Browsing by Author "Hauken, Marit"

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Soil erosion by water causes and cures with special reference to Mazimbu ANC-farm, Morogoro Tanzania
(Sokoine University of Agriculture, 1988) Kosaka, Sukenobu; Hauken, Marit
Literature concerning general theory about soil erosion by water, and soil conservation is studied. Emphasis is laid on literature concerning tropical climates and mechanized farming. Data of importance for soil erosion are collected for the Mazimbu ANC - farm in Tanzania. The collected data are used to assess present soil erosion at the farm, and to prepare a soil conservation plan for the farm. The main forms of soil erosion are splashing erosion, interrill erosion, sheet erosion, rill erosion and gully erosion. Soil erosion is affected by the erosive forces of the rain (ero-sivity), the vulnerability of the soil to be eroded (erodibility) and topographic factors such as slope steepness, slope length and slope shape. Live plants or plant residues on the soil surface are very effective in reducing erosion. erosion, Soil erosion assessment is a study of soil erosion state, erosion rate or erosion risk in an area. The assessment of erosion is important in land use planning and soil conservation work. Soil erosion models are valuable tools in the study of erosion. The Universal Soil Loss Equation (USLE) is an empirical model derived in USA. USLE predicts soil loss caused by rill and interrail and the equation can be used for the determination of conservation practices. There are several objections to transferring USLE to tropical climates. Another empirical model, Soil Loss Estimation Model for Southern Africa (SLEMSA) has been developed in Zimbabwe. Less input data is needed for SLEMSA thar for USLE. SLEMSA estimates soil loss by interrail erosion. Soil erosion can be controlled with soil and crop management and/or mechanical practices. The main objectives of soil and crop management in erosion control are to provide a soil surface that is resistant to erosion and to provide a protective cover of live plants or plant residues (mulch) on the soil surface. The main crop management factors in erosion control are crop rotations, the use of cover crops, multiple cropping, mulching, and strip cropping. It is also important to provide suitable nutrient conditions and growth conditions for the crops. Soil management in erosion control is mainly connected to tillage. Conservation tillage is tillage systems which reduce soil loss since crop residues are left on the soil surface and/or the surface is left rough, porous, cloddy or ridged. Several conservation tillage systems are described under the headings stubble mulch tillage, reduced tillage and no tillage.