Objectives  Adequate fertilization is critical for high crop yield and a reliable recommendation in this regard could help achieve a result-driven soil amendment. In this study, field experiments were conducted to evaluate the effect of applying Nutrient Expert system (NE) in soybean fertilization in China.

  Methods  A total of 21 field experiments were conducted in spring soybean production areas including Heilongjiang, Jilin, and Liaoning provinces from 2014 to 2015, and a total 11 field experiments were conducted in summer soybean areas including Henan, Anhui, and Jiangsu provinces from 2017 to 2018. The local popular soybean varieties were used in these experiments. The experimental treatments included fertilization based on Nutrient Expert system (NE), soil testing (OPTS), and farmers’ practice (FP). Fertilization rate, seed yield, nutrient uptake, and the economic benefit of soybean production was compared among the three fertilization treatments.

  Results  In spring soybean production areas, NE and OPTS increased N fertilization rate in Liaoning Province, P fertilizer rate in Jilin Province and K fertilizer rate in Heilongjiang and Jilin provinces, compared with those in the corresponding FP treatments. but NE and OPTS had similar rates for N, P, and K fertilizers. In summer soybean production areas, the rate of N, P, and K fertilizers recommended in NE and OPTS were significantly higher than that in the FP treatment for all trials. In spring soybean production areas, compared with FP treatments in Heilongjiang, Jilin and Liaoning provinces, the OPTS treatment increased seed yield by 135, 518 and 478 kg/hm², and the economic benefit of soybean by 699, 1684 and 856 yuan/hm², respectively. Compared with the OPTS treatment, NE increased seed yield by 168, 542 and 1225 kg/hm², and economic benefits by 1096, 2591, and 4610 yuan/hm², respectively. Meanwhile, the OPTS treatment increased N uptake by 9.1%−32.3% and K uptake by 0−41.4% than FP for all trials in spring soybean area. OPTS treatment improved the partial productivities of P fertilizers relative to FP treatment in Liaoning Province. In Heilongjiang, the N and K absorption by NE treatment increased by 13.6% and 23.5% than that in OPTS. In summer soybean production areas, soybean seed yield was similar between OPTS and FP treatments in Anhui and Jiangsu provinces; however, compared with FP treatment in Henan, Anhui and Jiangsu provinces, NE increased seed yield by 1021, 694, and 622 kg/hm². Also, farmers economic benefit increased by 3991, 3955, and 2069 yuan/hm², respectively. Soybean seed yield and economic benefit were similar between OPTS and NE treatments in Henan; while in Anhui and Jiangsu provinces, NE increased seed yield by 868 and 545 kg/hm², and economic benefit by 2876 and 2823 yuan/hm² compared with OPTS treatment. Except for the K uptake in Anhui Province, there were no significant differences in the uptake of N, P, and K between OPTS and FP treatments in summer soybean production areas; NE increased the soybean uptake of N, P, and K by 15.8%−41.3%, 19.0%−35.5% and 23.9%−27.3% compared with FP in summer soybean production area. NE treatment increased the partial factor productivity of N, P in Jiangsu Province.

  Conclusions  The recommended rate of N and P fertilization in NE and OPTS treatments were similar to that in FP treatment in spring soybean production areas. The rate of N, P and K fertilization in NE and OPTS are significantly higher than that in FP treatment in summer soybean production areas. Whereas OPTS presented a similar seed yield and economic benefit to FP treatment, NE treatment (P<0.05) increased seed yield and economic benefit compared with the FP treatment. Overall, fertilization based on the NE system is more conducive to optimize and balance the application of nutrients to improve the yield and economic benefit of soybean production. Besides, it does not require soil analysis and testing and is a simple and efficient method of recommending fertilizer application.