Optimized controlled-release nitrogen strategy achieves high yield and nitrogen use efficiency of wheat following rice in the lower reaches of Yangtze River of China

Context and problem: Wheat following rice manly distributed in the lower reaches of Yangtze River of China, its major challenge is to cope with simultaneous improvement in yield and nitrogen use efficiency (NUE) without increasing the input of fertilizer.

Objective: Controlled-release urea (CRU) offer several advantages in agricultural practices. However, the effectiveness of CRU was strongly affected by the application strategy, types and region environmental conditions. This study investigated if and how the controlled-release nitrogen strategy could achieve high yield and high NUE.

Methods: Field experiments across two years using two spring wheat varieties were conducted with five nitrogen application treatments, including no nitrogen (T1), conventional urea (T2, CK), controlled-release urea (T3), CRU combined with one-time basal CU (T4) and CRU combined with split CU (T5).

Results: The results showed that yield and NUE were significantly increased in optimized controlled-release nitrogen strategy (T4 and T5) compared to T2, especially for T4. T4 significantly improved biomass accumulation after anthesis, non-structural carbohydrates remobilization and harvest index (HI), increased nitrogen absorption and nitrogen harvest index (NHI), enhanced leaf photosynthetic capacity (leaf area index, photosynthetic rate, chlorophyll content) and leaf nitrogen metabolism enzyme activities. The diversity of nitrogen-fixing microorganisms and relative abundance of Bradyrhizobium in rhizosphere after anthesis were significantly increased in T4. Correlation analysis showed that the above morpho-physiological indexes were positively and significantly correlated with grain yield and NUE.

Conclusions: This study indicates that the appropriate combined application strategy (CRU combined with one-time basal CU) could hold great promise to increase yield and NUE of wheat via facilitating carbon-nitrogen allocation and optimizing rhizosphere environment in the lower reaches of Yangtze River of China.

Implication: This study would offer theoretical basis for achieving high yield and nitrogen use efficiency through combined application strategy of controlled-release and convention urea, and provide practical guidance in high efficiency production in wheat-rice rotation system.