EFFECT OF SIAM WEED (Chromolaena odorata, L.M. King & Robison) ON COMPACTION OF DIFFERENT AGRICULTURAL SOILS.

Abstract

The effect of incorporation of fresh Siam weed (Chromo/aena odorata, L.M. King & Robison) into six different agricultural soil samples on the magnitude of compaction and penetration resistance was investigated in a laboratory experiment in the Federal University of Technology, Alrure. The magnitude of compaction in terms of cone penetration resistance was measured at different levels of addition of fresh Siam weed (thereby varying the organic matter content), number of blows of proctor's hammer and moisture content of the soil. Siam weed was incorporated into six different soil samples thereby raising their organic matter content to between 1.7 and 14% dry mass basis of the soil. The samples of soil were obtained from Okitipupa, Ode Irele, Ondo, Igbara-Oke, Owo and Oke-agbe, towns noted for tractor tillage operations in Ondo State. The samples were analysed in the laboratory to classify them appropriately using the USDA classification system. For the determination of compaction strength, the fresh Chromo/aena was incorporated into the soil samples before compacting using 10, 20, 30 and 40 blows of proctor hammer at moisture content levels ranging froml.l to 21.2% dry basis. The data obtained was analyzed statistically using ANOV A. Results from the study show that the penetration resistance (an index of compaction) of the six soil samples were influenced significantly by addition of fresh Chromo/aena. For all the soil types, the compaction strength decreased with increase in fresh Siam weed addition, with the compaction strength increasing to maximum at about 10% dry basis, and subsequently decreasing with further increase in soil moisture content The penetration resistance of the soil decreased with increase in v moisture content levels in all soil types. Furthermore, the addition of fresh Siam weed as organic material during tillage operation is recommended because it will reduce soil compaction. However, heavy tillage machinery should not be used at 10% moisture content and above, as it will cause higher compaction on such soils.