非干旱气候区的水稻产量和水生产率：针对特定季节的策略


低地灌溉系统对撒哈拉以南非洲的水稻生产贡献最大，在满足日益增长的水稻需求方面发挥着关键作用。然而，在西非干旱地区，气候变化和普遍缺水带来的负面影响阻碍了提高灌溉水稻生产力的努力。量化水稻产量和水生产率并确定普遍变异的驱动因素有助于确定和传播适当的土壤、水和作物管理实践。这项研究的主要目标是：(i) 量化西非干旱地区代表性灌溉系统在雨季和旱季的水稻产量差距，并确定有助于缩小差距的因素，以及 (ii)评估生产力和资源（水和肥料）利用效率之间的权衡或协同作用。我们在 2018 年至 2020 年期间分别监测了布基纳法索四个对比灌溉方案的雨季和旱季 203 个和 192 个小农田，并评估了关键绩效指标（粮食产量、水生产率和养分利用效率）。我们计算了水稻产量差距（可利用产量与实际农民产量之间的差异），并使用机器学习和沙普利附加解释（SHAP）特征重要性确定了产量和水生产率变异的驱动因素。生产力和可持续性指标因灌溉计划和季节而异。水稻产量在雨季（5.3 毫克·公顷）高于旱季（3.7 毫克·公顷），而旱季变异性（CV = 46%）高于雨季（CV = 29%）。此外，旱季的产量差距（36%）略高于雨季的产量差距（31%）。 虽然每山秧苗数量和种子来源的差异是湿季水稻产量变异的关键驱动因素，但氮肥施用、鸟类控制和土壤干燥指数的分配是旱季最重要的因素米。此外，在季节内，高产田的水分生产率和氮、磷、钾利用率较高。这些发现表明，无需牺牲水生产率和养分利用效率即可提高水稻产量。这是第一项强调西非灌溉水稻产量和水生产力变异性决定因素的季节特异性的研究。改善水和肥料管理有助于实现缩小产量差距和提高水生产率的双重目标，同时提高养分利用效率，特别是在旱季。