Root Response to Nitrogen Fertilization and Water Availability in KDML 105 Rice Cultivar

Abstract

The effects of nitrogen application and water availability upon root growth and yield of KDML 105 rice cultivar were studied under rainfed and irrigated conditions at Phitsanulok Rice Research Center (PSL) during the wet season in 1993 and 1994. Four rice cultivars were tested in 4 x 6 m plot arranged in RCB in 1993 and two rice cultivars with four nitrogen rates arranged in 2 x 4 Factorial in RCB design in 1994 with four replications. It is clear that more than 80% of the total root of rice plant is restricted to the top 10 cm of the soil layer. Root growth responded slightly to nitrogen when water availability was limiting wherease the response was greater under fully irrigated conditions. Root mass density (RMD) at flowering generally decreases with a change from limiting water to fully water availability conditions and with soil texture from sandy loam to clay. KDML 105 produces greater RMD and root-shoot ratio whereas IR57514-PMI-5B-1-2 was found to be a line which tended to produce the highest yield at high nitrogen rate in both rainfed and irrigated environments