Objectives Excessive and unbalanced fertilization is common in the spring soybean production of Heilongjiang Province, leading to low fertilizer utilization efficiency and production profits. We constructed a soybean nutrient expert system based on the yield responses and agronomic efficiencies, and tested its yield and economic effect through field experiments.

Methods From 2021 to 2024, 47 field experiments were conducted in the main spring soybean-producing areas of Heilongjiang Province. Six treatments were set up, including the fertilization treatment recommended by the soybean nutrient expert system (NE), as well as treatments without nitrogen fertilizer application (NE-N), without phosphorus fertilizer application (NE-P), and without potassium fertilizer application (NE-K) based on the NE treatment. Additionally, the farmers’ fertilization practice (FP), and fertilizer recommendation based on soil testing (ST). The soybean yield, nutrient utilization efficiency and economic benefit responses were investigated at harvest.

Results In the main soybean production area of Heilongjiang, the above-ground N, P and K requirements of spring soybeans for producing 1 t of soybean grain were 54.8, 7.9 and 20.5 kg, respectively; the average yield responses of N, P and K fertilizer were 421.4, 395.8 and 418.3 kg/hm², respectively; the average agronomic efficiencies of N, P and K fertilizers were 9.5, 8.1 and 9.1 kg/kg, respectively; the average fertilizer use efficiencies of soybean for N, P, and K were 37.3%, 18.9%, and 24.0%, respectively. Compared with FP, both the soybean yields and economic benefits under NE and ST treatments increased significantly, the yields rose by 12.6% and 7.1% respectively, while the economic benefits improved by 14.2% and 6.7% respectively. Additionally, the amount of fertilizer applied was substantially reduced. Compared with ST, the yield of soybeans treated with NE increased by an average of 5.2%, and the economic benefit increased by an average of 7.1%.

Conclusions A large number of field trials proved the priority of NE-based fertilization recommendation over the conventional method based on soil testing in increasing yield, economic benefits, and nutrient utilization efficiency of spring soybeans, so is a available soybean fertilization recommendation technique for the actual production of soybean.