Response of soil nutrients and cotton yield to nitrogen reduction rate in continuous cropping cotton field

Objectives The effects of nitrogen reduction rates on continuous cropping cotton yield and soil main nutrients in northern Xinjiang were studied, and the closely correlated factors for rapid response to the reduced nitrogen input were analyzed, in order to provide support for the sustainable and high production efficiency of cotton in Xinjiang.

Methods In 2020 and 2021, field experiment was conducted in a 10 year continuous cotton cropping field, with cotton cultivar “Xinnongda 4” as the test material. Four treatments were set up, including: conventional N application rate control (375 kg/hm², CK), and reducing 20%, 40%, and 100% of conventional nitrogen rate (N2, N4, and N0). Cotton yield was investigated, and the main soil nutrient contents in 0−20 cm and 20−40 cm soil layers were analyzed.

Results Compared with CK, N2 treatment increased soil available P and K content, the average increment were 44.58% and 9.94% in 0−20 cm soil, and 44.47% and 22.60% in 20−40 cm layer, respectively; N2 treatment also increased dry matter accumulation of cotton by 15.66% on two-year average, which was conducive to the yield formation. The seed cotton yield was consequently increased by 13.88% and the lint cotton yield was increased by18.10%, respectively, and the nitrogen utilization efficiency were enhanced as a result. The grey correlation analysis showed that the soil nutrient indexes closely related to nitrogen reduction were nitrate and ammonium nitrogen content, and closely related to crop yield were readily available K and total P content.

Conclusions In the continuous cropping cotton fields of northern Xinjiang, reducing nitrogen input from 375 kg/hm² to 300 kg/hm² will significantly increase soil available N, P and K content, and the dry matter accumulation, thus achieving yield increase and fertilizer reduction.