Influence of temperature and solar radiation on grain yield and quality in irrigated rice system

• Three temperature–radiation (T&R) combinations were classified based on T&R in different rice phenological stages of single rice season in the Yangtze River Valley.
• HL pattern, which have relatively high T&R in vegetative stage and low T&R in grain filling stage, respectively, is optimal to obtain not only high grain yield, but also high T&R utilization efficiency in the three combinations.
• The optimal average daily temperature for achieving relatively high grain yield is from 26 to 28 °C in vegetative stage and from 22 to 27 °C in grain filling stage. In addition, the average temperature of nearly 28 °C in vegetative stage combined 22 °C in grain filling stage contributes to achieving the highest yield in this place.
• Average daily temperature is positively correlated with leaf area index, crop growth rate and biomass in vegetative stage, and negatively correlated with harvest index, grain filling percentage, grain weight and grain quality-related traits in grain filling stage.

An insight into optimal temperature and radiation (T&R) in different rice phenological stages will contribute to rice cultivation management and crop modeling. This study was aimed to unravel the responses of various rice cultivars to different T&R conditions and to identify the optimal T&R for both yield and quality in the Yangtze River Valley in China. For this purpose, two Indica and three Japonica cultivars were grown under irrigation conditions, respectively, on three sowing dates (April 30, May 10 and May 30) in 2012 and 2013 to acquire different combinations of T&R conditions. Various morphological, yield- and quality-related traits were investigated. This study demonstrated that temperature in this region is a limiting factor compared with radiation. Besides, there was a smaller variation of the average T&R in reproductive stage than in vegetative and grain filling stages. Therefore, T&R in various phenological stages were classified into three major combinations, namely, HL, LH, MM mainly based on temperature in vegetative and grain filling stages. MM combination had similar average daily temperature in both vegetative and grain filling stages compared with the average temperature of rice growth season. HL combination was of higher (at least 1 °C) average daily temperature in vegetative stage and lower (at least 1 °C) in grain filling stage compared with MM. Opposite to HL, LH combination was of lower average daily temperature in vegetative stage and higher in grain filling stage compared with MM. Most of the cultivars harvested the highest grain yield with highest T&R use efficiency in HL combination compared to the other two combinations. When the average temperature in vegetative stage was estimated to be 26–28 °C and 22–27 °C in grain filling stage, higher grain yield can be gained. Moreover, highly significant correlation was found between temperature and LAI (leaf area index), CGR (crop growth rate), and TDW (total above ground biomass) in vegetative stage. HI (harvest index) and all grain-processing and appearance-quality-related traits was highly significantly correlated with temperature in grain filling stage. In conclusion, HL combination with average daily temperature ranges of 26–28 °C in vegetative stage, and 22–27 °C in grain filling stage are recommended to achieve high grain yield and quality for irrigated rice in the Yangtze River Valley in China by adjusting sowing date and crop establishment.