Abstract

Under conditions of limited water supply, intermittent irrigation instead of continuous flooding is necessitated in rice cultivation. To assess the response of lowland transplanted rice to intermittent irrigation vis-a-vis continuous submergence, field experiments were conducted at the Agricultural College, Killikulam during rubi seasons (Oct-Feb) of 1990 and 1991. The effect of partial substitution of inorganic nitrogen through bio fertilizers-azolla and blue green algae (BGA) - was also evaluated. The results indicated that rice yield was reduced by 3 to 19 per cent by intermittent irrigation compared to continuous submergence. The practice of irrigation immediately after disapperance of ponded water was most suitable under limited water supply. With this practice, the yield reduction was only marginal (3-5%) but it helped to save about 28.7 per cent of irrigation water compared to continuous submergence. Substitution of 25 per cent of inorganic nitrogen through inoculation of azolla or BGA maintained the grain yield of rice on par with the application of 100 per cent of N through inorganic fertilizers.

Keywords: Lowland Rice, Limited Water, Nitrogen, Water, Management