Interactive influence of nitrogen and phosphorus application rate on wheat yield in North Henan, China
氮磷用量对豫北地区小麦产量的交互效应研究

A pot experiment was conducted to evaluate the interactive effects of nitrogen and phosphorus fertilizer application rates on wheat yield via measuring agronomic and physiologic indicators such as root activity (RA), acid phosphatase activity (APA) and nitrate reductase activity (NRA). Six treatments 200 kg(N)·hm-2+100 kg(P2O5)·hm-2, 200 kg(N)·hm-2+160 kg(P2O5)·hm-2, 220 kg(N)·hm-2+100 kg(P2O5)·hm-2, 220 kg(N)·hm-2+160 kg(P2O5)·hm-2, 240 kg(N)·hm-2+100 kg(P2O5)·hm-2 and 240 kg(N)·hm-2+160 kg(P2O5)·hm-2] were used in the study. The highest wheat yield occurs under the combination application of 220 kg(N)·hm-2, 160 kg(P2O5)·hm-2. Wheat yield is significantly correlated with RA, APA and NRA, and is in turn strongly related with wheat cumulative N and P. RA, APA and NRA increase with increasing application rate of phosphorus and nitrogen, but continue to increase until the application rate of nitrogen reaches 220 kg·hm-2 before declining. This indicates that over-application of nitrogen fertilizer might reduce RA, APA and NRA, which in turn reduce the absorption rate of N and P and thereby decreasing wheat yield.