Soil Compaction in Sugarcane Fields under Mechanized and Labor Farming Prathuang USABORISUT Kasetsart University, Kampahaengsaen Campus, Faculty of Engineering at Kamphaengsaen, Department of Agricultural Engineering, Nakhon Pathom 7314, THAILAND fengptu@ku.ac.th Abstract: The problem of soil compaction is getting more and more awareness by both government and private sectors in Thailand. Transition to more mechanized sugarcane production can be recognized as one of main causes to accelerate the problem. To clarify such problem, investigations of soil compaction in terms of cone penetration resistance and bulk density were conducted in 16 sugarcane fields including 1 fields with mechanized farming and 6 fields with mainly labor farming. From investigation, it was found that average value of bulk densities of soil in mechanized farming fields were 12.9% significantly higher than one in labor farming fields. The contour of cone penetration resistance across cane row presented that distribution pattern was more scattering and the concentration seemed to appear in the cane row rather than between rows. There were cone penetration resistances exceeding 2 MPa especially for the fields with higher year of ratoon canes. Besides, higher compaction zone began at the depth from 5 cm. On the other hand, in case of labor farming fields, soil cone penetration resistances across cane row were lower than 2 MPa and showed less scattering distribution pattern. More similar variation in cone penetration resistance were found among labor farming fields and at depth less than 4 cm. Key words: Soil compaction, sugarcane, mechanized farming, labor farming INTRODUCTION Sugarcane is one of the most important economic crops in Thailand. In 28, Thailand produced about 73 million tons of sugarcane with a production area of about one million hectares, which ranked third among world producers, after Brazil and China (CAI, 28). Sugarcane serves as both food and fuel crops. Ethanol production from sugarcane is in line with the gasohol promotion policy of the Thai government, which aims to increase domestic ethanol demand to three million litres per day by 211 (Cane and Sugar Industry Policy Bureau, 26). In the past, manual work for sugarcane production was popular due to low cost of labor. However, in the present, mechanization in sugarcane farm is becoming important day by day due to great increasing demand of sugarcane together with problem of labor shortage. Grange (25) reported that high numbers of machine traffic passes are used in Thailand, with the thirteen passes being observed for the conventional tillage treatment. Heavy equipment and intensive use of machine can cause damage to the soil structure, which is important to the ability of a soil to hold and conduct water, nutrients, and air necessary for plant root activity, and eventually reduced yields. Soil compaction that come along with mechanization have to put as one of negative consequences in sugarcane production. Land Development Department in Thailand (29) reported that soil compaction have been found for 4,364,82 hectares which occupy 8.5 % of total area of Thailand. As the continuous cropping of sugarcane, formation of soil hardpan due to extensive use of heavy machinery has gradually become apparent. Alakukku and Elonen (1995), presented that as a mean of first 8 years, compaction of the clay soil with four passes reduced the yields by 4 % and nitrogen uptake of annual crop by 9%. Usaborisut and Niyamapa (21) also reported that the greatest reduction in yield of sugarcane compared with the control field was 22.9%, which resulted from fields compacting with 15 tractor passages. For sugarcane farming in Thailand, which soil compaction is being recognized as one of the serious problems, many efforts have to be done in order to clarify its behavior and to prepare managing its effect. Firstly soil compaction developed in sugarcane fields should be characterized. Therefore, this research work is intended 345
