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Nitrogen use efficiency of monoculture and hedgerow intercropping in the humid tropics

机译：热带湿润地区单作和树篱间作的氮利用效率

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摘要

The design of productive and efficient intercropping systems depends on achieving complementarity between component species’ resource capture niches. Spatiotemporal patterns of capture and use of pruning and urea nitrogen (N) by trees and intercrops were elucidated by isotopic tracing, and consequences for nitrogen use efficiency were examined. During the first cropping season after applying urea−15N, maize accounted for most of the plant 15N recovery in Peltophorum dasyrrachis (33.5%) and Gliricidia sepium (22.3%) hedgerow intercropping systems. Maize yield was greatest in monoculture, and maize in monoculture also recovered a greater proportion of urea 15N (42%) than intercropped maize. Nitrogen recovery during active crop growth will not be increased by hedgerow intercropping if hedgerows adversely affect crop growth through competition for other resources. However, hedgerows recovered substantial amounts of 15N during both cropping cycles (e.g. a total of 13–22%), showing evidence of spatio-temporal complementarity with crops in the spatial distribution of roots and the temporal distribution of Nuptake. The degree of complementarity was species-specific, showing the importance of selecting appropriate trees for simultaneous agroforestry. After the first cropping season 17–34% of 15N applied was unaccounted for in the plant-soil system. Urea and prunings N were recovered by hedgerows in similar amounts. By the end of the second (groundnut) cropping cycle, total plant 15N recovery was similar in all cropping systems. Less N was taken up by the maize crop from applications of labelled prunings (5–7%) than from labelled urea (22–34%), but the second crop recovered similar amounts from these two sources, implying that prunings N is more persistent than urea N. More 15N was recovered by the downslope hedgerow than the upslope hedgerow, demonstrating the interception of laterally flowing N by hedgerows.
机译：生产高效的套作系统的设计取决于实现组成物种资源捕获壁ni之间的互补性。通过同位素示踪阐明了树木和间作对树木和间作的捕获和使用修剪和尿素氮（N）的时空模式，并研究了其对氮素利用效率的影响。在施用尿素-15 N后的第一个种植季节中，玉米占据了Psytophorum dasyrrachis（33.5％）和Gliricidia sepium（22.3％）树篱间作系统中植物15 N回收的大部分。单作玉米产量最高，单作玉米比间作玉米还回收更多比例的尿素15 N（42％）。如果树篱通过竞争其他资源而对作物的生长产生不利影响，则作物间作不会增加活跃作物生长过程中的氮素回收。但是，在两个种植周期中，树篱恢复了大量的15 N（例如总计13–22％），显示出根的空间分布和Nuptake的时间分布与作物时空互补的证据。互补程度是特定于物种的，这表明为同时农林业选择合适的树木非常重要。在第一个播种季节后，植物-土壤系统中未施用的15 N中有17-34％未占。绿篱中回收的尿素和修剪N量相近。在第二个（花生）种植周期结束时，所有种植系统的总植物15 N回收率相似。施用玉米标签的修剪作物（5-7％）吸收的氮量少于使用尿素的标签（22-34％）吸收的氮，但是第二种作物从这两个来源回收的氮量相似，这表明修剪的氮元素更加持久。比尿素氮高。下坡树篱比上坡树篱能回收更多的15 N，这表明树篱可以拦截侧向流动的氮。

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