SOME PHYSICAL AND MECHANICAL PROPERTIES OF A VERTISOL IN NORTHEASTERN NIGERIA AFTER LOAD APPLICATIONS AT DIFFERENT MOISTURE CONTENTS

Abstract

<abstract><title>Abstract.</title> In Nigeria prior to oil boom era, a substantial proportion of foreign exchange earning was from agricultural exports of crops such as cotton and sugar cane from the north and palm oil, cocoa from southern Nigeria to mention a few. Substantial amount of sugar cane and cotton from the north are produced on vertisol (dark clay soil). Unfortunately, the swelling and cracking characteristics of the vertisol when wet and dry made farmers to abandon their farms, reducing productivity level which drastically affected income earning from agriculture. Since cultivation using farm machines is practically impossible during wet and dry seasons, the effect of load applications on the physical and mechanical properties of a vertisol from Ngala in the northern part of Maiduguri was investigated in the laboratory of Agricultural Engineering Department of University of Maiduguri, Nigeria. Measurements were made of consistency limits; bulk density; penetration resistance; shear strength; saturated hydraulic conductivity and cracking patterns of the soil after load applications at different moisture contents. Results indicated that bulk density, penetration resistance and shear strength of the soil increased with increase in moisture content at all load applications. However, the saturated hydraulic conductivity of the soil decreased with increased moisture contents at which loads were applied. The results of the cracking patterns of the vertisol showed that compaction reduced crack length and surface area of cracks and with further drying and high compaction, the width and depth of cracks of the vertisol increased substantially. The implications of the results on managing vertisol for agricultural productivity are discussed.