Impact of Land Use Types on Soil Degradation in Meja Watershed, Jeldu District, West Shoa, Ethiopia
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Journal of Science and Sustainable Development (JSSD), 2014, 1(3) 15-30 Copyright © Ambo University ISSN: 2304-2702 (print); 2414-4479 (online) DOI: https://doi.org/10.20372/au.jssd.2.1.2014.023 Impact of Land Use Types on Soil Degradation in Meja Watershed, Jeldu District, West Shoa, Ethiopia Birhanu Ayana1, Tesfaye Balemi2 and P. Natarajan3 1Department of Biology, Shenen Preparatory School, Jibat woreda, West Shoa Zone, Oromia Region, Ethiopia 2Department of Biology, Ambo University, P.O.Box 19, Ambo, Ethiopia, E-mail: [email protected] 3Department of Plant Science and Horticulture, College of Agriculture and Veterinary Science, Ambo University P.O.Box 19, Ambo, Ethiopia Abstract Poor land resources management with the consequence of soil degradation is the main cause of low agricultural productivity and food insecurity in the rural highlands of Ethiopia. The current study was undertaken at Meja watershed, located in the Jeldu district, Oromia region. The aim of the study was to assess the impacts of different land use types on soil quality parameters in the watershed. Soil samples collected from the upper 0-20 cm depth from cultivated, grazing and forest lands was analyzed for various soil quality parameters. The results indicated that soil parameters such as, cation exchange capacity (CEC) and organic matter (OM) content were significantly higher for forest and grazing land than for cultivated land whereas electrical conductivity (EC), total nitrogen (TN), available phosphorus (AvP), exchangeable K, Ca and Mg contents were significantly higher for forest land compared to both grazing and cultivated lands. Other soil parameter such BD was higher for cultivated land than for the other land use types. The results clearly indicated that land use types significantly influenced soil quality suggesting that a change from forest land to the other land use types aggravated soil degradation resulting in soil fertility decline in the study watershed. Key Words: cultivated land, grazing land, Forest/plantation land, soil quality, soil degradation index Introduction Ethiopia, where agriculture is the backbone of the economy, severe food insecurity and natural resource Improper land use is being observed degradation have been a challenge to as a result of the challenges to increase the livelihood of many rural food production to meet the demand communities. The causes of land of increased population potentially degradation in Ethiopia could be resulting in land degradation. Land attributed to the cultivation of steepy degradation in turn has severe lands, fragile nature of soils with negative impact on agronomic inadequate soil conservation practices productivity of crops, environmental or vegetation cover, erratic and quality and on food security and erosive rainfall patterns, declining use overall livelihood of human beings of fallow system, limited nutrient (Omotayo and Chukwuka, 2009). In Birhanu Ayana et al. [2] recycling from manures and crop be implemented. It is assumed that residues, limited application of awareness creation on the extent of external sources of plant nutrients, land degradation among the farmers, deforestation and overgrazing (Belay, policy makers and other stakeholders 2003; Hurni, 1988). would help easy adoption of research recommendations and any decisions It has been estimated that 2 million ha made by policy makers to safeguard of Ethiopia’s highlands have been soil from further degradation. Thus, degraded beyond rehabilitation, and there is a need to investigate the an additional 14 million ha are relationship between land use types severely degraded (UNEP, 2002). The and soil quality to further influence removal of vegetation cover exposes farmers in their decision to choose the soil to wind and water erosion. appropriate land resource Soil compaction occurs in areas where management strategy in Meja there is excessive trampling by Watershed. The objective of the animals. In cultivated areas soil present study was, therefore, to fertility is declining as a result of the investigate the impacts of different exhaustion of soils by mono-specific land use types on soil quality based cropping and reduction of fallow on selected physico-chemical periods (UNEP, 2002). Although there properties of soil. is an overall understanding that soils of the study area are being degraded, the extent and magnitude of the Materials and Methods degradation is, however not known. This necessitated an investigation of Description of the Study Area the extent of soil degradation in terms The study was conducted at Meja of soil fertility under different land watershed, Jeldu district, West Shewa use systems. A decline in soil fertility Zone of Oromiya Regional State, induced by change in land use system Central Ethiopia (9° 02' 47" to 9° 15' was observed in many parts of the 00" N and 38° 05' 00" to 38° 12' 16" E). world (Mulumba, 2004; Ayoubi et al., The district has an undulating terrain 2011; Aghasi et al., 2011). Such