The effects of land use types, management practices and slope classes on selected soil physico-chemical properties in Zikre watershed, North-Western Ethiopia
© Selassie et al.; licensee Springer. 2015
Received: 19 November 2014
Accepted: 5 January 2015
Published: 12 February 2015
Land degradation is one of the major threats to food security and natural resources conservation Zikre watershed. The objective of the study was to investigate the effects of land use types, management practices and slope classes on soil physico-chemical properties.
Results of the experiment indicated highest mean values of total nitrogen (0.23%), organic matter (5.01%) and cation exchange capacity (35.44 cmol(+) kg−1) were recorded under the natural forest and the lowest values of the same (0.12%, 2.57% and 26.08 cmol(+) kg−1, respectively) were registered in crop lands. Available phosphorus content was the highest (6.18 mg kg1) in crop lands and the lowest (1.33 mg kg−1) in grazing lands. Comparing management practices the highest mean values of available phosphorus (18.41 mg kg−1), organic matter (5.88%) and total nitrogen (0.29%) were recorded from the cultivated land treated with both manure and soil bund compared to sole soil bund, sole manure and the control plots. Considering the slope classes, the higher mean values of total nitrogen (0.19%), organic matter (4.49%) and cation exchange capacity (33.09 cmol(+) kg1) were recorded in the lower slope classes followed by middle (0.17%, 3.39% and 30.58 cmol(+) kg−1, respectively) and upper slope classes (0.14%, 2.65% and 27.36 cmol(+) kg−1, respectively).
To conclude, conversion of forest lands to cultivated and grazing lands had detrimental effects on the soil physico-chemical properties; whereas construction of soil bunds on farm fields and application of manure improve the same under subsistence farming systems.
Environmental degradation caused by inappropriate land use is a worldwide problem that has attracted attention in sustainable agricultural production systems. Ethiopia is considered to be one of the least developed countries where agriculture had always played a central role in the country’s economy. Although agriculture has always been the mainstay of the economy, it is characterized by very low growth rate. The rapidly increasing population has led to a declining availability of cultivable land and a very high rate of soil erosion (Abera 2003). It is apparent that soil is one of the most important and determinant factors that strongly affects crop production. Soil is the foundation resource for nearly all land uses, and the most important component of sustainable agriculture (Mulugeta and Karl 2010). Therefore, assessment of soil quality indicators with respect to land use types, management practices and slope classes is useful and primary indicator for sustainable agricultural land management. Understanding the effect of these factors on soil properties is useful for devising land management strategies. The information can also be used to forecast the likely effects of any potential changes in land use types and management practices on soil properties. It is apparent that the destruction of vegetative cover can promote soil erosion, which eventually increases the magnitude of soil related constraints to crop production. Generally, a sound understanding of land use and management effects on soil properties provides an opportunity to evaluate sustainability of land use systems (Woldeamlak 2003).
There is increasing awareness that soil nutrient depletion from the agro ecosystem is a very widespread problem and an immediate crop production constraint in Ethiopia (Stoorvogel and Smaling 1990; Stoorvogel et al. 1993). A change in land use, poor soil management, topography of the area and socioeconomic activities can negatively affect the potential use of an area and may ultimately lead to land degradation and loss of productivity. Loss of arable land due to soil degradation is a wide spread phenomenon in the highlands of Ethiopia, which accounts for 45% of Ethiopian total land area and 66% of the total land area of Amhara Region (Lakew et al. 2006). Low soil fertility was reported as one of the major factors affecting crop production in west part of Amhara region (Yihenew 2002, 2007). Therefore, the objective of this research was to assess the effects of different land use types, management practices and slope classes on selected soil physico-chemical properties of Zikere watershed, North-western Ethiopia.
Results and discussion
Land use and slope versus soil physical properties
Selected soil physical properties of different land use type and slope classes
Bd (t m −3 )
Land use types
Bulk density was significantly different (p < 0.05) among land use types and slope classes. The mean value of bulk density was lowest (1.05 t m−3) under the natural forest and highest (1.33 t m−3) in grazing land. High bulk density values in grazing land and cultivated land might be due to the result of excessive wet season livestock trampling and continuous shallow depth cultivation and low organic matter input. This result was in line with the works of Islam and Weil (2000), Woldeamlak (2003), Mulugeta (2004) and Yihenew and Getachew (2013). The reason for the lowest soil bulk density on the forest land as well as in the lower slope position could be due to the higher clay content and accumulation of organic matter. Similarly, less disturbance of the land unlike other land uses could be the other reason.
Land use and slope versus soil chemical properties
The effect of land use systems and slope classes on selected soil chemical properties
pH (H 2 O)
AP (mgkg −1 )
CEC (Cmol (+) kg −1 )
Land use type
The mean OM was significantly different (p < 0.05) among the land use types and slope classes (Table 2). Soil OM content was highest (5.01%) under the natural forest land and lowest (2.57%) on the cultivated land. The result was in agreement with that of Yihenew and Getachew (2013) who reported that lowest organic carbon was registered in cultivated land and highest in the natural forestland. The mean TN was significantly different among land use types and slope classes (p < 0.05). The average values of TN were highest (0.23%) on the natural forest and lowest (0.12%) under the cultivated land. The results were similar with the reports of Yihenew and Getachew (2013). The N contents in the lower slope soils of the forest land were medium; while on cultivated land and grazing lands were low based on classification of Landon (1991).
