黄土高原间作大豆对幼龄果园土壤水分及氮素累积的影响

为探明间作豆科作物对幼龄果园土壤水分、硝态氮含量以及树木生长的影响，并对黄土高原旱作果园土壤肥力提升与可持续发展提供指导，以黄土丘陵区苹果/黄豆复合系统为研究对象，通过测定种植黄豆整个生育期内试验小区水分、硝态氮含量以及果树叶片含氮量和生理指标的变化来评价不同间作密度黄豆对果树生长的影响。结果表明：(1)相较于清耕果园，中密度间作在黄豆花期前对果园土壤水分含量有一定的提升作用，而高密度间作加剧行间水分的消耗，显著降低土壤含水量。(2)不同土层硝态氮相对累积量随黄豆生育期后移呈现逐渐下移且分布逐渐均衡的趋势，土壤总硝态氮累积量处理间未表现出显著差异。(3)中、高密度间作均可有效提升果树叶片氮含量，促进果树生长，而中密度间作黄豆使土壤含水量最高提升17.6%,叶片氮含量最高增加8.04%。因此，中密度间作黄豆在黄土高原旱作苹果园更具有间作优势。

Effects of Intercropping Soybean on Soil Water and Nitrogen Accumulation in Young Orchards on the Loess Plateau

It is of great significance to investigate the effects of intercropping leguminous crops on soil moisture, nitrate nitrogen content and tree growth in young orchards for the improvement of soil fertility and sustainable development of dryland orchards on the Loess Plateau. Taking apple-soybean compound system in the loess hilly-gully region as the research object, the influence of different density of intercropping soybean on fruit tree growth were evaluated by measuring the changes in water and nitrate nitrogen content, as well as the nitrogen content and physiological indicators of fruit tree leaves in the experimental plot during the entire reproductive period of soybean planting. The results showed as follows:(1) Compared with clear tillage orchard, medium density intercropping had a certain effect on the soil moisture content of orchard before soybean flowering, while high density intercropping increased the water consumption between rows and significantly reduced the soil moisture content. (2) The relative accumulation of nitrate nitrogen in different soil layers gradually decreased and the distribution gradually balanced with the reproductive period of soybean, and there was no significant difference in the total nitrate nitrogen accumulation of soil between treatments. (3) Both medium and high density intercropping could effectively increase the leaf nitrogen content of fruit trees and promote fruit trees growth. Soil water content and leaf nitrogen content of medium density soybean intercropping increased by a maximum of 17.6% and 8.04% respectively. Therefore, medium density soybean intercropping had more advantages in dryland apple orchards on the Loess Plateau.