Objectives Experimental results of stabilized fertilizers from one region or one type of crop represent limited soil and climate conditions, hardly provide precise support for the extension of different geological regions. So continuous field experiments in large area were conducted in the seven typical regions of China for the scientific application of stabilized fertilizer.
Methods Field experiments were carried out throughout China by Strategic Alliance of Stabilized Fertilizer Industry and Technology from 2009 to 2018. All the stabilized fertilizer treatments (SF) were applied in the same amount of N with the local controls, and the P and K input amounts were made equal by chemical fertilizers as well, and 80% of SF treatments (80%SF) were applied in 80% of the N, P, K amount with the SF. The experimental results in 2014–2018 were summarized.
Results Compared with the local fertilization controls, the SF treatments increased the average yield by 5.00%, 13.40%, 6.96%, 8.68%, 16.30%, 8.72% and 5.80% in South China, Southwest China, East China, Central China, North China, Northwest China and Northeast China, respectively, and increased the nitrogen agronomic efficiencies (NAE) by 36.11%, 29.84%, 27.25%, 51.02%, (no data for North China), 54.73% and 21.00%, respectively; the 80%SF treatments increased the average yield by 1.62%, 10.38%, 1.78%, 6.34%, 8.35%, 1.44% and 0.09%, respectively, and enhanced the NAE by 78.24%, 81.41%, 49.22%, 20.10%, 38.96% and 62.10%, respectively. The average yield increase rate of 80%SF were 3.92%, 1.22%, 1.25%, 3.49%, 0.07%, 1.08% and 0.05% lower than those of SF, the NAE growth rate of 80%SF were 30.95%, 40.11%, 17.27%, –20.48%, –10.19% and 33.97% higher than those of SF. The national average growth rate of yield and NAE were 8.54% and 21.77% higher under SF, and 3.13% and 26.39% higher under 80%SF. According to the principal component analysis, soil nutrient content and pH were founded as the two main factors affecting the effect of stabilized fertilizers. The yield growth rate of stabilized fertilizer was negatively correlated with soil nutrient content (P < 0.05), and positively correlated with soil pH. The higher the soil pH, the better the yield promotion effect of stabilized fertilizer.
Conclusions Stabilized fertilizer is capable of replacing the conventional nitrogen fertilizers in China. Application of 100% stabilized fertilizer is recommended in the East, Central, North, Northwest and Northeast China, and application of 80% stabilized fertilizer is more adaptable in South and Southwest China. Soil nutrient contents and pH values are the two key factors that affect the function of stabilized fertilizer.
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