Abstract:

Based on the staged sowing test data of Guangdong Nanhai early rice 'Yefengzhan' from 2018 to 2021 and the daily meteorological data of the Nanhai national basic station, a Logistic growth model was used to simulate the dynamic changes in the total aboveground dry matter weight from early rice transplanting to maturity and the thousand−grain weight from heading to maturity. The modified Gompertz model was used to simulate the dynamic changes of early rice leaf area index from transplanting to the milky stage, and established the correlation path of meteorological factors−growth parameters−yield changes, in order to analyze the regulation of early rice growth parameters by changes in meteorological conditions at different growth stages of early rice and its impact on yield. The results showed that the Logistic model based on the aboveground dry matter weight from transplanting to maturity stage, leaf area index from transplantation to milk maturity stage, thousand−grain weight from 10d after heading to maturity stage and meteorological data from 2018 to 2021 for Nanhai early rice 'Yefengzhan', the fitting accuracy of simulating aboveground dry matter weight and thousand−grain weight of early rice and the modified Gompertz model simulating early rice leaf area index were both high, with goodness of fit R²>0.98 and normalized root mean square error NRMSE≤5.71%. A total of 11 early rice growth parameters were derived from the two model simulations, of which five parameters (maximum dry weight potential, dry weight accumulation inflection point, maximum leaf area index, maximum thousand−grain weight potential and grain filling inflection point) were significantly related to early rice yield and were determined as core parameters (P＜0.05). Correlation analysis between yield, core parameters and meteorological factors at different growth stages showed that there were two main physiological regulatory paths through differences in meteorological conditions drived changes in core parameters and thus affected early rice yield changes: one was the path of photosynthetic production and grain capacity building, which could be significantly improved by increasing the number of sunshine hours during the sowing−heading stages. The maximum leaf area index (LAI_max) and thousand−grain weight (G_max) led the foundation for the high yield of early rice. The second was the growth process and grain filling path of early rice. The number of high−temperature days during the tillering−heading stages significantly delayed the early rice filling inflection point (DAH_m), extending the effective grain filling period, which was conducive to an increase in grain weight. Precipitation and lack of sunshine during the sowing−jointing stage were the main stress factors that reduce the yield of early rice. In summary, ensuring sufficient light during the jointing−heading stages of early rice in the south China Sea and avoiding rainy weather during the sowing−jointing stages and high temperature stress during the grain filling stage are key to improving the climate adaptability of early rice in this region.

Key words: Early rice, Meteorological conditions, Growth model, Yield influencing, Nanhai