Effect of Tyre Inflation Pressure and Tractor Passes on Sandy Loam Soil

Transcription

1 Effect of Tyre Inflation Pressure and Tractor Passes on Sandy Loam Soil 1 Ogunjirin, O. A., James David and M. Y. Kasali National Centre for Agricultural Mechanization P.M.B. 1525, Ilorin ntslola@yahoo.com 1 Corresponding author Abstract The issue of mechanized agriculture had gained recognition and the aftermath effect compaction is of great concern to stakeholders in the agricultural sector. This informed the study to investigate the effect of tyre pressure and number of passes on sandy loam soil in the Teaching and Research Farms of the National Centre for Agricultural Mechanization in a randomized block design. Results show that soil physical properties increases as the number of passes and tyre inflation pressure increases. To reduce the compaction effect of the tyre pass on the soil, tractor to be utilized for sandy loam soils should be operated at tyre inflation pressure ranging between 100 and 140 kpa. Also, to avert the effect of tractor passes on the soil, it is best for farmers to use medium range tractor and also consider the option of minimum tillage so as to reduce the damage done to the soil. 1. Introduction The role of agriculture in the face of increasing world population cannot be under estimated. Therefore, increased land cultivation can ensure adequate provision of food and fibre for the world population and raw materials for emerging industries. This can only be achieved through the introduction of tractors and equipment which brings about excessive traffic on the agricultural land and thus compaction of agricultural soil is a common occurrence in the face of mechanized agriculture around the world. This is worrisome in the developing countries where the soil structures are not studied before introducing tractors and equipment on the farms. Artificial soil compaction occurs in most mechanized farms through farm tractors and equipment as a result of wrong selection of equipment. Anazodo and Onwualu (1984) reported that soil are compacted when the total porosity and particularly the air filled porosity are so low as to restrict aeration as well as the soil is so tight and its pores so small as to impede root penetration and drainage. Raper (2005) reported that efficient mechanization in agriculture is a major factor underlying high productivity. Larger machinery is often related with timeliness, higher work rates, and lower labour requirements. The drawback of it is that larger machinery usually means increased machinery weight which increases the danger of soil compaction. Soil compaction affects the physical, chemical, and biological properties of soils and is one of the main causes of agricultural soil degradation (Hakansson and Voorhees, 1998). Antille et. al. (2008) reported that soil compaction alleviation is usually costly in terms of the energy and power that the process of soil loosening requires. Generally, an increase in tyre size is accompanied by a decrease in tyre 164

2 inflation pressure to support a given axle load. Since the compaction of agricultural soil occurred when the soil particles are rearranged in such a manner that they are brought closer to each other, the soil bulk density and porosity are affected. Thus other soil properties such as hydraulic conductivity, aeration, moisture availability, infiltration rate are affected and leading to decreased crop yields. Recently, the Federal Ministry of Agriculture and Rural Development embarked on tractorization programme with a view to making tractors and implements available to the Nigerian farmers through Public Private Partnership (PPP) arrangement. The success of the programme would also engender the problem of soil compaction in the field if it is not considered from the onset of the programme. Oni, 2003 reported that in Nigeria, agricultural mechanization is the answer to the subsistence nature of the farming system presently constituting about 70% farming population. Tillage operation is carried out when the soil is wet, this gives room for appreciable compaction because the soil is now plastic in behavior. It can be therefore compressed by the movement of tractor tyres on the farm and when the soil lacks sufficient strength to support the pressure exerted by the tractor and implement weights, compaction sets in. Another farming operation that contributes to soil compaction is land clearing. The operation is carried out prior to tillage operation and requires equipment and tools that are naturally heavy and thus soils are susceptible to compaction. The effect of soil compaction can not be over emphasized because many researchers have come up with various reports on how soil compaction affected the root development and yield of several crops adversely (Ohu et. al. (1994), Albas et. al. (1994), Lowery and Schuler, (1994) Ohu and Folorunso, (1989)). Adeoti (1997) reported that even though the top soil is being relieved during tillage operation, the sub soil is correspondingly being compacted. Ogunjirin and Kamal (1999) reported that most tyre inflation pressure specified for tractor tyre are not adhered to, thus the continual need to investigate the effect of tractor tyre inflation pressure on soil compaction. It was further asserted that tractor passes on the field increases soil bulk density between 0 and 20 cm depth. Ogunjirin and Kamal reported that at a tyre inflation pressure of 165 kpa, the tractive performance was poorest and quality of tillage operation was very poor. It was further reported that the soil bulk density increases with increase in soil compaction which invariably decreases the pore spaces in the soil. The objective of this study was to investigate the effect of tyre inflation pressures and wheel traffic on some soil physical properties. 2. Methodology The research study was conducted at the teaching and research farm of the National Centre for Agricultural Mechanization (NCAM), Idofian, Kwara State which lies in the Northern Guinea Savannah zone of Nigeria. The particle analysis of the site indicated that the soil type is sandy loam. The weather condition during the experiment showed that the temperature of the day ranged between 33 º C and 40 º C while the relative humidity ranged between 46 and 58. The soil physical properties measured before the commencement of the experiment is as shown in Table

