Inorganic fertilizer application ensures high crop yields in modern agriculture: A large-scale field case study in Central China

Inorganic nitrogen (N), phosphorus (P) and potassium (K) fertilizers in modern agriculture are irreplaceable. However, the reasonable applications of combined N, P and K have not been completely determined especially under different fields and production conditions. In order to understand the effect fa combined application of N, P and K (NPK) on crop yields, the investigations of fertilizer contribution rate (FCR, the ratio of the increase in crop yield to the fertilized yield) and fertilizer agronomic efficiency (AE(NPK), kg crop yield increase per kg N+P+K applied) of different crops including rice, wheat, oilseed rape and cotton were carried out by multipoint field experiments conducted in 251, 47, 62 and 26 sites, respectively, in 21 counties of Hubei Province, Central China in 2007-2010. Compared with unfertilized control, the yield for the reasonable combination of N,P and K increased significantly with the average yield increase rate of 46.7% for rice, 109.8% for wheat, 173.7% for oilseed rape and 68.6% for cotton. The FCR to rice, wheat, oilseed rape and cotton yield, respectively, was 29.6%, 48.6%, 56.2% and 38.0%, with the corresponding AE(NPK) of 8.5, 9.2, 4.8 and 3.6 kg kg(-1), respectively. Both yield increase rates of fertilizer and FCRs on the four crops in 2007-2010 have been highly improved compared with the results in 1980s, which means that inorganic fertilizer plays a much more important role in agricultural production at present than in the past. The responses of different crops to fertilizer were different, suggesting it is necessary to optimize the allocation of fertilizers among different crops for maximizing yields.