The effect of addition of organic matter on the compaction of a Vertisol from Northern Nigeria

Abstract

The quantitative effect of organic matter incorporation in alleviating compaction of dark clay soil (Vertisol) of Borno State of Nigeria was determined. Groundnut haulms were incorporated into the dark clay soil at three different levels (2, 4 and 6% by weight). Each of the soil-organic matter mixtures was subjected to three levels of compaction (5, 15 and 25 blows of a Proctor hammer) at six moisture contents. The moisture levels of compaction were selected according to the consistency limits of the soils. Measurements were made of the dry bulk density, penetration resistance, shear strength, saturated hydraulic conductivity and water retention properties of the soils. Results obtained indicated a reduction in dry bulk density, penetration resistance and shear strength of the soils. On the contrary, the saturated hydraulic conductivity and the water retention of the soils were significantly increased by organic matter. The implications of the results on the productivity of the dark clay soils are discussed.