Crop weather relation in kharif rice for North-west Alluvial Plain Zone of Bihar

Abstract

Studies on crop weather relationship in rice were carried out over six kharif seasons from 2009 to 2014 at Pusa, Samastipur falling under North-west Alluvial Plain Zone of Bihar. Three rice varieties viz. Rajendra Bhgwati, RW 3055 and Saroj were grown under irrigated conditions with four sowing dates viz. 31 May, 15 June, 30 June and 15 July. The results revealed that accumulated heat units decreased with delay in sowing till crop reached tillering stage and increased thereafter till crop maturity. The grain yield was higher when maximum temperature (Tmax) during heading phase remained between 32.2 and 32.6 0C and decreased appreciably when Tmax was above 33 0C during this phase. Grain yield declines by 4.31 q ha-1 per 1 0C rise in Tmax during heading stage due to reduction in ‘pollen viability’, resulting in greater spikelet sterility and subsequently lower yield. Except during tillering and flowering phases, the minimum temperature was negatively correlated with grain yield. Daily bright sunshine hours (BSH) of 7 to 8 hours during flowering phase led to enhanced grain yield. However, BSH of less than 7 hours resulted in decline of grain yield. Significant positive correlation was recorded between bright sunshine hours and grain yield.