Runoff, sediment yield and erodibility characteristics of some soils of central eastern nigeria under simulated rainfall
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Department of Soil Science, University of Nigeria, Nsukka, Nigeria
Acceptance date: 1999-03-17
Int. Agrophys. 2000, 14(1): 57–65
Failure of soil conservation plans in the subsaharan Africa is partly due to the lack of data on soil erosion hazard. This necessitated studies of runoff, sediment yield and erodibility characteristics of ten soils from different parts of central eastern Nigeria that were evaluated with simulated rainfall. The aim of the study was to obtain information which will aid better soil management. Rainfall intensity of approximately 180 mm h-1 was applied for 60 min to the soils packed in 0.30 x 0.12 x 0.10 m micro runoff plots situated at a slope with 3% inclination. Dry and wet runs were used. The soils varied in texture and are low in organic carbon (OC) and cation exchange capacity (CEC). Measured soil bulk density ranged from 1.20 to 1.80 Mg m-3. Runoff amount for dry runs varied between 77.6 mm and 235 mm representing between 13.2 and 40.4% of total rain applied. Variation in water infiltration into the soils was attributed to the differences in particle sizes, OC, structural properties and dithionite-citrate-bicarbonate iron oxide (Fed) content. The overall soil loss due to splash was between 0.10 and 2.60 kg m-2h-1. Splash losses were higher in dry than wet run indicating that potential erosion hazard due to splash is higher at the inception than the end of rains. Sediment yield of between 0.46 and 9.64 kg m-2h-1 for dry run and between 0.25 and 3.96 kg m-2h-1 for wet run was obtained. These values were also related to clay dispertion index (CDI), dispertion ratio (DR), OC and Fed. Waterstable aggregates greater than 0.5 mm (WSA > 0.5 mm) were found to negatively relate with splash and sediment yield. The measured and calculated erodibility ratings did not agree with the ranking of the soils. However, such parameters as exchangeable sodium percentage (ESP), OC, Fed, DR and CDI could be utilized in the prediction of erodibility of these and similar soils.