Objectives In southern Sichuan, high temperatures and drought occur during summer, subjecting rice growth to heat stress. This leads to a decline in the seed-setting rate and plumpness of rice grains, with generally poor milling quality and appearance quality. We investigated the effects of environmental conditions and soil nutrient status on the yield and quality components of hybrid indica rice, aiming to provide cultivation strategies for achieving high yield and superior quality in the hot and drought-prone areas of southern Sichuan during summer.

Methods Field experiments were conducted from 2018 to 2020 at seven locations across four prefecture-level cities—Luzhou, Yibin, Neijiang, and Zigong. The hybrid rice varieties tested were‘Nei 6 You 107’(N6Y107, high-quality type) and ‘Rong 18 You 1015’ (R18Y1015, common type). Four nitrogen application rates for grain fertilizer were set: 0, 60, 120, and 180 kg/hm², with a no-fertilizer plot serving as the control (CK). Soil samples were collected before transplanting to determine the baseline fertility of the paddy fields. Yield was measured at harvest, and grain samples were taken to assess rice processing quality.

Results 1) Three quality traits—head rice rate, chalky grain rate, and chalkiness degree—were significantly influenced by environmental conditions (CV ranging from 28.31% to 58.45%), whereas grain length-to-width ratio, gel consistency, and amylose content were minimally affected (CV ranging from 2.75% to 6.53%). Yield was moderately influenced by environmental conditions (CV of 11.52%). 2) Significant differences (F values ranging from 28.15** to 602.82) were observed in yield, head rice rate, grain length-to-width ratio, chalky grain rate, chalkiness degree, gel consistency, and amylose content across the three years. A highly significant negative correlation (r = −0.4991, n = 56) was found between rice amylose content and nitrogen application rate for grain fertilizer. 3) Rice yield and quality traits, including head rice rate, grain length-to-width ratio, chalky grain rate, chalkiness degree, gel consistency, and amylose content, exhibited highly significant or extremely significant linear relationships with geographical location and soil nutrient background values (F values ranging from 13.98* to 14155.2), with determination coefficients (R²) as high as 89.48% to 99.99%. However, the key factors influencing each quality trait varied across different years and varieties. Overall, over the three years, increasing soil available nitrogen and potassium contents while controlling phosphorus content was beneficial for reducing chalky grain rate and chalkiness degree and increasing amylose content. 4) The correlations between yield and quality traits varied across different years. Combined correlation analysis from 2018 to 2020 revealed highly significant negative correlations (r ranging from −0.1898 to −0.3192**, n = 210) between yield and grain length-to-width ratio, gel consistency, and amylose content, and highly significant positive correlations (r ranging from 0.1516* to 0.1661*) between yield and chalky grain rate and chalkiness degree. Under the ecological conditions of high temperatures and summer drought in southern Sichuan, the common variety ‘Rong 18 You 1015’exhibited significantly higher head rice rate and amylose content than ‘Nei 6 You 107’, demonstrating stronger environmental adaptability.

Conclusions Significant interactions exist among ecological conditions across years, soil nutrient levels, and cultivar characteristics on rice quality. Higher soil available nitrogen and potassium contents and lower available phosphorus content are conducive to improving rice quality. Increasing nitrogen application for panicle fertilizer can enhance rice yield, but overall rice quality tends to decline with increasing yield. Therefore, to achieve high yield and superior quality of hybrid medium rice in the hot and drought-prone areas of southern Sichuan, it is essential to select suitable varieties, improve soil fertility, and focus on nutrient management during the early growth stages, with an emphasis on increasing potassium and controlling phosphorus, to synchronously enhance yield and quality.