Effect of mulch type, mulch rate and slope on soil loss, runoff and infiltration under simulated rainfall for two agricultural soils in Ghana
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Date
2011
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Abstract
To study the effect of mulch type, mulch rate and slope on soil loss, runoff and infiltration of some agricultural soils in the Ashanti Region of Ghana, soil loss experiments were conducted. A rainfall simulator was developed to measure soil loss, runoff and infiltration for two agricultural soils. The average drop size was 1.49 mm. The unit provided mean velocity of 7.5 m/s, which is 83% of terminal velocity of natural rain, given kinetic energy of 4.91 x 10-5 Joules. The effectiveness of using maize stover (Zea mayz L.), Rice straw (Oryza sativa L.), Elephant grass (Pennisetum purpureum), and Cyperus haspan L., as mulching materials were evaluated using the rainfall simulator which was set at rainfall intensities typical of the tropics. Soil samples, from two sites at KNUST (Anwomaso Research Farm) and Kotei (a suburb of KNUST) representing the main agricultural soils in the area were collected, placed at four different slopes, and covered with different rates of mulch materials. The surface runoff, soil loss, and infiltration were measured under each condition. The results with cyperus haspan compared favourably with elephant grass, which also compared favourably with results from rice straw and the rice straw also compared favourably with results from the maize stover. This finding confirms results from previous researchers. Runoff and soil loss decreased as mulch rate increases and increases with slope. It was determined that the mulch rate and field slope at which runoff and infiltration become equal were 2.25 t/ha and 3.14% respectively. Soil bulk density for the Anwomaso soil (sandy clay loam) increases linearly with increasing mulch cover and that of the Kotei soil (sandy loam) increases slightly, plateau and then decreases with increasing mulch cover.
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A Thesis submitted to the Department of Agricultural Engineering, Kwame Nkrumah University of Science and Technology, Kumasi
in partial fulfillment of the requirement for the degree of Master of Science in Agricultural Machinery Engineering,