Objectives The suitable replacement ratio of organic fertilizer in total nutrient input for high and stable wheat yields and maintenance of soil fertility was studied.

Methods Field trials were conducted at the Agricultural College of Shihezi University in Xinjiang Autonomous Region from 2018 to 2020. Wheat cultivar of Xinchun 38 was used as the test material, and the test soil was gray desert soil. The treatments in the experiment included no fertilization control (CK), conventional chemical fertilizer treatment (CF), and four replacement ratios (i.e., replacement of chemical N and P by 6%, 12%, 18%, 24% organic fertilizer). Organic fertilizers were applied to the soil before wheat sowing, N and P topdressing amount and rate with drip irrigation were applied in similar pattern for all the fertilization treatments, and all straws were returned to the field after wheat harvest. In 2020, plant samples were taken at six growing stages of wheat to analyze the N and P contents, and dry matter accumulation, while wheat yield and yield components were investigated at maturity stage. Soil samples were taken at 0–20 cm depth to analyze available N, P, K and organic matter (OM) contents.

Results The soil available N, P, K and OM content increased with the increase of the input of organic fertilizers. The available N, P, K and OM contents at filling and maturity stage in replacement ratios of 18% and 24% were significantly higher than those in CK and CF treatments. The dry matter and nutrient accumulation of wheat at the blooming, filling and harvesting stages all increased with the increase of organic fertilizer replacement rate. The wheat dry matter and nutrient accumulation under replacement rates of 18% and 24% were significantly higher than those under CF treatment. N and P fertilizer utilization rate, partial productivity and agronomic utilization efficiency were improved by the inclusion of organic fertilizer in the total nutrients input, with the highest and significant improvements in replacement rates of 18% and 24%. Compared with CF, the substitution treatment of 18% significantly increased the 1000-grain weight and yield.

Conclusions Replacement of chemical N and P input with organic fertilizers increased soil available N, P, K contents at late growing stage of wheat, improved chemical fertilizer utilization efficiency and yield. The suitable replacement ratio of organic fertilizers dominant its effect, under the experimental conditions, replacing 18% of N and P input by organic fertilizer is recommended for stable wheat yield and maintenance of soil fertility.