Reducing irrigation water requirement of dry season rice (boro) in coastal areas using timely seeding and short duration varieties

Abstract

Dry season rice, popularly called as boro rice, has the potential to bridge the gap of production and consumption in the eastern India. High salinity of surface water in this area during the dry season however limits the cultivation of boro rice. Farmers have to resort to pumping ground water for dry season irrigation. Indiscriminate ground water pumping may lead to ground water depletion, salinity intrusion into the aquifers and increased cost of pumping. Judicious and conservative use of precious irrigation water is essential to enable boro rice and sustain the productivity of this fragile ecosystem. This study aimed at reducing irrigation water and increasing irrigation water productivity (Wp) in boro rice by optimizing the date of sowing and the use of suitable rice varieties. The experiment was conducted in 2012 – 2013 and 2013 – 2014 boro rice seasons at Central Soil Salinity Research Institute, Canning Town, India. Eight tested rice varieties, including 4 from Bangladesh, were sown during the first week (early sowing) and the last week of November (late sowing). Twenty one day seedlings of early sown and late sown crops were transplanted in adjacent fields. In each field, rice varieties were randomized with three replications. For both two cropping seasons, and under early sowing, yields of BINA dhan 8 (6.04t ha-1), BRRI dhan 47(5.89 t ha-1), CSR 22 (5.95 t ha-1), and IR 10206-29-2-1-1 (5.87 t ha-1) did not differ significantly and were significantly higher than those of other varieties. Under late sowing, BINA dhan 8 produced significantly the highest grain yield (5.86 t ha-1). In both sowings, CSRC(S) 50-2-1-1-4-B produced significantly the lowest yield. Irrigation water input for different varieties increased with their growth durations. Depth of irrigation water was lowest (117 cm for early sowing; 145 cm for late sowing) in the variety BRRI dhan 47, followed by IR 10206-29-2-1-1. Varieties CSR 34 and CSR 22 had the highest irrigation water inputs. For all cultivars, early sowing consumed 17% less irrigation water than late sown crop. The difference was due to higher water inputs for land soaking, land preparation and puddling in the late sown crop. The grain yields of late sown crops (4.92 t ha-1) were 13% less than those of early sown crops (5.56 t ha-1).WP under early sowing (41-45 kg grain/ha-cm) was about 30% higher than that under late sowing (31-35 kg grain/ha-cm) during both the years of study. Among the varieties, highest WP was recorded in BRRI dhan 47 under early sowing and in BINA dhan 8 in case of late sowing.