PERFORMANCE EVALUATION OF TRACTOR IMPLEMENT SYSTEMS AT PART LOADS IN SANDY LOAM SOIL

Transcription

1 PERFORMANCE EVALUATION OF TRACTOR IMPLEMENT SYSTEMS AT PART LOADS IN SANDY LOAM SOIL THESIS SUBMITTED TO THE MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY, UDAIPUR IN PARTIAL FULFILLMENT OF THE REQUIRMENTS FOR THE DEGREE OF MASTER OF ENGINEERING IN AGRICULTURE (FARM MACHINERY AND POWER ENGINEERING) BY PATIL SUHAS BAPUSO (2003) MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY, UDAIPUR COLLEGE OF TECHNOLOGY AND ENGINEERING, UDAIPUR

2 Dated: 26/02/2003 CERTIFICATE - I THIS IS TO CERTIFY THAT MR. PATIL SUHAS BAPUSO HAS SUCCESSFULLY COMPLETED THE COMPREHENSIVE EXAMINATION HELD ON 17 TH AUG AS REQUIRED UNDER THE REGULATIONS FOR THE DEGREE OF MASTER OF ENGINEERING IN THE SUBJECT OF AGRICULTURAL ENGINEERING (FARM MACHINERY AND POWER). (Dr. Y. C. BHATT) HEAD DEPARTMENT OF FM&PE COLLEGE OF TECHNOLOGY AND ENGINEERING, UDAIPUR

3 MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY, UDAIPUR COLLEGE OF TECHNOLOGY AND ENGINEERING, UDAIPUR Dated: 26/02/2003 CERTIFICATE - II THIS IS TO CERTIFY THAT THIS THESIS ENTITLED PERFORMANCE EVALUATION OF TRACTOR IMPLEMENT SYSTEMS AT PART LOADS IN SANDY LOAM SOIL SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING IN THE SUBJECT OF AGRICULTURAL ENGINEERING (FARM MACHINERY AND POWER) EMBODIES BONAFIDE RESEARCH WORK CARRIED OUT BY MR. PATIL SUHAS BAPUSO UNDER MY GUIDANCE AND SUPERVISION AND THAT NO PART OF THIS THESIS HAS BEEN SUBMITTED FOR ANY OTHER DEGREE. THE ASSISTANCE AND HELP RECEIVED DURING THE COURSE OF INVESTIGATION HAVE BEEN FULLY ACKNOWLEDGED. THE ADVISORY COMMITTEE ALSO APPROVED THE DRAFT OF THE THESIS ON 31/12/2002. (Dr. Y. C. BHATT) HEAD FM&PE DEPARTMENT (Dr. AJAY KUMAR SHARMA) MAJOR ADVISOR (Dr. A. N. MATHUR) DEAN CTAE, UDAIPUR

4 MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY, UDAIPUR COLLEGE OF TECHNOLOGY & ENGINEERING, UDAIPUR CERTIFICATE III DATED: 02/04/2003 THIS IS TO CERTIFY THAT THIS THESIS ENTITLED PERFORMANCE EVALUATION OF TRACTOR IMPLEMENT SYSTEMS AT PART LOADS IN SANDY LOAM SOIL SUBMITTED BY MR. PATIL SUHAS BAPUSO TO MAHARANA PRATAP UNIVERSITY OF AGRICULTURE & TECHNOLOGY, UDAIPUR, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING IN AGRICULTURAL ENGINEERING IN THE SUBJECT OF FARM MACHINERY AND POWER ENGINEERING, WAS AFTER RECOMMENDATION BY THE EXTERNAL EXAMINER AND DEFENDED BY THE CANDIDATE BEFORE THE FOLLOWING MEMBERS OF THE EXAMINATION COMMITTEE. THE PERFORMANCE OF THE CANDIDATE IN THE ORAL EXAMINATION ON HIS THESIS HAS BEEN FOUND SATISFACTORY; WE THEREFORE, RECOMMEND THAT THE THESIS BE APPROVED. (Dr. AJAY KUMAR SHARMA) MAJOR ADVISOR (Prof. R.K. AERON) ADVISOR (Dr. Y. C. BHATT) HEAD DEPTT. OF FM&PE. (Dr. G. S. TIWARI) ADVISOR (Dr. S. C. MAHNOT) DRI NOMINEE (Dr. A.N. MATHUR) DEAN CTAE, UDAIPUR APPROVED (DR. L.L. SOMANI) DIRECTOR RESIDENT INSTRUCTION MPUAT, UDAIPUR

5 MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY, UDAIPUR COLLEGE OF TECHNOLOGY AND ENGINEERING, UDAIPUR DATED: 02/04/2003 CERTIFICATE - IV THIS IS TO CERTIFY THAT MR. PATIL SUHAS BAPUSO STUDENT OF MASTER OF ENGINEERING IN AGRICULTURE IN THE SUBJECT OF FARM MACHINERY AND POWER ENGINEERING, DEPARTMENT OF FARM MACHINERY AND POWER ENGINEERING HAS MADE ALL CORRECTIONS/MODIFICATIONS IN THE THESIS ENTITLED PERFORMANCE EVALUATION OF TRACTOR IMPLEMENT SYSTEMS AT PART LOADS IN SANDY LOAM SOIL WHICH WERE SUGGESTED BY THE EXTERNAL EXAMINER AND THE ADVISORY COMMITTEE IN THE ORAL EXAMINATION HELD ON 02/04/2003. THE FINAL COPIES OF THE THESIS DULY BOUND AND CORRECTED WERE SUBMITTED ON.. (Dr. AJAY KUMAR SHARMA) MAJOR ADVISOR (Dr. A. N. MATHUR) DEAN CTAE, UDAIPUR (Dr. Y. C. BHATT) HEAD DEPARTMENT OF FARM MACHINERY AND POWER ENGINEERING, CTAE, UDAIPUR

6 ACKNOWLEDGEMENTS I feel great pleasure and privilege in expressing profound sense of gratitude and indebtedness for my Major Advisor Dr. Ajay Kumar Sharma Assoc. Professor Department of Farm Machinery and Power Engineering, College of Technology and Engineering, Udaipur whose constant encouragement, helpful guidance and constructive suggestions throughout the investigation, let this work to successful completion. I am highly grateful to the members of my advisory committee, Dr. G. S. Tiwari, Associate Professor, Department of Farm Machinery and Power Engineering, Prof. R. K. Aeron, Professor and Head, Department of Computer Science and Engineering and Dr. S.C. Mehnot, (DRI Nominee) Professor, Department of Soil and Water Engineering, C.T.A.E., Udaipur for their kind co-operation and valuable suggestions. I am deeply indebted to Dr. Y.C. Bhatt, Head, Department of Farm Machinery and Power Engineering, CTAE, Udaipur for his precious guidance and providing all the necessary facilities to carry out the project work. I am extremely thankful to Dr. A.N. Mathur, Dean, College of Technology and Engineering, Udaipur for providing all the needed facilities, which were essential for successfully completion of the project work. I owe my special thanks to Dr. R.N. Verma Professor, Dr. Ravi Mathur, Professor, Dr. S. M. Mathur, Assoc. Professor, Dr. A.K. Mehta Assoc. Professor, Sh. A.L.S. Mathur, Assistant Professor, Sh. K.N.Kaviraj, Assistant Professor Department of FM&PE, CTAE for their timely help and valuable advice. I am very much thankful to Institution of Engineers (India) for their partial financing this research from their grant for industry oriented research projects. I am highly thankful to Sh. M.M. Sharma, Farm manager, and all technical staff of CTAE, Udaipur for providing facilities. Also I am thankful to Sh. S.H. Thakare, Sh. C.P.Doshi and all my colleagues for their kind help during the preparation of thesis. Place : Udaipur Date : 26/02/2003 (PATIL SUHAS BAPUSO)

7 CONTENTS Serial Particulars No. Page No. (i) ABBREVIATIONS AND SYMBOLS I (ii) LIST OF TABLES II (iii) LIST OF FIGURES III (iv) LIST OF APPENDICES IV (v) ABSTRACTS IN ENGLISH V (vi) ABSTRACTS IN HINDI VI I INTRODUCTION 1.1 IMPORTANCE OF TRACTORS IN INDIAN AGRICULTUTRE 1.2 TRACTOR IMPLEMENT SYSTEMS 1.3 SCOPE AND JSTIFICATION OF PRESENT STUDY Testing and evaluation of tractor implement systems Causes of low efficiencies Need of part load setting 3 II. REVIEW OF LITERATURE 2.1 DRAFT REQUIREMENT Effect of soil type on draft requirement Effect of depth of operation on draft requirement Effect of speed of operation on draft requirement Effect of soil moisture content on draft requirement 2.2 ENERGY REQUIREMENT 2.3 FIELD CAPASITY AND FIELD EFFICIENCY 2.4 TRACTIVE PERFORMANCE Effect of moisture content on tractive performance Effect of ballasting on tractive performance Effect of speed of operation on tractive performance 2.5 FUEL EFFICIENCY Effect of speed of operation on fuel consumption Effect of depth of operation on fuel consumption Drawbar fuel consumption 2.6 SOIL INVERSION AND PULVERIZATION

8 III. MATERIALS AND METHOD 3.1 TERMS USED IN THE STUDY Drawbar power requirement Energy requirement Effective field capacity Theoretical field capacity Field efficiency Tractive efficiency Fuel efficiency Vehicle efficiency 3.2 SELECTION OF IMPLEMENTS 3.3 FIELD LAYOUT 3.4 MEASUREMENT OF DIFFERENT PARAMETERS USED IN.THE STUDY Soil moisture content Bulk density Measurement and setting of engine speed (rpm) Speed of travel Zero condition Slip calculation Productive and non-productive time Fuel consumption Calibration of load cell Measurement of rolling resistance Draft Soil pulverization 3.5 PLAN OF EXPERIMENTS 3.6 TEST PROCEDURE

