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首页> 外文期刊>Plant and Soil >Niche-based assessment of contributions of legumes to the nitrogen economy of Western Kenya smallholder farms.
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Niche-based assessment of contributions of legumes to the nitrogen economy of Western Kenya smallholder farms.

机译：基于生态位的豆类对肯尼亚西部小农农场氮经济贡献的评估。

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Nitrogen (N) deficiency is a major constraint to the productivity of the African smallholder farming systems. Grain, green manure and forage legumes have the potential to improve the soil N fertility of smallholder farming systems through biological N2-fixation. The N2-fixation of bean (Phaseolus vulgaris), soyabean (Glycine max), groundnut (Arachis hypogaea), Lima bean (Phaseolus lunatus), lablab (Lablab purpureus), velvet bean (Mucuna pruriens), crotalaria (Crotalaria ochroleuca), jackbean (Canavalia ensiformis), desmodium (Desmodium uncinatum), stylo (Stylosanthes guianensis) and siratro (Macroptilium atropurpureum) was assessed using the 15N natural abundance method. The experiments were conducted at three sites in western Kenya, selected on an agro-ecological zone (AEZ) gradient defined by rainfall. On a relative scale, Museno represents high potential AEZ 1, Majengo medium potential AEZ 2 and Ndori low potential AEZ 3. Rainfall in the year of experimentation was highest in AEZ 2, followed by AEZ 1 and AEZ 3. Experimental fields were classified into high, medium and low fertility classes, to assess the influence of soil fertility on N2-fixation performance. The legumes were planted with triple super phosphate (TSP) at 30 kg P ha-1, with an extra soyabean plot planted without TSP (soyabean-P), to assess response to P, and no artificial inoculation was done. Legume grain yield, shoot N accumulation, %N derived from N2-fixation, N2-fixation and net N inputs differed significantly (P<0.01) with rainfall and soil fertility. Mean grain yield ranged from 0.86 Mg ha-1, in AEZ 2, to 0.30 Mg ha-1, in AEZ 3, and from 0.78 Mg ha-1, in the high fertility field, to 0.48 Mg ha-1, in the low fertility field. Shoot N accumulation ranged from a maximum of 486 kg N ha-1 in AEZ 2, to a minimum of 10 kg N ha-1 in AEZ 3. Based on shoot biomass estimates, the species fixed 25-90% of their N requirements in AEZ 2, 23-90% in AEZ 1, and 7-77% in AEZ 3. Mean N2-fixation by green manure legumes ranged from 319 kg ha-1 (velvet bean) in AEZ 2 to 29 kg ha-1 (jackbean) in AEZ 3. For the forage legumes, mean N2-fixation ranged from 97 kg N ha-1 for desmodium in AEZ 2 to 39 kg N ha-1 for siratro in AEZ 3, while for the grain legumes, the range was from 172 kg N ha-1 for lablab in AEZ 1 to 3 kg N ha-1 for soyabean-P in AEZ 3. Lablab and groundnut showed consistently greater N2-fixation and net N inputs across agro-ecological and soil fertility gradients. The use of maize as reference crop resulted in lower N2-fixation values than when broad-leaved weed plants were used. The results demonstrate differential contributions of the green manure, forage and grain legume species to soil fertility improvement in different biophysical niches in smallholder farming systems and suggest that appropriate selection is needed to match species with the niches and farmers' needs..
机译：氮缺乏是非洲小农农业系统生产力的主要制约因素。谷物，绿肥和饲草豆科植物具有通过生物固氮作用改善小农耕作系统土壤氮肥的潜力。豆（菜豆），大豆（大豆），花生（花生），利马豆（菜豆），扁豆（扁豆），鹿茸豆（M豆），猪屎豆（猪屎豆）、,豆的N2固定用15N自然丰度法评估了（Canavalia ensiformis），除mo（Desmodium uncinatum），铁笔（stylo（Stylosanthes guianensis）和siratro（Macroptilium atropurpureum）。该实验是在肯尼亚西部的三个地点进行的，地点是根据降雨确定的农业生态区（AEZ）梯度。在相对规模上，Museno代表高潜力AEZ 1，Majengo中潜力AEZ 2和Ndori低潜力AEZ3。在实验年份中，AEZ 2的降雨量最高，其次是AEZ 1和AEZ 3。 ，中低肥力类别，以评估土壤肥力对固氮性能的影响。豆科植物在30 kg P ha-1处种植三重超磷酸盐（TSP），并在没有TSP的情况下种植额外的大豆田（soyabean-P），以评估对P的反应，并且不进行人工接种。降雨和土壤肥力差异显着（P <0.01），豆科作物的籽粒产量，地上部氮积累，来自固氮，固氮和净氮输入的％N差异显着（P <0.01）。平均谷物产量在AEZ 2中为0.86 Mg ha-1，在AEZ 3中为0.30 Mg ha-1，在高肥力田中为0.78 Mg ha-1，在低肥力田中为0.48 Mg ha-1。肥沃的田野。氮素的累积量从AEZ 2的最大486 kg N ha-1到AEZ 3的最小10 kg N ha-1。根据芽生物量估计，该物种固定了其氮素需求的25-90％。 AEZ 2，在AEZ 1中占23-90％，在AEZ 3中占7-77％。平均由绿豆类农作物固氮的范围从AEZ 2中的319 kg ha-1（天鹅绒豆）到29 kg ha-1（波豆）。 ）在AEZ 3中。对于饲草豆科植物，平均N2固定范围从AEZ 2中的除臭剂的97 kg N ha-1到AEZ 3中的siratro的39 kg N ha-1，而对于谷物豆类，其范围为在AEZ中，lablab的172 kg N ha-1在AEZ 3中为大豆-P的3 kg Nha-1。Lablab和花生在农业生态和土壤肥力梯度范围内始终表现出更高的固氮和净氮输入。与使用阔叶杂草植物相比，将玉米用作参考作物可降低氮素固定值。结果表明，在小农耕作系统中，不同生物物理生态位的绿肥，牧草和谷物豆类物种对土壤肥力的贡献不同，并建议需要进行适当的选择，以使生态位和农民的需求相匹配。

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