EFFECTS OF LAND USE TYPES AND SOIL DEPTH ON SELECTED SOIL PHYSICOCHEMICAL PROPERTIES AT SENGEYE KEBELE IN DUNA DISTRICT, SOUTHERN ETHIOPIA

Abstract

The study was conducted with the objective to evaluate the effect of land use types and soil depth on selected soil physicochemical properties. A total of 24 disturbed and 24 undisturbed soil samples were taken from the depth of 0-20 and 20-40 cm for the determination of soil physicochemical properties. The soil samples were analyzed with standard laboratory procedures and varied significantly (P < 0.01 and < 0.05) among land use types and soil depths. Sand, silt FC,PWP,AWHC,Soil OM, total nitrogen, available P, CEC and micronutrients were significantly affected (P ≤ 0.05 and/or P ≤ 0.01) by land use, soil depth and their interactions. High percentage mean value of sand and silt were obtained in the surface of GL while the low was on the subsurface of the FL.High clay was observed in the subsurface of FL and lowest was on the surface of GL.The higher ﴾1.52g/cm3,58.24mg/kg and 2.86mg/kg)mean value of soil BD,Mn and Cu was obtained in the surface of the GL and low(1.20 g/cm3,41.04mg/kg and 1.96mg/kg) in surface of FL,subsurface of CLs respectively, while high(52.00%)TP were recorded in the surface FL and low(40.39%) in surface of GL.The higher (48.72%,30.92% and 17.80%) water content at FC, PWP and AWHC was obtained in the subsurface of the FL and lower (32.28%,22,72%, 9.56%) were surface of the GL.Highest(4.90%,0.25%,36.32mg/kg and 34.02cmol(+)/kg) SOM, TN, Fe, CEC content were obtained in the surface layer of FL to low(1.83%,0.16%,28.62mg/kg and 22.00 cmol(+)/kg on the subsurface of GL and CEC on CLs respectively. The higher (18.42mg/kg 1.52mg/kg and 0.60 cmol (+)/kg) Av.P, Zn and EA were obtained in the surface of the CL and low (4.21mg/kg, 0.86mg/kg and 0.48 cmol (+)/kg in the subsurface of the GL; low EA in the surface of FL, respectively. The highest (6.42 and 1.00 cmol (+)/kg) and lowest (5.50 and 0.42 cmol (+)/kg) pH and Na were recorded in the subsurface layer of FL and surface of CL, respectively. The range of pH in surface and subsurface layers of all land use types were moderately acidic to slightly acidic. Values of exchangeable bases (Ca K, and Mg) were higher (15.24, 2.68, 9.96 cmol (+)/kg) on surface of FL compared to lower (0.86, 3.84 and 6.62 cmol (+)/kg) on the subsurface CL,CL and GL uses, respectively. Most of the soil physicochemical properties in the study area varied among the land uses types due to inappropriate land uses.Therefore,the soil productiveness were maintained relatively under the forest land,whereas the influence on most soil parameters were negative on the cultivated and grazing land, indicating the need for crop rotation,decreasing over grazing and integrated soil fertility management in sustainable manner to enhance and maintain the favorable soil physicochemical properties and replenish the degraded soil of the study area. Key words: Land use types; Soil depth and physicochemical properties 1. INTRODUCTION Land use is defined as the arrangements, activities and inputs people undertake in a certain land cover type to produce, change or maintain it (Ufot et al., 2016). Successful agriculture requires the sustainable use of soil resource, because soil can easily lose its quality and quantity within a short period of time for different reasons such as intensive cultivation, leaching and soil erosion (Kiflu and Beyene, 2013 ; Zenebe, 2015 ). Land degradation resulting from land use change has been a major global challenge since the 20thC and was remained on the international agenda in the 21st century (Bahrami et al., 2010 ; UNDP, 2019). Particularly, deforestation which was conversion of forestland into agricultural land caused significant changes to soil properties in many parts of the tropical regions (Adolfo-Campos et al., 2007; Eyayu Molla, 2018; Zenebe, 2015). Several studies in the past have shown that deforestation and cultivation of soils often lead to depletion of nutrients (N,P and K) with annual average losses ranging from 1.5 - 7.1 tons ha-1year-1 mainly due to crop harvest, soil erosion, leaching and low inputs applied to the soil (Adesodu et al., 2007 ; Addis et al.,2016). On the other hand, the ever-increasing human population is most challenging in countries like Ethiopia, where there is a very high population density and heavy dependence on land resources(Barbier et al., 2018). This is the atrocious threat in which soil properties are adversely damaged thereby leading to land degradation and hampering of the sustainability of soil resources (Yimer and Abdulkadir, 2011).The major causes of land degradation in Ethiopia include cultivation on steep soil with inadequate soil conservation, erratic and heavy rainfall patterns, deforestation and overgrazing (Aytenew and Kibret, 2016; Gebeyaw Tilahun, 2015).The outcomes are deterioration of soil properties, or soil compaction (Eyayu and Mamo, 2018) and land degradation (Khresat et al., 2008;Louwagie et al., 2009). As a result, cultivated soils in different part of tropics are now below their potential (Woldeamlak Bewket, 2003). These effects of land degradation as the result of land use types on soil properties provide an opportunity to assess sustainability of land use types and must be given high research priority