9 IV RESULTS AND DISCUSSION 4.1 POWER REQUIREMENT PER UNIT VOLUME OF SOIL TILLED AT DIFFERENT LOAD SETTINGS Power requirement at 1/3 rd load setting Power requirement at 2/3 rd load setting Power requirement at full load setting 4.14 Comparison of power requirement at different load settings 4.2 ENERGY REQUIREMENT AT DIFFERENT LOAD SETTINGS Energy requirement at 1/3 rd load setting Energy requirement at 2/3 rd load setting Energy requirement at full load setting Comparison of energy requirement at different load settings 4.3 FIELD EFFICIENCY AT DIFFERENT LOAD SETTINGS Field efficiency 1/3 rd load setting Field efficiency at 2/3 rd load setting Field efficiency at full load setting Comparison of field efficiency at different load settings 4.4 TRACTIVE EFFICIENCY AT DIFFERENT LOAD SETTINGS Tractive efficiency at 1/3 rd load setting Tractive efficiency at 2/3 rd load setting Tractive efficiency at full load setting Comparison of tractive efficiency at different load settings 4.5 FUEL EFFICIENCY AT DIFFERENT LOAD SETTINGS Fuel efficiency at 1/3 rd load setting Fuel efficiency at 2/3 rd load setting Fuel efficiency at full load setting Comparison of fuel efficiency at different load settings 4.6 VEHICLE EFFICIENCY AT DIFFERENT LOAD SETTINGS Vehicle efficiency at 1/3 rd load setting Vehicle efficiency at 2/3 rd load setting Vehicle efficiency at full load setting Comparison of vehicle at different load settings 4.7 SLIP DRAFT RELATIONSHIP 4.8 SOIL PULVERIZATION AT DIFFERENT LOAD SETTINGS

10 4.8.1 Soil pulverization at 1/3 rd load setting Soil pulverization at 2/3 rd load setting Soil pulverization at full load setting Comparison of soil pulverization at different load settings 4.9 SELECTION OF SUITABLE GEAR THROTTLE COMBINATION FOR DIFFERENT IMPLEMENTS Suitable gear throttle combination for tractor rotavator system Suitable gear throttle combination for tractor disc plough system Suitable gear throttle combination for tractor cultivator system V SUMMURY AND CONCLUSIONS * SUGGESTIONS FOR THE FUTURE WORK 70 ** LITERATURE CITED *** APPENDICES

11 LIST OF ABBREVIATIONS AND SYMBOLS ASAE : American Society of Agricultural Engineers CTAE : College of Technology and Engineering d.b. : Dry basis e.g. : Example gratia Engg. : Engineering Fig. : Figure ha : Hectare hp : Horse power km/h : Kilometer per hour kwh/ha : Kilo watt hour per hectare lit/ha : Liter per hectare MPUAT : Maharana Pratap University of Agriculture and Technology No. : Number rad/s : Radian per second rpm : Revolutions per minute S.No. : Serial number Trans. : Transactions viz : Namely Wt. : Weight

12 LIST OF TABLES Table No. Particulars Page No. 3.1 Engine speed (rpm) at different throttle positions Theoretical forward speed at different throttle positions Sieve analysis of soil sample Plan of experiments Drawbar power requirement per unit volume of soil tilled of different tractor implement systems at different throttle positions Energy requirement of different tractor implement systems at different throttle positions Field efficiency of different tractor implement systems at different throttle positions Tractive efficiency of different tractor implement systems at different throttle positions Fuel consumption of different tractor implement systems at different throttle positions Vehicle efficiency of different tractor implement systems at different throttle positions

13 LIST OF FIGURES Table No. Particulars Page No. 3.1 Implements selected for the study Initial field condition selected for the study Adjustment of engine seed (rpm) through throttle rod adjustment An auxiliary fuel system fixed on tractor Schematic diagram of an auxiliary fuel system fixed on tractor Load cell calibration curve Draft measurement system Measurement of draft of different implements in the field Drawbar power requirement per unit volume of soil tilled for different tractor implement systems at different load settings 38 Relationship between drawbar power requirement and engine speed for different tractor implement systems 39 Energy requirement for different tractor implement systems at different load settings 41 Relationship between energy requirement and engine speed for different tractor implement systems 43 Field efficiency for different tractor implement systems at different load settings 45 Relationship between field efficiency and engine speed for different tractor implement systems 46 Tractive efficiency for different tractor implement systems at different load settings 48 Relationship between tractive efficiency and engine speed for different tractor implement systems 50 Fuel consumption for different tractor implement systems at different load settings 52 Relationship between fuel consumption and engine speed for different tractor 54 implement systems 4.11 Vehicle efficiency for different tractor implement systems at different load 56

14 settings 4.12 Relationship between vehicle efficiency and engine speed for different tractor implement systems Relationship between slip and draft for different tractor implement systems Field condition after the operation Mean soil clod diameter for different tractor implement systems at different load settings Relationship between mean soil clod diameter and engine speed for different tractor implement systems 62 LIST OF APPENDICES Appendix No. Particulars Page No. A Specifications of implements selected for the study 75 B Specifications of tractor selected for the study 76 C1 Different parameters measured and calculated for rotavator 77 C2 Different parameters measured and calculated for disc plough 78 C3 Different parameters measured and calculated for cultivator 79

15 ABSTRACT A field testing of three tractor implement systems viz. tractor-rotavator, tractor-cultivator and tractor-disc plough was carried out at three load settings (1/3 rd, 2/3 rd and full load). The soil type was sandy loam and field experiments were carried out in the stubbled field left after the harvesting of maize crop. The field moisture content was 8.25 per cent (d.b.) and bulk density was 1.37 g/cc. The depth of operation was varied between cm. Gears were selected to get a forward speed of operation in the recommended range. An auxiliary fuel tank was made for measurement of fuel consumption. A load cell with digital load indicator was utilized for measurement of draft and rolling resistance by towing two tractors. Two stop watches were used for the measurement of speed of operation and total time required to cover a plot area. Soil samples of about 10 kg weight were collected from the field and sieve analysis was done to know the soil pulverization. Results of the experiment showed an increasing trend of drawbar power per unit volume of soil tilled and mean soil clod diameter with increase in part load (engine rpm) fir all tractor implement systems studied except for tractor-rotavator system, which showed decreasing trend with increasing part load factor. Energy requirement and field efficiency increased with increase in part load factor for all tractor implement systems whereas, tractive efficiency, fuel efficiency and vehicle efficiency showed the decreasing trend with increase in part load factor. Suitable gear throttle combinations found were IV-L gear at 1/3 rd load setting and III-L gear at 2/3 rd load setting for all the tractor implement systems. Key words: Part load and Tractor implement systems.

16 I - INTRODUCTION The development of country parallels the mechanization. In India the rising graph of agricultural productivity is directly related to the graph of mechanical power and agricultural machines. One of the strongest, effective and visible constituents of this is the tractorisation. The low performance of existing draft animals is not sufficient for supplying the pre-condition of high yield plant cultivation, as offered by the tractor. 1.1 Importance of Tractors in Indian Agriculture Agriculture has benefited considerably from the wide scale use of tractors and associated implements. The importance of tractors lies mainly in the improvement of soil cultivation and transport in the field of agriculture (Alcock, 1986). With the increasing intensity of soil cultivation and increasing use of organic matter there is possibility of bringing the soil in better yield and thus achieving larger harvests. With the existing nature of soil, texture and taking into consideration the climatic conditions and water supply for the soil and considering those factors influencing plant yield like, for example, supplying the soil with organic fertilizers and organic substances, the pest control, an optimal physical structure of the soil is of great importance. The capacity of traditional hand tools and bullock drawn implements is much lower compared to improved machinery. This delays farming operations and consequently reduction in the yield if not sown in time, especially in case of photosensitive crops. Compared to the traditional local ploughs, disc harrows and cultivators cover an area three times more and ensure timeliness besides drudgery reduction as the operator walks behind the animal for lesser distance. Tractor drawn disc harrow and cultivator cover more area and good seedbed preparation (Singh, 2002). During last few years, there has been an increasing demand for the supply of tractors. The production of indigenous tractors, which was 880 in , reached to a level of 2.5 lakh in 1998, which was second highest in the world (Jain and Rai, 1999). Today more than 2,73,000 tractors are being manufactured every year. During the year the sale of tractors was 2,54,825 units and the population of tractors in the country is estimated to be more than 2.63 millions. But the average availability of tractors is less than 2 per cent of the total farm holders (Singh, 2002). Farmers preferred to get ploughing done by tractors first and other operations performed by animate power latter. All these technological inputs have helped the farmers to mechanize their agriculture and increase their production. The use of mechanized agriculture can

17 also be viewed through the increased use of diesel and electricity in the country in the agriculture sector. The level of mechanization, however, is very low, although, it has helped in increasing the productivity and saving in inputs. Average availability of farm power is one of the indicators of modernization of agriculture. At present the farm power availability at national level is about 1.35 kw/ha, which varies from 0.5 to 3.5 kw/ha from one state to another (Shrivastava, 2003). 1.2 Tractor Implement Systems The tractor cannot be isolated from the implement, nor from the environment in which both the tractor and implement are working. The tractor implement combination forms a system consisting of a set of interacting components, with environmental constrains provided by the terrain and atmosphere. The objective of the system can be simply defined as the performing of a specific task to some measurable standard. The tractor is complex power unit and requires expensive farm equipment, and as such it must provide the performance required at a minimum level of cost to the system. A tractor is also intended to provide transport options with trolley for movement of materials and for field work operations to power and propel agricultural machines. In transport mode, the tractor is required to operate with relatively low drafts over a wide range of operating speeds. For field work, the tractor is often used for tasks requiring high drawbar forces at lesser speeds. Thus, the tractor must interface with the implement in providing the operating parameters necessary to meet the performance objectives for both transport and field work functions. 1.3 Scope and Justification of Present Study section. The scope and justification of present study is discussed under different headings in this Testing and evaluation of tractor implement systems Most of the tractors on the Indian farms are in the range of hp. The configuration of tyres and chassis of most hp range tractors in the country is quite similar to each other therefore, it would be useful to the manufacturers and users to know the tractive performance behavior of tractor with implement and to evaluate methods and operational practice to optimize