3 The experiment was laid out in a randomized block design with a total of four treatment combinations replicated thrice. The treatment was randomly selected for the four tracks in each block in order to reduce bias to the barest minimum. The responses monitored in the course of the experiment were cone index, shear strength and bulk density. The measurement of the soil parameters were in accordance with Regional Network for Agricultural Machinery, RNAM, Test Codes A 90 Hp four wheel drive tractor was utilized for the experiment with rear tyre size of 18.4R30 and front tyre size of 12.4R24 3. Results and Discussion The moisture contents, bulk densities, shear strengths and cone indices of the soil were taken at four different rear wheel tyre inflation pressures of 138, 97, 69 and 48 kpa for two (2), four (4) and six (6) passes of the tyre on the soil. The results are found in Table 2. Considering the effect of number of tyre traffic on the soil, it was observed that the soil physical properties that were used to describe the soil, increase with increase in number of passes across all the tyre inflation pressure considered. During the study, it was observed that the higher the tyre inflation pressure, the lower the soil contact area of the tyre thus the higher the penetration resistance. This is explained by the fact that the area of pressure distribution is small, as such, the tyre pressure is acting on a small area thereby increasing the point pressure on the soil as shown in Figure 1. Therefore, the contact area of the driving wheel is a function of the tyre inflation pressure and this further affected the soil cone index, bulk density and soil shear strength (Figures 1-3). It was also observed that the number of passes have effect on the soil physical properties. The higher the number of passes, the higher the bulk densities, cone indices and soil shear strengths. However, the effect of the number of passes at tyre inflation pressures of 97 and 69 kpa revealed very minimal effect on the soil physical properties. This is because the tyre inflation pressure was not high enough to create the varied effect on the soil as shown in Figures ASAE (2002) reported that the tractor drive wheel could support about 10 kn when the tyre inflation pressure is set at 138 kpa, however Ogunjirin and Kamal (1999) reported that the best tyre inflation pressure suitable for tillage practices in Nigeria is 140 kpa but the tractor operators have been working below these pressures and the pressures that have been observed are as noted in this study. It was discovered that using the tractor at the tyre inflation pressure of about 100 kpa may be allowed depending on the soil type. However for effective tillage operation with minimum damage to the soil, tyre and implement, the operators should not operate the tractors below tyre inflation pressure of 100 kpa. At tyre inflation pressure of 138 kpa, the soil surface was visibly compacted for the soil type investigated and this was evident in the result obtained for the soil physical properties between 0 and 7 cm. At this depth there was compaction of the soil surface (Table 2). At all the depth considered for tyre inflation pressure of 138 kpa, there was consistent increase in all the soil physical properties Table 2. But from tyre inflation pressure of 166

