Reducing Dry Andisol Paddy Field Permeability of Direct-seeding Rice Cultivation Using Plowing and Compaction

Abstract

Using plowing and compaction, field surface compaction methods to reduce the water-requirement rate were investigated in a direct-seeding paddy field used for rice cultivation. The water-requirement rate, percolation rate, and soil hardness were surveyed on paddy plots that had been compacted under various soil water conditions with various compaction strengths. They were compacted in three steps, resembling assumed preparations for on-site seeding work. Overpercolation at the levee side and corners of a field increased the water requirements on the direct-seeding paddy field. Three-step compaction of the field surface steadily reduced the water requirement rate to 20mm/d, from 100mm/d, suggesting that gradual compaction provides useful functions for the direct-seeding paddy field at each step: drainage functions for seeding, water retention and drainage functions for emergence of rice, and water storage functions after seedling establishment. To reduce the water-requirement rate to about 20mm/d, it is desirable to compact the field surface with high soil water contents as much as possible during work with a tractor. After field surface compaction, the soil hardness at 5cm under the field surface must be about 20mm, as measured with a soil hardness meter.