18 their performance in the field. The tillage operations are costly operations amongst all the agricultural operations, tillage machinery requires a large amount of power for adequate seedbed preparation (Dahab and Mohamed, 2002). It was estimated that the tillage operations requires 60 per cent of the power used in the American farms (Jacobs et. al 1983). Therefore, the power is one of the criterias for selection of suitable tillage implement, which determines the size of the tractor. Therefore, it is imperative that an implement manufacturer must be aware of the importance of power of the various tillage implements, which could be designed and manufactured in accordance with the size of the tractors available in the country. Type of implement, depth of cut, width of implement, tool shape, tool arrangement, soil type, soil moisture content, shape of field and field condition, travel speed and part load on engine i.e. the ratio of the engine speed during work to the maximum speed (at which maximum power is developed) of an engine are the factors that are considered for testing and evaluation of tractor implement systems Causes of low efficiencies Ideally, the tractor operations should have high field efficiency, less fuel consumption and more tractive efficiency. However combined with highly variant field conditions and semi-literate operators, the combined efficiency of the tractor implement system becomes poor. Among other reasons, the most important is the lack of information on correct operational settings of these systems. The ill matching of the tractor and the implement and incorrect setting by the operators cause low efficiencies Need of part load setting For economical use, 70 per cent of the tractor power must be utilized for any operation. The tractor engines frequently operate at considerably less than full load. A tractor operator normally sets the governor control to maintain the engine speed at a rated or a maximum speed and adjusts the forward speed of the tractor by selection of transmission gear ratio which will provide a forward speed suited to the field conditions and the job to be done. The tractor engine develops that power corresponding to the load. As the power is the product of speed time torque, a given power level may be developed at high speed with low torque or at a lower speed with higher torque. Power developed in response to a less than a full load therefore can be developed at less than full speed (Barnes, 1969).

19 For higher fuel economy, an engine speed should be so selected that the power required for job will be near the maximum, which the engine can develop at that speed. Selection of engine speed at which the power required by the job is substantially less than the maximum, which the engine can develop at that speed, will result in wastage of fuel. It is known that the tractor operator makes minor adjustments to the engine to match field conditions at a given instant can improve output of a tractor considerably. To accomplish this the operator must know the engine load speed, torque level and slip for the fuel economy and high tractive efficiency. As very less work has been done on the part load concept and very less information is available to the tractor operators in this regard. Hence, this should be widely understood and brought to the attention of the owners and operators of the tractor. This information would enable the manufacturers and users in selection of correct size implement, their adjustments and instructional settings of the tractor for better different efficiencies improving the tractor implement combination performance in the field. Keeping these points in view a study was undertaken with following objectives: 1. To evaluate power and energy requirements for tillage implements at part load settings in sandy loam soil. 2. To evaluate field, tractive, fuel and vehicle efficiency (power delivery efficiency) for tillage implements at part load settings. 3. To select a suitable gear-throttle combination for tillage operations at part loads.

20 II - REVIEW OF LITERATURE This chapter deals with the review of literature discussed under different sections. 2.1 Draft Requirement Studies show that the draft depends on soil condition, depth of an operation, speed of operation and soil moisture content. The effect of these parameters on draft and energy requirement studied by different researchers is explained in this section Effect of soil type on draft requirement Bloome et. al. (1983) measured the effect of speed on the draft characteristics of a mould board plough, chisel plough, sweep, a V blade plough and tandem disc in loamy fine sand. The draft of chisel plough with sweeps was found nearly independent of speed, whereas in silt loam soils it was speed dependent. Sherruddin et. al. (1991) conducted an experiment in northeastern part of the Sind Agricultural University, Tandojam. For draft measurement, a hydraulic dynamometer was attached to the front of the tractor on which the implement was mounted. The draft was recorded in the measured distance of 50 m as well as the time taken to travel the same distance was measured. In case of mould board plough, the power requirement was greater in clay loam soil than in silt loam soil. Same results were found in case of disc plough and cultivator Effect of depth of operation on draft requirement Bloome et.al. (1983) studied the draft requirement by tandem disc and V-blade chisel plough in the loamy fine sand soil and showed that the draft of tandem disc was a linear function of depth. Summers et.al. (1986) studied draft relationship for primary tillage in Oklahoma soils and concluded that, the draft varies linearly with depth for mouldboard plough, chisel plough, discs, and sweep plough.

21 Summers (1986) reported that the draft was directly proportional to depth of operation for mould board plough, chisel plough discs and sweep plough. Gebresenbet (1992) and Ploufee et.al. (1995) have shown non-linearity in draft-depth relationship. Plough stability is a measure concern in shallow conditions. Lucican (1992) stated that plough operating depth variations should be less than 10% to achieve a uniform ploughed surface, which leads to proper vegetation burial. Younis et.al. (1994) carried out a study for draft requirement with depth at University of Agriculture, Faislabad, Pakistan. A dynamometer was installed between the two tractors for measuring the draft. The implement was pulled through the soil at desired depth with a constant speed of 2.5 km/h. The depth of cultivation varied from 5 to 45 cm. The draft requirement of disc harrow was 4710, 5101 and 6925 N for 15, 20 and 25 cm depth of an operation. For disc plough the draft requirement was 4905, 6867 and 9810 N for 15, 20 and 25 cm depth of an operation The relationship between draft requirement and the depth of operation was linear for cultivator. The draft requirement per centimeter of cutting width at shallow depth is very close for all the implements. Grisso et.al. (1996) studied tillage implement forces operating in silty clay loam soil and concluded that, 1. Draft force varied quadratically with depth for the tandem disc when used as primary tillage implement in a silt clay loam soil on wheat stubble surface. 2. The chisel plough in silt clay loam soil on wheat stubble surface was mostly influenced by tillage depth although the linear effect of travel speed was found significant, speed showed almost little effect on chisel plough draft. 3. The field cultivator draft in a silt clay loam soil on wheat stubble surface was quadratically dependent on depth. Janobi and Shaibani (1998) conducted an experiment on draft of primary tillage implement on sandy loam soil. The average value of draft for all the implements during the experiments at different depths of operations, specific draft of implement to changed with travel

22 speed and tillage depth. An increasing response in specific draft was observed with an increase in tillage depth (Khalilian et. al. 1988) for all the implement tested in field. The disc plough and mould board plough showed greater draft requirement than offset disc harrow for the same depth using to the influence of the different shapes and sizes of the cultivating element of the implement. Loghavi et. al. (1999) studied the effects of three levels of soil moisture content (10-12, and 16-18% d.b.) and three levels of ploghing depth (15, 20 and 25 cm) on draft, specific draft, and drawbar power requirements of a 3 - bottom disc plough in a clay loam soil. The effect of ploughing depth was highly significant only on draft and drawbar power requirement of disc plough, in such a way that the mean values of these two parameters significantly increased with ploughing depth, while specific draft showed only a mild decreasing trend Effect of speed of operation on draft requirement Bloome et.al. (1983) measured the effect of speed on the draft characteristics of a mould board plough, chisel plough, sweep, a V blade plough and tandem disc in loamy fine sand. The draft of chisel plough with sweeps was nearly independent of speed, whereas draft in silt loam soils was speed dependent. The draft requirement by tandem disc and V-blade chisel plough in the loamy fine sand soil showed little influence from speed. Summers et.al. (1986) studied draft relationship for primary tillage in Oklahoma soils and concluded that, the draft varied linearly with speed for chisel plough, discs, and sweeps plough and is quadratic with speed for mould board plough. Cullum et.al. (1989) reported that the draft requirements of tandem disc, hoe drill, one way disc with seeder and packer exhibited linear dependence on speed. Mani and Panwar (1992) studied the performance of tractor implement systems at part load settings. They operated the implements at 1/3 rd, 2/3 rd and full speed. They concluded that mould board plough required maximum energy per hectare at all the three speed settings.

23 Shirin et.al. (1993) conducted an experiment for the effect of soil moisture content on the specific draft requirement of the disc plough with 45 0 disc angle at different tilt angles and ploughing speeds. At 17 0 tilt and 45 0 disc angle the specific draft decreased with an increase in soil moisture content, for all the ploughing speeds. Grisso et.al. (1996) studied tillage implement forces operating in silty clay loam soil and concluded that, draft of a field cultivator in silt clay loam soil on wheat stubble surface was linearly dependent on speed. Titular (1998) studied the effects of three types of discs (spherical with smooth edge, spherical with notched edge, and conical with smooth edge) in combination with four travel speeds (4.0, 5.0, 6.0 and 7.0 km/h) of a fixed three point hitch mounted plough in a field experiment. The results led to the following conclusions: a) Cutting width, disc operating depth, percentage of crop residue incorporation and energy consumption had no significant response to the different travel speeds but were influenced by the type of disc. b) The spherical smooth-edged disc produced greater cutting width and a smaller percentage of residue incorporation. c) The spherical smooth edged disc showed lower performance than the other disc types. Janobi and Shaibani (1998) conducted an experiment on draft of primary tillage implement on sandy loam soil. The disc plough and mould board plough showed greater draft requirement than offset disc harrow for the same range of speed. Tanihuchi et.al. (1999) studied the draft required by a mould board plough at different forward speeds and body attachments in Eniwa volcanic ash soils using an open air soil bin. Soil moisture content was maintained at 36% (d.b.) while forward speed ranged from 0.1 to 4 m/s at an increment of 0.5 m/s. They concluded that draft of mould board plough increased with increase in travel speed. This was in agreement with previous researchers. However from the observed speed-draft behavior and also from previous research implications, the relation changed from being of an

