Soil erosion prediction using RUSLE in central Kenya
Abstract
Soil erosion by water is a serious global problem responsible for the loss of billions of tons of sediments from land to oceans each year. While there are many soil conservation methods for any area, effective erosion control starts with appropriate intervention techniques. First, there needs to be meaningful and accurate estimation of soil loss by water, and then there needs to be subsequent monitoring to ensure the control measures are effective. This study was conducted at the Kianjuki catchment in central Kenya to estimate annual soil loss using the Revised Universal Soil Loss Equation (RUSLE ver. 1.06) and to determine the support practice subfactor p for contour calliandra-napier hedges for soil and water conservation under direct farmer management practices. Biomass production as well as total nitrogen (N) and total phosphorus (P) retention by the hedges were measured. Rainfall erosivity R factor determined as 852 7 MJ mm ha−1 h−1 yr −1 while soil erodibility K factor was found to be 0.17 Mg ha h ha−1 MJ−1 mm−1. Overall LS values varied between 1 and 25 depending on slope and location within the catchment. The C factor values were computed for corn-bean one-year rotation (0.314), coffee (0.145), and banana (0.122). Support practice P factor varied between 0.47 and 1. Total annual soil loss predicted varied from one overland flow segment to the next and ranged from 134 Mg ha −1 yr−1 for slopes with LS values of 0–10 to 549 Mg ha−1 yr−1 for slopes with LS values of 20–30. A support practice subfactor of 0.7 was determined for the calliandra-napier hedge soil conservation barrier. The hedge significantly reduced N and P losses. Combined biomass yield from calliandra and napier was about 10 Mg ha −1 yr−1. Overall, there is a need for strict soil conservation intervention procedures in the catchment to bring soil loss down to acceptable limits. The calliandra-napier soil conservation technology can be recommended for small-scale farmers in the humid tropics who practice mixed farming agriculture to enhance sustainable farming.
Degree
Ph.D.
Advisors
Stott, Purdue University.
Subject Area
Soil sciences|Agronomy
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