The relationship of rice yield and quality with the utilization of temperature and light resources in regions at...

Existing studies on the effects of altitude on rice yield and quality have drawn different conclusions. However, the underlying mechanisms of how altitude-induced differences in the utilization of temperature and light resources drive the differential responses of yield and quality formation remain unclear. In particular, the synergistic effects of the ecological adaptability of rice varieties, altitude-mediated distribution of light and temperature resources, and nitrogen regulation on rice yield and grain quality have not yet been clearly elucidated.

A two-year field experiment was conducted in low-altitude (520.70 m) and high-altitude (1640.56 m) rice-growing regions using two rice varieties with differential altitude responsiveness of core agronomic traits, Meixiangzhan 2 and Yunjing 39. Under a nitrogen (N) application rate of 150 kg N ha-1, three N management strategies with basal: tiller: panicle fertilizer ratios of 5:3:2 (N1), 3:3:4 (N2), and 3:1:6 (N3) were implemented, with a no-N treatment (N0) as the control.

Altitude, variety, and N management significantly affected grain yield, rice quality, and the utilization of temperature and light resources. Compared with the low-altitude site, the rice growth period at high altitude was prolonged by 27.25-30.77 days, while effective panicles and seed-setting rates increased by 16.53%-27.37% and 2.71%-6.68%, respectively, contributing to a 4.10%-4.12% yield increase. Meixiangzhan 2 showed higher yields at low altitude (4.84%-8.12%) but significantly lower yields at high altitude (19.80%-25.13%) compared with Yunjing 39. High altitude improved grain quality by increasing head rice rate (5.10%-9.42%) and reducing chalkiness (2.87%-6.38%), although lower temperatures from the heading to maturity stage increased amylose content (13.71%-19.82%) and reduced taste value (2.29%-5.22%). Among the N treatments, N2 consistently improved both yield and rice quality of two varieties at different altitudes.

Optimizing temperature and light resource allocation during key growth stages-particularly increasing the effective accumulated temperature over the entire rice growth period, the diurnal temperature range from heading to maturity stage, the average daily sunshine hours, and the solar radiation-is critical for achieving high yield, high quality, and efficient resource utilization across altitudes.