testing and evaluation of a rototiller with new ridged blades

introduction recently, employment of rotary tillers has been expanded in gardens and small farms, especially in the northern of iran. however using the l-shaped blades in the conventional rotary tillers have some problems such as severe vibration problems, weeds stucking around the blades, forming the plow pan and lower performance due to the less powers of such small rototillers. therefore in order to overcome the above mentioned problems, a rototiller with new ridged blades was designed, fabricated and tested in this research. materials and methods experiments were carried out in one of the citrus orchards in mazandaran, sari. the experimental design was split plots based on randomized complete block design with three replications. the soil moisture as main plot varied in two levels of 13.5-21.9 and 21.9-30.3 percent based on dry weight and the rotational speed of blades as subplots varied in three levels of 140-170, 170-200 and 200-230 rpm. the measured parameters consist of soil particle mean weight diameter, soil bulk density, soil crumbling percentage, specific fuel consumption and machine efficiency. the diameter of soil particles was measured using a set of standard sieves with diameter ranging from 0.5 to 8 mm. then a laboratory shaker was used to sift the samples. each sample was shaken in 30 sec. the fuel consumption during the experiments was determined by the filled fuel tank method. analysis of variance (anova) and mean comparisons and interaction between the parameters were performed using the spss 16 software. results and discussion the results indicated that the soil particle mean weight diameter reduced by increasing blades rotational speed in both examined soil moisture contents. results indicated that the soil crumbling percent increases with increasing the rotational speed. the main reason for this effect could be due to the more energy transferring to the soil at higher rotational speeds, which result in further crumbling of the soil slices. regarding the results obtained in this study, the specific fuel consumption increased at first in a light slope, then in a steep rise with increasing the blades rotational speed. the reason can be the higher crumbling percent of the soil at higher rotational speeds and higher soil moisture contents (at the range of 21.9-30.3%), providing the more specific energy consumptions. the specific fuel consumption was the maximum at higher soil moisture content of 30 %. the results indicated that the blades rotational speed and soil moisture content had no significant effect on the field efficiency of the examined rototiller. the field efficiency varied in the range of 92 to 97% in all of the experiments, i.e., rotational speed between 140 to 230 rpm and moisture content ranging from 13.5 to 30.3%. the reason for that was due to the roughly similar turning times, minor adjustments, changing operators and some other parameters influencing the field efficiency. reduction of the rotational speed of the rototiller from high-to-moderate speeds leads to decrease the fuel consumption to 17 liter ha-1, which could be significant in wide scale of soil tillage operations. as a general result, reduction of the rotational speed had some considerable advantages such as reducing power requirements, reducing blade wearing and maintaining soil structure. conclusions influence of soil moisture and rotational speed of blades on the soil particle mean weight diameter, soil crumbling percentage and specific fuel consumption were significant (p<0.01) for fabricated rototiller with new ridged blades. statistical analysis indicated that the soil crumbling percentage and specific fuel consumptions increased linearly with increasing the rotational speed of blades. the determination coefficients of the crumbling percentage and specific fuel consumption as a function of rotational speed were 0.996 and 0.860, respectively. meanwhile, clod mean weight diameter decreased linearly by increasing the rotational speed with a determination coefficient of 0.990. for achieving fine soil aggregates, combining high rotational speed and higher soil moisture (20 to 30%) is suggested, while to obtain a coarse soil gradation, low rotational speed and low soil moisture are more suitable compositions. the use of high rotational speed is not recommended due to increasing fuel consumption and consequently the soil erosion and environmental issues.