Yield effect change of fertilizers in the past 14 years and optimized fertilization of winter wheat in north of China

Objectives Clarifying the winter wheat yield change and the effect of fertilization will set up a fundamental basis for scientific nutrient management in the winter wheat production in north of China.

Methods Ninety-six localized field experiments were carried out, in which the treatments were all composed of no fertilizer control and conventional fertilizer rate, and the yield effect and agronomic efficiency of N, P and K fertilizers of winter wheat were investigated. The fertilizer optimization experiments were carried out in 120 sites, using local winter wheat cultivars and fertilizers as tested materials. The experiment used split plot design, with the main factor of different levels of N, P and K, and the secondary factor was high, middle and low levels of the other two nutrients. The yield effects of N, P and K were calculated, and the recommended rates were proposed.

Results From 2002 to 2016, the supply capacity of soil nutrients were kept increasing. The average soil fertility yield increased from 4721 kg/hm² in 2002 to 5828 kg/hm² in 2016, with an average annual increase of 1.6%. Application of N P K fertilizers significantly increased wheat yield, however, the yield increase rate became lower with diminishing returns (quadratic equation of one variable), the growth rate decreased from 30.9% in 2005 to 20.2% in 2016. The agronomic efficiency of NPK decreased from 9.0 kg/kg in 2002 to 6.7 kg/kg in 2010, and remained at 6.3–6.7 kg/kg after 2010. Based on the yield effect function of N, P and K in different periods, the calculated average N, P₂O₅ and K₂O rates for maximum yield were 180.5 kg/hm², 107.4 kg/hm² and 55.9 kg/hm², and for the economic yield were 167.8 kg/hm², 102.5 kg/hm² and 53.7 kg/hm², and for the reasonable yield were 155.5 kg/hm², 99.9 kg/hm² and 52.8 kg/hm², and the optimized formula was 18–18–8 in 2002–2006. The average rates of N, P₂O₅ and K₂O for the maximum yield in 2012–2016 were 184.3 kg/hm², 125.1 kg/hm², 52.4 kg/hm², for economic optimal yield were 171.7 kg/hm², 118.5 kg/hm² and 48.6 kg/hm², and for the reasonable yield were 159.2 kg/hm², 114.9 kg/hm² and 47.0 kg/hm², and the optimized formula in 2016 was 16–20–8, the total nutrient input was reduced by 12%, compared with the original formula.

Conclusions From 2002 to 2016, the supply capacity of soil nutrients is kept improving in the main winter wheat yield areas in north of China. The yield increase rate and the agronomic efficiency are decreased, in spite of the significant yield effects. The averaged fertilizer yield increase rate is about 20.2%, and the agronomy efficiency is maintained at 6.5 kg/kg in 2016. The proposed regional compound fertilizer formula of winter wheat is 16–20–8, the recommended total base NPK fertilizer nutrient rate is 600 kg/hm², and top-dressing rate is N 69 kg/hm².