Comparative Field Evaluation of Three Models of a Tractor

Comparative Field Evaluation of Three Models of a Tractor Ahaneku, I. E. 1+, O. A. Oyelade 2, and T. Faleye 2 1. Department of Agricultural and Bioresources Engineering, Federal University of Technology, Minna. 2. National Centre for Agricultural Mechanization, Ilorin. + Corresponding author s e-mail address: drahaneku@yahoo.com Abstract Field tests were conducted to evaluate the performance of three different ranges of Mahindra tractors at the National Centre for Agricultural Mechanization, Ilorin, under identical operating conditions. The tractor Models are Mahindra B-275DI, Mahindra 575DI and Mahindra 605DI. The parameters evaluated were travel reduction (wheel slippage), draught force, speed of operation, drawbar power, volume of soil disturbed, fuel consumption, effective field capacity, theoretical field capacity, field efficiency, and average width and depth of cut during ploughing and harrowing operations. The soil physical and dynamic properties were also measured. The experimental plots were laid side by side in a randomized complete block design (RCBD). Results indicate that Mahindra tractor Model 605 DI performed better than the other two models (575DI and B-275DI) during both ploughing and harrowing operations with respect to the parameters evaluated. The 605DI model was therefore recommended among the three tractors from the standpoint of operational efficiency and economy. Keywords: Evaluation, Tractor, Tillage, Performance 1. Introduction In order to meet the food demand of the ever-increasing world population, one of the approaches being adopted is the substitution of human power with mechanical power in agricultural production. Different terms in different situations have been used to connote this mechanical power substitution. These include Appropriate technology, Tractorization, Selective Mechanization or simply, Mechanization (FAO 1980). The major operation carried out in the field with mechanical power is tillage. Agricultural tillage involves soil cutting, soil turning, and soil pulverization and thus demands high energy, not just due to the large amount of soil mass that must be moved, but also due to inefficient methods of energy transfer to the soil. The most widely used energy-transfer method is to pull the tillage tool through the soil. This is mainly realized with the use of tractors. The primary purpose of agricultural tractors is to provide drawbar work since drawbar is the most commonly used power outlet of a tractor. According to Kathirvel et al. (2001), the ability to provide draft to pull various types of implements is a primary measure of the effectiveness of a tractor. Drawbar work is achieved through the drive wheel to move the tractor and or implements through the soil. Drawbar work can be expressed as the product of pull and travel speed. Therefore, the ideal tractor converts all the energy from the fuel into useful work at the drawbar. In practice, most of the potential energy is lost in the conversion of chemical energy to mechanical energy, 90

along with losses from the engine through the drive train and finally through the tractive device (Zoz and Grisso, 2003). Reports from literature indicate that about 20% to 55% of the available tractor energy is wasted wears at the tractive device-soil interface. This energy wears the tires and compacts the soil to a degree that may cause detrimental crop production (Burr et al. 1982; Baloch, et al. 1991; Zoz and Grisso 2003). Ownership of a tractor and associated items of equipment can involve a substantial investment. Improper choice of size of tractor can be costly because a very small tractor can result in long hours of field work, excessive delays and premature replacement, while a too large tractor can result in excessive operating and overhead costs (Summer and Williams, 2007). The ideal tractor with matching equipment should get the work completed on time at the lowest possible cost. The performance of tractor depends on the performance of a combination of traction devices and the performance of the tractor drive train. While the efficiency of a traction device is defined as tractive efficiency, the efficiency of a complete tractor is defined as power delivery (Zoz et al., 2002). Farm size, availability of labour and custom services, crop selection, and cultural practices, such as choice of tillage system, all affect the selection of optimum equipment and, ultimately, the number of tractors necessary to carry out farming operation. Although demand for tractor power generally increases with farm size, excess labour requirements may permit owners of one tractor to allow several operators to keep the machine running for extended periods of the day during highdemand times. This means that tractors to be used for these strenuous activities should undergo extensive test to avoid incessant break down. To select and match tractors with implements, information is needed about the capacity of both the tractor and implement as well as the likely load to be imposed on the tractor. Accordingly, draft requirements will vary with implement size, soil type, speed of operation and depth of operation. Therefore, for effective tractor-implement matching, there is the need to ascertain actual field efficiencies and draft requirements along with other indices of tractive performance. It has been advocated that the determination of tractor performance under field conditions involves a rather complex apparatus. Therefore, a few methods were developed for various agricultural scopes by utilizing tractor test results and considering tractor mechanics in order to predict tractor performance (Ozarslan and Erdogan, 1996). Low rate of adoption of new four wheel drive tractors has been adduced to lack of information of the real field performance of these machines (Ortiz-Laurel et al., 2006). It is only through the results of field tests of the available tractors that farmers can make informed decisions as to the model of tractor to purchase based on their performance. Under agricultural mechanization, field machines such as tractors constitute a major portion of the total cost of crop production. The proper operation of these machines is essential for profitable agricultural production. Therefore, performance data for tractors and implements under different soil conditions are important for farmers, machinery operators and tractor manufacturers alike (Al-Suhaibani et al., 2010). Accordingly, Grisso et al. (2008) enumerated actions that are necessary for efficient operation of farm tractors to include: 91

