Document Type : Research Paper
Authors
1 Assistant Professor, Department of Mechanical Engineering of Biosystems, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran
2 Professor, Department of Agricultural Machinery Engineering, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
3 Agroscope, Department of Natural Resources and Agriculture, Zurich, Switzerland and Professor, Swedish University of Agricultural Sciences, Department of Soil and Environment, Sweden
Abstract
Introduction Soil compaction is a serious concern in modern agriculture. Field traffic using machines with high axle loads is likely to compact the soil below the plough layer. Compaction of the subsoil should be avoided since soil productivity is at risk of being reduced, and because the effects are very persistent, perhaps even permanent. Precompression stress is widely applied as a border between elastic and plastic soil deformations under stress application. As long as the stress does not exceed the precompression stress, soil deformation is expected to be recoverable after the removal of stress (i.e. passage of the tire). The precompression stress is conventionally determined using the standard procedure of Casagrande from the log stress – void ratio curve resulting from confined uniaxial compression of intact soil samples taken at the field. With advances in the technology of precision agriculture, site specific management of machinery traffic is under focus by researchers. Field mapping of soil precompression stress would allow for site specific modifying the machine parameters (e.g. the tire inflation pressure) to control the applied stress below the precompression stress. For example, where the soil moisture is high, a decrease in tire inflation pressure increases the soil-tire contact area and thus decreases the severity of stress propagation in soil. However, the conventional method of estimating the precompression stress is time-consuming, labor intensive thus not suitable for mapping applications. Horizontal penetrometer is a popular device for on-the-go measuring of soil strength. Horizontal penetrometer resistance is an attractive measurement because it is relatively simple, fast and cheap, can be carried out on-the-go, thus yielding spatial information with a high resolution. A multi-tip horizontal penetrometer would also allow for discrete-depth measuring the soil strength. As penetrometer resistance and precompression stress are both measures of soil strength, it was hypothesized that they are highly correlated. Therefore, the relationship between precompression stress (σpc) and horizontal penetrometer resistance (PR) was investigated in a wide range of soil textures. This would suggest an alternative for on-the-go measurement of σpc for field mapping and site-specific management of soil trafficability.
Materials and Methods Field measurements were conducted in different soil textures in Switzerland. The clay content of the soils varied from 189 to 584 g kg-1. Horizontal penetrometer resistance was measured at 0.25 m depth at a traveling speed of 0.25 m s-1. Cylindrical core samples were taken at the local minima and maxima of PR along the transects. Cone index measurements were also performed to a depth of 0.5 m at the points of core samples. The samples were subjected to stepwise compression stresses by an Oedometer and the resulting deformation was recorded. The void ratio was calculated with particle density and bulk density at the end of each stress step. The precompression stress was estimated at the point of maximum curvature of log stress- void ratio with fitting Gompertz function. Correlation and regression analyses were performed in SAS software.
Results and Discussion The results showed that the Gompertz function explains well the void ratio versus log of stress for different soil textures. The Gompertz parameters were characterized with respect to soil physical characteristics. Precompression stress decreased with increasing soil moisture, soil clay and organic matter content. A relatively strong correlation was found between σpc and PR (R2= 0.47, RMSE= 15.4 kPa) which was significantly improved (R2= 0.59, RMSE= 13.7 kPa) with the effect of soil water content. The high scatter of the relationship between precompression stress and horizontal penetrometer resistance was discussed to be likely due to the difference between the soil failure mechanisms around a penetrating tip and under uniaxial compression. A comparison of different compaction tests (e.g. semi-confined and plate sinkage) with PR may suggest stronger correlations. A strong correlation (R2= 0.6) was also found between PR and cone index (CI). CI was found to be larger than PR for all the soils.
Conclusion It was concluded that the soil compaction characteristic (log stress versus void ratio) is strongly governed by the soil initial void ratio with an increase of precompression stress with decreasing the initial void ratio. In the range of variations tested, the relationship between PR and σpc was not affected by soil texture (clay content). The study suggests that measurement of PR can be a fast alternative for mapping of soil precompression stress by compensating for the effect of soil moisture (by e.g. a dielectric sensor). therefore, a combined horizontal penetrometer needs to be employed.
Keywords
Main Subjects
- Alexandrou, A. and Earl, R. 1998. The relationship among the pre-compaction stress, volumetric water content and initial dry bulk density of soil. Journal of Agricultural Engineering Research, 71: 75–80.