24 increasing rate at lower speed to decreasing rate type at higher speeds. This called for further detailed research covering wider speed range at closer experimental intervals (0.5 to 5 m/s). Within the practical and economical tillage operation ranges, the speed draft relationship can be represented by a straight line of positive slope was quite logical Effect of soil moisture content on draft requirement Shirin et.al. (1993) conducted an experiment for the effect of soil moisture content on the specific draft requirement of the disc plough with 45 0 disc angle at different tilt angles. At 17 0 tilt and 45 0 disc angle the specific draft decreased with an increase in soil moisture content, for all the ploughing speeds. At 3 km/h speed the specific draft were 14.1, 13.1 and 12.4 N/cm 2 for average soil moisture content of 23.3, 29.4 and 33.4 per cent respectively. Grisso et.al. (1996) studied tillage implement forces operating in silty clay loam soil and concluded that the wide range of soil moisture contents, bulk density and cone index observed in this study did not significantly affect the implement draft force of the chisel plough and field cultivator. Loghavi et. al. (1999) studied the effects of three levels of soil moisture content (10-12, and 16-18% d.b.) on draft, specific draft, and drawbar power requirements of a 3 - bottom disc plough in a clay loam soil. Mean values of draft, specific draft and drawbar power requirements and clod mean weight diameter were minimized at 13-15% and 16-18% soil moisture contents respectively Energy Requirement Smith and Fornstorm (1980) studied the energy requirement of selected dry land wheat cropping systems and found that, the specific draft (draft/unit width) for S-cultivator (3.5m) was 2.3 kn/m at the forward speed 4.8 km/h and for mould board plough (three bottom 35.6 cm bottoms) at the forward speed 4.0 km/h was 14.6 kn/m which was about 6.5 times more than S- cultivator. Mani and Panwar (1993) studied the energy requirement for different tillage implements at part load settings. The energy was calculated in terms of kwh/ha for all implements in the field

25 at different engine speed settings. They reported that the mould board plough required the maximum energy/ha at all the three speed controls followed by disc plough, subsoiler, cultivator planker, cultivator, disc harrow, land leveler and seed-cum-ferti-drill. 2.3 Field Capacity and Field Efficiency These are one of the and good measures of a performance of tractor-implement systems. Speed of an operation is a major influencing factor, which affects the field capacity and field efficiency Pearson et. al.(1976) carried out a series of field experiments for the empirical prediction of tractor implement field performance. The performance of two-wheel tractor was measured in 14 different fields. Ploughing gear number and the number of plough bodies were varied to find the combinations, which gave optimum work rate. In the fields used, 4 th gear and four plough bodies giving a forward speed of approximately 5.64 km/h was most likely to result in optimum work rate for the particular plough and tractor used. Tractor and plough performance were modeled using empirical relationships. The draft requirements of the plough was predicted reasonably well, 74% of the predicted value were within 20% of the measured value. The forward speed and work rate of the tractor plough combination were predicted with 86% of the predicted values within 20% of the measured values. The empirical equations were considered accurate enough for the computational method to be used for a general parametric study of tractor-plough field performance. Mourya (1977) carried out the field experiments to investigate the effect of speed of operation on field efficiency. The speed of operation was found to have no significant effect on field efficiency. The predicted and field results were found to be in good agreement. The results also indicated the trend of increasing the field efficiency with increase in length-width ratio and size of plot. Hasen et. al. (1986) studied the power demand mapping of tractor operations. A series of tests were performed with the tractor pulling a two-furrow mould board plough. Four trials were carried out involving different gear settings and different governor control lever settings. In each trial tractor operated for approximately half an hour and area ploughed was measured.

26 At governor control setting of 1900 rpm, changing gear second to third in a low ratio caused an increase in loading of the engine to a region focused approximately midway between idle and full load curve. This adjustment resulted in an increase in work rate of 30%. In shifting up from third to fourth gear in the low ratio the engine was loaded further with the region of loading focused closer to the full load curve. With the higher ground speed and lower effective torque, greater variation in engine loading occurred. The improvement in work rate was not as marked as for the shift from second to third gear, however, a small decrease in fuel consumption took place. The time consumption index for field performance in the fourth gear had decreased further by 23% as a result of the combined improvement in the work rate and fuel consumption. The fourth trial involved the tractor operating in third gear with low lever and governor control lever set at high idle speed of 2500 rpm. The area of loading was concentrated at approximately 80% of the full load. The results showed the marked improvement in work rate and fuel consumption resulting in corresponding decrease in time consumption index of 64% as compared to the operation in the fourth gear at the lower governor control speed setting. Mani and Panwar (1992) studied the performance of tractor implement systems at part load settings. They operated the implements at 1/3 rd, 2/3 rd and full speed and at three different field conditions of unploughed soil, stubbled soil and unploughed fallow. The soil type was silt loam soil. They reported that almost in all soil covers, disc harrow had a maximum capacity at three speed controls followed by the cultivator, disc plough, sub-soiler and mould board plough. 2.4 Tractive Performance of Tractor-Implement Systems The slip, tractive efficiency and performance index are the measures of tractive performance. The factors which affects the tractive performance of tractor-implement systems are, soil type, field condition, soil moisture content, speed of operation, ballasting and load on engine. Different studies have been made to study the effect of these parameters on the tractive performance are discussed in this section.

27 2.4.1 Effect of field moisture content on tractive performance Clough (1979) studied the tractive performance of two-wheel drive tractor in wet soils. The effect of soil moisture on tractive performance of large tractor had been found by measuring draft of the disc plough at various moisture levels. It was found that in the flooded soils the loss of power on an average was 62% of the maximum power achieved in moist soils. Stafford and Mattos (1981) observed that tractive efficiency was dependent on the rate of deformation and moisture content of soil. They observed the soil compaction by the driven wheel reduced tractive efficiency and was dependent on the increase in the speed due to increase in the shear strength. Sherruddin et. al. (1992) conducted an experiment to evaluate and compare the performance of a trailed tandem disc harrow and mounted sat haree in clay loam soil at 6.2 per cent moisture content at Sind Agricultural University, Tandojam. The travel reduction increased with the increase in the speed. The travel reduction was greater for disc harrow and the field capacity, fuel consumption and drawbar pull were greater for sat haree at all the speed selected for the study. The draft of both the implements increased with increase in speed of operation. Dahab and Mohammed (2002) studied the tractor s tractive performance as affected by the soil moisture content, tyre inflation pressure and implement type and reported the highest tractive efficiency values of 76.7 per cent and 76.6 per cent were recorded in dry soil with lower tyre inflation pressure by the disc and chisel plough respectively and lowest tractive efficiency values were 60.0 per cent and 62.8 per cent in the moist soil with high tyre inflation pressure for chisel and disc plough respectively Effect of ballasting on tractive performance Zoz (1973) concluded that equal productivity could be achieved with the various combinations of width and speed. At slow speeds investment costs increase due to added ballast and increased implement width. At higher operating speeds investment cost increase due to higher energy consumption.

28 Dwyer (1975) indicated that two wheel drive tractor do not achieve maximum tractive efficiency because of insufficient ballast and/or low field speeds. Four-wheel drive tractors have a higher load/power ratio and can achieve maximum tractive efficiency at lower field speeds. Ahuja. (1986) studied tractive performance over different soil cover conditions and reported that the use of ballast in ploughed field caused the decrease in slip. The performance index increased by 286, 168, 149 and 197 per cent respectively in fallow, stubble and ploughed soil and by use of ballast in ploughed field as pull increased by 235, 145, 162 and 183 per cent Effect of speed of operation on tractive performance Clough et. al. (1977) observed small improvement in the traction efficiency with increase in the speed from 3.2 km/h to 6.4 km/h. Voorhie and Walker (1977) reported that the effect of increase in velocity from 1.8 m/sec to 2.7 m/sec was negligible on the slip and tractive performance. Domier and Willians (1978) reported that maximum tractive efficiency usually occurs at low values of travel reduction, or at a gross traction ratio of 0.4 to 0.5. On concrete this point attainable at high forward speeds not suitable for most field operations. For some operations, the forward speed required to utilize the power available is too high, and at low forward speeds amount of ballast to be added is not economical. To achieve optimum performance a compromise is necessary between maximum tractive efficiency, highest field capacity and minimal capital cost. For two wheel drive tractors operating at wheel speed in the range of 8 to 12 km/h a load to power ratio of approximately 60 kg/kw will result in optimum tractive efficiency and optimum performance. Burt and Lyne (1985) observed the influence of velocity within the range of 0.2 to 0.6 m/sec on tractive efficiency and net traction at constant travel reduction. They concluded that there was no measurable velocity effect on either the net traction or tractive efficiency. Ahuja (1986) reported that the effect of speed on performance index was so small that for a given level of pull an average value could be used for all levels of speed.

