A six-year field experiment involving 136 cultivars of ratoon rice has revealed essential characteristics of their yields. The average yield of the main season stands at 8.73 t. ha− 1, aligning with the outcomes of prior studies11,15. It indicates that under existing cultivars and cultivation methods, the main yield has reached a stable level. The average yield of the ratoon yield was 4.7 t. ha− 1, higher than the previously reported average of 2.4 to 3.3 t. ha− 1 15,11. This can be attributed to the use of a high-yield culture technique which ensured high and stable yields in the ratoon season16.
This research corroborates that spikelets per panicle were the critical component for the main yield, in agreement with certain studies8,18. To improve the main yield, prioritizing the selection and cultivation of large-panicle cultivars is imperative, as these can produce a greater number of grains and thus significantly enhance the main yield18,19.
Correlation and path analyses indicated a complex relationship between yield and yield components in the ratoon season, with panicles per m², grain filling rate, and 1000-grain weight showing significant positive correlations with the ratoon yield, differing from previous studies5,7,13. Their results showed that the panicles per unit land area [8], panicles per unit land area and spikelets per panicle13, spikelets per panicle, panicles per unit land area, and grain filling rate7 were the critical components for the ratoon yield. This variation can be attributed to our study's use of 136 widely cultivated rice cultivars over a six-year field experiment in the same region, obtaining more comprehensive results. To achieve high yields in the ratoon season, it is crucial to enhance the panicles per unit area, grain filling rate, and grain weight.
Previous research has shown that the main factors influencing the panicles per unit area of the ratoon season include variety type17, nutrient management5,20, different stubble heights10,21, and mechanical compression22. To increase the panicles per unit area in the ratoon season, two approaches can be adopted: firstly, selecting varieties with strong regenerative capacity13; secondly, implementing effective cultivation measures, including reduced mechanical compression during the main season's rice harvest23; and timely application of sprout-promoting fertilizer9.
The heading and grain filling stages are critical periods affecting the grain filling rate and grain weight of the ratoon season. Over 70% of rice yield is derived from dry matter accumulated through leaf photosynthesis during this period24,25. Temperature26 and water management27 are key factors in the accumulation and transportation of dry matter during those periods, affecting the grain filling rate and grain weight. High temperature reduces the rate of dry matter transport to the panicle, decreasing the accumulation of dry matter in the panicle and thus lowering the grain filling rate28. Alternate wetting and drying irrigation can significantly increase the grain filling rate and shorten the grain filling period29. This is particularly important for improving the grain weight and uniformity of grain filling in ratoon rice. Moreover, efficient water management can increase grain weigh30,31. Therefore, to enhance the grain filling rate and grain weight of the ratoon season, strategies such as water management and avoiding damage from low temperatures during the heading and grain filling stages of ratoon rice can be adopted to promote substance transport.