Objectives Aiming at the current situation that farmers in Inner Mongolia blind fertilizer application, resulting in crop yield potential not being able to realized, low fertilizer use efficiency and soil nutrient imbalance, we curried out recommended fertilizer application field experiments for maize, sunflower and potato in Inner Mongolia using a nutrient expert system based on yield response and agronomic efficiency, and compared it with local farmers’ fertilization practices, to verify the feasibility of applying the system in Inner Mongolia in terms of for yields, economic benefits and nutrient use efficiency.

Methods A total of 146 field experiments were conducted in the main maize, sunflower, and potato production areas of Inner Mongolia from 2017 to 2023. There were five fertilizer treatments for each treatment: 1) fertilizer recommendation based on the nutrient expert system (NE); 2) farmers’ practices (FP); and 3)-5) omission nitrogen (N), omission phosphorus (P) and omission potassium (K) treatments based on NE. The differences in the yield, net benefits, nutrient uptake and fertilizer use efficiency between NE and FP were compared.

Results Compared with FP treatment, the NE treatment significantly increased the yields and economic benefits of maize, sunflower and potato (P<0.001), and the yields increased by 1167, 235 and 2433 kg/hm², and the economic benefits increased by 1546, 1572 and 2582 yuan/hm², respectively. The NE system balanced the amount of N, P and K fertilizer, and in particular, it increased K fertilizer application rate. The NE treatment increased the fertilizer input costs for maize and sunflower, so all of their net benefits derived from increased yields. The balanced fertilizer application in the NE treatment increased nutrient accumulation at maturity, and compared with the FP treatment, N accumulation in maize, sunflower and potato increased by 8.4%, 9.1% and 9.9%, P accumulation increased by 8.4%, 6.6% and 10.9%, and K accumulation increased by 11.5%, 9.9% and 11.5%, respectively. The increase in yield and nutrient uptake significantly improved the nutrient use efficiency of NE. As compared to FP, the recovery use efficiency of N fertilizer (REN) increased by 4.6, 13.6 and 14.3 percentage points in maize, sunflower and potato, respectively, and the recovery use efficiency of P fertilizer (REP) by 7.6, 8.7 and 7.1 percentage points, respectively; the agronomic efficiency of N fertilizer (AEN) increased by 3.2, 2.1, 17.4 kg/kg, respectively, and P fertilizer agronomic efficiency (AEP) by 12.6, 4.0, and 27.9 kg/kg, respectively. The recovery use efficiency of K fertilizer (REK) increased by 13.8 percentage points in potato, and K fertilizer agronomic efficiency (AEK) by 8.7 kg/kg, respectively.

Conclusions Fertilizer recommendation for maize, sunflower and potato using nutrient expert system which based on yield response and agronomic efficiency in Inner Mongolia, will play an important role in guaranteeing food security and improving the agricultural productivity by balancing the amount of N, P, and K fertilizers to increase crop yield and net benefits, while improving nutrient uptake and fertilizer use efficiency. Therefore, this recommended fertilization method is applicable to smallholder production systems in Inner Mongolia.