Effects of water-nitrogen interaction on sunflower growth, grain filling, and Yield in an arid oasis region

To address the critical challenges of water scarcity and nitrogen over-application in the arid regions of northwest China, a field experiment was conducted to investigate the impacts of water-nitrogen interaction on plant growth, yield formation of sunflower under mulched drip irrigation in arid oasis region of Northwest China. The experiment comprised three irrigation levels (W1: 55-65% of field capacity (FC); W2: 65-75% FC; W3: 75-85% FC) and four nitrogen (N) application rates (N0: 0 kg ha-¹ control; N1: 120 kg ha-¹; N2: 180 kg ha-¹; N3: 240 kg ha-¹). The results showed that when comparing W3 to W2, the differences in plant height, stem diameter, and yield at maturity were not statistically significant. However, under W1 treatment, these three indicators exhibited significant reductions of 13.07%, 11.79%, and 21.96%, respectively. Furthermore, when the N application rate exceeds 180 kg ha-1, the increases in plant height, stem diameter, and yield become negligible; there may even be a declining trend observed. Among all combinations of water and N treatments, the W3N2 treatment yielded the highest output at 5247.7 kg ha-1. Therefore, to optimize growth and maximize sunflower yield in the arid oasis regions of northwest China, W3N2 treatment is recommended as an effective combination strategy for sunflower cultivation.