Effect of deficit irrigation on salinity dynamics and productivity of maize in coastal saline soil

Abstract

Shortage of good quality irrigation water is one of the major constraints that limit agricultural production during post rainy season in the Sundarbans. Soil salinity is another inherent bottleneck to sustainable crop production in the region. Much of the land is therefore mono-cropped and a vast expanse is left fallow during the dry season. There is an urgent need to shift towards practices that allow use of fresh, as well as, poor quality water in an efficient way not only to mitigate the problems of water shortages but also to sustain crop productivity and increase cropping intensity in the region. In view of the above, a study was carried out at ICAR-Central Soil Salinity Research Institute, RRS, Canning Town, West Bengal to study the salinity dynamics and yield response of maize to saline water irrigation. The treatments consisted of three irrigation water qualities viz., good quality water (EC < 2 dSm-1) and saline water having electrical conductivity (EC) of 4 and 8 dSm-1 in combination with application of irrigation water levels at 125, 100, 75 and 50 % of cumulative pan evaporation (CPE). Results indicated that soil salinity was higher at the end of the crop growth period and increased at higher levels of irrigation water salinity. Highest mean ECe of 7.1 dSm-1 of saturation paste was observed in the surface soil layer with the application of irrigation water having salinity level 8.0 dSm-1. With the application of decreasing level of good quality water, soil ECe showed an increasing trend. However the trend was reverse when saline water was applied in decreasing amounts due to higher salt loading resulting from application of saline water in increasing quantities. Maize growth and yield parameters (grain yield, cob yield, dry biomass, plant height) declined with deficit irrigation and saline irrigation. The reduction in grain yield and dry biomass was by 17.3 and 21.5 % respectively in deficit irrigation treatment (50% CPE) as compared to irrigation level of 100% CPE. Statistically at par maize yields were obtained at 100 and 75 % CPE. The above ground biomass and seed yield of plants irrigated with 8.0 dSm-1 irrigation water were reduced by 44.3 and 31.1 % respectively over that obtained with good quality water. However, the differences in yield of maize irrigated with good water to that with saline water of 4.0 dSm-1 was insignificant. Highest value of water productivity (5.52 t ha-1 mm-1) was obtained with irrigation level at 125% CPE and the lowest for 50% CPE (3.84 t ha-1 mm-1). The water productivity values at 100% and 75% CPE was at par. Irrigation with fresh water provides higher advantage in terms of yield and water productivity of maize. In case of limited water supply irrigation with 4 dSm-1 saline water or deficit irrigation at 75% CPE could be an alternative for irrigation in maize production under coastal saline environment.