- Arvidsson, J. and Keller, T. 2004. Soil precompression stress I. A survey of Swedish arable soils. Soil and Tillage Research, 77: 85-95.
- ASTM D2216-10. 2016. Standard test methods for laboratory determination of water (moisture) content of soil and rock by mass. ASTM International, West Conshohocken, PA, 2010, www.astm.org.
- Berisso, F.E., Schjønning, P., Lamandé M., Weisskopf, P., Stettler, M. and Keller, T. 2013. Effects of the stress field induced by a running tyre on the soil pore system. Soil and Tillage Research, 131: 36–46.
- Burger, N., Lebert, M. and Horn, R. 1988. Prediction of the compressibility of arable lands. In: Drescher, J., Horn, R., De Boodt, M. (Eds.), Impact of Water and External Forces on Soil Structure. Catena, Supplement 11. Catena, Cremligen-Destedt, pp. 141–151.
- Canarache, A., Horn, R. and Colibas, I. 2000. Compressibility of soils in a long term field experiment with intensive deep ripping in Romania. Soil and Tillage Research, 56: 185–196.
- Casagrande, A. 1936. The determination of pre-consolidation load and its practical significance. In Proceedings of the international conference of soil mechanics and foundation engineering, Cambridge, MA, 22-26 June (Vol. 3); (pp. 60-64).
- Chukwu, E. and Bowers Jr., C.G. 2005. Instantaneous multiple-depth soil mechanical impedance sensing from a moving vehicle. Transactions of the ASABE, 48 (3): 885–894.
- Chung, S.O. and Sudduth, K.A. 2006. Soil failure models for vertically operating and horizontally operating strength sensors. Transactions of the ASABE, 49 (4): 851–863.
- Chung, S.O., Sudduth, K.A. and Hummel, J.W. 2006. Design and validation of an on-the go soil strength profile sensor. Transactions of the ASABE, 49 (1): 5–14.
- Chung, S.O., Sudduth, K.A., Plouffe, C. and Kitchen, N.R. 2008. Soil bin and field tests of an on-the-go soil strength profile sensor. Transactions of the ASABE, 51(1): 5–18.
- Da Veiga, M., Horn, R., Reinert, D.J. and Reichert, J.M. 2007. Soil compressibility and penetrability of an Oxisol from southern Brazil as affected by long-term tillage systems. Soil and Tillage Research, 92: 104-113.
- Eriksson, J. 1982. Soil compaction and root environment. Report 126. Division of Agricultural Hydrotechnics, Department of Soil Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden, 138 pp.
- Flint, A.L. and Flint, L.E. 2002. Particle density. p. 229-240. In J.H. Dane and G.C. Topp, (eds.) Method of Soil Analysis, Part 4: Physical Methods. SSSA Book Series No. 5. SSSA, Madison, WI.
- Gompertz, B. 1825. On the nature of the function expressive of the law of human mortality, and on a new mode of determining the value of life contingencies. Philosophical Transactions of Royal Society of London, 115: 513–585.
- Gregory, A.S., Whalley, W.R., Watts, C.W., Bird, N.R.A., Hallett, P.D. and Whitmore, A.P. 2006. Calculation of the compression index and precompression stress from soil compression test data. Soil and Tillage Research, 89: 45-57.
- Hamza, M.A. and Anderson, W.K. 2005. Soil compaction in cropping systems: A review of the nature, causes and possible solutions. Soil and Tillage Research, 82: 121-145.
- Heege, H.J. 2013. Precision in Crop Farming. Site Specific Concepts and Sensing Methods: Applications and Results. Springer Netherlands. DOI 10.1007/978-94-007-6760-7.
- Hemmat, A. and Adamchuk, V.I. 2008. Sensor systems for measuring soil compaction: Review and analysis. Computers and Electronics in Agriculture, 63: 89-103.
- Hemmat, A., Tahmasebi, M., Vafaeian, M. and Mosaddeghi, M.R. 2009. Relationship between pre-compaction stress and shear strength under confined and semi-confined loadings for a sandy loam soil. Biosystems Engineering, 102: 219-226.
- Hemmat, A., Khorsandi, A. and Shafaie, V. 2012. Soil failure mode in front of a multiple tip horizontally-operated penetrometer. Turkish Journal of Agriculture and Forestry, 36: 476–485.
- Hemmat, A., Yaghoubi-Taskoh, M., Masoumi, A. and Mosaddeghi, M.R. 2014. Relationships between rut depth and soil mechanical properties in a calcareous soil with unstable structure. Biosystems Engineering, 118: 147-155.
