Nitrogen Fertilizer Rates can be Lowered without Compromising Cotton Yield under Drip Irrigation System

The effects of reducing N fertilizer use on soil NO3--N content and cotton yield were studied through a three-year (2015 to 2017) field experiment in South Xinjiang of China. Cotton was sown under drip irrigation system using five N fertilizer reduction treatments as: conventional N application rate (N100), N application rate reduced by 16.67% (N-16.67), 33.33% (N-33.33), 50% (N-50), and 100% (N-100). The data were recorded for changes in soil NO3--N content, and the SPAD value of cotton leaves was recorded at the peak bolling stage. The total N content of the plant was recorded at the boll formation stage, while yield was recorded at maturity. The results revealed that the soil NO3--N content in N-16.67, N-33.33, N-50, and N-100 treatments decreased by 10.8, 45.5, 60.7 and 72.3% compared to N100 treatment, respectively. The SPAD values of N-16.67 and N-33.33 treatments were significantly higher than those of N100 treatment, while the SPAD values of N-50 and N-100 treatments were significantly decreased. The total N content of cotton was significantly decreased with the increase in the proportion of N fertilizer reduced. The seed cotton yield in N-16.67 and N-33.33 treatments increased by 9.2 and 7.9% compared to the N100 treatment, respectively. However, the cotton yield decreased significantly when the N application rate was reduced by 50 and 100%. The relationship between the N fertilizer reduction rate and cotton yield suggested that the N application rate can be reduced by 18.47–45.50% without compromising the cotton yield in South Xinjiang of China. © 2021 Friends Science Publishers