Wheat yield, nutrient use efficiencies and soil nutrient balance under reduced fertilizer rate

ObjectivesExcessive chemical fertilizer application is unfavorable for sustainable agricultural development. It is important to conduct optimize fertilization experiment for achieving fertilizer zero increase in China.

MethodsTwo on-farm experiments were conducted in wheat-corn and wheat-rice rotation systems in a purple soil in the Sichuan Basin, southwest China. Taken conventional N, P₂O₅, K₂O input of 180, 120, 45 kg/hm² as control, reduced fertilizer rate (N, P₂O₅, K₂O input of 96, 60, 45 kg/hm²) in wheat was applied. The wheat yield and its components, grain filling characteristics, translocation of dry matter and chlorophyll contents of flag leaves at the post-anthesis, nutrient balance and use efficiency were investigated.

ResultsCompared with conventional fertilizer rate, wheat yield, the numbers of spikes, grains per spike and 1000-grain weight were not significantly changed under reduced fertilizer rate, expect for the 1000-grain weight in fields of wheat-maize cropping system. Based on the Logistic simulation model for the grain filling, the reduced fertilizer rate treatment significantly enhanced the maximum 1000-grain weight, the net increase of grain weight during the gradual and slow grain-filling periods, but not significant on other parameters. Reduced fertilizer rate increased the dry matter translocation, efficiency and contribution to grain by 28.5%, 17.5% and 20.7%, respectively, but accelerated the decline of chlorophyll in wheat flag leaves after flowering. Under conventional fertilizer rate, the soil N and P had surplus of 22.6 and 80.4 kg/hm², respectively; under reduced rate soil N had a deficit of 30.2 kg/hm², but still had a surplus P of 22.8 kg/hm². The respective nutrient use efficiencies indicated by the partial factor productivity, agronomic efficiencies and apparent recovery efficiencies were significantly improved by 79.2%, 69.1% and 27.9% for the N fertilizer, and 91.1%, 72.7% and 68.5% for the P fertilizer.

ConclusionsIn Sichuan Basin, the reduced fertilizer rate maintained the wheat yield, improved the nutrient use efficiencies, P balance, efficient translocation of dry matter and contribution to grain filling, but caused the deterioration of flag leaves and the soil N loss, which might result in a fertility decline especially in a long-term period due to an insufficiency under the current reduction rate of N fertilizers. Therefore, rational N fertilization rate needs to be further optimized in the future.