小麦/玉米/大豆和小麦/玉米/甘薯套作的氮素吸收利用及氮肥残效研究

采用¹⁵N土壤稀释标记法研究了“小麦/玉米/大豆”和“小麦/玉米/甘薯”(以下简称“麦/玉/豆”和“麦/玉/薯”)在不同根系分隔方式下的氮素吸收利用及氮肥残效。结果表明,不分隔与完全分隔相比,2种体系的小麦植株¹⁵N当季吸收量和回收率提高,土壤残留¹⁵N%丰度及总N含量降低;“麦/玉/豆”的玉米植株¹⁵N当季吸收量和回收率提高25.16%和25.16%,玉米土壤残留¹⁵N%丰度及总N含量提高13.89%和10.15%,“麦/玉/薯”的则分别降低15.98%,15.99%,17.37%和5.19%;大豆植株的¹⁵N当季吸收量和回收率、土壤残留¹⁵N%丰度降低,土壤总N含量提高3.03%;甘薯植株的¹⁵N当季吸收量和回收率提高,土壤残留¹⁵N%丰度和总N含量降低0.91%和4.95%。在利用前茬作物残留在土壤中的¹⁵N时,“麦/玉/豆”的小麦、玉米对残留¹⁵N的吸收量与回收率高于“麦/玉/薯”的小麦、玉米;大豆对前茬小麦、玉米残留¹⁵N的吸收量与回收率低于甘薯,对前茬大豆残留¹⁵N的吸收量与回收率高于甘薯。“麦/玉/豆”较“麦/玉/薯”更有利于作物间氮素的转移、周年氮肥的高效利用和土壤肥力保持。

Analysis of the nitrogen uptake and utilization efficiency and N fertilizer residual effect in the wheat-maize-soybean and wheat-maize-sweet potato relay strip intercropping

The aim of this paper was to study the mechanisms of interspecific nitrogen facilitation and transfer in the relay strip intercropping systems of “wheat/maize/soybean” and “wheat/maize/sweet potato”. The methods of root barrier and ¹⁵N-isotope dilution were used to investigate the nitrogen transfer, nitrogen uptake and residual effect in the two relay strip intercropping systems. Comparing the no barrier with solid barrier, the results showed that in-season ¹⁵N uptake and ¹⁵N recovery efficiency of wheat increased remarkably, and ¹⁵N% abundance left in soil and total N content reduced obviously. In the “wheat/maize/soybean” system, the in-season ¹⁵N uptake and ¹⁵N recovery efficiency, ¹⁵N% abundance left in soil and total N content of maize with no barrier increased by 25.16%, 25.16%, 13.89% and 10.15%. But in the “wheat/maize/sweet potato” system, the value of above indices reduced by 15.98%, 15.99%, 17.37% and 5.19%. For soybean, the in-season ¹⁵N uptake and ¹⁵N recovery efficiency, ¹⁵N% abundance left in soil reduced, the soil total N content increased by 3.03%. For sweet potato, the in-season ¹⁵N uptake and ¹⁵N recovery efficiency increased, ¹⁵N% abundance left in soil and total N content reduced by 0.91% and 4.95%. In the “wheat/maize/soybean” system, the ¹⁵N uptake and ¹⁵N recovery efficiency of wheat and maize obtained from previous wheat, maize and soybean were higher than that of the “wheat/maize/sweet potato” system. The ¹⁵N uptake and ¹⁵N recovery efficiency of soybean obtained from previous wheat or maize were lower than that of sweet potato, but that from previous soybean was higher than that from previous sweet potato. The “wheat/maize/soybean” system was more beneficial to increase annual nitrogen uptake, nitrogen residual effect and maintaining soil fertility.