Objectives  Irrational fertilization practices in some of China’s major sunflower-producing regions lead to significant yield loss and low nutrient use efficiency. This study aimed to quantify the yield response of sunflower to nitrogen (N), phosphorus (P), and potassium (K) fertilization, determine the resulting nutrient use efficiency, and identify key influencing factors. The goal is to provide a scientific basis for optimizing nutrient management strategies in sunflower production.

Methods Data were collected from 551 field experiments carried out in the main sunflower-producing areas in northern China, and the relevant literature were retrieved from China National Knowledge Infrastructure (CNKI) using keywords “sunflower”, “sunflower + fertilization”, and “sunflower + nutrient use efficiency”. The experimental types included different fertilizer application rate trials, recommended fertilization experiments, and 3414 experimental designs. Treatments without specific nutrient application were used as controls, to explore the differences in yield-increasing effect and nutrient use efficiency of sunflower under different application rate levels. Random forest analysis was employed to assess the relative contributions of soil available nutrients, organic matter, pH, soil nutrient supply and fertilizer application rate to yield-increasing effect and nutrient use efficiency of sunflower.

Results The yield-increasing effects of applying N, P, and K fertilizers to sunflower were 19.3%, 14.9%, and 12.1%, respectively. The yield increase rate of N and K fertilizers increased initially and then declined with increasing fertilizer application rate, whereas that of P fertilizer increased initially and then leveled off. Under optimized fertilization, the agronomic efficiencies of N, P, and K fertilizers were 4.8, 7.2, and 5.3 kg/kg, with corresponding recovery efficiencies of 34.9%, 20.5%, and 54.8%, respectively. Higher yield increases and nutrient use efficiencies were achieved at application rates of 150−200, 100−150, and 100−150 kg/hm² for N, P, and K fertilizers, respectively. Higher soil available nutrient content led to lower yield increase rate and recovery use efficiency. There was a significant positive effect between fertilizer application rate and yield increase, but a negative correlation with recovery efficiency. Soil available nutrient content, fertilizer application rate and soil baseline yield jointly determined sunflower yield and nutrient recovery efficiency. Specifically, soil alkali-hydratable N, available P, and available K content accounted for 18.6%, 29.1%, and 38.8% of the relative importance in yield increase rates for N, P, and K fertilizers, respectively. Meanwhile, N, P, and K fertilizers application rates contributed 26.5%, 39.2%, and 22.3% to the relative importance of recovery efficiency for the respective nutrients. Soil nutrient content is the main factor to cause regional differences in the effects of N and P fertilizers, while the variation in K fertilizer efficacy stems primarily from the soil indigenous K supply.

Conclusions In major sunflower-producing regions in northern China, the yield-increasing effects of N, P, and K fertilizers on sunflowers exhibit significant differences. N fertilizer demonstrates the highest yield-increasing effect, while P and K fertilizers also achieve yield increase rates exceeding 10%. However, there are significant regional differences in soil available nutrient content and basic soil fertility in this area. Therefore, Implementing balanced fertilization adapted to soil fertility conditions is an important approach to achieving stable and efficient sunflower yields. Nitrogen and phosphorus nutrient management can be established based on regional soil characteristics. However, soil available potassium content shows no significant correlation with the yield increase rate of K fertilizer, and the effects of K fertilizer need to be determined through experiments in various regions.