Root Growth in Rice (Liangyou 152) Under Alternate Wetting and Drying Irrigation and Mixed Application of Polymer-coated and Common Urea

Root growth markedly influences crop yield and resource use efficiency. The present study investigated the effects of alternate wetting and drying irrigation (AWD) and the mixed application of controlled-release nitrogen fertilizer (CRNF) and common urea (CU) on the physiological and morphological characteristics of roots and their relationships with grain yield, crop water productivity (CWP), and nitrogen use efficiency (NUE) in rice (Oryza sativa L.). Three nitrogen (N) fertilization treatments (100% CU (N1), 60% CRNF + 40% CU (N2), and 100% CRNF (N3)) were applied to rice (N rate = 240 kg ha-1) under conventional flooded irrigation (CI) and AWD conditions. Compared to N1, N2, and N3 increased the length, number, dry weight, surface area, oxidation activity, and zeatin + zeatin riboside, and indole-3-acetic acid contents of the roots at the latter (heading and maturity) stages under both AWD and CI. In the same N compounding mode, AWD provided better root parameters. Although grain yield, CWP, and NUE were positively associated with these root traits at the latter stages of growth, they showed a negative correlation with the root traits at the early (tillering) stage. Additionally, the AWDN2 treatment enhanced the number of panicles per m2, spikelets per panicle, filled grain percentage, and 1000-grain weight, providing the greatest grain yield, CWP, and NUE. The combination of AWD and the mixed application of CRNF and CU can improve root growth and root activity, contributing to high grain yield, CWP, and NUE in rice. The results also provide scientific basis for CRNF management strategy mediates rice yield and resource use efficiency under AWD.