Sowing of the dry and semi-dry crop should be done in right time for getting maximum yield. Yield of late sown crop is invariably low due to reduction in field duration, poor plant stand and growth of the crop, more weed infestation and higher sterility percentage of grains. As dry system is followed in rainfed uplands and semi-dry system in rainfed medium and low lands, their optimum sowing time depends upon the onset of monsoon. Sowing with onset of monsoon is the best, if monsoon sets in timely. Pre-monsoon sowing or dry-seeding 10 days before anticipated monsoon is better than late sowing with about 15 per cent yield advantage in case of delayed monsoon (Singh et al. 1997). However, if there is a longer gap of a month or so between dry seeding and receipt of rain it is very likely to cause reduction in yield due to poor crop stand as a result of inadequate soil moisture, high soil temperature and bird/ termite attack. Fifteen and 30 days delay in sowing from the optimum sowing time reduces the yield on an average by 16 and 45 per cent, respectively (Dinesh Chandra et al. 1991; Chopra et al. 1993; Sing et al. 1997), the corresponding per day reduction in yield being 1 and 1.5 per cent. Optimum sowing time in Assam and Kerala, receiving rainfall early in the season is middle of April to first week of May. Based on rainfall analysis, the probable sowing periods in different states of eastern India, which constitutes 88 per cent of total rainfed rice area, have been worked out by Sastri (2000) (Table 16.4). Sowing time starts early and also continues for longest period in Assam.