V.M. Salokhe

A decision support system for compaction assessment in agricultural soils

Abstract Research was conducted to develop a knowledge-based decision support system to assess the degree of compaction in agricultural soils. The experiments were conducted in a laboratory soil bin at the Asian Institute of Technology in three soils, namely, clay, silty clay loam, and silty loam. The research was likewise aimed to quantify the effect of tire variables (section width, diameter, inflation pressure); soil variables (soil moisture content, initial cone index, initial bulk density); and external variables (travel speed, axle load, number of tire passes) on soil compaction and to develop compaction models for soil compaction assessment. Dimensional analysis technique was used in the development of the compaction models. The soil compaction models were found to provide good predictions of the bulk density and cone index. Using the compaction models and other secondary data, the decision support system was developed to assess the compaction status of the soil in relation to crop yield. The predictions by the decision support system were validated with actual field data from earlier studies and high correlation was observed. Thus, the output of the decision support system may be able to provide useful recommendations for appropriate soil management practices and solutions to site-specific soil compaction problems.

Coating of cage wheel lugs to reduce soil adhesion

Abstract Cage wheel blocking with mud is a serious impediment to vehicle mobility in wetland rice fields in Asia, most of which have heavy clay soils. In order to find a suitable coating material on a lug surface to reduce soil sticking to the lugs, experiments were conducted in a laboratory soil bin in wet Bangkok clay soil. The lug surface was coated with various materials, all readily available in the region, viz. lead oxide paint, silicone lubricant oil, gloss paint, gloss apint and varnish, ceramic tile, Teflon tape and sheet, chromium plating and enamel plating to find a practical method of reducing clay soil adhesion to the lugs. Results showed that the coating of a lug surface significantly affected the soil adhesion. The most promising coating seems to be enamel plating and further experiments are being carried out to determine the practicality of this method.

Regression analysis of some factors influencing soil compaction

Experiments were conducted in a laboratory soil bin, at the Regional Research Center of Asian Institute of Technology, to develop compaction models for a silty clay loam soil. The development of the models made use of dimensional analysis techniques. Three independent parameters were investigated: (1) tire variables (section width, diameter, inflation pressure), (2) soil variables (moisture content, initial cone index), and (3) external variables (travel speed, axle load, number of passes). Bulk density and cone index were considered as dependent variables. Results showed that axle load and number of tire passes were the most prominent factors which greatly influence soil compaction. Furthermore, soil moisture content, aspect ratio, and tire inflation pressure also revealed significant effects. The greatest soil compaction occurred during the first three passes of the tire. Soil compaction models were established and were found to provide good predictions. The trend established by the models signifies that general relationships can be established to predict soil compaction related to soil types. Furthermore, the models provided predictions at different soil and machine working conditions. Using the models, assessment of soil compaction can be made to develop a decision support system to establish useful recommendations for appropriate soil management practices and solutions to site-specific soil compaction problems.

Technology showcase applications of enamel coating in agriculture

Abstract Recently various experiments were conducted at the Asian Institute of Technology, Bangkok, to study the effect of enamel coating on the performance of some agricultural equipment. In order to reduce soil adhesion on cage wheel lugs, nine different coating materials were tried and enamel coating was found to be the best among these materials. It reduced soil adhesion on cage wheel lugs considerably to avoid cage wheel blocking. To investigate effect of coating on lug forces detailed lab studies were undertaken to measure the lug forces. The effects of lug slip, soil moisture content and sinkage were investigated. It was observed that enamel coating did not affect the lug forces. The pull and lift forces generated by the enamel coated and uncoated lugs were almost the same. When enamel coated bolt-on plates were mounted on the power tiller cage wheel lugs and trials were conducted in actual field conditions, it was observed that in actual field conditions enamel coated bolt-on plates on cage wheel lugs improved the performance of a power tiller. Studies about coating effects on the drag force required to pull floats on soil surface were also conducted. It was observed that enamel coating on floats reduced the drag force significantly. It also greatly improved the scouring of a mouldboard plough used in a wet, sticky clay soil.

Modeling compaction in agricultural soils

Abstract Research was conducted to quantify the effect of tire variables (section width, diameter, inflation pressure); soil variables (soil moisture content, initial cone index, initial bulk density); and external variables (travel speed, axle load, number of tire passes) on soil compaction and to develop models to assess compaction in agricultural soils. Experiments were conducted in a laboratory soil bin at the Asian Institute of Technology in three soils, namely: clay soil (CS), silty clay loam soil (SCLS), and silty loam soil (SLS). A dimensional analysis technique was used to develop the compaction models. The axle load and the number of tire passes proved to be the most dominant factors which influenced compaction. Up to 13% increase in bulk density and cone index were observed when working at 3 kN axle load in a single pass using a 8.0–16 tire. Most of the compaction occurred during the first three passes of the tire. It was also found that the aspect ratio, tire inflation pressure and soil moisture content have significant effect on soil compaction. The initial cone index did not show significant effect. The compaction models provided good predictions even when tested with actual field data from previous studies. Thus, using the models, a decision support system could be developed which may be able to provide useful recommendations for appropriate soil management practices and solutions to site-specific compaction problems.