There was a significant difference of available P (AP) contents among various land uses and slope classes (p < 0.05) (Table 2). The AP content in the cultivated land appeared to be significantly higher than the rest land use types. Hence, the highest (6.18 mg kg−1) and the lowest (1.33 mg kg−1) AP contents were observed under the cultivated and the grazing lands, respectively (Table 2). Similar findings were reported by Gebeyaw (2007) and Woldeamlak (2003). Although the OM content of the cultivated land was lowest, AP content was highest under the cultivated land than the other land use types. This could be due to the application of Diammonium phosphate (DAP) fertilizer on the cultivated land in line with the explanation made by Woldeamlak (2003) and Gebeyaw (2007).
Cation exchange capacity (CEC) values were significantly different among the land use types and slope classes (p < 0.05) (Table 2). The highest (35.44 cmol(+) kg−1) and the lowest (26.08 cmol(+) kg−1) values were observed under natural forest and the cultivated lands, respectively. However, cultivated land and plantation forest showed statistically non-significant difference between them. It is a general truth that both clay and colloidal OM have the ability to absorb and hold positively charged ions. Thus, soils containing high clay and OM contents have high CEC. According to Belayneh (2009), land use highly significantly influenced the change in CEC.
Management practices versus soil properties
The effect of management practices on selected soil physico-chemical properties
pH (H 2 O)
AP (mg kg −1 )
CEC (Cmol (+) kg −1 )
Bd (g cm −3 )
Manure and soil bund
No manure and no soil bund
There was significant difference in mean value of pH (p < 0.05) among the treatments (Table 3). The non-managed plot has the lowest pH value than other treatments. Soil reactions for all the soil samples were moderately acidic to slightly acidic (5.63 - 6.36). This result was in agreement with results of Alemayhu (2007) for Anjeni catchment who explained that the mean pH value of both the terraced and the non-terraced farm plots were rated moderately acidic. The same work discussed that the overall acidity situation might have resulted from the moist climatic conditions prevailing in the study areas.
Soil organic matter (OM) contents between the managed and non-managed plots were also significantly different (p < 0.05) (Table 3). The non-conserved plots had significantly lower mean value of OM than all other treatments considered in the study. The result agrees with the finding of Tadele et al. (2011). The variations in mean value of OM could have attributed to the effect of management practices implemented and biomass accumulated. However, physical soil and water conservation (SWC) measures complemented with organic manure application raised soil OM content better than soils with only soil bund construction. Mohammed (2003) showed that manure addition had significantly increased the amount of OM level at a nearby watershed called Anjeni. Total nitrogen content was significantly different among land management practices (p < 0.05) (Table 3). Physical SWC measures complemented with manure gave higher TN compared to other measures and the non-conserved lands. Mulugeta and Karl (2010) stated that physical SWC measures stabilized with nitrogen fixing plants have given much higher TN than other biological measures. They also discussed that the non-conserved land had the smallest mean value of TN compared to the conserved catchment.
The mean values of CEC were highly significantly different (p < 0.05) among land management practices (Table 3). High organic matter and clay contents increase CEC in soils (Yihenew and Getachew 2013). Similarly, Mulugeta and Karl (2010)) supported the idea that high clay soils can hold more exchangeable cations than a low clay containing soils. There was highly significant difference in mean value of AP among the land management practices (p < 0.05). The mean value of the same parameter from managed plots was higher than that of the non-managed plot. According to Mulugeta and Karl (2010), AP was significantly different between the conserved and non-conserved fields. The variation was reported to be due to the soil OM content difference.
From the study, it was possible to conclude that soil physico-chemical properties significantly vary among land use types, land management practices and slope classes. It was apparent that shift in land use types from natural forest to the other land use types had negative effect on soil physical and chemical properties. The overall qualities of the soils under the cultivated land were inferior to soils attributes of the adjacent natural forest, plantation forest and grazing lands. Therefore, integrated land management practices are the most effective ways in reducing soil erosion and increasing soil fertility of cultivated lands.
Description of the study area
The soil samples were air dried under the shade, ground using pestle & mortar and sieved to pass through 2 mm sieve. Soil bulk density was determined using undisturbed core sampling method following the procedures described in Black (1965). Particle size distribution (soil texture) was determined by the hydrometer method (Bouyoucos 1962) Soil pH was determined in a 1:2.5 soil to water suspension following the procedure outlined in Sahelemedhin and Taye (2000). The organic carbon content was analyzed by wet digestion method using the Walkley and Black oxidation method (Walkley and Black 1934). Soil organic matter (OM) content was calculated by multiplying soil organic carbon content by a factor of 1.724. The total nitrogen (TN) content was determined using the Kjeldahl method (Bremner and Mulvaney 1982); while the available phosphorus (AP) was determined following the Olsen procedure (Olsen et al. 1954). The cation exchange capacity (CEC) was determined after extraction of the samples with 1 N ammonium acetate (Chapman 1965).
Statistical data analysis
Analysis of variance (ANOVA) was done to determine the presence of significant difference among the treatments. In conditions where there was significant difference, mean comparison was performed with Duncan’s multiple range test (DMRT) using SAS software (SAS institute 2002).
This study would never be completed without the contribution of many people to whom we would like to express our gratitude. The administrative kebele’s development agents, district agricultural officials, local guiders, committee leaders and respondent households in each of the sampling kebeles were indispensable for the successful completion of the field work. We would like also to acknowledge people who contributed their knowledge and time in data collection and entry processes.
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