29 2.5 Fuel Efficiency A number of studies have been done for evaluation of fuel consumption of tractor in different field operations. These studies show that the fuel consumption of a tractor generally depends on speed, type of an implement and depth of operation. The effect of these parameters studied by different researchers is discussed in this section Effect of speed of operation on fuel consumption Smith and Fornstorm (1980) studied the energy requirement of selected dry land wheat cropping systems and found that the mean specific fuel consumption for S-cultivator (3.5m) was 6.3 lit/ha at the forward speed 4.8 km/h and for mould board plough (three bottom 35.6 cm bottoms) at the forward speed 4.0 km/h was 34 lit/ha which was about 6.5 times more than sweep cultivator. Sherruddin et. al. (1992) conducted an experiment at speed I (at second low gear), the fuel consumed by tractor in disc harrow was 8.16 lit/h. At II speed (at third low gear)) 9.27 lit/h and at third speed (at fourth low gear) it was lit/h. The comparison shows that for the Sat haree at speed I, fuel consumption was 9.25 lit/h, lit/h at speed II and lit/h at speed III. It is evident that both disc harrow and sat haree required more fuel lit/hr for higher engine speed. Mani and Panwar (1992) studied the performance of tractor implement systems at part load settings and found that, the economical fuel efficiency occurred corresponding to a load factor of 0.68 of full load. The fuel efficiency was lit/kw/h at the load factor of 0.25 and it improved with increase in load factor to a minimum of lit/kw/h at a load factor of 0.68 and reduced again reaching to a maximum specific fuel consumption of lit/kw/h at full load. The operations of the implement causing wheel slip within a range of 2.6 to 33.5 per cent were included. Khandelwal and Jain (1999) studied the specific fuel consumption of tractor in different field operations and found that there was slight variation in the specific fuel consumption with

30 increase in the draft requirement and the speed of an operation. The increase in the draft also increased the wheel slip. The minimum specific fuel consumption for ploughing, harrowing and sowing operation was found at 600, 500 and 290 kg draft requirement Effect of depth of operation on fuel consumption Singh (1969) studied the performance of tractor in different power ranges for primary tillage operation. He found that there was difference in fuel consumption and output for the same tractor even during the same operation. This was mainly owing to varying field condition or difference in depth, which carries soil resistance on implement. Frisby and Summers (1979) carried out a study on energy related data for selected implements using a John Deere 2630 diesel tractor. They found that three-bottom mould board plough with 1.07 m width of cut and 20.5 cm depth of cut at the speed of 5.95 km/h on loamy soils fuel consumed was lit/h. The tandem disc harrow having width of cut 3.97 m and depth of cut 10.2 cm at the speed of 6.14 km/h on loamy soils fuel consumed was lit/h. Shelton et.al. (1979) studied the farm fuel use in Nebraska and found that the mean diesel fuel consumed for ploughing was lit/ha, disking was 39 lit/ha and harrowing was 5.52 lit/ha Drawbar fuel consumption ratio Identical to specific fuel consumption at the flywheel, fuel consumption ratio at the drawbar (fuel consumed per drawbar horse power-hour at the drawbar) describes fuel use efficiency of the tractor for drawbar. Some of the investigations have compared this ratio in their studies. Macnab et.al. (1977) observed that maximum fuel economy occurred at 27 and 13 per cent wheel slip while, the maximum tractive efficiency occurred at 15 and 9 per cent slip for soil having cone indices of 345 and 1034 kpa, respectively. The tractive efficiency curves changed only slightly between the maximum tractive efficiency-wheel slip and maximum fuel economywheel slip, while coefficient of traction substantially increased. On coefficient of traction vs. tractive efficiency and fuel consumption curves, drop in tractive efficiency, between the

31 maximum efficiency point and maximum fuel economy point, is very small, while the coefficient of traction increases substantially. Approximately 30 per cent more pull could be developed on firmer soils by increasing wheel slip to the minimum fuel consumption ratio level. Lyne and Meirings (1984) evaluated specific fuel consumption per kwh at the drawbar power corresponding to the maximum tractive efficiency values for the test at various loads and inflation pressures. They observed that with increase in load, drawbar power increases and specific fuel consumption ratio decreases. Their results for 18.4 R X 30 radial ply tyre on soft soil condition, showed that the maximum specific fuel consumption ratio of 0.53 liter per kw/h occurred at high (but not maximum) tractive efficiency. It was observed that the maximum drawbar power was developed corresponding to the maximum fuel consumption ratio. Similar conclusion was reached for bias ply tyres. 2.6 Soil Inversion and Pulverization Soil pulverization indicates the general fragmentation of soil mass resulting from the action of tillage forces. Many researchers studied the effect of different parameters on it is discussed in this section. Loghavi et. al.(1999) studied the effects of three levels of soil moisture content (10-12, and 16-18% d.b.) and three levels of plowing depth (15, 20 and 25 cm) on soil pulverization in a clay loam soil by a 3 - bottom disc plough. In order to provide a quantitative index to express the degree of soil pulverization by tillage implements, a tractor-pulled rotary sieve was designed and fabricated. With this apparatus, in-field determination of soil clod mean weight diameter (MWD) following ploughing was possible. The results showed that the effect of soil moisture content on MWD was highly significant, such that, ploughing at per cent moisture content produced the largest clods, whereas the effect of ploughing depth on MWD was not significant. The decreasing trend of MWD with soil moisture content persisted to the highest moisture level studied (16-18%), in which the average clod MWD (33.8 mm) was about 72 per cent smaller than those formed at per cent moisture content. Tanihuchi et. al. (1999) studied the soil manipulation by a mould board plough at different forward speeds and body attachments, in Eniwa volcanic ash soils using an open air soil bin. Soil moisture content was maintained at 36% (dry basis) while forward speed ranged from

32 0.1 to 4 m/s at an increment of 0.5 m/s. The effects of speed and plough optional attachments on soil pulverization have indicated some results of an economic interest. Soil pulverization increased with increase in speed and when plough options were used. Thampatpong (1999) studied optimum parameters for rotary tiller design. A study was conducted in a soil bin in clay soil at moisture content of per cent (db) and dry bulk density of 1.29 g/cc. The power requirement to cut and throw the soil was found to be affected by the rotor speed, the forward travel speed and the tilling depth. The power requirement increased with an increase in rotor speed, forward speed and the tilling depth. These three parameters also affected the soil breakage. The bigger clods size was found when the tilling depth and the forward speed were high and the rotor speed was low. The smaller clods size was occurred when the tilling depth and the forward speed were low and the rotor speed was high. The optimum parameter for the design of rotary tiller were found to be 18 cm depth of the tilling, forward speed of 0.35 m/s and rotor speed of 165 to 220 rpm which will take power requirement of 2.70 to 3.50 kw. At this condition of rotary tiller working the clod size developed will be the one recommended for soybean cultivation. The review suggests that draft and energy requirement, field capacity, field efficiency, tractive efficiency, fuel consumption and soil pulverization are some of the important parameters which are to be considered for performance evaluation of tractor implement system.

33 III - MATERIALS AND METHODS This chapter deals with the different experimental techniques used in the study to evaluate performance of tractor implement systems at part loads in sandy loam soil. It included the determination of power and energy requirements, field efficiency, tractive efficiency, fuel efficiency and vehicle efficiency (power delivery efficiency) of tractor implement systems to select a suitable gear-throttle combination for different tillage implements selected for the study. 3.1 Terms Used in The Study Various terms used in the study are discussed in this section Drawbar power requirement per unit volume of soil tilled Drawbar power requirement is the amount of power required to operate different implements at a given condition per unit volume of soil tilled and was calculated as: D S DBHP. (3.1) W d 75 where, DBHP = drawbar power, hp; D = draft, kg; S = forward speed of operation, m/s; W = width of implement, m and d = depth of operation, m Energy requirement Energy requirement for a given tractor implement system was calculated from the fuel consumed in a given time. Considering calorific value of diesel fuel as kcal/kg and specific gravity of 0.84, energy requirement was calculated as:

34 E F (3.2) EFC 860 where, E = energy requirement, kwh/ha; F = fuel consumed per unit time, liter and EFC = effective field capacity, ha/h Effective field capacity (EFC) It was defined as the actual area covered by the implement, based on its time consumed and it s width. It was calculated as: A EFC... (3.3) T t where, EFC = effective field capacity, ha/h; A = actual area covered, ha and T t = total time required, h Theoretical field capacity (TFC) It is the rate of field coverage of the implement, based on its 100 per cent of the time at the rated speed and covering 100 per cent of it s rated width. It was calculated as: W S TFC. (3.4) 10 where, TFC = theoretical field capacity, ha/h; W = width of implement, m and

35 S = speed of operation, km/h Field efficiency (FE) It gives an indication of time lost in the field and the failure to utilize the working width of the implement. It is expressed in percentage and was calculated as: EFC FE X 100. (3.5) TFC Tractive efficiency (TE) It is defined as the ratio of output power to input power for a traction device. It is the measure of efficiency with which the traction device transforms the torque acting on the axle into linear drawbar pull. It was calculated using following expression: P V TE a. (3.6) T where, TE = tractive efficiency, per cent; P = pull, kg; T = wheel torque (input), kg-m; = wheel rotation, rad/s and V a = actual speed, m/s. This can be rewritten as: P V P TE a 1 s... (3.7) T V F r

36 where, F = gross thrust force acting on the wheel (P + R), kg; V t = theoretical velocity, m/s; r = radius of wheel, m; s = slip and R = rolling resistance, kg Thus, P TE 1 s. (3.8) P R Fuel efficiency (FE) It is the measure of amount of fuel required for a given tractor-implement system to cover one hectare field. It was calculated as: where, FE = Fuel consumed per unit time A A = covered plot area, ha.. (3.9) Vehicle efficiency (Power delivery efficiency) It is the measure of efficiency with which engine power is utilized by the tractorimplement system. It was calculated as: where, DBHP VE 100. (3.10) BHP VE = vehicle efficiency, per cent; DBHP = drawbar horse power, hp and BHP = brake horse power, hp.

37 3.2 Selection of Implements Amongst all the field operations the land preparation operations require large amount power. Primary tillage operations consume larger portion of energy required for tillage operations (Dahab and Mohamed, 2002). Keeping this in view primary tillage implements, which are commonly used for tillage operations viz. disc plough, cultivator and rotavator (Fig.3.1) were selected for the study. The specifications of these implements are given in Appendix-A. Fig. 3.1 Implements evaluated in the study.

