Dissertation Research: Nitrogen Dynamics in a Legume- Nonlegume Intercrop System

本研究的总体目标是量化豆科作物在豆科间作中产量高于单作的不同机制的贡献，并量化每种机制的贡献如何随间作距离的变化而变化。最终目标是利用这些信息来设计最佳的间作系统。被豆科植物包围的玉米植株的生物量和氮产量可能高于被同等密度的玉米植株包围的玉米植株，这可能是因为土壤氮的竞争减少（土壤氮对玉米的可用性更高）和/或由邻近的豆科植物固定的大气氮的转移，即促进作用。这两种来源可以通过向土壤中添加同位素氮来区分。相对于单作玉米，间作减少竞争会导致土壤氮素绝对含量的增加。促进会导致间作玉米中标记土壤氮的比例降低（大气源氮的比例增加）。

The overall goals of the proposed research are to quantify the contributions of different mechanisms by which nonlegumes yield more in intercrops with legumes than in monocultures and to quantify how the contribution of each mechanism varies with interplant distance. The ultimate goal is to use this information to design optimal intercrop systems. Biomass and nitrogen yield of a corn plant surrounded by legumes may be higher than that of a corn plant surrounded by an equal density of corn plants either because of reduced competition for soil nitrogen (greater availability of soil nitrogen to the corn) and/or the transfer of atmospheric nitrogen fixed by the neighboring legume plants, i.e facilitation. These two sources can be distinquished by adding isotopic nitrogen to the soil. Reduced competition would result in an increase in the absolute quantity of labeled soil nitrogen in the intercropped relative to monoculture corn. Facilitation would result in a decrease in the proportion of labeled soil nitrogen in the intercropped corn (increase in proportion of atmospheric-derived N).