Impact of sowing date on yield, dry matter and nitrogen accumulation, and nitrogen translocation in dry-seeded rice in North-West India

The aims of the present study were to determine the optimum sowing time of newly developed rice genotypes for high crop water productivity in non-flooded dry-seeded rice (DSR) in north-west India, and to identify the factors underlying high yielding genotypes by comparing their sink production in DSR. We evaluated differences in dry matter, nitrogen accumulation, translocation, yield formation and evapo-transpiration requirement of the selected genotypes developed for DSR (two cultivars; PR-115 and PR-121, two recombinant inbred lines; RIL-367 and RIL-1649) under three sowing dates (1, 10, and 20 June), for two years in the rainy seasons of 2014 and 2015 in north-west India. RIL-1649 sown on 1 June had higher grain yield (9.4 t ha−1) and similar or higher water productivity (1.3 kg m−3) than the other sowing date x genotype combinations. Delaying sowing from 1 to 10 June reduced yield of all genotypes except PR-121, and there was no further decrease in yield with delay to 20 June of PR-115 and RIL-1649. The yield of RIL-1649 sown on 20 June (7.9 t ha−1) was similar to that of PR-115 sown on 1 June.The high grain yield of RIL-1649 (7.9 t ha−1) for the late sowing was due to high pre- and post-anthesis dry matter accumulation, coupled with greater contribution of dry matter translocation to grain yield. RIL-367 not only produced similar yield (8.5 t ha−1) to the check variety PR-115 (8.3 t ha−1) for the 1 June sowing, but also matured 13 days earlier than PR-115.These results suggest that RIL-367 could be useful for DSR-based intensive cropping systems in north-west India, and with higher crop water productivity (1.32 kg m−3) than PR-115 (1.20 kg m−3). In the late sown condition, grain yield had a positive relationship with harvest index, leaf area index at flowering, preanthesis dry-matter accumulation, and dry matter translocation. A greater amount of dry matter and nitrogen uptake at anthesis, in combination with an increased harvest index, resulted in a greater amount of translocated material during the grain filling period. This, in turn, contributed to higher grain yield during late sowing. This study suggests that, for widening the sowing window, and for sustained yields of DSR in north-west India, high dry matter and nitrogen accumulation at anthesis, together with high harvest index, are useful selection traits.