A simulation test of the impact on soil moisture by agricultural machinery

To study the impact by agricultural machinery on changes in soil moisture, we used a simulated test method employing round iron plate based on the ground pressure ratio between the front and rear wheels of wheeled tractors and crawler tractors. We conducted soil compactions with five pressure loads (35, 98, 118, 196 and 345 kg), and measured soil moistures at different depths and under different compaction times, as well as compared those before the loads was applied. The results indicate that soil moisture was generally lost after compaction by agricultural machinery and its loss was related to pressure load, soil depth and compaction times. Generally, moisture loss increased with the increase of pressure load and mostly occurred at the soil surface (0 to 5 cm) for light loads (110 kg). Moreover, the moisture loss decreased gradually with the increases in soil depth for light loads (37 and 98 kg), although it was first increased and then quickly decreased for heavy loads (>= 118 kg). The loss of soil moisture by 5 compactions was pattern with 1 compaction, but was much larger with the gap by 0.5 to 1.5% between them.