to investigate soil compaction that occur in sugarcane fields with labor farming compared to mechanized farming. MATERIALS and METHOD Investigation site The investigation of soil compaction were conducted in 16 sugarcane fields around Kasetsart university, Kamphangsaen campus, Nakorn Pathom, which located on central plain area of Thailand. Soil type in the fields can be categorized into loam as specified in Table 1. Kamphaeng Saen soil series, which dominate in this area, are mostly used for sugarcane farming in Thailand. In addition to Nakorn Pathom province, they are found in some provinces in central and northern areas (Land Development Department, 29). First 1 fields in Table 1 are subjected to mechanized farming while the rest mainly rely on manpower practices except the tillage that is done by tractor with disk plow. Replanting sugarcane are taken about every three years, and five years for the former and the latter, respectively. The sugarcane crops included plant to 5 th ratoon crops. Mechanized farming fields have 2, 3, 3 and 2 of plant, 1 st, 2 nd and 3 rd ratoon crops, respectively. On the other hand, labor farming fields were 1, 3, 1 and 1 of plant, 1 st, 3 rd and 5 th ratoon crops, respectively. Definition of field code shown in second column can be explained as follows: first letter specifying farming method which M standing for Mechanized farming while L being labor farming, following number giving crop type and last number telling about field number. Data measuring Cone penetrometer was used to measure soil resistance. Measurements were done 1 cm apart across a row of cane for 2 cm long and put into soil at deepest level of 1 cm. The middle of row was set at 1 cm as shown in Figure 1. Profile of soil surface was also measured. Samples for bulk density and moisture content were taken at depth of 2 cm and 4 cm using a core soil sampler. Figure 1 Distance to measure soil resistance Table 1. Field specification and soil property Field No. Field code Farming method Crop Soil Texture Sand(%) Silt(%) Clay(%) Soil type 1 M1-1 mechanized planted 47.51 34.42 18.7 Loam 2 M1-2 mechanized planted 67.4 22.6 1. Sandy loam 3 M2-1 mechanized 1 st ratoon 36.37 4.67 22.96 Loam 4 M2-2 mechanized 1 st ratoon 27.16 36.42 36.42 Clay loam 5 M2-3 mechanized 1 st ratoon 44.96 33.65 21.39 Loam 6 M3-1 mechanized 2 nd ratoon 54.51 27.32 18.17 Sandy loam 7 M3-2 mechanized 2 nd ratoon 21.25 51.97 26.78 Silt loam 8 M3-3 mechanized 2 nd ratoon 62.72 24.32 12.96 Sandy loam 9 M4-1 mechanized 3 rd ratoon 42.74 37.58 19.68 Loam 1 M4-2 mechanized 3 rd ratoon 21.39 5.52 28.9 Clay loam 11 L1 labor planted 17.72 42.11 4.17 Silt clay loam 12 L2-1 labor 1 st ratoon 25.78 35.3 38.92 Clay loam 13 L2-2 labor 1 st ratoon 45.41 33.53 21.5 Loam 14 L2-3 labor 1 st ratoon 25.8 5.84 23.36 Silt loam 15 L4 labor 3 rd ratoon 23.89 39.81 36.29 Clay loam 16 L6 labor 5 th ratoon 43.86 33.88 22.26 Loam RESULTS and DISCUSSION Bulk density in the fields Soil bulk densities in the fields varied from 1.24 to 1.79 kg/m 3. As expected, mechanized fields seemed to show higher values of soil bulk densities. The highest value of 1.79 kg/m 3 was found in mechanized farming field of 2 nd ratoon crop (M3-3), while the lowest value existed at labor farming field of planted 346
crop (L1) with 31% lower. It is of interest that the bulk density in labor farming field with 5 th ratoon crop (L6), which is the highest ratoon crop in this research, was 21% lower than the highest value In average, bulk densities of soil in mechanized farming fields were 12.9% significantly higher than one in labor farming fields. However, it has to note that bulk density is dependent on soil texture. Sandy soils have relatively high bulk density since total pore space in sands is less than that of silt or clay soils. NRCS Soil Quality Institute (23) reported that bulk densities that may affect root growth are 1.63, 1.6 and 1.55 kg/m 3 for sandy loam, silt loam and silt clay loam, respectively. Base on this data, most of mechanized fields are in the state of severe harmfulness to root growth. Table 2. Soil bulk density in the field Field code Average bulk density at 2 cm, Average bulk density at 4 cm, kg/m 3 kg/m 3 Average bulk density, kg/m 3 M3-3 - - 1.79a M3-1 1.62a 1.61a 1.62b M1-2 - - 1.58bc M2-1 1.54b 1.54b 1.54cd M4-1 1.54b 1.51b 1.52d M1-1 1.51b 1.52b 1.51d L2-3 - - 1.47ef L2-2 1.46c 1.42c 1.44fg M2-2 1.45cd 1.43c 1.43fg L6 1.42de 1.42c 