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首页> 美国卫生研究院文献>Elsevier Sponsored Documents >Understanding variability in the benefits of N2-fixation in soybean-maize rotations on smallholder farmers’ fields in Malawi
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Understanding variability in the benefits of N2-fixation in soybean-maize rotations on smallholder farmers’ fields in Malawi

机译：了解马拉维小农户田间玉米－玉米轮作中固氮作用的收益差异

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Soybean production can contribute to the nitrogen economy of smallholder farming systems, but our understanding of factors explaining variability in nitrogen fixation and rotational benefits across farms and regions is limited. Biological nitrogen fixation (BNF) was quantified with the natural abundance method in 150 farmer-managed soybean plots under different varieties and inputs in Dowa, Mchinji and Salima districts of Malawi. Soybean yielded on average 1.2 t ha−1 grain and the above-ground biomass at mid pod filling (R5.5) was 2.8 t ha−1 and contained in total 63 kg ha−1 nitrogen derived from the atmosphere (Ndfa). Locally sourced varieties obtained a larger %Ndfa (65%) than the ‘improved’ variety Nasoko (53%). The %Ndfa was positively associated with soil sand content, sowing date, plant population and biomass accumulation, but it was not affected by inoculation with rhizobia or the combination of inoculation and NPK fertiliser application. Quantities of N2 fixed differed between regions and years, and was enhanced by applying inoculant and fertiliser together, leading to more biomass accumulation and larger grain yields. Soil available P and exchangeable K contents also increased the total amount of N2 fixed. In a related trial, continuous maize yields were compared with maize following soybean in 53 farmer-managed fields. Average yield in continuous maize was 2.5 t ha−1, while maize after soybean produced 3.5 t ha−1 (139% of continuous maize). Farmers with higher maize yields, who applied external nutrient inputs, and with a larger value of household assets achieved greater yield responses to rotation with soybean. A relative yield increase of more than 10% was observed on 59, 90 and 77% of the fields in Dowa, Mchinji and Salima respectively. We conclude that fields of soybean and maize that receive adequate nutrient inputs and good management to ensure good yields benefit most in terms of quantities of N2 fixed by the legume and the yield response of the following maize crop. The results suggest that the promotion of soybean-maize rotations should be done through an integrated approach including the promotion of appropriate soil and crop management techniques. Furthermore, they suggest that wealthier households are more likely to apply adequate nutrient inputs and good crop management practices and are likely to receive larger maize yield responses to the incorporation of soybean.
机译：大豆生产可以促进小农耕作系统的氮经济，但是我们对解释不同农场和地区固氮和轮作收益变化的因素的理解是有限的。使用自然丰度法对马拉维Dowa，Mchinji和Salima地区不同品种和投入的150个农民管理的大豆田进行了生物固氮（BNF）定量分析。大豆平均单产1.2 tha -1 谷物，中荚（R5.5）灌浆时地上生物量为2.8 t ha -1 ，总共包含63源自大气（Ndfa）的kg ha -1 氮。与“改良”品种Nasoko（53％）相比，本地来源的品种获得的％Ndfa（65％）更大。 ％Ndfa与土壤沙含量，播种期，植物种群和生物量积累呈正相关，但不受根瘤菌接种或接种与NPK肥料结合使用的影响。固定的N 2的数量在地区和年份之间有所不同，并且通过一起使用孕育剂和肥料而增加，从而导致更多的生物量积累和更大的谷物产量。土壤有效磷和可交换钾含量也增加了固定氮的总量。在一项相关试验中，在53个农民管理的田地中，将连续玉米产量与大豆种植后的玉米产量进行了比较。连续玉米的平均产量为2.5 t ha -1 ，而大豆生产后的玉米平均产量为3.5 t ha -1 （占连续玉米的139％）。玉米单产较高的农民采用外部营养输入，家庭资产价值较大，对轮作大豆的单产反应更大。分别在Dowa，Mchinji和Salima的59、90和77％的田地上发现相对增产超过10％。我们得出的结论是，就豆科植物固定的N2数量和后续玉米作物的产量响应而言，接受充足养分投入和良好管理以确保高产的大豆和玉米田对大多数人有利。结果表明，应通过综合方法来促进大豆－玉米轮作，包括推广适当的土壤和作物管理技术。此外，他们认为，较富裕的家庭更有可能采用适当的营养投入和良好的作物管理规范，并可能因掺入大豆而获得更大的玉米单产响应。

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