decline with altitude ranging from 2,900-3,200 in soil fertility was mainly attributed meters above sea level. Rainfall to loss of nutrients and organic matter pattern of the area is bimodal with the through soil erosion as a result of main rainy season from June to conversion, mainly of forestland to September and short rainy season cropland. Due to the dearth of from February to March. Mean annual detailed information on the extent of rainfall ranges from 1800 to 2200 mm. land degradation under different land The maximum and minimum use systems in Ethiopia, sound soil temperature ranges from 17 to 22OC reclamation practices and land use (District’s Agriculture and rural decisions by policy makers could not development office annual Report of Journal of Science and Sustainable Development (JSSD), 2014, 1(3) 15-30 Impact of Land Use Types on Soil Degradation in Meja Watershed, Jeldu District, West Shoa, Ethiopia [3] 2009, unpublished). The farming type, but the riverbed has a loam and system of the study area is mainly rain sandy-loam type of soil (Hurst et al., fed. The soil is clay and clay-loam 1959 cited in Dereje, 2010). Figure 1: Map of the study location Soil sampling and analysis homogenized and sieved through 2 Soil samples were collected from three mm sieve. A separate undisturbed soil land use types (cultivated, grazing sample for bulk density determination and forest/plantation lands) in the (BD) was collected by a core sampler watershed, to assess the status of soil (cylindrical metal sampler) from the degradation. Soil samples were taken same site. from the top soil (depth of 0-20 cm) The soil was analysed for selected soil from each land use type in a zigzag chemical properties, such as soil pH, manner using an Auger. The electrical conductivity (EC), soil composite sample from each land use organic matter content (OM), total type was separately ground into fine nitrogen (TN), available phosphorous tilth using mortar and pestle, (AvP), cation exchange capacity (CEC) Journal of Science and Sustainable Development (JSSD), 2014, 1(3) 15-30 Birhanu Ayana et al. [4] and basic exchangeable cations. Soil it to constant weight in an oven at pH and electrical conductivity of soil 1050C for 24 hours and reweighing samples were determined at 1:2.5 after cooling. Bulk density was then (soil: water suspension) using pH calculated from the measurement of meter and portable conductivity the bulk volume, using the core length meter, respectively according to Black and the diameter of the cutting edge (1965). The Walkley and Black (1934) of the sampler. wet digestion method was used to determine soil carbon content and …………(1) percent soil OM was calculated by multiplying percent soil OC by a 2 factor of 1.724 with the assumptions Volume of sample = π r h………… (2) that OM is composed of 58% carbon. Where: π = 3.14, r = radius of internal Total nitrogen was determined using diameter of the core sampling tube, Kjeldahl method according to Black h= height of core sampler (1965). Available P in soil was tube. analyzed according to the standard procedure of Olsen et al. (1954). Cation Determination of soil degradation exchange capacity (CEC) and index: the soil degradation index (DI) exchangeable bases (K, Ca and Mg) was computed by the procedure of were determined after extracting the Islam and Weil (2000) as cited in soil samples by ammonium acetate Mulugeta (2004). To compute DI, the (1N NH4OAc) at pH 7.0. difference between mean values of Exchangeable Ca and Mg in the each soil quality parameter under extracts were determined using cultivated and grazing lands, and the atomic absorption spectrophotometer, baseline values of similar soil quality while K was determined by flame parameter for forestland were photometer (Chapman, 1965; Rowell, computed and expressed as a 1994). Cation exchange capacity was percentage of the value under the estimated titrimetrically by distillation forestland. These percentage changes of ammonium that was displaced by were summed across all soil quality sodium from NaCl solution parameters to compute the cumulative (Chapman, 1965). DI value for each land use types, which was used as an overall index of Physical degradation was assessed soil degradation or improvement. using bulk density. Bulk density of F − I undisturbed soil sample was DI = ×100% (3) determined using core sampler I …………. (cylindrical metal sampler) (Blake, Where DI = Degradation index 1965) and determining the mass of solids and the water content of the core, by weighing the wet core, drying Journal of Science and Sustainable Development (JSSD), 2014, 1(3) 15-30 Impact of Land Use Types on Soil Degradation in Meja Watershed, Jeldu District, West Shoa, Ethiopia [5] F= the mean value of soil quality lowest BD (1.58 mg m-3). The parameter for cultivated land or compaction of the top soil of the grazing land cultivated land by livestock during grazing after harvest and during I = the mean value of soil quality fallow period and intensive parameter for soil from forestland agricultural practices might be the reasons for the higher BD in the case Data analysis of cultivated land.