1.42fgh M2-3 1.4ef 1.44c 1.42fghf M4-2 1.39ef 1.38c 1.39gh M3-2 1.37f 1.38c 1.38h L4 1.26g 1.28d 1.28i L2-1 1.24g 1.24d 1.24i L1 1.24g 1.24d 1.24i Remark: The figures in the same column which have the same attached alphabet are not significantly different analyzing by DMRT method at 95%significance Cone penetration resistance Penetration resistance of soil in sugar cane field was varying throughout the field depending on the obligations derived from the use of agricultural machinery and operations acting on the ground. This survey explored the soil throughout the soil profile so as to study the behavior of the soil compaction arising from the use of agricultural machinery. In order to view clear picture of soil compaction in the field, soil penetration resistance were plotted in form of contour lines along soil profile. The Natural neighbor model was applied since it can show boundary of the surface line and resulted in low standard deviation of.496. Shown in Figure 2 is resistance contour lines along soil profile of the sample M4-2 with four years of sugar cane cultivation under mechanized farming. The horizontal distance was the distance measured across a sugarcane row with sugarcane located at the position 1 cm. The white color represents the highest value of penetration resistance of the soil. The penetration resistance value reduces with higher intensity of black color. The general characteristics of the soil compaction can be observed from a soil penetration resistance contour. 2.8Mpa 2 4 6 8 1 12 14 16 18 2 2.6Mpa 2.4Mpa 2.2Mpa 2.Mpa 1.8Mpa 1.6Mpa 1.4Mpa 1.2Mpa 1.Mpa.8Mpa.6Mpa.4Mpa -1.2Mpa Figure 2. Soil penetration resistance contour lines As shown in Figure 2, soil penetration resistance were very high from the depth of about 5 cm showing that these areas were highly compacted soil. These areas were the areas under tillage layer where the soil was not plowed causing the soil compaction called subsoil compaction. The conventional plowing depth is about 4 cm. In the depth near surface, soil 347
compaction was alleviated during the cultivation, soil structure will be improved every time of plowing covering the area between the cane rows. Therefore, penetration resistance of soil was low. However, there were some areas at horizontal length 8 cm and 1-14 cm showing penetration resistance greater than 2 MPa even moisture content were at moderate level of 19.78% (db). Murdock (1995) and Sojka et. al. (199) reported that the soil penetration resistance more than 2 MPa made penetration of the roots very difficult. The intensity of penetration resistance around 1-14 cm horizontally at depth of about 2-3 cm seems to be caused by the forces acting on the ground due to the running devices of agricultural machinery continuously or repeatedly. Radcliffe et. al. (1988) reported that the soil under the tractor wheel at 15-3 cm deep from the surface will be compressed more than the same depth with no tractor trace. However, the higher soil penetration resistance on near soil surface at horizontal distance of 8 cm may be due to other causes, which seems to relate to change in conditions of soil after flooding and then water dried up. Comparative penetration resistance contour lines Figure 3 to Figure 8 are typical examples of contour lines of soil penetration resistance in the field under different circumstances and uses of agricultural machinery. In general, subsoil compaction existed at the depth lower than 5 cm for all fields even in the field with new planted crop. This is because problem of soil compaction have not get awereness by farmer due to the lack of understanding and high cost of subsoiling. Soil penetration resistance in mechanized farming field were higher than the labor farming fields, especially at the depth from the surface to about 4 cm. There were some areas with penetration resistance greater than 2 MPa scattering in the soil profiles especially at near sugarcane row. Additionally, severe value of penetration resistance was found particularly on higher year. Interestingly, in third year field with mechanized farming, soil penetration resistance higher than 4 MPa at 8-1 cm as shown in Figure 5, a value that root penetration cannot penetrate or to absorb water and nutrients available. On the other hand, at the depth from the surface to about 4 cm, soil penetration resistance in sugar cane fields from Year 1 to Year 6 with labor farming were not higher than 2 MPa (Figure 6 to 8). Beside, the distribution of soil compaction was fairly uniform. 