38 3.3 Field Layout Experiments were conducted at instructional farm C.T.A.E, Udaipur. Stubbled field left after harvesting of maize crop (Fig. 3.2) was selected for the study. A 100 X 120 m size field was selected for the experiments. Field was divided in to two parts of 60 X 100 m size. The area was taken such that each implement has sufficient number of turns to measure productive and nonproductive time. 3.4 Measurement of Different Parameters in the Study This section deals with the different measurement techniques used for measuring various parameters in the study Soil moisture content For measurement of soil moisture content, core samples of soil were taken at different locations of test plot selected randomly were collected in the sample boxes. These boxes were oven dried in a hot air oven at C for 24 hours. At the end of 24 hours weight of sample boxes with dry soil and weight of empty boxes were taken. The soil moisture content was calculated by using the formula: MC W 1 W (3.11) W 2 where, MC = moisture content, per cent (dry basis); W 1 = weight of moist soil sample, kg and W 2 = weight of dry soil sample, kg Bulk density

39 It is the mass of oven-dried soil per unit volume. For measurement of bulk density of soil, a cylindrical core sampler mm was taken and soil samples were taken at different locations in a plot. Core sample was kept in air oven for 24 hours and after 24 hours weight of soil sample was taken with electrical balance. Bulk density was calculated by using following formula. BD M V 4M. (3.12) D 2 L where, BD = bulk density, kg/m 3 M = mass of soil sample contained in the core sample, kg; V = volume of core sample, m 3 ; D = diameter of cylindrical core sample, m and L = length of cylindrical core sample, m Measurement and setting of the engine rpm Different part load settings were achieved through engine rpm. The test tractor was calibrated at no load condition and 1/3 rd, 2/3 rd and full load engine rpm were calculated. The screw on the throttle rod which controls the governor (which controls the amount of fuel allowed to enter the combustion chamber) was adjusted (Fig. 3.3) to get desired engine rpm. The corresponding ranges of engine speed (rpm) is given in Table 3.1 Table 3.1 Engine speed (rpm) at different throttle positions. S.No Throttle position Engine speed (rpm) 1 1/3 rd /3 rd Full 2000

40 3.4.4 Speed of travel The speed of operation was measured in field by fixing two poles in the test plot 30 m apart. Time required to cover the 30 m distance was measured with the help of stopwatch and actual speed of operation in km/h was calculated from an average of 5 readings. The forward speed during the experiments was kept in recommended range Zero condition for measurement of slip Zero condition selected in study was the tractor operating in self propelled condition on a hard surface (smooth tar road). The theoretical speed was measured as discussed in section at all the three throttle positions (Table 3.2) Table 3.2 Average theoretical forward speed at different throttle positions. S.No. Throttle position Theoretical speed Km/h 1 1/3 rd throttle position /3 rd throttle position Full throttle position Slip calculation Time required to cover 30 m distance on zero condition (smooth tar road) was measured and theoretical speed of operation was calculated from an average of 5 readings. The actual speed of operation was calculated as described in The slip was calculated as: V t V s a. (3.13) V t where, s = slip, V a = speed of tractor in a field, m/s and V t = speed of tractor on hard surface, m/s.

41 3.4.6 Productive and non-productive time Time lost for turning, adjustment, repair etc. was taken as non-productive time. Total time required minus non-productive time i.e. the time utilized for actual working of implement to cover the plot size without time loss is taken as productive time. The total time required by the tractor to cover the selected plot was measured with the stopwatch. Time lost during turning, adjustment, repair etc. was also recorded with another stop watch. The productive time was calculated as: T p = T-T l. (3.14) where, T p = productive time, sec; T = total time required to cover a plot, sec. and T l = total time lost in turning, repair etc. in covering plot size, sec Fuel Consumption Fuel consumed by the tractor during field operation was measured using an auxiliary fuel system (Fig ). The fuel system consisted of auxiliary M.S. fuel tank, which was fixed on the tractor. A supply pipe was connected in between on off valve of fuel tank and fuel pump. An overflow pipe was connected in between fuel injectors and fuel tank. To find out the consumption of fuel, the auxiliary tank was filled up to full level before starting of operation and measured quantity of fuel was taken out in a separate jar to avoid spoilage of fuel during operation. After the operation, tractor was stopped and fuel taken out in jar was added to the auxiliary fuel tank and then the tank was filled to the previous level by adding fuel in measured quantity with help of measuring cylinder. The additional fuel added to fill the fuel tank to the marked level was taken as fuel consumption.

42 1. Auxiliary fuel tank 2. Fuel supply pipe 3. Overflow pipe Fig. 3.4 Photograph of an auxiliary fuel system made on tractor

43 1. Auxiliary fuel tank 2. Fuel feed pump 3. Fuel filters 4. Fuel injection pump 5. Fuel injectors 6. Overflow line Fig. 3.5 Line diagram of an auxiliary fuel system fixed on tractor Calibration of load cell The load cell was calibrated by using a universal testing machine. A known load was applied to the load cell and the sensitivity of digital load indicator was adjusted through calibration adjust button. Load was removed and zero setting was made with zero setting adjust button. A known load was applied gradually up to the load bearing capacity of load cell and corresponding counts of digital load indicator were read and recorded. A calibration curve (Fig.3.6) was plotted by taking load and counts of digital load indicator.

44 y = x R 2 = Counts of load indicator Load, kg Fig.3.6 Calibration curve of load cell Measurement of rolling resistance Rolling resistance of a tractor was measured by towing a dummy tractor to test tractor through load cell connected with digital load indicator. Rear tractor was kept in neutral position and front tractor pulled the rear one. The reading of load indicator was read and noted from digital indicator at fixed interval of time. An average of 10 readings was considered to compute the force required to pull a tractor, which was found from load cell calibration curve Draft To determine the draft of implement load cell with digital indicator was used. Load cell was placed in between two tractors (Fig. 3.7) and implement was hitched to the rear tractor. The gear of the rear tractor was kept in neutral position and implement hitched behind the tractor and a desirable depth was given with hydraulic control lever. Front tractor pulled the rear tractor with implement as shown in Fig The reading of load indicator was recorded from digital load

45 indicator. The draft was calculated using the calibration curve. The difference of calculated draft and rolling resistance was taken as draft of implement for further calculations Load cell 2. Digital load indicator 3. S - Hooks Fig. 3.7 Draft measurement system

46 Fig. 3.8 Measurement of draft of different implements Soil pulverization Soil pulverization indicated the general fragmentation of soil mass resulting from the action of tillage forces, and it was evaluated by using a set of sieves using RNAM test code. The soil samples were collected from three different (randomly selected) places. Soil sample was passed through a set of different size mesh sieves. Soil retained on largest aperture sieve then passed to next sieve and then passed through smallest apertures sieve. The samples were weighed. The mean soil clod diameter was calculated as given in Table 3.3.

47 Table:- 3.3 Sieve analysis of soil sample dsc 1 5A 15B 25C 35D 45E NF. (3.15) W where, dsc = mean soil clod diameter, mm; W = A + B + C + D + E + F N = mean of measured diameters of soil clods retained on the largest aperture sieve, mm. 3.5 Plan of work The experiments were conducted in the field left after harvesting of maize crop. The tractor implement systems consisted of a 40 hp tractor and three tillage implements viz. rotavator, cultivator and disc plough. Table 3.4 gives the details of the parameters considered in the study.

48 Table 3.4 Plan of experiments S. No. Independent Variable Level Dependent Variable Method 1. Type of an implement Disk plow (2-bottom) Cultivator (9-tyne) EFC Field efficiency Time and area (EFC/TFC) x100 Rotavator (1.2 m) Soil pulverization Sieve analysis To be taken in 2. Gear setting combination with throttle position to get a forward speed in the recommended range Slip Rolling resistance Draft Fuel consumption Velocity. Load cell and indicator Load cell and indicator Auxiliary fuel system 3. Throttle position 1/3 throttle 2/3 throttle Full throttle rpm of engine RPM-meter connected to the tractor crank shaft. 3.6 Test procedure Experiments were conducted in two phases. First the observations were taken while tractor operating in the field and second for measurement of draft and rolling resistance. The stepwise procedure to conduct the experiments was as: 1. Auxiliary fuel tank was filled and measured quantity of fuel was taken out in a separate jar. Load setting, gear selected, name of implement was recorded.

49 2. During the operation of the implement at all the throttle position the observations (speed, total time, time lost in turning and others, fuel consumption) were recorded. 3. Total time required was recorded by using another stop watch. 4. Using dummy tractor rolling resistance and draft of implement was measured at all the throttle positions. 5. Soil samples weighing at about 10 kg each, were collected for sieve analysis and mean soil clod diameter was calculated after sieve analysis as discussed in the section Data recorded during experiments were analyzed and are presented in the chapter IV.

