Field validation of Nutrient Expert Soybean in China

The Nutrient Expert (NE) fertilizer decision support system for soybean was calibrated based on collected data from Henan, Anhui, Jiangsu, and Sichuan Provinces in China. The objective was to compare the NE-based fertilizer recommendation with traditional soil test (ST)-based fertilizer application and farmer's practice (FP) on soybean yield and nutrient use efficiency. Additionally, nitrogen (N) and phosphorus (P) rate experiments were conducted to test the N and P application rates for soybean in Henan and Heilongjiang Provinces.

The average nutrient application rates in the on-farm comparative studies were 62-43-60 kg N-P₂O₅-K₂O/ha, 26-9-9 kg/ha, and 44-54-54 kg/ha for the NE, FP, and ST treatments, respectively. Soybean yield responses to N, P, and K based on the NE treatment were 260 kg/ha, 166 kg/ha, and 300 kg/ha, respectively. The average highest grain yield was obtained in the NE treatment (2,840 kg/ha), but there was no significant yield difference between the NE, FP (2,760 kg/ha), and ST (2,590 kg/ha) treatments. Based on the experiment with various rates of N and P fertilizer, the application of 40-50 kg N/ha and 25-50 kg P₂O₅/ha can ensure high soybean yield, and the addition of rhizobium can increase yield by 200 to 450 kg/ha.

Results indicated that NE can maintain or improve soybean yields with appropriate fertilizer application rates. Rhizobium inoculation was a recommended practice, which should be integrated into Nutrient Expert for Soybean systems.