a) Maximizing fuel efficiency of the engine and mechanical efficiency of the drive train, b) Maximizing attractive advantage of traction devices and c) Selecting an optimum travel speed for a given tractor-implement system. This study was undertaken to evaluate the performance of three different models of Mahindra tractor in the field under identical operating conditions in order to guide farmers in selecting suitable tractor-implement combination for cost-effective operations. 2. Materials and Methods The study was carried out at the research farm of the National Centre for Agricultural Mechanization (NCAM), Ilorin (370m above sea level, Longitude 4 0 30 E, Latitude 8 0 26 N) in the north central states of Nigeria under the southern guinea savannah vegetation in a sandy loam soil (Ahaneku and Onwualu, 2007). All the parameters of the tractor-implement performance were measured and recorded in line with the recommendations of RNAM test codes and procedures for farm machinery technical series (1995). The tested tractors were from Mahindra and their specifications are shown in Table 1. The implements used for the trials were tractor mounted disc plough and disc harrow. The specifications of the matching implements are shown in Table 2. Each tractor was tested on an area of 0.25 hectares (25 m x 100 m) laid side by side in a randomized complete block design with three replications. 2.1 Measurement and calculation 2.1.1 Operating speed Outside the long boundary of the test plot, two poles 20 m apart were placed approximately in the middle of the test run. On the opposite side also two poles were placed in a similar position 20 m apart so that all four poles form corners of a rectangle, parallel to one long side of the test plot. The speed was calculated as the ratio of the distance (20 m) to the time taken for the machine to travel the distance. 2.1.2 Travel reduction (wheel slip) A mark was made on the tractor drive wheel with coloured tapes and the distance the tractor moves forward at every 10 revolutions under no load and the same revolution with load on same surface was measured. Expressed mathematically as: TR = (1) where: TR = travel reduction (%) M 2 = distance covered at every 10 revolutions of the tractor drive wheel at no load (m) M 1 = distance covered at every 10 revolutions of tractor drive wheel with load (m). 92

2.1.3 Draft of implements Draft was measured using a digital dynamometer attached to the front of the tractor on which the implement was mounted. Another auxiliary tractor was used to pull the implement mounted tractor through the dynamometer. The auxiliary tractor pulls the implement-mounted tractor with the latter in neutral gear but with the implement in the operating position. Draft was recorded in the measured distance (20 m) as well as the time taken to traverse the distance. On the same field, the implement was lifted out of the ground and the draft recorded. The difference between the two readings, gives the draft of the implement. This procedure was repeated for each of the tractors evaluated. 2.1.4 Fuel consumption The fuel required for each tillage operation was determined by filling the tank to full capacity before and after the test. Amount of refueling after each test is the fuel consumption for the test. 2.1.5 Effective field capacity Effective field capacity (S) was evaluated using the relation: (2) where: 2.1.6 Field efficiency S = Effective field capacity (ha/hr) A = Area covered (ha) T p = Productive time (hr) T l = Non-productive time (hr) (time lost for turning, loading and adjustment excluding refueling and machine trouble). This gives an indication of the time lost in the field and the failure to utilize the full working width of the machine. It is calculated from the test data as follows: E f = = (3) where: E f = Field efficiency (%) W e = Effective working width (m) W t = theoretical working width (m) All other parameters are as earlier defined. 93

