Objectives  Imbalanced and over fertilization is common in potato growing areas in China, resulting in low nutrient use efficiency and serious nutrient losses. A simple and easy-to-use fertilizer recommendation method, Nutrient Expert for Potato, was established based on large number of field experiments, and validated in multi-point trials in the main potato producing areas.

Methods A total of 239 field experiments were conducted in the main potato producing areas of nine provinces from 2017 to 2020 to calibrate and improve the Nutrient Expert system. Each experiment included six treatments: fertilizer recommendation based on Nutrient Expert (NE), farmers’ practices (FP), conventional recommendation based on soil testing (ST), and N omission, P omission and K omission based on the NE treatment. The potato yield, economic benefit, nutrient use efficiency and apparent nutrient balance were investigated.

Results The average yield responses of N, P and K fertilizer application in the main potato producing areas of China were 8.1, 4.8 and 5.2 t/hm², with average agronomic efficiency of 45.2, 51.1 and 35.1 kg/kg, and average relative yield of 0.73, 0.83 and 0.82, respectively. Compared with the FP and ST treatments, the NE treatment reduced N fertilizer input by 24.4% and 4.2%, and P fertilizer input by 32.3% and 1.9%, but increased K fertilizer input by 4.9%; increased the potato yield by 2.63 and 0.62 t/hm², and net profits by 4283.4 and 799.0 yuan/hm². Compared with the FP and ST treatments, NE treatment increased the recovery efficiency of N, P and K fertilizer by 11.5 and 1.6 percentage points, 5.0 and 2.1 percentage points, and 9.1 and 1.1 percentage points, respectively; increased the agronomic efficiency of N, P and K fertilizer by 18.4 and 4.3 kg/kg, 32.2 and 7.5 kg/kg, 12.3 and 2.6 kg/kg, respectively; enhanced the partial factor productivity of N and P fertilizer by 37.3 and 8.6 kg/kg, 91.2 and 15.6 kg/kg, respectively. The partial factor productivity of K fertilizer in NE treatment was comparable to that in ST treatment, and 25.6 kg/kg higher than that in FP treatment. NE treatment resulted a 50.5% and 15.5% reduction in the apparent N surplus, and 49.6% and 7.3% reduction in the apparent P surplus, compared with the FP and ST treatments.

Conclusions After calibration by the data from large number of field experiments, which are based on the yield and agronomic efficiency responses, Nutrient Expert for Potato have been approved efficient in further optimizing fertilizer amount, improving potato yield and fertilizer use efficiency, and reducing N and P surplus, so can be used as a feasible fertilizer recommendation method for small farmers in China.