Seasonal and interannual change in under-drainage ability in clayey paddy fields
2008
Yoshida, S.(National Agricultural Research Center, Joetsu, Niigata (Japan). Hokuriku Research Center) | Adachi, K. | Tanimoto, T.
Ability of under-drainage facility is influenced by the permeability of the soil above the filler layer. Interannual depression of the filler layer or the formation of an impermeable layer by tillage and puddling practices can deteriorate the accessibility of water from topsoil to the filler layer. On the other hand, shrinkage cracks induced by field desiccation contribute to the flow of subsurface water to the filler layer in clayey fields. The present study employed long-term measurement of under-drainage discharge, soil moisture status, crack growth, and the depth of the filler layer to analyze the seasonal and interannual variation in the ability of the under-drainage facility. Although the practice of puddling completely ceased the percolation of water to the under-drainage facilities, the practice of mid-summer drying, which induced cracks, effectively enhanced the drainage ability, while the interannual increase in depth of filler caused an unrecoverable decline in drainage ability. Because of filler depression, the water flow between the topsoil and the filler layer in aged under-drainage facilities depended on narrow cracks in the deep soil layer. The narrow cracks were probably so subject to clogging that the discharge in the aged under-drainage tended to decline during an event of water release.
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