2.1.7 Soil volume disturbed The soil volume disturbed in m 3 /hr was calculated by multiplying the field capacity with the depth of cut. V = 10000SD where: V = Soil volume disturbed (m 3 /hr) S = Effective field capacity (ha/hr) D = Depth of cut (m) 2.1.8 Drawbar power Drawbar power was evaluated using the relation between draft and speed as follows: Drawbar power = (4) 3. Results and Discussion 3.1 Soil conditions The average soil physical properties within 40cm depth are presented in Table 3. There are no significant differences (p < 0.05) exhibited in the soil properties with the use of the three tractor models during both ploughing and harrowing operations. 3.2 Draft of implements The results of the performance tests on the three tractors are shown in Table 4. Lighter tractors (B-275DI and 575DI) exhibited higher total draft force when compared with that from the heavier (605DI) tractor. The results are in agreement with the findings of Bukhari, et al. (1988) and Abubakar et al. (2009) that lighter tractors perform better on soft soils because the driving force increases proportionally with the driving axle load and travelling resistance increases exponentially with tractor weight. As a consequence, drawbar pull (draft) is less when the tractor is heavy. The results also show that speed of operation and depth of cut affected the draft of the implements. As expected, the draft recorded during ploughing operations were consistently higher than those of harrowing operations, irrespectively of the tractor model used. Draft was highest with the 575DI model than in both the B-275DI and 605DI models. This may be attributable to the higher depth of cut achieved by the tractor during the ploughing operations. 3.3 Drawbar power Drawbar power is a function of draft and speed. Like draft, tractor model 575DI gave the highest drawbar power of 10.61kW since a large pull and high speed will result in 94

a large drawbar power. In the same vein, tractor model 605DI gave the lowest drawbar power of 7.07 kw, followed by tractor model B-275DI with 8.65 kw. 3.4 Field capacity and soil disturbance Field capacity and soil disturbance has been reported as two major factors in determining the performance of tillage implements (Bukhari et al., 1988). The field capacity of a machine is a function of its width, speed and efficiency of operation. The data regarding these parameters is presented in Table 4. Tractor model 605DI with relatively higher values of width of cut, speed of operation and field efficiency achieved better results for field capacity. The tractor model 575DI gave the least field capacity despite the high width of cut achieved and higher speed of operation than tractor model B-275DI. This could be explained by the higher travel reduction associated with the tractor model during tillage operations which may have resulted from the higher depth of cut attained during operation. This result is in agreement with the findings of Ortiz-Laurel et al. (2006) that travel reduction has effect on field capacity. Soil volume disturbed depends on the effective capacity and the depth of cut. The comparative performance of the three tractor models in terms of soil disturbance shows that tractor model 605DI with the same implement achieved highest soil disturbance. The results also indicated that higher speed of operation affected soil volume disturbed positively. Thus, tractors operating at higher speed yielded higher disturbed soil volume. 3.5 Travel reduction Travel reduction affects the traction efficiency of any tractive device. Table 4 presents the results of the travel reduction emanating from the field test of the three tractor models. Tractor model 575DI consistently gave the highest values of travel reduction or wheel slip during both ploughing and harrowing operations. This high wheel slip may have given rise to the large fuel consumption recorded and the lower field efficiency of this tractor model. 3.6 Fuel consumption The parameters for fuel consumption did not show any significant differences between the tractor models (Table 4). However, the largest amount of fuel was consumed with the use of tractor model 575DI for the same area and operation. The higher fuel consumed by this model could be ascribed to its higher speed of travel with a higher wheel slip. 4. Conclusion The total draft of the implements using the three tractor models were close except for tractor model 605DI with a relatively low draft associated with heavy tractors. The tractor model 575DI travelled faster with high depth of cut and higher travel reduction leading to low field efficiency and higher fuel consumption. Since width of operation is directly proportion to area and inversely proportional to time, efficiency and speed of operation, a tractor with high speed of operation and field efficiency will take less time to complete the field operation. An efficient tractor must ensure small wheel slip 95

