Extinction coefficient and photosynthetically active radiation use efficiency of summer rice as influenced by transplanting dates

Abstract

Aim: The present study was conducted to quantify the extinction coefficient and photosynthetically active radiation (PAR) use efficiency of widely cultivated variety "Shatabdi" under changing dates of transplanting and to suggest the farmers for proper transplanting window in this zone. Methodology: Thirty five-day-old rice seedlings were transplanted during January and February at three different dates (D1 D2 and D3) at a gap of 14 days with four irrigation regimes under strip plot design having three replications. Plant samples were taken at 14 days interval from each experiment and biometric parameters like LAI etc. and meteorological parameters like Incident PAR were estimated. Results: The results showed that the extinction coefficient decreased with delay in transplanting. The PAR use efficiency for biomass accumulation ranged from 2.07 to 2.19 g MJ-1 when transplanting dates varied from D1 to D3. The maximum grain yield was noted under D1 or D2 with no significant variation but a sharp reduction in yield was observed under D3. The PAR use efficiency for grain yield was noted under D2 (1.23 g M J-1). The intercepted PAR at different phenophases significantly affected the grain yield. Interpretation: On the basis of radiation utilization efficiency the crop may be transplanted within first fortnight of February in this zone.