Effect of Soil Texture on Rice Growth and Paddy Soil Percolation under Lysimeter Condition

The lysimeter experiment was conducted to investigate the temporal changes of irrigation requirement, soil water percolation and rice root distribution during rice growing period under different soil texture that were sandy loam, clay loam and clay paddy soil in 1999 and 2000. The irrigation requirement in the first year was 3,306 l/ in clay loam, 2,650 l/ in sandy loam and 2,002 l/ in clay soil. However, the highest irrigation requirement was 5,281 l/ in sandy loam and the next was 4,984 l/ in clay loam and 3,968 l/ in clay soil in the second year, Soil water percolation in the first year was 2,141 l/ in clay loam, 1,228 l/ in Sandy loam and 862 l/ in clay soil. However, in the second year, the highest water percolation of 4,448 l/ was measured in sandy loam, and was followed by 3,833 l/ in clay loam and 2,925 l/ in clay soil. Distribution ratio of rice roots measured in 0-10cm of soil depth was 56.0% in sandy loam, 61.4% in clay loam and 72.1% in clay soil, respectively. It was interpreted that the greater water percolation measured in the second year was caused mainly by the large amount of rice root growth. Therefore, it was concluded that the soil water percolation in rice paddy soil was affected greatly not only by soil texture but also the growth of rice root.