- Horn, R. and Fleige, H. 2003. A method for assessing the impact of load on mechanical stability and on physical properties of soils. Soil and Tillage Research, 73: 89-99.
- Horn, R., Fleige, H., Richter, F-H., Czyz, E.A., Dexter, A., Diaz-Pereira, E., Dumitru, E., Enarche, R., Mayol, F., Rajkai, K., de la Rosa, D. and Simota, C. 2005. SIDASS project: Part 5: Prediction of mechanical strength of arable soils and its effects on physical properties at various map scales. Soil and Tillage Research, 82(1): 47-56.
- Keller, T. and Arvidsson, J. 2007. Compressive properties of some Swedish and Danish structured agricultural soils measured in uniaxial compression tests. European Journal of Soil Science, 58: 1373–1381.
- Keller, T., Défossez, P., Weisskopf, P., Arvidsson, J. and Richard, G. 2007. SoilFlex: A model for prediction of soil stresses and soil compaction due to agricultural field traffic including a synthesis of analytical approaches. Soil and Tillage Research, 93: 391-411.
- 27-Keller, T., Lamandé, M., Schjønning, P. and Dexter, A.R. 2011. Analysis of soil compression curves from uniaxial confined compression test. Geoderma, 163: 13-23.
- Keller, T., Arvidsson, J. Schjønning, P., Lamande, M., Stettler, M. and Weisskopf, P. 2012. In situ subsoil stress-strain behaviour in relation to soil precompression stress. Soil Science, 177(8): 490-497.
- Lamandé, M, Schjønning, P. and Tøgersen, F.A. 2007. Mechanical behaviour of an undisturbed soil subjected to loadings: Effects of load and contact area. Soil and Tillage Research, 97(1): 91–106.
- Lamandé, M. and Schjønning, P. 2011a. Transmission of vertical stress in a real soil profile. Part I: Site description, evaluation of the Söhne model, and the effect of topsoil tillage. Soil and Tillage Research, 114(2): 57–70.
- Lamandé, M. and Schjønning, P. 2011b. Transmission of vertical stress in a real soil profile. Part III: Effect of soil water content. Soil and Tillage Research, 114(2): 78–85.
- Lebert, M. and Horn, R. 1991. A method to predict the mechanical strength of agricultural soils. Soil and Tillage Research, 19: 275–286.
- Mosaddeghi, M.R., Hemmat, A., Hajabbasi, M.A. and Alexandrou, A. 2003. Pre-compression stress and its relation with the physical and mechanical properties of a structurally unstable soil in central Iran. Soil and Tillage Research, 70: 53-64.
- Naderi-Boldaji, M., Alimardani, R., Hemmat, A., Sharifi, A., Keyhani, A., Dolatsha, N. and Keller, T. 2012. Improvement and field testing of a combined horizontal penetrometer for on-the-go measurement of soil water content and mechanical resistance. Soil and Tillage Research, 123: 1–10.
- Naderi-Boldaji, M., Sharifi, A., Alimardani, R., Hemmat, A., Keyhani, A., Loonstra, E.H., Weisskopf, P., Stettler, M. and Keller, T. 2013. Use of a triple-sensor fusion system for on-the-go measurement of soil compaction. Soil and Tillage Research, 128: 44–53.
- Naderi-Boldaji, M., Weisskopf, P., Stettler, M. and Keller, T. 2016. Predicting the state of compactness of arable soil from on-the-go horizontal penetrometer measurements. Soil and Tillage Research, 159: 23-32.
- Rücknagel, J., Hofmann, B., Paul, R., Christen, O. and Hülsbergen, K.J. 2007. Estimating precompression stress of structured soils on the basis of aggregate density and dry bulk density. Soil and Tillage Research, 92: 213–220.
- Saldago, R. and Prezzi, M. 2007. Computation of cavity expansion pressure and penetration resistance in sands. International Journal Of Geomechanics, 7: 251-265.
- Schulte, E.E. and Hopkins, B.G. 1996. Estimation of soil organic matter by weight Organic Matter (LOI) 3loss- on - ignition. Pp.21- 31. InF.R. Magdoff, M.A. Tabatabai, and E.A. Hanlon, Jr. (eds.), Soil Organic Matter: Analysis and Interpretation. Soil Science Society of America, Madison, WI.
- Wösten, J.H.M., Lilly, A., Nemes, A. and Le Bas, C. 1999. Development and use of a database of hydraulic properties of European soils. Geoderma, 90: 169–185.