Effects of clod size, raindrop size and initial moisture conditions on surface sealing [soil crusts] of Kunigami mahji soil [Okinawa, Japan]
1999
Nishimura, T. (Tokyo Univ. of Agriculture and Technology, Fuchu (Japan). Faculty of Agriculture) | Nakano, M. | Miyazaki, T.
Mechanisms in sealing during a rainfall is so complex. Initial moisture content is not always the dominant factor in clod break down as many researcher have suggested. Two experiments were conducted with a Japanese acid son (Kunigami mahji son, LiC) to clarify the mechanisms of clod breakdown due to raindrops. In the first experiment the relation between clod breakdown and sizes of raindrops and clods were studied with a single drop former for different initial moisture conditions. The effect of clod and raindrop sizes on the structure of surface seal under a multiple drop rainfall simulator was observed in the second experiment. Two clod sizes, 1 to 3 and 3 to 5 mm, and three initial moisture conditions, from airdry to near-saturation, were employed in this study. Kinetic energy of drops was Varied from 0.34 to 18.1 J m(-2) mm(-1) by changing drop size and falling height. Clods with different moisture conditions showed similar breakdown features when raindrops were smaller than clods. In contrast, when raindrops were larger than clods, the initial moisture condition affected clod breakdown. Slaking predominated when raindrops were larger than clods and initial moisture content of clods was low. The structure of the seal was also affected by raindrop and clod sizes
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