Effect of tine rake angle and aspect ratio on soil failure patterns in dry loam soil

Studies were conducted in a laboratory glass-sided soil bin with dry compact loam soil (c = 0.02 kPa, Φ = 20° and cone index 210 kPa) with the specific objective of observing the effect of flat tine rake angle and aspect ratio on soil failure patterns. The tine was moved in the soil in a quasi-static condition and soil failure patterns were observed through a glass window. Tine rake angles of 50°, 90° and 130° were used while aspect ratio effects were studied by varying both width and depth of the tine. Individual effects of width and depth were investigated by maintaining a constant aspect ratio of 2.0 but varying width and depth. Results obtained indicated that soil failure patterns are affected by tine design parameters. Soil failure patterns were observed to be of progressive shear type in all cases. For 50° rake angle tines, the patterns consisted of inclined shear lines starting from the tine tip and gradually moving upwards towards the horizontal soil surface, intersecting it at an average failure angle of 32°. In the case of 90° rake angle tines, the inclined shear surface was at a distance from the tine tip whereas, for 130° rake angle tines, prismatic-shaped stationary soil wedges were formed adjacent to the tine. Failure angles for the 90° and 130° rake angle tines were almost the same as those for 50° rake angle tines. The results of this study also indicated that aspect ratio alone cannot account for changes in soil failure patterns, their corresponding soil reactions, forward rupture or surcharge profiles. The effects are mainly due to the individual changes in width and depth. There were no distinct zones as described in the passive soil pressure theory. Soil failures were in regular cycles resulting in corresponding variations in the soil reactions on the tines.

Force and pressure distribution under vibratory tillage tool

Abstract Experiments were conducted to study the force requirement and pressure distribution under vibratory tillage tools in a soil bin with a sandy loam soil. The tool was oscillated sinusoidally in the direction of soil bin travel. An octagonal ring transducer and pressure sensors were used to measure the forces and soil pressure on the blade. The tool was operated at oscillating frequency of 4.5–15.6 Hz and amplitude of 11–26 mm. The soil bin travel speed was varied from 0.05 to 0.224 m/s. The test results obtained showed both the horizontal force and the vertical force decreased with increase in oscillating frequency. The normal pressure on the blade surface varied considerably. The peak normal pressure was found to increase with increase in oscillating frequency, oscillating amplitude and soil bin travel speed. The change in average normal pressure with change in oscillating frequency and amplitude was also investigated.

Vibration characteristics of a power tiller

Abstract The vibration characteristics of a power tiller (two-wheel tractor) were studied. Tests were conducted at 1000, 1200, 1400, 1600, 1800, 2000, and 2200 rpm engine speeds in a stationary condition, and at 1000, 1200, 1400, 1600, and 1800 rpm engine speeds during transportation and tillage. Tests during tillage operation were conducted in the Bangkok clay soil. For the measurement of vibration, three semiconductor strain-gauge-type accelerometers, capable of sensing vibration signals in three mutually perpendicular directions, i.e. horizontal, lateral and vertical modes at the same time, were used. Vibration characteristics of the power tiller were found to be quite complex. In general, it was observed that, in any working condition, due to an increase in engine speed of the power tiller, the acceleration and frequency of vibration increased. At the same operating speed and test condition, the intensity of the vibration was the highest in the vertical mode and the lowest in the lateral mode. The maximum vibration intensities were observed during second plowing and the lowest vibration intensities were when stationary on an off-road surface. The vibration intensities, when compared to the ISO standard 2631, were found to exceed the standard during field operations.

Pull and lift forces acting on single cage wheel lugs

Abstract The lug forces, normal and tangential, on a single model cage wheel lug were measured in a wet clay soil. These normal and tangential forces were converted into lug pull and lift forces. The effect of lug sinkage, slip and soil moisture content on lug forces was investigated. Lug normal and pull forces increased up to a certain degree of lug rotation and then after attaining a peak value decreased. The lug tangential and lift force also increased up to a certain angle of lug rotation, then dropped continuously, attained a negative peak value and finally rose again to become zero at lug exit. Increase in lug sinkage showed an almost proportionate increase in lug forces while increase in soil moisture content caused a decrease in lug forces. The effect of lug slip on lug forces at constant sinkage was found to be statistically nonsignificant as lug slip was always high. Using the passive pressure soil failure theory the lug forces were predicted and compared with the measured values. It was found that the theory did not predict the lug forces accurately.

The measurement of forces on a cage wheel lug when operating in wet clay soil

Abstract The forces acting on a single model cage wheel lug were measured when operating in a wet clay soil. After initial lug entry into the soil, the normal and tangential forces acting on the lug increased up to a certain peak value and then dropped as lug rotation increased further. The tangential force later attained a negative peak value. The pull force showed the same trend as lug normal force. The lift force showed the same trend as tangential force, however, the positive peak value of lift force was much higher than the positive peak value of tangential component. The lift force was higher than the pull force. Increase in lug sinkage showed almost proportionate increase in lug forces while increase in soil moisture showed decrease in lug forces. The effect of lug slip on lug forces at constant sinkage was found to be statistically non-significant.