Water use efficiency of flooded rice fields II. Percolation and seepage losses

Abstract

The concept of a constant seepage and percolation ( SP) rate in monitoring the water balance of flooded rice fields, as often used in e.g. irrigation system design and management, was investigated. First, magnitude and variability of percolation rate were studied for different combinations of soilhydraulic properties and hydrologic conditions using the validated water balance model SAW AH.Percolation losses from fields with relatively low subsoil permeability ( ks,sub < 10- Only in the latter case, percolation rates are largely affected by the depth of ponded water. Next, the constancy of combined SP rates was studied in a field experiment on a permeable subsoil. Simple book-keeping of the water balance using a fixed SP rate proved accurate to predict the depth of ponded water in time in case of a poorly permeable plow sole and a small seepage component. A decision tree was suggested based on soil-hydraulic properties and characteristics ofbunds to estimate the magnitude and variation of SP rates, and to decide whether book-keeping with a fixed SP rate is an appropriate tool in monitoring the water balance of paddy fields.

Effects of Soil Clay Content on Water Balance and Productivity in Rainfed Lowland Rice Ecosystem in Northeast Thailand

“…However, D determined when separate perched water and groundwater tables were observed (5.1 mm day -1 ) was similar to the reported values. Therefore, among the lowland fields with standing water and one continuous water table, those with low clay content maintain low D, whereas the lowland field that tends to have separate perched water and groundwater tables has high D (Bouman et al, 2001). There is little effect of puddling on D on clayey soils (Sharma and De Datta, 1986), so the (saturated) hydraulic conductivity of the topsoil can be similar to that of the subsoil, resulting in no separate groundwater table below the hardpan.…”

Estimating Percolation and Lateral Water Flow on Sloping Land in Rainfed Lowland Rice Ecosystem

“…Rainfall is measured at fi elds or nearby weather stations, while runoff may be estimated from bund height, rainfall and runoff from the neighbouring fi elds. Evaporation and/or transpiration can be measured and determined using micro-lysimeters, and evapotranspiration may be estimated from potential evapotranspiration or pan evaporation (Bouman et al, 1994;Fukai et al, 2000). Therefore, if the change in free water level is known, the total amount of percolation and seepage can be determined.…”

A Comparative Study on Energy Use and Cost Analysis of Rice Varieties Under Traditional and Semi-Mechanized Farming Systems in North of Iran

“…Yield function of paddy yield, straw yield, husk yield and biomass yield for rice production was obtained by STATISCA software. Simulation growth indices of rice cultivars were obtained by model ORYZA2000 " Figure 3" [7].…”

“…In the middle of 1990s, Rice Research Institute of Iran (IRRI), Wageningen University, and the Research Centre developed the ORYZA model series to simulate the growth and development of tropical lowland rice. In 2001, a new version of the ORYZA model was released that improved and incorporated all previous versions into one model called ORYZA2000 [7]. The model ORYZA2000, simulates the growth and development of rice under conditions of potential production, water and nitrogen limitations.…”