INCREASED SOIL-WATER RETENTION BY MIXING HORIZONS OF SHALLOW SANDY SOILS

Shallow, sandy-textured surface soils underlain by clay-textured B horizons may be improved by mixing a controlled fraction of subsoil with topsoil. Mixtures of 0, 10, 20, 30, 40 and 50% by volume of the clay B horizon with A horizon were made and tested for water retention at -33 and -1500 kPa [kilopascal]. Tests of infiltration rate under simulated rainfall indicated that increasing percentages of subsoil significantly reduced infiltration rates, although the final rates remained within acceptable limits. Increasing percentages of subsoil resulted in increased plant-available water measured as the difference between -33 and -1500 kPa. Soil mixing will result in deeper A horizons, which may help to increase rooting depth and plant-available water. Na content of the B horizon was not expected to be a problem in the soils tested. Innovative equipment must be developed to mix controlled amounts of subsoil and topsoil.