but large tractive force to be able to overcome implement draft. Though all the three tractor models performed well based on established standards, however, from the standpoint of efficiency and fuel economy, the tractor model 605DI is preferred among the tractor models. References Abubakar, M. S., D. Ahmad, J. Othman, and S. Suleiman (2009). Present State of Research on Development of a High Clearance Vehicle for Paddy Fields. Research Journal of Agriculture and Biological Sciences, 5(4): 489 497. Ahaneku, I. E. and A. P. Onwualu (2007). Tillage effects on maize performance and physical properties of a sandy soil. Journal of Applied Science, Engineering and Technology. Vol. 7, No. 1:42 49. Al-Suhaibani, S. A., A. A. Al-Janobi and Y. N. Al-Majhadi (2010). Development and Evaluation of Tractors and Tillage Implements Instrumentation System. American J. of Engineering and Applied Sciences 3(2):363-371. Baloch, M. J.; Mirani B. A. and Bukhari S. (1991). Prediction of Field Performance of Wheel Tractors. AMA, 22(4): 21-24. Bukhari, S., M. A. Bhutto, J. M. Baloch., A. B. Bhutto and A. N. Mirani (1988). Performance of Selected Tillage Implements. Agricultural Mechanization in Asia, Africa and Latin America. 19(4): 9 14. Burr, E. C.; Lyne, P. W. L.; Metring P. and Keen J. F. (1982). Ballast and inflation pressure effects on tractive efficiency. ASAE paper No. 82 1567. St. Joseph, MI:ASAE. F.A.O. (1980). Production year Book Food and Agriculture Organization of the United Nations, Rome. Grisso, R. D.; D. H. Vaughan and G. T. Roberson (2008). Fuel Prediction for Specific Tractor Models. Applied Eng. Agric., 24:423 428. Kathirvel, K.; Manian R. and Balasubramanian M. (2001). Tractive Performance of Power Tiller tyres. Agricultural Mechanization in Asia, African and Latin America. 32 (2):32-36. Ortiz-Laurel, H. D. Rossel and J. G. Hermosilo-Nieto (2006). Front wheel drive effect on the performance of the Agricultural Tractor. Agricultural Mechanization in Asia, Africa, and Latin America. 37(1):14 17. Ozarslan, C. and Erdogan D. (1996). Optimization of Tractor Plowing Performance. Agricultural Mechanization in Asia, Africa, and Latin America. 27(3):9-12. RNAM (1995). Regional Network for Agricultural Machinery Test codes and Procedures for Farm Machinery. Technical Series No. 12. General Guidelines in the use of Test Codes. Summer, P. E. and E. J. Williams (2007). What size Farm Tractor do I need? Cooperative Extension Service. University of Georgia college of Agriculture, Athens, G. A. Miscellaneous Publication No. ENG 07 003. Zoz F. M.; Turner, R. L. and Shell L. R. (2002). Power Delivery Efficiency: A Valid Measure of Belt and tire Tractor Performance. Transactions of the ASAE 45 (3): 509 518. 96

Zoz, F. M. and Grisso R. D. (2003). Traction and Tractor Performance, ASAE Distinguished Lecture Series #27, ASAE Publication Number 913C0403. Paper presented at Agricultural Equipment Technology Conference held at Louisville, Kentucky, USA between February 9 11, 2003. 97

