套作模式下玉米和大豆根际土壤磷有效性研究

Intercropping system plays a significant role to strengthen the agro-ecosystems of biological diversity and ecological stability, is one of the main direction of research and development of ecological agriculture. However, the crop species in intercropping system have competitive inhibition or promoting effects in nutrient uptake. Currently only a small number of studies have shown that intercropping leguminous and cereal crops can be increased the utilization of soil phosphorus through the possbile promoting interaction effect of the roots of inter-species, whether such a system is conducive to the utilization of soil phosphorus and the control mechanism of soil phosphorus utilization needs further study. Corn and soybean are major grain and forage crops in China. There are lots of studies on soil nitrogen utilization in corn/soybean intercropping system so far, whereas the bioavailability of rhizosphere soil phosphorus in corn/soybean intercropping system is still a lack of systematic research. The object of this project is to study the rhizosphere soil phosphorus forms transformation and bioavailability in corn/soybean intercropping system in the typical purple soil area in Sichuan province. By using a combination of field trials and pot experiments to study the rhizosphere soil phosphorus bioavailability in three cropping patterns, including corn/soybean intercropping and corn or soybean sole cropping, we try to illustrate that the rhizosphere soil phosphorus transformation mechanism in corn/soybean intercropping system. The study results can support theoretical basis for improving the utilization of soil phosphorus and developing the excellent planting patterns in order to keep the sustainable fertility of purple soil in Southwest China.

间套作体系对农业生态系统的生物多样性及生态强化起着巨大作用，是生态农业研究与发展的主要方向之一。然而，间套作模式下作物种间在养分吸收利用上存在竞争或促进作用。目前仅少数研究表明豆科和禾本科作物间套作可能是因为作物根系的交互作用而提高了土壤磷利用率，究竟这种体系是否有利于作物对土壤磷的利用以及操纵土壤磷利用率的机制如何有待于进一步研究。玉米和大豆是我国主要的粮饲作物，目前有关玉米/大豆间套作体系对土壤氮的吸收利用已有较多研究，而对此模式下作物根际土壤磷的有效性尚缺乏系统研究。本项目以四川紫色土区的典型旱地农田系统为研究对象，采用大田试验和盆栽试验相结合的研究方法来研究玉米/大豆套作及大豆净作、玉米净作模式下作物根际土壤磷形态转化及生物有效性，进而阐明套作模式下大豆和玉米根际土壤磷的形态转化机制，以其为提高土壤磷利用率，发展西南地区优良的种植模式及紫色土肥力可持续发展提供理论依据。

在耕地资源紧缺，磷肥利用率低的农业生产背景下，本项目利用田间定位试验和盆栽试验，研究了玉米/大豆套作模式下作物根际土壤磷素有效性。盆栽试验结果表明，在作物株距较小，种植模式为替代式套作的情况下，套作提高了单株玉米和单株大豆的地上部生物量、籽粒产量、植株吸磷量，以及根际土壤磷素有效性。田间小区试验表明，在田间作物株距适中，种植模式为添加式套作的情况下，套作玉米显著提高了土壤磷素利用率，随着种植年限的增加，施磷与否对套作玉米产量及吸磷量影响逐年减小。由于种植地区多雨，日照条件交差，套作大豆的产量显著低于单作大豆，而套作玉米和单作玉米产量差异不大。根箱试验结果表明，套作模式下，根系交互作用提高了玉米灌浆期根际土壤NaHCO3-Po和NaHCO3-Pi含量，促进玉米对NaOH-Pi的吸收利用。大豆对土壤残留磷具有较强的活化作用。得出结论，玉米/大豆套作系统通过作物种间根系交互作用及年际间轮作效应提高了土壤磷素利用率，在生产中可以考虑减少化学磷肥的施用。该结果对当前农业生产中提倡的减少肥料施用，利用生物多样性来提高肥料利用率的目标具有重要的理论指导意义。