THE EFFECT OF ADDITION OF ORGANIC-MATTER ON THE COMPACTION OF A VERTISOL FROM NORTHERN NIGERIA

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 soi l 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 m oisture levels of compaction were selected according to the consistenc y limits of the soils. Measurements were made of the dry bulk density, penetration resistance, shear strength, saturated hydraulic conductiv ity and water retention properties of the soils. Results obtained indi cated a reduction in dry bulk density, penetration resistance and shea r strength of the soils. On the contrary, the saturated hydraulic cond uctivity and the water retention of the soils were significantly incre ased by organic matter. The implications of the results on the product ivity of the dark clay soils are discussed.