Soil Fertility Status and Productivity Trends Along a Toposequence: A Case of Gilgel Gibe Catchment in Nadda Assendabo Watershed, Southwest Ethiopia

Abstract

The Impact of landscape positions and land use type on properties as well as land productivity are commonly observed in Ethiopia. The study was therefore conducted to quantify soil fertility and productivity trends under three land uses along the gradient (lower, middle and upper slope positions) of Nadda Assendabo watershed, Southwest Ethiopia. Thus field survey was covered a total of 54 composite soil samples using split plots (for soil physical properties) and split-split factorial arrangements with randomized complete block design from woodlot, grazing and crop land following topographic positions then different parameters were analyzed. The highest mean soil moisture content (56.68%) and porosity (71.09%) were observed for woodlot at the lower slope while the highest soil bulk density (1.74 g/cm 3 ) was observed for soil crop land at the upper slope where as the lowest (0.94 g/cm 3 ) was for woodlot at the lower slope. Sand, silt and clay fractions were significantly affected by interaction effects of slope and land uses (P≤0.01). Soil pH, electrical conductivity, organic carbon, cation exchange capacity, total nitrogen, available phosphorus, base saturation percentage and exchangeable basic cations for all land uses were increased down slope while they were affected significantly by slope steepness, land use and soil depth (P≤0.01). Therefore, electrical conductivity at middle and upper slope in grazing land and woodlot; total nitrogen, available phosphorus in crop land at lower slope was significantly different (P≤0.05) due to interaction effect. Furthermore, above ground biomass and grain yields of sorghum, maize and teff were also calculated on farm fields using split plots arrangements. Thus both yields were significantly affected by interaction effect of slope and crop type. Finally, based on the results woodlot, grazing and crop land were recommended for upper, middle and lower slopes respectively.

Influence of Slope Gradient on Coffee Soil Fertility in Goma Woreda of Oromia Region

“…Correspondingly, the data showed that the minimum value of PSB (31.69%) was obtained from strongly sloping and the maximum value of PBS (40.95%) was obtained from moderately steep slope (Table 2). This result disagrees with findings of Mulugeta (2015) and Siraj et al, (2015) reported that PBS was affected by slope positions.…”

“…According to Likassa (2014) reported the shade trees were more environmental sound as compared to chemical fertilization is added to soil. On the other hand, according to Siraj et al, (2015), Mulugeta (2015) and Fanuel et al, (2016), who, revealed that exchangeable potassium was significantly influenced by the slope gradient classes, which were opposite to the present study. Similarly, Mulugeta (2015) reported that the accumulation of exchangeable magnesium contents were relatively higher on lower slope gradient over medium slope and upper slope gradients, respectively.…”

“…Soil pH can be affected by several factors other than slope positions. Of these, the parent materials, soil textures, mineral contents, climates and the degree of weathering and translocation of basic cations in the soil might be responsible for soil acidity variations because inherent factors that affect soil pH.On contrary aforementioned, according to Siraj et al, (2015), Mulugeta (2015) and Kehali et al, (2017) depicted that soil pH was significantly influenced by slope gradients.…”

Implication of Long-Term Terracing Watershed Development on Soil Macronutrients and Crop Production in Maybar Subwatershed, South Wello Zone, Ethiopia

“…39 Most of the soil nutrients significantly decreased due to soil erosion and landscape features with increasing slope steepness and unwise utilization of land. 40 The deposition of sediment on the lower slope has had a noticeable effect on the soil's physical and chemical properties. 41 Soil bunds reduce runoff, as well as soil and nutrient losses and organic carbon loss from cultivated lands.…”

Effects of Land Use/Land Cover Changes on Selected Soil Physical and Chemical Properties in Shenkolla Watershed, South Central Ethiopia

“…However, soil nutrient removal, organic matter depletion, and soil erosion are seriously threatening the sustainability of agricultural production in Ethiopia [6,7]. e shortage of land in densely populated areas of the country, to meet the demand for food production, led to conversion of vast tracts of forestlands into cultivated crop lands [8].…”