Table 1: Specifications of tested tractors Specification MODEL OF MAHINDRA TRACTOR B-275DI 5757DI 605DI Effective output (hp) 39 45 60 Type of Engine 3-Cylinder 4-Cylinder 4-Cylinder Type of Fuel Diesel Diesel Diesel Type of Steering System Mechanical Mechanical Power-assisted Transmission 8 x 2 8 x 2 8 x 2 Type of Injector Pump In-line injector In-line injector In-line injector Firing Order 1-2-3 1-3-4-2 1-3-4-2 Fuel Tank Capacity (L) 55 55 55 Lifting Capacity (kg) 1000 1640 1800 Rated Engine Speed (rpm) 2600 2300 2100 Type of Cooling System Water-Cooled Water-Cooled Water-Cooled Country of Manufacture India India India Front tyres (size) 6.0 16 6.0 16 7.50 16 Inflation Pressure (Psi) 24 24 24 Rear Tyres (size) 12.4 28 13.6 28 16.9 28 Inflation Pressure (Psi) 17 17 17 Table 2: Specifications of matching implements Specifications Disc Plough Tandem Disc Harrow Implement type Mounted Mounted Overall length (mm) 1870 2290 Overall Width (mm) 960 1440 Overall height (mm) 1060 1100 Number of bottoms/blades 3 24 Width of cut (mm) 1310 1080 Diameter of disc (mm) 605 - Diameter of blade (plane) - 510 (mm) Diameter of blade (Notched) (mm) - 505 Table 3: Effect of field operations on soil physical properties Disc Ploughing Disc Harrowing Tractor Parameters* Model MC (%) BD (g/cm 3 ) CI (N/cm 2 ) SS (MPa) MC (%) BD (g/cm 3 ) CI (N/cm 2 ) SS (MPa) B-275DI 9.49 1.39 10.10 0.004 5.59 1.36 6.2 0.004 575DI 9.53 1.40 9.09 0.004 4.98 1.41 3.91 0.005 605DI 9.58 1.38 10.33 0.005 5.27 1.32 3.91 0.004 * MC = Soil Moisture Content, SS = Shear Strength, BD = Soil Bulk Density, CI = Cone Index 98

Table 4: Results of field test performed on the mahindra tractors during ploughing Operation Parameter* TRACTOR MODEL B-275DI 5757DI 605DI Travel reduction (%) 20.38 21.29 17.22 Width of cut (cm) 114.33 135.25 129 Depth of cut (cm) 18.17 19.33 19.03 Speed of operation (km/hr) 6.00 6.43 6.43 Effective field capacity 0.74 0.72 0.85 (ha/hr) Theoretical field capacity 0.93 0.91 1.02 (ha/hr) Operation time (hr/ha) 1.35 1.39 1.18 Field efficiency (%) 79.45 78.98 83.48 Draught force (kn) 5.19 5.94 3.96 Fuel consumption (L/ha) 4.92 5.90 4.78 Fuel consumption (L/hr) 3.64 4.25 4.07 Soil volume disturbed (m 3 /hr) 1,342.76 1,391.76 1,619.45 Drawbar Power (kw) 8.65 10.61 7.07 * Parameter values are average of three replicates Table 5: Results of field test performed on the mahindra tractors during harrowing operation. Parameter* TRACTOR MODEL B-275DI 5757DI 605DI Travel reduction (%) 20.95 23.82 15.87 Width of cut (cm) 231.00 215.00 229.33 Depth of cut (cm) 12.00 13.00 12.00 Speed of operation (km/hr) 7.20 8.18 8.78 Effective field capacity 1.28 1.24 1.55 (ha/hr) Theoretical field capacity 1.73 1.59 1.97 (ha/hr) Operation time (hr/ha) 0.78 0.80 0.65 Field efficiency (%) 73.87 78.06 78.57 Draught force (kn) 4.01 4.21 3.34 Fuel consumption (L/ha) 3.28 4.12 3.33 Fuel consumption (L/hr) 4.20 5.12 5.15 Soil volume disturbed (m 3 /hr) 1,537.20 1,617.20 1,855.20 Drawbar Power (kw) 8.02 9.57 8.15 * Parameter values are average of three replicates 99