American Journal of Engineering Research (AJER) 2017 American Journal of Engineering Research (AJER) e-ISSN: 2320-0847 p-ISSN : 2320-0936 Volume-6, Issue-7, pp-01-05 www.ajer.org Research Paper Open Access www.ajer.org Page 1 Determination of the Effect of Tillage on Soil Resistance to Penetration. A Study of South-East Agricultural Soils O. Oduma 1 *, E. I. Ugwu 2 and F. N. Orji 3 1&3 Department of Agricultural and Bioresources Engineering, College of Engineering and Engineering Technology, Michael Okpara University of Agriculture, Umudike. 2 Department of Civil Engineering, College of Engineering and Engineering Technology, Michael Okpara University of Agriculture, Umudike. ABSTRACT: The effect of tillage on soil resistance to penetration was determined on three agricultural soil types (clay-loam, sandy-loam, and sandy-clay) in south-east Nigeria. Four tillage treatments namely: plough, harrow ridger and zero tillage were used for the study under twelve (12) arbitrary depth ranges (0 to 600mm). Results obtained showed that clay-loam had its highest penetration resistance at depth range of 350-400mm with average resistance of 14.3kg/mm 2 for plough, 10.4kg/mm 2 for harrow, 7.9kg/mm 2 for ridger and 13.3kg/mm 2 for zero tillage. However, at the end of 600mm depth, the overall average penetration resistance was found to had improved from 9.84kg/mm 2 of zero tilled soil to 8.08kg/mm 2 , 6.48kg/mm 2 and 4.23kg/mm 2 with plough, harrow and ridger respectively. Sandy-loam gave its highest penetration resistance of 12.3kg/mm 2 , 10.5kg/mm 2 , 7.2kg/mm 2 and 12.8kg/mm 2 for plough, harrow, ridger and zero tillage respectively at depth range of 250-350mm. But at the end of 600mm depth, the overall mean penetration resistance reduced from 8.43kg/mm 2 of zero tilled soil to 7.22kg/mm 2 for plough, 5.26kg/mm 2 for harrow and 3.33kg/mm 2 for ridger. Finally, sandy-clay showed its highest resistance to penetration at depth of 300-400mm with average resistance of 13.3kg/mm 2 for plough, 11.5kg/mm 2 for harrow, 7.4kg/mm 2 for ridger and 13.8kg/mm 2 for zero tillage. At the end of 600mm depth, the overall mean penetration resistance was brought down from 8.46kg/mm2 of zero tilled soil to 7.22kg/mm 2 , 5.26kg/mm 2 and 3.83kg/mm 2 for plough, harrow, and ridger respectively. Keywords: Implements, tillage, penetration, resistance, agricultural soils, south east Nigeria. I. INTRODUCTION Tillage is the first agricultural operation upon which depends the success or failure of the agricultural season, it is the preparatory stage of seedbed which is the critical stage in plant life [1]. At the same time soil tillage is one of the main energy inputs for agricultural production [2]. It consumes about half of the entire seasonal energy budget before the seed is planted [3] Tillage according to [4] is the change of the soil condition for the purpose of crop production. It includes all operations leading to seedbed preparation that optimizes both soil and environmental conditions for good seed germination, seedling establishment, and crop growth [5]. [6] maintained that tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. According to [7], tillage operation changes the soil surface in a number of ways, such as roughing or smoothing of the surface. [8] argued that, undisturbed soil seems to be harder and more resistant to root penetration than tilled soil. [9] observed that high soil strength reduces and even stops root growth or penetration to the soil. He stipulated that one of the aims of tillage is to reduce soil bulk density (increase soil porosity), and that the large pores in the soil generally favor high infiltration rates, good tilth, and adequate aeration for plant growth. [10] defined soil penetrability as a measure of the ease with which an object can be pushed or driven into the soil. According to [11] it is one method of measuring soil strength. The most common variables used to assess the soil strength in tillage studies are bulk density and penetration resistance because they are interrelated and the use of only one of the variables will not give a perfect result [8]. According to [12], Cone indices, computed from static penetrometer data, is used to characterize available soil compaction, resistance to root growth, and tillage effects, wheel traffic effects and hard pan resistance into the soil. The cone indices values depend on cone properties such as diameter, height, and included angle; as well as soil properties such as bulk density, shear strength, soil water content, texture, organic matter, particles surface roughness [13]. Mechanical impedance of soil increases as bulk density increases and water content decreases [14]. [10] noted that the strength in some horizons of soil can restrict root growth even when water content is at field capacity, and strength increases as the soil dries. As a consequence