Surface Runoff Generation and Soil Loss Under Different Soil and Rainfall Properties in The Uluguru Mountains, Tanzania

Abstract

Water erosion is one of the main concerns driving land degradation in mountainous areas throughout the world, and its characteristics change widely with soil and climate conditions in different locations. To investigate the effects of soil and rainfall properties on surface runoff and soil loss, we installed runoff plots (width 0·8 m × slope length 2·4 m) enclosed by corrugated iron sheets, and evaluated water budgets for rainfall, surface runoff and soil moisture for every rainfall event over a rainy season at four sites (designated NY, TA, SO and MA) in the Uluguru Mountains of Tanzania. Two of the sites, NY and TA, were located in mountainous areas and had steep slopes and higher rainfall amounts, while the two foothill sites, SO and MA, were flatter and with coarser textures. Runoff amount was related to rainfall amount, but also to infiltration capacity. Runoff amounts in mountainous areas were higher than in foothill sites while runoff ratio was low at sites with high permeability in the surface layer, TA and MA. Sediment concentrations and soil loss were basically enhanced by high rainfall amount and intensity at mountainous sites. Soil texture also controlled the erodibility of soils; MA had twice the soil loss of SO owing to sandy soil despite similar rainfall amounts at MA and SO. Our results show that the high rainfall amounts in the mountainous areas and high susceptibility of sandy soils to erosion enhanced soil loss by water erosion in this study.

Effect of Mulching with Vegetative Residues on Soil Water Erosion and Water Balance in an Oxisol Cropped by Cassava in East Cameroon

“…The intensity of rainfall did not differ between the early and late rainy season, and the proportion of strong intensity observed in this study was comparable with the rainfall intensities in other tropical areas with high rainfall intensities (Funakawa et al, ; Nishigaki et al, ).…”

“…These physical properties of Oxisols greatly contributed to the high drainage rate even at wet soil moisture condition and resulted in a low total runoff coefficient in all treatment plots. The runoff coefficient in this study was less than half of that for Alfisols (16·0–16·6%) reported by Nishigaki et al ()), in which the characteristics of surface runoff generation were also evaluated using the same water budget data sets in the Uluguru Mountains in Tanzania. Nishigaki et al () observed that the 0‐ to 30‐cm layer of Alfisols captured rainwater in most of the rainfall events, and the soil moisture content in the 30‐ to 60‐cm layer did not increase as frequently as that of the Oxisol in the present study regardless of the antecedent soil moisture condition.…”

“…The runoff coefficient in this study was less than half of that for Alfisols (16·0–16·6%) reported by Nishigaki et al ()), in which the characteristics of surface runoff generation were also evaluated using the same water budget data sets in the Uluguru Mountains in Tanzania. Nishigaki et al () observed that the 0‐ to 30‐cm layer of Alfisols captured rainwater in most of the rainfall events, and the soil moisture content in the 30‐ to 60‐cm layer did not increase as frequently as that of the Oxisol in the present study regardless of the antecedent soil moisture condition. These contrasting results between two soil types were probably caused by the greater volume of large pores in the 0‐ to 30‐cm layer of the Oxisol in this study than that of Alfisols (0·07–0·23 m 3 m −3 ) in Tanzania.…”

“…The application of residue was conducted twice during the experimental period because the applied residues were quickly decomposed because of high activity of termites; the first application was just after the planting of cassava on 10 April 2013, and the second [Colour figure can be viewed at wileyonlinelibrary.com] application was on 1 August 2013. The plot size (width 0·8 m × slope length 2·0 m) was small enough to clarify the water balance and the timing of runoff generation within the plot and to exclude the microtopography that might influence runoff dynamics (Funakawa et al, 2007;Nishigaki et al, 2016). The plots were enclosed by corrugated iron sheets on a smooth slope of 17·5°.…”

Event‐based deep drainage and percolation dynamics in Vertosols and Chromosols

“…Furthermore, infiltration may be affected by the drop size distribution (Foley & Silburn, ). Other rain event properties such as event depth or duration may affect infiltration rates through the development of soil hydraulic properties (e.g., Angel, Palecki, & Hollinger, ; Struthers, Sivapalan, & Hinz, ), or through effects on other water balance components including runoff generation (e.g., Nishigaki, Sugihara, Kilasara, & Funakawa, ) and canopy interception (e.g., Zeng, Shuttleworth, & Gash, ).…”