MOLE DRAINAGE - PROSPECTIVE DRAINAGE SOLUTION TO BANGKOK CLAY SOILS

A field experiment in conjunction with soybean (Glycine max) crop was conducted to assess the effects of mole drainage on various soil prope rties and plant growth. Mole drains were installed at a depth of 55 cm , spaced 2 m apart and at a 1% slope by means of a mole plough having a torpedo of 8.5 cm and an expander of 9.5 cm in diameter. Its impacts on infiltration, bulk density, porosity, suction, moisture content, h ydraulic conductivity and air permeability were observed. The temporal variation of pH and EC in the soil profile was also observed during t he experiment. Experimental field results revealed that there were sig nificant improvements in soil properties (both physical and chemical) owing to mole drainage. Lime application proved to be very effective u nder the influence of mole drains. The total water-loss through mole d rains after irrigation was found to be about 2% of the total water app lied, indicating that the crop water requirement will not significantl y be affected by this drainage system. The grain yield and dry matter yield of soybeans increased by about 46% and 118%, respectively. It wa s concluded that the mole drainage is effective in improving heavy cla y acid sulfate soils of the Bangkok Plain.