50 IV - RESULTS AND DISCUSSION The results of the experiment carried out are presented and discussed in this chapter under the headings: 1. Power requirement per unit volume of soil tilled at different load settings. 2. Energy requirement for tractor-implement systems at different load settings. 3. Field efficiency of tractor-implement systems at different load settings. 4. Tractive efficiency of tractor-implement systems at different load settings. 5. Fuel efficiency of tractor-implement systems at different load settings. 6. Vehicle efficiency (power delivery efficiency) of tractor-implement systems at different load settings. 7. Selection of suitable gear throttle combination for different tractor implement systems. The three tillage implements were operated in stubbled field (field left after the harvesting of maize crop) at their recommended forward speeds. The depth of operation ranged between cm. As the soil could not have sufficient moisture content, higher depth of operation could not be achieved. 4.1 Power Requirement Per Unit Volume of Soil Tilled at Different Load Settings Power requirement per unit volume of soil tilled for different tractor-implement systems at different load settings (Fig. 4.1) is discussed in this section and average values are reported in Table Power requirement per unit volume of soil tilled at 1/3 rd load setting The drawbar power requirement for rotavator (3.72 hp) was least among all the implements evaluated. In case of cultivator the drawbar power requirement was 3.5 times more than that of rotavator and highest drawbar power was required for disc plough, which was 4.67 times more than rotavator and 33.5 per cent more than cultivator. In case of rotavator the rotary motion of tines added the forward thrust in the direction of motion reducing draft requirement, which reduced the drawbar power requirement. Whereas draft

51 was more in the case of disc plough which increased the drawbar power requirement as compared to all other implements Power requirement per unit volume of soil tilled at 2/3 rd load setting At 2/3 rd load setting disc plough required the highest drawbar power (20.20 hp), which was 7.7 times more than the drawbar power required by the rotavator (3.47 hp) and about 35.4 per cent more than the cultivator drawbar requirement. The reason may be the same as discussed at 1/3 rd load setting Power requirement per unit volume of soil tilled at full load setting Similar to 1/3 rd and 2/3 rd load setting, minimum drawbar power per unit volume of soil tilled (2.60 hp) was observed in case of tractor-rotavator system. For tractor-disc plough and tractor-cultivator it was hp and hp respectively. Table 4.1 Drawbar power requirements per unit volume of soil tilled of different tractor implement systems at different throttle positions Drawbar power per unit volume of soil tilled, hp Throttle position Rotavator Disc Plough Cultivator 1/3 Throttle /3 Throttle Full Throttle

52 25 At 1/3 rd load setting Drawbar power per unit vol. of soil tilled Rotavator Disc plough Cultivator 25 At 2/3 rd load setting Drawbar power per unit vol. of soil tilled Rotavator Disc plough Cultivator 25 At full load setting Drawbar power per unit vol. of soil tilled Rotavator Disc plough Cultivator Fig. 4.1 Drawbwr power requirement per unit volume of soil tilled at different load settings.

53 4.1.4 Comparison of power requirement per unit volume of soil tilled at different engine speeds Results of the drawbar power requirement of tractor-rotavator, tractor-disc plough and tractor cultivator systems at different engine speeds are presented in the Fig Rotavator Disc plough Cultivator Power requirement per unit volume of soil tilled Engine speed, rpm An increasing trend with increasing engine speed was observed for tractor disc plough and tractor cultivator systems. Between these two systems tractor disc plough system required higher power at all the throttle positions selected for the study. This may be due to higher draft requirement of disc plough. Similar results were observed by Janobi and Shaibani (1998). The reverse trend was observed for the tractor-rotavator system. The power requirement decreased with the increase in the engine speed. This may be due to the increase in forward thrust because of higher rotor speed at higher engine speed that reduced the draft of implement, thereby reducing the power requirement. 4.2 Energy Requirement for Tractor-Implement Systems at Different Load Settings Energy requirements for different tractor-implement systems at different load settings

54 (Fig. 4.3) is discussed in this section and average values are reported in Table Energy requirement at 1/3 rd load setting Among all the tractor implement systems evaluated, tractor-disc plough combination required maximum energy ( kwh/ha), which was 18.7 per cent and 44 per cent more than tractor-rotavator and tractor-cultivator combination respectively. This could be due to the higher value of draft requirement for the tractor-disc plough combination Energy requirement at 2/3 rd load setting Energy required by the tractor-rotavator combination ( kwh/ha) was 43.4 per cent more than the tractor-disc plough combination and about 2 times more than tractor-cultivator system. This may be due the fact that more energy is required to handle the soil at a higher rate by rotor blades with the increase in rotor speed of Rotavator Energy requirement at full load setting At full throttle position, maximum energy ( kwh/ha) was required by tractorrotavator combination followed by tractor-disc plough and tractor-cultivator system. The reason for this may be same as postulated at 2/3 rd load setting. Table 4.2 Energy requirements of different tractor implement systems at different throttle. positions Throttle position Energy requirement kwh/ha Rotavator Disc Plough Cultivator 1/3 Throttle /3 Throttle Full Throttle

55 Energy requirement, kwh/ha At 1/3 rd load setting Rotavator Disc plough Cultivator Energy requirement, kwh/ha At 2/3 rd load setting Rotavator Disc plough Cultivator Energy requirement, kwh/ha At full load setting Rotavator Disc plough Cultivator Fig. 4.3 Energy requirement at different load settings

56 4.2.4 Comparison of energy requirement at different engine speeds. It was observed that energy requirement per hectare increases with the increase in engine speed for all the three tractor implement systems selected for the study (Fig. 4. 4). Energy requirement, kwh/ha Rotavator Disc plogh Cultivator Engine speed, rpm Fig. 4.4 Relation between energy requirement and engine speed for different tractor implement systems The maximum energy ( kwh/ha) was observed, at full throttle position in I-L gear, for rotavator followed by tractor-disc plough ( kwh/ha) and tractor-cultivator system ( kwh/ha) respectively. Whereas minimum energy ( kwh/ha), at 1/3 rd throttle position in IV-L gear, was observed for cultivator followed by tractor-rotavator ( kwh/ha) and tractor-disc plough ( kwh/ha) system. Tractor-rotavator system required the higher energy at all the gear throttle combinations in comparison to other tractor implement systems. This may be because of the fact that rotavator consumed energy both for rotating the blades and for overcoming drawbar load resulting in higher rate of increase in energy requirement. Only at 1/3 rd throttle position, tractor-disc plough system required higher energy than other two tractor implement systems. This may be due to the fact that increased draft of the implement, which exceeded energy requirement than other two said tractor implement systems.

57 4.3 Field Efficiency of Tractor-Implement Systems at Different Load Settings The results of field efficiency for different tractor implement systems at 1/3 rd, 2/3 rd and full load settings (Fig. 4.5) are discussed in this section and average values are reported in Table Field efficiency at 1/3 rd load setting At 1/3 rd load setting the field efficiency of tractor-cultivator system (88.37 %) was maximum among all tractor implement systems evaluated. The tractor-disc plough system possessed the minimum field efficiency (73.85 %), which was per cent less than that of tractor-rotavator system (83.81 %). This may be because of actual working width of implement and slip causing reduction in working speed Field efficiency at 2/3 rd load setting At 2/3 rd load setting maximum field efficiency was observed for tractor-cultivator system followed by tractor-rotavator and tractor-disc plough systems. The field efficiency for tractorcultivator, tractor-rotavator, and tractor-disc plough system was 89.74, and per cent respectively. The reason for this may be same as postulated for 1/3 rd load setting Field efficiency at full load setting Similar trend as that of 1/3 rd and 2/3 rd load setting for field efficiency was observed for all tractor implement systems. The field efficiency for tractor-cultivator, tractor-rotavator, and tractor-disc plough system was 90.15, and per cent respectively.

58 Table 4.3 Field efficiency of different tractor implement systems at different throttle positions. Field efficiency, per cent Throttle position Rotavator Disc Plough Cultivator 1/3 Throttle /3 Throttle Full Throttle At 1/3 rd load setting Field efficiency,% Rotavator Disc plough Cultivator 100 At 2/3 rd load setting Field efficiency,% Rotavator Disc plough Cultivator

59 100 At full load setting Field efficiency,% Rotavator Disc plough Cultivator Fig. 4.5 Field efficiency at different load settings Comparison of field efficiency at different engine speeds It was observed that field efficiency increased with increase in engine speed for all the tractor implement systems studied (Fig.4.6). This may be due to the fact that increase in engine speed increases the speed of operation resulting in increased actual field capacity thereby increasing the field efficiency Rotavator Disc plough Cultivator Engine speed, rpm. Fig. 4.6 Relation between field efficiency and engine speed for different tractor implement systems

60 Among the three tractor implement systems studied, the rate of increase of field efficiency with increase in engine speed was observed to be less for tractor cultivator system as compared to other two tractor implement systems. This may be due to the fact that, the slip increased at a higher rate with increase in engine speed for tractor cultivator system than other two tractor implement systems which reduced the rate of increase of actual field capacity thereby reducing the rate of increase of field efficiency. 4.4 Tractive Efficiency of Tractor-Implement Systems at Different Load Settings Results of tractive efficiency of different tractor-implement systems at different load settings (Fig.4.7) are discussed in this section and average values are presented in Table Tractive efficiency at 1/3 rd load setting Tractive efficiency of tractor-rotavator system was minimum (23.4 %) among the three tractor implement systems evaluated. Tractor-disc plough and tractor-cultivator system gave almost same tractive efficiency of about 61.0 %. This may be attributed to the lower drawbar pull required in case of rotavator, which decreased the numerator of the eq n 3.8 resulting in lower tractive efficiency Tractive efficiency at 2/3 rd load setting Almost similar trend as that of 1/3 rd load setting, of tractive efficiency was observed at 2/3 rd load setting, for all tractor implement systems studied. The two tractor implement systems gave about 33 per cent higher tractive efficiency than tractor-rotavator system. At this load setting the similar reason may be postulated for the performance as that of at 1/3 rd load setting Tractive efficiency at full load setting Similar to 1/3 rd and 2/3 rd a load setting, minimum tractive efficiency (13.9%) was observed in case of tractor-rotavator system. The other two combinations resulted in about same tractive efficiency (59%).

