M. Mohammadi; S. H. Karparvarfard; S. Kamgar; M. Rahmatian
Abstract
Introduction Due to problems such as water resources constraints, poor soil and soil organic matter, and the problems related conventional tillage, the attention paid to protective tillage equipment should be taken into consideration by farmers. Today, agricultural machinery designers and manufacturers ...
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Introduction Due to problems such as water resources constraints, poor soil and soil organic matter, and the problems related conventional tillage, the attention paid to protective tillage equipment should be taken into consideration by farmers. Today, agricultural machinery designers and manufacturers are looking for ways to resolve the problems due to the lack of water and soil resources and the reduction in fuel resources. One of these solutions is the optimization of agricultural machinery. The blade is one of the most important consumed components of tillage tools, which is very important for how it is adjusted and its effect on soil. According to research conducted on the importance of optimizing tillage implements, this study was carried out with the aim of optimizing the operating conditions for combined tillage with a new narrow blade. Materials and Methods The tests were taken place in the 10th section of farms in Agriculture school (Bajgah zone) of Shiraz University. Those tests were arranged as the split-split plot based on a completely randomized design. The treatments included the tillage depth, tilt angle and forward speed. The levels for the tillage depth, tilt angle and forward speed were 15, 20 cm and 0, 10, 15, 20, 25 degree and 3, 4, 5 km h-1 respectively. The experiments were performed in three replications. The test variables were draft, soil upheaving and disturbance areas, specific draft, fuel consumption and tractor wheel slippage. The CK 45 steel was used to make blades. The blades were made of the same dimensions and the difference between the blades was only at their tilt angle. Before starting the field tests, some properties of soil such as soil moisture content, soil texture and soil bulk density were measured. The RNAM test code was then used for measuring the draft force. The encoder and the fifth wheel were also employed to measure the slippage. For measuring the fuel consumption, two flow meters were used in the round way. The profilometer was applied for measuring the soil upheaving and disturbance areas. The specific draft was also computed. The data analysis was performed by SAS software (9.4 edition). Multiple regression method was used for modeling the desired treatments. Results and Discussion The results of multivariate regression method for optimizing forward speed, tillage depth and tilt angle for the blades including winged were 3.3 km h-1, 20 cm and 25°, respectively, and for the non-winged, 3.5 km h-1, 20 cm and 24.8°. Providing the tilt angle on the blade surface is considered as an innovation in this research, therefore, it can be seen from the results that with increasing this angle, the draft of the tillage was decreased. This could be due to the increased surface of the blade in the face of the soil on the diagonal surface. This increase was proportional to the cosine tilt angle at the initial surface of the blade. Therefore, the shear strength of the soil was decreased with increasing of this surface and ultimately decreased the amount of draft of the tillage. This variable had a significant difference with the depth of tillage and the forward speed of tractor and fuel consumption for the winged new narrow blade. Although the interactions of the above mentioned variables on the fuel consumption for the new blade condition were not significantly different, the minimum fuel consumption for the non-winged blade condition was also obtained at the same tilt angle as the winged new blade. In general, considering all of factors, the 25 degree inclination angle was proposed for both conditions. The interaction of this factor (tilt angle) on the wheel slip rate was also significant. The effect of the angle of inclination for both blades was significant on the slip of the wheel drive, so that the increase in the tilt angle reduced the amount of wheel slip. However, if the amount of slip of the tractor's wheel for an optimum angle of 25° was considered, according to the graph which representing the relationship between tractive efficiency vs. wheel slip and for Cn = 50, the tractive efficiency will be determined by calculation. It should be noted that the tractor's tractive efficiency was equivalent to 82%. This value reflects the effect of the tilt angle on the amount of tractor output power according to the definition of the tractive efficiency of the tractor. Conclusion Considering the increasing growth of using combined tillage tools in dry soil and its low moisture content, and considering the necessity of replacing the custom chisel blades with new blades which resistance to the soil reaction forces upon them, the non- winged blades with the tilt angle about 25° for working depth of 20 cm and forward speed of 3.5 km h-1 can increase the tractive efficiency of tractors to 82% and also decrease the fuel consumption by 34% compared to conventional tillage blades.
