International Journal of Environment and Climate Change

Radiation use efficiency serves as a valuable indicator for evaluating how effectively plants utilize solar radiation and is a key parameter in assessing crop productivity in relation to photosynthesis. It integrates both the quantity of solar radiation intercepted by the crop canopy and the resulting dry matter production. The present study was conducted to examine how growing environments and nitrogen levels affects the radiation-use efficiency. A field experiment was conducted at the Agricultural Meteorology farm of Anand Agricultural University, Anand, Gujarat during the rabi season of 2024-25.The experiment was laid out in a split-plot design with three replications, comprising three sowing dates viz. (D₁: 1^st November, D₂: 15^th November, and D₃: 30^th November) as main plot treatments, and four nitrogen levels viz. (N₁: 0 (control), N₂: 60, N₃: 120, and N₄:180 kg N ha⁻¹) as sub-plot treatments. The reflected radiation from the canopy was measured by an inverted line quantum sensor over the canopy. Transmitted radiation was recorded by placing the sensor below the canopy on the ground across rows. These measurements were conducted across all treatments with three replications.  The findings revealed that wheat sown on D₂ (15^th November) recorded the highest Leaf area index and dry matter accumulation, along with the highest RUE (1.85 MJ m⁻² day⁻¹), which was statistically at par with 30^th November sowing (1.70 MJ m⁻² day⁻¹). Among the nitrogen levels, the highest RUE (2.02 MJ m⁻² day⁻¹) was observed with N₄ which was statistically at par with N₃ (1.87 MJ m⁻² day⁻¹), while the lowest RUE was recorded in the N₁ (1.36 MJ m⁻² day⁻¹). Early sowing D₁ (1^st November) resulted in reduced yield and RUE. Among the treatments, D₂N₄ stood out with the highest APAR value (532.8 MJ m⁻² d^-1), mean dry matter accumulation (138.4 g per row meter length) and mean LAI, suggesting highly efficient radiation use. The findings offer valuable guidelines for nitrogen management and optimal sowing dates in wheat cultivation, highlighting the importance of radiation use efficiency for maximizing yields and ensuring efficient resource utilization. Therefore, sowing wheat on 15^th November with 180 kg N ha⁻¹ is recommended for achieving higher grain yield, above-ground biomass, and radiation use efficiency in the middle Gujarat region of Anand.