CHANGES OF SOIL BULK-DENSITY DURING THE GROWING-SEASON UNDER 3 TILLAGE SYSTEMS

Field experiments were conducted to measure soil bulk density on a san dy loam and a clay soil under three tillage and two fertilizer managem ent schemes. Measurements were taken of tillage energy input to the so il and bulk density throughout the growing season for two cropping yea rs. Soil bulk density was shown to decrease linearly with increasing o f input tillage energy within the range of this study. Based on the fi eld data, soil bulk density was estimated in the tillage zone. The cha nge of soil bulk density with time and depth after tillage varied amon g the soil, tillage and fertilizer treatments. The approach shows pote ntial in predicting and describing soil bulk density changes related t o tillage practices. However, data from further experiments are requir ed to assess the validity over a wider range of soils and tillage prac tices.