the effects of axle load and 4wd mode on field capacity and fuel consumption of massey ferguson 399 tractor during moldboard plowing

field capacity, fuel consumption and drive wheel slippage in massey ferguson (mf399) tractor with standard and liquid ballasted (630 kg) axle load and at 4wd mode was evaluated and compared. the tests were conducted at the experimental station, college of agriculture, shiraz university, in a field with clay loam soil at average moisture content of 18% d.b. the experiment was of a randomized complete block design with a 3x3 factorial of three replications. the treatments consisted of a mf399 tractor at three conditions (2wd mode either with standard or liquid ballasted tires and 4wd mode along with standard axle load) and three levels of plowing depth; shallow (15-20 cm), medium (20-25 cm) and deep (25-30 cm) using a semi-mounted 4-bottom moldboard plow. the assessed parameters included; field capacity, wheel slip as well as fuel consumption. the results demonstrated that by water ballasting the rear drive wheels of mf399, its wheel slippage during medium and deep plowing decreased from 20% and 59% to 16% and 34.6%, respectively. this slippage rate stands at the threshold of acceptable range for medium depth plowing but is still extremely high for deep plowing. in the 4wd mode, the average wheel slip page during moldboard plowing for medium and deep plowing was reduced to 12.24% and 15.6%, respectively,both of which were in the acceptable range. the fuel consumption during deep plowing was reduced from 31.52 to 27.42 l/hr through water ballasting of the rear drive wheels and further reduced to 22.84 l/ha by shifting to 4wd mode with no wheel ballasting. considering the overall results of this experiment, including values of wheel slippage, fuel consumption and field capacity, it would be wise to suggest using mf399 tractor with standard load rear axle drive, water ballasted rear wheel drive and standard load (4wd mode) for conducting shallow, medium and deep plowing, respectively.