Water and Nitrogen Economy of Rainfed Rice as Affected by Soil Puddling

Abstract

AbstractIn a field experiment conducted to study the water and nitrogen economy of rainfed rice (Oryza sativa L. variety, ‘Tongil’) grown on montmorillonitic clay, much more water was lost from nonpuddled soil than from puddled soil. In rainfed treatments, the crop suffered from moisture stress for 2 weeks during panicle development. During this time soil moisture tension 10 cm deep was 70 centibars in nonpuddled soil compared with 25 centibars in puddled soil. Water‐use efficiency was calculated by dividing the grain yield values by the amount of water received from rain or applied through irrigation. Water‐use efficiency of rice in the irrigated controls, was 2.5 times higher in the puddled soil than in the nonpuddled soil.Ammonium and nitrate nitrogen in the soil and plant nitrogen were determined periodically. The large losses of water from nonpuddled soil caused greater nitrogen losses and less nitrogen uptake by rice at all stages of growth. As a result, grain yields of rice grown on nonpuddled soil were significantly lower than yields of rice grown on puddled soil, with or without nitrogen.