Percolation losses of water in relation to puddling intensity and depth in a sandy loam rice (Oryza sativa) field

Percolation loss of water in rice fields is a major factor of low water use efficiency of irrigated rice thus threatening its sustainability. The process of water percolation was studied in a puddled sandy loam rice field with three puddling intensities—no puddling (unpuddled), two passes of tractor-drawn cultivator+one planking (medium-puddling), and four passes of tractor-drawn cultivator+one planking (high-puddling), each at shallow (5–6 cm) and normal (10– 12 cm) depths. Percolation losses of water decreased with medium-puddling by 54–58%, but it remained unaffected by increased puddling intensity and puddling depth. Percolation rate (PR) decreased with time with both mediumand high-puddling but it increased with increased depth of ponding water. The PR of water recorded in infiltration rings was 1.8, 38.8 and 42.1% less than that recorded in the whole plots thereby indicating the role of under-bund losses. Seepage ratio (ratio of seepage plus percolation to percolation alone) increased with increase in puddling intensity indicating that the magnitude of under-bund percolation was a direct function of puddling intensity. The hydraulic conductivity of the puddled layer decreased with increased puddling intensity (0.064 cm h^-1 with mediumpuddling to 0.009 cm h-1 with high-puddling) whereas the hydraulic gradient between puddled and unpuddled layers increased with increase in puddling intensity (0.84 cm cm-1 with medium-puddling to 1.86 cm cm-1 with highpuddling)