Full root-zone nitrogen fertilizer application during rice transplanting promoted root development to increase rice yield and improve nitrogen use efficiency in South China

Introduction The current nitrogen fertilizer application methods during rice ( Oryza sativa L .) transplanting have many problems. To address the problems, a new method, the full root-zone fertilizer application method (RF), was applied during transplanting. Methods To investigate the impact of the RF method compared with other fertilizer methods on rice productivity, three repeated experiments were carried in different sites in South China from 2022 to 2023, involving four treatments being four fertilizer application methods: no nitrogen fertilizer applied throughout whole growth cycle (C), RF, deep-side fertilizer application (DF), and manually broadcasting fertilizer application (BF). All treatments applied 100 kg ha -1 N during transplanting except C. Results and Discussion The experiment results demonstrated that at the tillering stage, the RF method significantly enhanced rice root characteristics over the BF method, with increases of 24.41% in average root length, 34.93% in diameter, and 25.22% in total root surface area. The tiller number and the antioxidant enzymes activity under the RF method were significantly higher than the DF and BF methods during the rice growth period. The rice yield under RF method increased 13.87% to 33.41% compared with BF and DF methods. This increase was associated with superior performance in effective panicle number and seed setting rate at maturity. The RF method also significantly enhanced nitrogen use efficiency (NUE) compared to other methods, by reducing nitrogen loss and improving plant nitrogen uptake. Additionally, the RF method increased net income by 31.77% to 45.33% over the DF and BF methods by raising the total rice value.