Abstract:

【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. 【Method】 The methods of root barrier and 15N-isotope dilution were used to investigate the nitrogen transfer, nitrogen uptake and utilization in the two relay-planting systems.【Result】 Comparing the no barrier with solid barrier, the results showed that the 15N total uptake and crop recovery rate of wheat were highly remarkable and 15N% abundance and N% content of soil was lower obviously than that of solid barrier. In the wheat/maize/soybean system with no barrier, the 15N total uptake, 15N grain uptake, 15N crop recovery rate, soil 15N% abundance and N% content of maize increased by 17.62%, 24.52%, 17.63%, 13.9% and 10.1%, respectively. But in the wheat/maize/sweetpotato system with no barrier, the value of above index reduced by 50.19%, 42.58%, 33.42%, 29.6% and 5.2%, respectively. For soybean, the 15N total uptake, 15N grain uptake, and 15N crop recovery rate reduced, but the soil N% content increased by 6.06%. For sweetpotato, the 15N total uptake and crop recovery rate increased, but soil 15N% abundance and N% content reduced by 0.9% and 4.95%. 【Conclusion】 There existed nitrogen interspecific competition and facilitation and nitrogen transfer in the two relay-planting systems. In the wheat/maize/soybean system, the nitrogen uptake from fertilizer, soil fertility remaining and sustainable crop production were better than the system of wheat/maize/sweetpotato.

Key words: wheat/maize/soybean')">wheat/maize/soybean, wheat/maize/sweetpotato, replay-planting, nitrogen uptake and utilization, nitrogen transfer, 15N-isotope dilution