Assessment of Water Requirements of Rice Crop: An Innovative Approach

Abstract

The actual water requirement of rice crop measurement is very susceptible particularly in large paddy fields with high water table and wet climate. In this study an innovative method was applied to measure actual water requirements of rice crop in Nanjing, China. The main reason behind this study was to assess the actual evapo-transpiration (ET) of rice crop in paddy soil at field and laboratory for ET prediction by empirical equations. CROPWAT 8.0 model (Penman-Monteith) and other empirical equations were used to predict the effective evapo-transpiration. Four treatments were applied with three replications both field and at laboratory. During experiments surface water fluctuations were measured by wooden gauge installed at different locations in the field, whereas in the laboratory with iron gauge fixed in each container. The ground water fluctuations were monitored by piezometers installed in field and in laboratory containers. The result reveals that effective evapo-transpiration in field was 484.6mm, while the predicted ET by CROPWAT was 510.3mm. It further reveals that effective evapo-transpiration predicted by Cropwat and Blaney-Criddle methods were 5.04% and 36.6%. The ET predicted by Thornwaite, Hargreaves-Samani and Priestly-Taylor methods were 3.2%, 8.8% and 9.3% less as of the field.