Balanced Nitrogen Reduction for Improved Grain Yield and Eating Quality in Mechanically Transplanted Hybrid Indica Rice

Excessive nitrogen application may adversely impact grain yield and quality of rice. This study aimed to evaluate the impact of several nitrogen-reduction strategies on the grain yield and quality of mechanically transplanted hybrid indica rice. Field experiments were performed in 2020 and 2021 using Yixiangyou2115 and Fyou498. The research investigated variations in grain yield and quality of rice under different nitrogen-reduction strategies, including NR1, balanced N reduction; NR2, N reduction in basal fertilizer; NR3, N reduction in tillering fertilizer; and NR4, N reduction in earing fertilizer, compared to the conventional nitrogen application for high-yield cultivation (CK). Compared to CK, the grain yield of rice decreased by 1.63% to 19.71% under nitrogen-reduction strategies. Relative to NR3 and NR4, NR1 and NR2 exhibited an increase in grain yield ranging from 1.81% to 22.51%, attributed to increases in panicle number (0.61% to 13.19%) and spikelet number per panicle (1.60% to 12.28%). Meanwhile, NR1 and NR2 also had relatively high LAI and dry matter accumulation in rice plants at maturity. Compared to CK, NR1 and NR2 improved the processing quality of rice grain, while NR3 and NR4 resulted in reduced processing quality. The chalkiness rate and chalkiness degree of rice under the NR1, NR3, and NR4 treatments were reduced by 2.97% to 23.73% and 3.35% to 52.49%, respectively, in comparison to CK. Additionally, the NR1 and NR4 treatments were linked to an increase in taste value by 1.44% to 3.66% and gel consistency by 13.87% to 46.01% relative to CK. These findings suggest that balanced nitrogen reduction can maintain a high yield while improving the appearance and eating quality of mechanically transplanted hybrid indica rice. This study offers a theoretical basis for rational nitrogen reduction and high-quality cultivation in rice.