A Moderate Wetting and Drying Regime Combined with Appropriate Nitrogen Application Increases Grain Yield and Nitrogen Use Efficiency in Rice

Abstract

This study investigated whether and how irrigation regimes interact with nitrogen (N) application rates to mediate the grain yield, N use efficiency (NUE) and water use efficiency (WUE) in rice and to understand the underlying mechanism. A field experiment was conducted with two irrigation regimes, continuously flooded (CF) and alternate wetting and moderate drying (AWMD), and three N application rates, 120 kg ha−1 N (a low N rate, LN), 240 kg ha−1 N (a medium N rate, MN) and 360 kg ha−1 N (a high N rate, HN) in 2021 and 2022. The results showed that the grain yield exhibited the lowest values at the LN, regardless of the irrigation regime, while it was the highest at the MN when the CF regime was adopted. The grain yield was comparable between the MN and HN regarding the AWMD regime. AWMD significantly increased the grain yield, NUE and WUE compared to CF at the same N rate, which was attributed to a higher photosynthetic rate, improved population quality, enhanced nonstructural carbohydrate remobilization from stems to grains during grain filling, and elevated activities of enzymes involved in N assimilation in the roots. The results suggest that an AWMD regime combined with MN treatment could pronounce a synergistic interaction on the grain yield, NUE and WUE in rice by improving root and shoot physiological performances.

Exogenous Spermidine and Amino-Ethoxyvinylglycine Improve Nutritional Quality via Increasing Amino Acids in Rice Grains

“…The applications of Spd and AVG significantly increased the percentage of fully filled grain, grain weight, and grain yield, whereas had no significant effects on the panicle number and spikelet number per panicle of the two rice varieties because of the chemical treatments were applied at the early grain filling stage (Table 1). In August 2022, the experimental site (Yangzhou) experienced extremely high temperatures during the meiosis, flowering, and pollination period of the two rice varieties (JXY-1 and YD-6) (Figure 2), leading to a significant decrease in the percentage of fully filled grains and grain yield of the two rice varieties by 28.3-29.2% and 31.5-32.4%, respectively, compared to those of a normal year (2021) [34,35]. The statistical significance at the p = 0.05 level among the various chemical application treatments is represented by distinct lowercase letters assigned to the average values (n = 3) of each treatment within the identical column and rice variety.…”