文献类型： 外文期刊

第一作者： Yinbo, G

作者： Yinbo, G;Peoples, MB;Rerkasem, B

作者机构：

关键词： N fertilizer;N-2 fixation;starter N;Xylem ureides;vegetable soybean

期刊名称：FIELD CROPS RESEARCH （ 影响因子：5.224； 五年影响因子：6.19 ）

ISSN： 0378-4290

年卷期： 1997 年 51 卷 3 期

页码：

收录情况： SCI

摘要： Vegetable soybean (Glycine max) is a lucrative cash crop predominantly grown in Japan, Taiwan, China, Thailand, and Vietnam. Although soybean has the capacity to satisfy a large proportion of its own nitrogen (N) requirements via N-2 fixation, farmers are recommended to apply several side-dressings of fertilizer N during growth in the belief that this will maximize pod yield. A field experiment was conducted in northern Thailand to evaluate the effect of six different N fertilizer management strategies on crop growth and marketable pod yield of vegetable soybean and to assess the impact of fertilization on the potential carry-over of residual fixed N remaining after harvest. A vegetable soybean crop was supplied with 25 kg N ha(-1) ammonium sulphate as starter N at sowing, then areas of the crop either received no further fertilizer N, or received one (50 kg N ha(-1)), or two (50 + 25 kg N ha(-1)) urea top-dressings at different stages of vegetative and/or reproductive growth. The field trial demonstrated that the appropriate timing of N fertilization could improve both crop growth and pod yield. Crop biomass was increased by 11 to 16% and pod yield improved by up to 44% if starter N was followed by a single top-dressing at either early vegetative growth or at flowering. However, there was no additional benefit from the standard farmer practice of supplying two top-dressings prior to flowering. However, if an early vegetative application of fertilizer N was followed by a second dressing either during flowering or pod-fill a further 20% increase in marketable pod yield was achieved. The effect of fertilizer N on soybean's capacity to fix N was complex. The proportion of plant N derived from N-2 fixation (Pfix) was highest when only starter N was applied (seasonal average of 84% of crop N coming from N-2 fixation). Any further top-dressing with N-fertilizer depressed nodulation and Pfix, but also increased crop growth so that amounts of N-2 fixed were similar for most fertilizer treatments (adjusted to account for below-ground N: 149 to 153 kg N ha(-1) cf 147 kg N ha(-1) fixed in the presence of starter N alone). However, N-2 fixation was significantly depressed by the farmer practice of top-dressing N twice before flowering (117 kg fixed N ha(-1)), and was highest when fertilizer N was supplied during a period of peak N demand at pod filling (180 kg N ha(-1)). Between 53 and 92 kg N ha(-1) was removed from the crop in marketable pods. But since N, fixation remained the dominant N source for crop growth in all treatments, substantial amounts of fixed N (64 to 91 kg of fixed N ha(-1)) were estimated to remain in leaf, stem and root residues after harvest. However, the potential N benefit from including vegetable soybean in a cropping sequence disappeared if the above-ground residues were removed from the field as is the common practice in many Asian farming systems. (C) 1997 Elsevier Science B.V.

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