Response of Milling and Appearance Quality of Rice with Good Eating Quality to Temperature and Solar Radiation in Lower Reaches of Huai River

The effects of temperature and solar radiation on milling and appearance quality of rice (Oryza sativa L.) were evaluated to find the optimal temperature and solar radiation for optimizing milling and appearance quality of rice in the lower reaches of Huai River. Field experiments were conducted with two medium-maturing japonica soft rice varieties (SMR), two late-maturing japonica soft rice varieties (SLR) and two late-maturing japonica non-soft rice varieties (LR) as experimental materials. Seeds were sown on 10 May (T1), 17 May (T2), 24 May (T3), 31 May (T4), 7 June (T5), 14 June (T6), and 21 June (T7) in 2017 and 2018. Compared with solar radiation, temperature was the main environmental factor affecting the milling and appearance quality of rice in the lower reaches of Huai River. Under the condition of ensuring relatively high-yield, the milling quality of SMR and SLR can reach the second grade of China’s national standard of high quality paddy. The mean daily temperature (Tmean) range were 20.2–22.7 °C and 20.4–22.0 °C respectively. The temperature range for LR to obtain a relatively high-yield, good milling and appearance quality was 20.4–20.7 °C. The optimal sowing dates of SMR, SLR and LR were 15 May to 1 June, 15 May to 20 May and 15 May to 20 May, respectively.