Effects of harvest time on rice yield and quality: A meta-analysis

Harvest timing significantly affects rice yield and quality, with optimal timing varying by variety and region. In order to elucidate the effects of different harvest timings on rice yield and quality, and emphasize the impact of rice varieties and regions on harvest timing and suitable grain moisture content. Using 35 days after heading and 22–24 % moisture content as controls, 32 studies (977 data pairs) from CNKI and Web of Science (up to 2024) were meta-analyzed. The results showed that premature harvesting (compared to harvesting 35 days after heading) reduced yield by 5.76 %, while delayed harvesting increased yield by 8.31 % and grain weight by 9.32 %—though no significant yield change in torrid zones. Delayed harvesting also improved head rice rates from 25 to 55 days after heading, but decreased them by 20.51 % in torrid zones, and both early and late harvests increased chalkiness by 15.37 %. Additionally, delayed harvesting raised amylose content by 3.36 % and taste value by 42.93 % while reducing protein content and viscosity measures. It is particularly necessary to note that harvesting outside the optimal 22–24 % moisture range significantly lowers yields and head rice rates. Overall, while delayed harvesting can improve some quality traits, it may reduce appearance quality, with effects varying by zone and variety. In contrast, the benefits of the optimal moisture range are consistent, with the highest yield and head rice rate achieved at 22 %–24 % moisture. These findings provide a theoretical basis for determining optimal harvest timing to achieve high-yield, high-quality rice.