ASSESSMENT OF SOIL COMPACTION LEVELS BY FARM MACHINERY IN CULTIVATED SANDY LOAM SOILS

Abstract

The increasing soil degradation due to soil compaction may be linked to the increase in weight of agricultural machinery, in the more use of machinery even under unfavorable soil conditions and to poor crop rotation. The objective of the research was to assess the levels of soil compaction in cultivated fields. The research experiment was done in Elfam farm in Moiben Sub County, Uasin Gishu County, Kenya. The soils type was classified as Ferralsols with sandy loam texture. A four wheeled 70 kN tractor was used in the experiments. A multiple linear regression was used to describe the relationships of load, depth and number of passes for both bulk density and penetration resistance. The experiment was conducted at three levels of normal loads of 26 kN, 30 kN and 34 kN at four levels of number of passes 1,5,10 and 15 all with three replications. The field bulk density and penetration resistance were determined at varying levels of loading and number of passes using sand replacement method and Dynamic cone penetrometer respectively. The data was analyzed using statistical software for analysis of variance (ANOVA) at 95% confidence level and p < 0.05. From the results the highest bulk density at 34 kN and 15 passes was 1513 kg/m3 on the top soil. The lowest bulk density was 1116 kg/m3 on the subsoil layer below 45cm at 26 kN and one pass. The highest penetration resistance was found to be 52.50 J/cm at 30 kN and a depth below 45cm. The lowest penetration resistance obtained was 9.52 J/cm at 26 kN on the top soil layer. During the test period the moisture content average was 25%. The findings indicated that there was an increase in bulk density with the increase of loading and number of passes. The penetration resistance increased with loading, number of passes and depth. The iv increased loading and number of passes was particularly found to affect the soil layer above 45cm. From the study it was found that the effect of number of passes on bulk density increased with the increase in the number of passes. Also, loading and number of passes were found to have significant impact on penetration resistance. The coefficients of determination (R2) for bulk density and penetration resistance were found to be of 0.8822 and 0.8674, respectively. The relative compaction from the test results indicate that the soil was 95.5% compacted.