2 4 6 8 1 12 14 16 18 2 2.8MPa.8MPa.6MPa -1.4MPa. Figure 3. Soil penetration resistance contour lines in field M1-1 2 4 6 8 1 12 14 16 18 2.8MPa.6MPa.4MPa. MPa Figure 4. Soil penetration resistance contour lines in field M2-3 4.4MPa 2 4 6 8 1 12 14 16 18 2 4. 4MPa 3.8MPa 3.6MPa 3.4MPa 3. 3MPa 2.8MPa.8MPa.6MPa.4MPa. Figure 5. Soil penetration resistance contour lines in field M3-1 2 4 6 8 1 12 14 16 18 2 2.3MPa 2. 1.9MPa 1.7MPa 1.5MPa 1.3MPa 1..9MPa.8MPa.7MPa.6MPa.5MPa.4MPa.3MPa. Figure 6. Soil penetration resistance contour lines in field L1-4 348
2 4 6 8 1 12 14 16 18 2.8MPa.6MPa.4MPa -1. Figure 7. Soil penetration resistance contour lines in field L4-2 3. 2 4 6 8 1 12 14 16 18 2 3MPa 2.8MPa.8MPa.6MPa.4MPa. MPa Figure 8. Soil penetration resistance contour lines in field L6-3 CONCLUSIONS The followings were concluded from the study: Average bulk density of soil in mechanized farming fields was 12.9% significantly higher than one of labor farming fields. Moreover, most of mechanized fields were in the state of severe harmfulness to root growth. Plotting soil penetration resistance in form of contour lines along soil profile by Natural neighbor model resulted in low standard deviation of.496. Soil penetration resistance contour can present visually soil compaction throughout soil profile and reflect effects of operations during sugarcane production. Soil penetration resistance was very high from a depth of about 5 cm showing problem of subsoil compaction. Soil penetration resistance in mechanized farming field were higher than the labor farming fields, especially at the depth from the surface to about 4 cm, and its values in some areas were greater than 2 MPa. Soil penetration resistance in labor farming fields at the depth from the surface to about 4 cm, from Year 1 to Year 6 were not higher than 2 MPa and distributed uniformly. ACKNOWLEDGEMENTS The author gratefully acknowledges the Thai Research Fund (TRF) for financial support. REFERENCES Alakukku, L. and Elonen, P. 1995. Long-term Effects of a Single Compaction by Heavy Field Traffic on Yield and Nitrogen Uptake of Annual Crops. Soil and Tillage Research, 37(3-4):141-152. CAI 26. Agricultural Statistics of Thailand, Crop Year 25/26. Centre for Agricultural Information, Office of Agricultural Economics, Ministry of Agriculture and Cooperatives, Bangkok, Thailand. Cane and Sugar Industry Policy Bureau, 26. Office of the Cane and Sugar Board of Thailand. Sugarcane and Sugar Industry and Renewable Energy Production. http://en.ocsb.go.th/images/119458944/article14325 49.pdf Grange I, Prammanee P and Prasertsak P. 25. Comparative Analysis of Different Tillage Systems Used in Sugarcane (Thailand): AFBM Journal, 2(1): 46-5. Land Development Department in Thailand. 29. Hardpan in Thailand. http://www.ldd.go.th/web_irw/hardpan/ hardpan.htm Murdock, L., Gray, T., Higgins, F., and Wells, K. 1995. Soil Compaction in Kentucky. Publication of the Cooperative Extension Service. University of Kentucky, College of Agriculture NRCS Soil Quality Institute. 23. Soil Quality Agronomy Technical Note No. 17. United States Department of Agriculture, Agricultural Research Service and Natural Resources Conservation Service. http://soils.usda.gov/sqi. Radcliffe, D.E., G.Manor,G.W.Langdale,R.L.Clark,and R.R.Bruce. 1988. Effect of Traffic and Tillage on Mechanical Impedance in a Layered Soil. Proceedings of the 11th Annual Southern Conservation Tillage Conference for Sustainable Agriculture Conservation Farming: Focus on a Better Future,1-12 August, 1988, Tupelo, Mississippi. 3-33. Sojka, R. E., W. J. Busscher, D. T. Gooden and W. H. Morrison. 199. Subsoiling for sunflower production in the southeast Coastal Plains. Soil Sci.. Soc. Am. J. 54(4):117-1112. Usaborisut, P. and T. Niyamapa, 21. Effects of Machine- Induced Soil Compaction on Growth and Yield of Sugarcane. American Journal of Agricultural and Biological Sciences, 5: 269-273. 349