【Objective】 The aim of this paper was to study the mechanisms of interspecific nitrogen facilitation and transfer in the relay-planting systems of wheat/maize/soybean and wheat/maize/sweet potato.

A root barrier pot experiment was employed to investigate the nitrogen uptake and utilization and interspecies reciprocity of "wheat/maize/soybean" and "wheat/maize/sweet potato".

By adopting the double optimal value method,the annual optimal amount of nitrogen fertilizer and the ratio of nitrogen fertilizer distributed among crops in the relay-planting system of "wheat/maize/soybean" were studied.

In order to establish a set of high efficiency regeneration system of wheat haploid from wheat×maize which induce wheat DH groups,factors affecting the frequency of haploid embryo and young plant production,such as culture condition,environmental temperature and T>10℃ effective accumulated temperature,etc.

The yield ( Ye ), water use efficiency ( WUE ), leaf area duration (LAD ), and crop growth rate ( CGR ) in the compound canopy of intercropped wheat and maize were analyzed under limited supplemental irrigation with water harvesting in dryland.

Relationships between photosynthetic characteristics and productivity of wheat/corn multiple canopy;