Field Performance of the Disk Harrow, Power Harrow and Rotary Tiller at Different Soil Moisture Contents on a Clay Loam Soil in Mazandaran

About 60% of the mechanical energy consumed in mechanized agriculture is used for tillage operations and seedbed preparation. On the other hand, unsuitable tillage system resulted in soil degradation, affecting soil physical properties and destroying soil structure. The objective of this research was to compare the effects of three types of secondary tillage machines on soil physical properties and their field performances. An experiment was conducted in a wheat farm in Jouybar area of Mazandaran as split plots based on randomized complete block design with three replications. The main independent variable (plot) was soil moisture with three levels (23.6-25, 22.2-23.6 and 20.8-22.2 percent based on dry weight) and the subplot was three types of machine (two-disk perpendicular passing harrow, Power harrow and Rotary tiller). The measured parameters included: clod mean weight diameter, soil bulk density, specific fuel consumption, machine efficiency and machine capacity. The effects of treatments and their interactions on the specific fuel consumption, machine efficiency and machine capacity and also the effects of treatments on bulk density were significant (P<0/01). The bulk density decreased 15.3%, the specific fuel consumption increased 11.8%, whereas the machine efficiency and machine capacity increased and decreased with the decrease in soil moisture, respectively. The maximum value of the bulk density and machine efficiency were obtained by the use of rotary tiller and the maximum value of the specific fuel consumption and machine capacity were obtained by the use of power harrow. A criterion was defined for selecting machine type and moisture content for optimum condition. The results suggested power harrow working at soil moisture condition of 24.3% (based on dry weight).