Yield Gaps, Indigenous Nutrient Supply, and Nutrient Use Efficiency of Wheat in China

Great advances in food production have been made in China, but the continuous increase of nutrient inputs has caused a series of environmental problems. Nutrient management for crops must be improved. Yield gaps, indigenous nutrient supplies, and nutrient use efficiencies (NUEs) must be assessed to design management strategies for further yield increase. In this study, data from 1022 field experiments with wheat (Triticum aestivum L.) conducted between 2000 and 2008 in north central China, the middle and lower reaches of the Yangtze River, and northwest China were analyzed. Treatments in these experiments consisted of a check without fertilizer use, an optimum nutrient application, the farmers' practice, and a series of nutrient omission treatments. The results showed that gaps between attainable yields and yields in experimental plots with farmers' practices averaged 0.76 Mg ha(-1). Indigenous nutrient supplies of N, P, and K averaged 133.0, 30.2, and 131.7 kg ha(-1), respectively, in the regions studied. On a national scale and under optimum fertilization, agronomic efficiency of N, P, and K were 9.8, 19.2, and 7.2 kg kg(-1), while recovery efficiencies were 37.9, 19.0, and 27.0%, respectively. Compared with values obtained 10 yr previous, agronomic efficiencies and recovery efficiencies determined between 2000 and 2008 were lower but also lower than world averages. Successive inputs of large amounts of nutrients significantly increased the indigenous nutrient supply and therefore are contributing to lower NUE because recommendations for N, P, and K have not been adjusted downward in China.