Abstract
The purpose of this study is to investigate the effects of pending depth treatment on water balance in paddy fields. The pending depth treatments were very shallow, shallow and deep. The experimental plots were three $80m{\times}25m$ rectangular plots. Daily values of rainfall amount, pending depth, irrigation water, drainage water, evapotranspiration, infiltration, and piezometeric head were measured in the field. The pending depth was continuously observered by water level logger during the growing season. The ET was measured in 1m diameter PVC lysimeters. Irrigation water volume was measured by 75m pipe flow meter and the drainage water volume was measured by 25mm and 75mm pipe flow meters and a recording Parshall fulume. PVC pipe piezometers with 12mm diameter were used. The results of the water balance showed that irrigation water of 881.1mm, 735.4mm, and 532.6mm in very shallow, shallow, and deep pending, respectively. The effective rainfall was 182.6mm(44.6%), 254.7mm(62.2%), and 188.6mm(46.0%) in very shallow, shallow, and deep pending, respectively. The results show that the shallow pending depth looks the best of the three treatments.
