Changes in penetration resistance of a clay field with organic waste applications

Effects of manure (M), hazelnut husk (HH), tobacco (TW) and tea (TEW) wastes on penetration resistance (PR) values in a clay field were determined after 8 months of organic wastes were incorporated into soil at four different rates (0, 2, 4 and 6 %) in a randomized plot design with three replicates. While bulk density (BD), relative saturation (RS) and PR values decreased, mean weight diameter (MWD), total porosity (F), gravimetric water (W) and organic matter (OM) contents of the clay soil increased with increasing the application rates of organic wastes. While the lowest PR (0.72 MPa) was determined in the highest application rate of HH which had the highest C:N ratio, the highest PR (1.72 MPa) was in the control. According to the control treatment, decreases in mean values of PR by the organic waste applications were in the following order; HH (52.10%) > TEW (42.07%) > TOW (30.73%) > M (25.17 %). PR values gave significant negative correlations with F (-0.551**), W (-0.439**) and MWD (-0.509**), and significant positive correlations with BD (0.550**) and RS (0.374*). Total porosity showed the highest direct effect (62.39%) on PR. The higher indirect effects of the other properties on PR were also obtained via F. Applications of the same doses of different organic wastes had different effects on the PR values with changing the structure of clay soil due to their C:N ratios