Soil Water Flow Around an Artificial Macro-Pore with the Shaft Tillage Cultivation.

The shaft tillage cultivation method is one of no-tillage methods for transplanting seedlings in an artificial macro-pore that is called shaft tillage to facilitate the crop roots much deeper than weeds. To evaluate water flow around high root density in a 20-cm long artificial macro-pore for the spot drilling method, we observed soil moisture, matric potential, evapotranspiration and plant root growth. Using an acrylic column experiment in a room temperature and light intensity controlled laboratory, the cultivation experiment was carried out. Two dimensional pressure head profile around the roots were measured by tensiometers. Water mass balance was evaluated successfully using soil moisture and evapotranspiration measurements. Our finding was ponding condition at the bottom of the 20-cm long artificial macro pore during the drip irrigation. This suggests preferential flow based on pressure head profiles. Within 6days from the seedling transplant, roots extended in the macro pore. After the period, however, root system developed along the wall of the macro pore, suggesting that water flows into the macro pore preferentially through the roots. Water movement occurred along the wall of macro pore where root density was high.