61 Table 4.4 Tractive efficiency of different tractor implement systems at different throttle positions. Throttle position Tractive efficiency, per cent Rotavator Disc Plough Cultivator 1/3 Throttle /3 Throttle Full Throttle At 1/3 rd load setting Tractive efficiency,% Rotavator Disc plough Cultivator 100 At 2/3 rd load setting Tractive efficiency,% Rotavator Disc plough Cultivator

62 100 At full load setting Tractive efficiency,% Rotavator Disc plough Cultivator Fig. 4.7 Tractive efficiency at different load settings Comparison of tractive efficiency at different engine speeds The slope of curves (Fig. 4.8) indicates that tractive efficiency decreased with increase in engine rpm for all tractor implement systems studied. This was more prominent in case of tractorrotavator system. This may be due to the decrease in drawbar pull because of increase in forward thrust due to increased speed of rotation of rotavator blades because of increase in engine speed. Tractive efficiency, % Tractive efficiency,% Rotavator Disc plough Cultivator Engine speed, rpm Fig. 4.8 Relationship between tractive efficiency and engine speed for different tractor implement systems

63 In case of other two systems this effect can be attributed to increase in the slip value with increase in draft of implement and speed of operation at higher engine speeds. Increase in slip with increase in speed of operation was found to be similar to the findings of Sherruddin et. al. (1992). 4.5 Fuel Efficiency of Tractor-Implement Systems at Different Load Settings Fuel efficiency is defined as fuel required to cover one hectare field. Results of fuel efficiency of different tractor-implement systems at different load settings (Fig.4.9) are discussed in this section and average values are presented in Table Fuel efficiency at 1/3 rd load setting Maximum fuel consumed per hectare (11.73 lit/ha) of field coverage was observed for tractor-disc plough system than other two tractor implement systems selected for the study. Whereas minimum fuel per hectare was consumed by tractor-cultivator system which was 60.4 per cent less than tractor-disc plough and 45.7 per cent less than tractor-rotavator system respectively. This may be because of higher working width of tractor-cultivator system, which covered more area in comparison with tractor-rotavator and tractor-disc plough system Fuel efficiency at 2/3 rd load setting At 2/3 rd load setting maximum fuel requirement was observed for tractor-rotavator system (15.15 lit/ha) followed by tractor-disc plough (12.17 lit/ha) and tractor-cultivator (7.45 lit/ha) system. This may be attributed to additional power requirement by rotating blades of rotavator at higher engine speeds. The fuel requirement of tractor-cultivator system was 57.3 per cent less than tractor-rotavator and about 39 per cent less than tractor-disc plough system was observed Fuel efficiency at full load setting

64 Similar to the 2/3 rd load setting, tractor-rotavator system required more fuel (18.81 lit/ha) to cover an area of one hectare. In case of tractor-disc plough system, fuel requirement was lit/ha, which was 7.87 per cent less than that of tractor-rotavator system. Whereas minimum fuel consumption (9.76 lit/ha), was observed for tractor-cultivator system which was 44 per cent less than tractor-disc plough and 48 per cent less than tractor-rotavator system. Reason for this may be same as that of tractor operating at 1/3 rd load setting. Table 4.5 Fuel efficiency of different tractor implement systems at different throttle positions. Throttle position Fuel consumption, lit/ha Rotavator Disc Plough Cultivator 1/3 Throttle /3 Throttle Full Throttle At 1/3 rd load setting Fuel consumption, lit/ha Rotavator Disc plough Cultivator 20 At 2/3 rd load setting Fuel consumption, lit/ha Rotavator Disc plough Cultivator

65 20 At full load setting Fuel consumption, lit/ha Rotavator Disc plough Cultivator Comparison of fuel efficiency at different engine speeds It was observed that fuel consumption per hectare increased with increase in engine speed for all tractor implement systems studied (Fig. 4.10). The fuel consumption per hectare increases at higher rate for tractor-rotavator system as compare to other two systems. 25 Rotavator Fuel consumption, lit/ha Fuel consumption, lit/ha Disc plough Cultivator Engine speed, rpm Fig Relationship between fuel consumption and engine speed for different tractor implement systems

66 At lower engine speeds more fuel was consumed by tractor disc plough system followed by tractor-rotavator and tractor cultivator system. With increase in engine speed the tractorrotavator system required more fuel per hectare of the field. This may be because of more power requirement for cutting the soil by rotavator blades at higher speed of rotation. 4.6 Vehicle Efficiency (Power Delivery Efficiency) of Tractor-Implement Systems at Different Load Settings Vehicle efficiency or power delivery efficiency is defined as ratio of the achieved drawbar power to the vehicle input power of the tractor. Results of vehicle efficiency for different tractor implement systems at 1/3 rd, 2/3 rd and full throttle position (Fig.4.11) are discussed in this section and average values are presented in Table Vehicle efficiency at 1/3 rd load setting Maximum vehicle efficiency (21.34%) was observed for tractor-disc plough system followed by tractor-cultivator (20.70%) and tractor-rotavator system (3.05%). The low efficiency of tractor-rotavator system may be due to low draft values resulting in low drawbar horsepower. Low draft requirement for rotavator may be attributed to additional forward thrust gained by the implement because of rotor blades working in the soil Vehicle efficiency at 2/3 rd load setting At 2/3 rd load setting tractor-disc plough system showed the maximum vehicle efficiency (11.67 %) followed by tractor-cultivator (11.18%) and tractor-rotavator (1.34%) system. The vehicle efficiency of tractor-disc plough system was 8.7 times more than tractor-rotavator system and about 4.47 per cent more than that of tractor-cultivator system. The further low efficiency of tractor rotavator system may be because of the more forward thrust gained because of increased rotary speed of rotavator blades Vehicle efficiency at full load setting

67 Similar to 1/3 rd and 2/3 rd throttle position, maximum vehicle efficiency was observed for tractor-disc plough system (8.72%) followed by tractor-cultivator (7.92%) and tractor-rotavator (0.63%) system. The vehicle efficiency of tractor-disc plough system was times more than that of tractor-rotavator system and per cent more than tractor-cultivator system was observed. The reason for this may be same as discussed for 1/3 rd and 2/3 rd load settings. Table 4.6 Vehicle efficiency of different tractor implement systems at different throttle positions. Throttle position Vehicle efficiency, per cent Rotavator Disc Plough Cultivator 1/3 Throttle /3 Throttle Full Throttle At 1/3 rd load setting Vehicle efficiency, % Rotavator Disc plough Cultivator

68 25 At 2/3 rd load setting Vehicle efficiency, % Rotavator Disc plough Cultivator 25 At full load setting Vehicle efficiency, % Rotavator Disc plough Cultivator Comparison of vehicle efficiency (power delivery efficiency) at different engine speeds Fig indicates that vehicle efficiency decreases with increase in engine speed for all tractor implement systems. The slopes of the curves suggest that there is rapid decrease in vehicle Rotavator Disc plough Cultivator Engine speed, rpm

69 efficiency of tractor-disc plough and tractor cultivator system. The trend of curve changes when tractor is operated at full throttle position. This trend may be due to the fact that the developed engine power increases at a higher rate with the increase in engine rpm whereas, the drawbar horse power for tractor implement system does not changes very much with the same increase in engine speed. Fig Relationship between vehicle efficiency and engine speed for different tractor implement systems At full throttle operation the input engine power becomes constant resulting in change in the nature of curve. The low vehicle efficiency of tractor rotavator system may be because of the additional forward thrust gained by the rotavator because of rotating blades. The nature of the curve indicates that decrease in vehicle efficiency is not rapid as compare to two other tractor implement systems. This supports that increase in input engine power with increase in engine speed is better utilized in tractor rotavator system in comparison to tractor disc plough and tractor cultivator system. 4.7 Slip Draft Relationship at Different Load Settings of Tractor Implement Systems Slip increases with increase in draft of the implement (Fig. 4.13) for all tractor implement systems studied. This effect was more prominent in case of tractor-rotavator system. This could be due to the fact that, at lesser rotary motion of rotavator blades (at lesser engine rpm) more force was required to pull the implement causing more slip whereas, when engine speed (rpm) was increased, rotating blades of rotavator added the forward thrust in the direction of motion reducing the slip. In case of other two tractor implement systems studied draft requirement increased with increase in engine speed (rpm) causing more slip to pull the implement.

70 20 Rotavator 15 Cultivator Disc plough Slip, Draft, kg Fig Relationship between slip and draft at different load settings 4.8 Soil Pulverization at Different Part Load Settings of Tractor Implement Systems Mean soil clod diameter, which shows the general fragmentation of soil was taken as a measure of soil pulverization. Figure 4.14 shows the soil condition obtained after the operation of different implements. Results of soil pulverization for different tractor implement systems at different load settings (Fig. 4.15) are discussed in this section and average values are reported in Table Soil pulverization at 1/3 rd load setting At 1/3 rd load setting, tractor-rotavator system produced the least mean soil clod diameter (15.73 mm), which was per cent and per cent less than tractor-cultivator system (28.91 mm) and tractor-disc plough system (42.39 mm) respectively. This may be due to the rotary motion of rotator blades, which resulted in better soil cutting Soil pulverization at 2/3 rd load setting

71 At 2/3 rd load setting the least mean soil clod diameter was produced by tractor-rotavator system (13.59 mm), which was per cent and per cent less than tractor-cultivator system and tractor-disc plough system respectively. The reason may be the same as discussed at 1/3 rd load setting Soil pulverization at full load setting At full load setting similar trend was found. Tractor-rotavator system produced least mean soil clod diameter (9.285 mm) that was per cent and percent less than tractorcultivator and tractor-disc plough system. The reason may be the same as discussed at 1/3 rd and 2/3 rd load setting. 50 At 1/3 rd load setting Mean soil clod diameter, mm Rotavator Disc plough Cultivator

72 At 2/3 rd load setting 50 Mean soil clod diameter, mm Rotavator Disc plough Cultivator 50 At full load setting Mean soil clod diameter, mm Rotavator Disc plough Cultivator Comparison of soil pulverization at different engine speeds The curves (Fig. 4.16) show the decreasing trend of mean soil clod diameter with increase in engine speed. This trend was more prominent in case of tractor-rotavator system. This may be due to the fact that increase in speed of engine increases the rotary motion of rotavator blades, which causes more break up of soil slice. Similar findings were also reported by Thampatpong (1998).

73 Mean soil diameter,mm Rotavator Disc plough Cultivator Engine speed, rpm. Fig Relationship between mean soil clod diameter and engine speed for different tractor implement systems

74 Cultivator Rotavator Disc plough Fig Field condition after the operation