Winter cover crops effects on soil strength, infiltration and water retention in a sandy loam Oakleaf soil in Eastern Cape, South Africa

Abstract

There is substantial evidence that cover crops increase soil fertility and plant nutrition but the few studies concerning soil physical properties are conflicting. This study determined the effects of monocultures of vetch (Vicia dasycarpa L.), lupin (Lupinus angustifolius L.), oats (Avena sativa L.) and bicultures of oats and vetch and a weedy fallow on the strength and water conservation properties of a hardsetting Oakleaf soil. Oats monoculture lowered the soil strength by 48.5%, whilst vetch and lupin increased soil strength by 43% and 31%, respectively, relative to the control. Bicultures decreased soil strength as the proportion of oats increased. Oats monoculture increased cumulative water infiltration relative to the control. Bicultures increased the water final infiltration rate by 105–163% compared to the control. Plant available water increased by 24–28% compared to the weedy fallow under monocultures. However, no significant differences were observed on plant available water after two rotations with bicultures compared to the weedy fallow. We concluded that oats monoculture reduced the strength and improved water conservation properties of the hardsetting soil but vetch and lupin monoculture worsened the deleterious effects of the hardsetting phenomenon.