4 97, 69 and 48 kpa, it was observed that the soil bulk density was highest at the depth of 8-14 cm. This was due to the fact that the soil had hard pan and could not transfer the tyre effect effectively beyond the depth of 14 cm. The regression analysis in Table 3 shows the relationship between the tyre inflation pressure and soil physical properties. The relationship was statistically significant at 5% level which implied that the tyre inflation pressure has effect on all the soil physical properties investigated. The coefficient of determination (R 2 ) was 99.7% indicating a perfect relationship between these variables. Regression of the data gave the following equations at different tyre passes: 4. Conclusion The study considered effect of utilizing tractors at a lower tyre inflation pressure and number of passes on soil physical properties such as cone index, bulk density and soil shear strength. It was concluded that to reduce the compaction effect of the tyre pass on the soil, tractor to be utilized for sandy loam soil could be operated at tyre inflation pressure ranging between 100 and 140 kpa. Also, to avert the effect of tractor passes on the soil, it is best for farmers to use medium range tractor and also consider the option of minimum tillage so as to reduce the damage done to the soil at the depth of 8 14 cm which is mostly required for crop growth. References Adeoti, S. J. (1997). Comparative Performance of Three Power Tillage System in Alleviating Soil Compaction and on Sorghum Yield. Paper presented at the International Soil Tillage Research Organization, ISTRO, Symposium, NCAM, Ilorin, Nigeria. Albas, J., Wanink, F., Van den Akker, J. and H. M. G. Van den Werf (1994). Impact of Traffic Induced Compaction of Sandy Soils on Yield of Silage Maize in the Netherlands. Soil Tillage Research 29: Anazodo, U. G. N. and A. P. Onwualu (1984). Evaluation of Soil Compaction due to Farm Tractor Traffic. Proceeding of the Nigerian Society of Agricultural Engineers, Symposium on Soil and Water Management pp Antille, D. L., Ansorge D., Dresser, M. L. and R. J. Godwin (2008). The Effects of Tyre Size on Soil Deformation and Soil Bulk Density Changes Paper Presented at ASABE Annual International Meeting, Rhode, Island Convention Center, Rhode Island. June 29 - July 2, Hakansson, I., and W. B., Voorhees (1998). Soil Compaction in: Methods for Assessment of Soil Degradation. Edited by: Lal, R., Blum, W. H., Valentine, C., and Stewart, B.A. (Advances in Soil Sciences). CRS Press, Boca Raton, FL pp. Mohammed, H. D. and Mutawalli, D. M. (2002). Tractor Tractive Performance as affected by Soil Moisture Content, Tyre Inflation Pressure and Implement Type. AMA Journal 33(1): Ogunjirin O. A. and A. R. Kamal (1999). Effect of Tyre Inflation Pressure and Speed of Operation on Tractor Tractive Performance during Tillage Operation. 167

5 Proceeding of Nigerian Institution of Agricultural Engineers (NIAE) 21: Ohu, J. O. and O. A. Folorunso (1989). The Effect of Machinery Traffic on the Physical Properties of a Sandy Loam Soil and on the Yield of Sorghum in North Eastern States. Soil Tillage Research 13: Ohu, J. O., Gbalapun, A. H. and O. A. Folorunso (1994). The Effect of Tractor Traffic on Cotton Production in Dark Clay Soil. Proceedings of the 13 th ISTRO Conference. July 24 29, Aalborg, Denmark pp. Oni, K.C Mechanization as a Vehicle for Rapid Agricultural Development. Invited Lecture to Participants of Senior Executive Course No. 25, National Institute for Policy and Strategic Studies Kuru Nigeria. 30th June; 43pp. Raper, R. L., (2005). Agricultural Traffic Impacts on Soil. Journal of Terramechanics. 42: Regional Network for Agricultural Machinery (1995). RNAM Test Codes and Procedure for Farm Machinery, Technical Series Number pp. 168

6 Table 1. Soil physical properties before experiment Depth (cm) Moisture Content (%) Bulk Density (g/cm 3 ) Shear Strength (kpa) Cone Index N/cm Table 2. Effect of tyre inflation pressure on soil physical properties A. 2 Passes of tractor rear tyre TI MC CI BD SS B 4 Passes of tractor rear tyre TI MC CI BD SS C 6 Passes of tractor rear tyre TI MC CI BD SS Note: data are average of three (3) readings Where, TI = Tyre inflation pressure, MC = Moisture content, CI = Cone index, BD = Bulk density, SS = Soil shear strength. Table 3. Model equations at different tyre passes S/No. No. of Passes Model Equation Adjusted R T= M+4.1C-89.8B-3.25 (2.27) T= M+0.2C B (2.27) T= M+0.001C-665.7B (2.27) 1 Where, T = Tyre inflation pressure, M = Moisture content, C = Cone index, B = Bulk density, S = Soil shear strength. 169

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