Objective While fertilizing the soil, straw return to the field puts a large amount of organic carbon into soil, stimulating the mineralization of organic nitrogen. The aim of this paper is to study the effects of long-term straw return on crop yield, nitrogen uptake and utilization, as well as soil ammonia volatilization under the winter wheat-summer maize rotation system in the North China Plain, thereby providing a scientific basis for improving crop yield and reducing nitrogen loss.

Methods The long-term straw return trial in Langfang City, Hebei Province, started in 2008, and the treatments included conventional fertilizer only (NPK) and conventional fertilizer with straw return (NPKSt). Ammonia volatilisation was monitored regularly during the crop growth period, and crop yield, plant nitrogen content were analyzed. At the same time, 0−100 cm soil samples were collected for analysis of enzyme activities and inorganic nitrogen content.

Results During 2018−2023, the yields of winter wheat and summer maize of NPKSt treatment increased by 6.20%−19.29% and 11.01%−21.42%, the total grain N uptake increased by 19.85% and 15.49%, and the partial nitrogen fertilizer productivity increased by 6.96% and 12.41%, respectively, compared with that of NPK treatment, and the effect of the maize season was better than that of the wheat season. Soil ammonia volatilization was mainly concentrated in 7 days after fertilizer application, and the average soil ammonia volatilization rate of NPKSt treatment was lower than that of NPK treatment. The total accumulation of ammonia volatilization of NPKSt treatment in the rotational year was significantly lower than that of NPK by 3.69 kg/hm², and the total ammonia loss rate was lower than that of NPK by 1.02 percentage points. Compared with NPK, NPKSt treatment increased soil urease activity in 0−20 cm layer by 14.84% to 25.35% in winter wheat and summer maize seasons. The ammonium nitrogen and nitrate nitrogen contents of surface soil under NPKSt treatment were significantly increased in both seasons, and the ammonium nitrogen contents of 0−20 cm soil layer under NPKSt treatment were significantly increased by 10.90%−27.73% compared with that of NPK, and the nitrate nitrogen contents of 0−100 cm soil layer under NPKSt treatment were increased by 18.35%−307.73% compared with that of NPK.

Conclusion Long-term straw return to the field not only significantly reduces the volatilization loss of ammonium nitrogen, but also improves soil aeration, enhances surface soil urease activity, increases soil inorganic nitrogen content, and improves soil nitrogen supply capacity. These effects are especially conducive to nitrogen uptake and utilization by summer maize plants. Therefore, straw return to the field under the winter wheat-summer maize system in the typical fluvo-aquic soil area in the northern North China Plain can reduce soil ammonia volatilisation losses on the basis of ensuring high crop yields, and it is an effective measure to achieve sustainable agricultural development.