ASSESSMENT OF SELECTED SOIL PHYSICAL AND CHEMICAL PROPERTIES UNDER DIFFERENT LAND USES IN MELKA GURA SUBWATERSHED IN DEGEM DISTRICT, NORTH SHEWA ZONE , OROMIA, ETHIOPIA

Abstract

Changes in land use, particularly the transformation of natural ecosystems into managed agroecosystems under poor management practices, are widespread in Melka Gura Subwatershed in North Shewa, Ethiopia. Therefore, studying variations and status in soil properties across land uses is essential to knowing the extent and magnitude of soil degradation across different land uses and planning suitable soil management strategies. Due to this, the current study evaluated certain soil physical and chemical properties under various land uses in Melka Gura Subwatershed in Degem District, North Shewa Zone,Oromia, Ethiopia. Based on the field survey, three types of land use (plantation forests, grazing lands, and cultivated land) were identified for describing the status and variation of soil fertility. A total of 54 soil samples were collected at 0–20 and 20–40 cm depths using a core sampler and auger, and they were then brought to the laboratory for the investigation of the soil physical and chemical properties and SOCS. The laboratory results showed that the soil textural classes of all land uses were classified as loam textural classes except for the surface layer (0–20 cm) of plantation forests, which showed a sandy loam textural class. The bulk densities in the study area ranged from 1.06 to 1.39 g/cm3 and were classified as low to moderate. Relatively, the highest AWC (194.8 mm/m) was recorded from grazing land at 0–20 cm depth, followed by plantation forest soils. The highest mean values of sand (50.67%), silt (39%), TP (60.13%), pH (5.68), AP (51.38 mg/kg), exchangeable basic cations, CEC (44.57 cmol(+)kg-1), PBS (63.36%), SOC (3.66%), TN (0.5%), SOC stock (68.62 ton/ha) and carbon dioxide equivalence (251.59 ton/ha) were registered in the soil of plantation forest lands. Whereas, the highest mean values of BD (1.39 g/cm3 ), clay content (19%), Ex. A (4.9 cmol (+)kg-1) and Ex. Al (3.86 cmol (+)kg-1) were obtained from the soil of cultivated lands. The average values of clay, BD, FC, PWP, pH, PBS, and exchangeable bases all indicated an increasing trend from the surface toward the subsurface. The soil of plantation forests has the highest soil carbon levels and the best-maintained carbon stocks. The highest mean values of SOC stock (68.62 ton/ha) was discovered in planted forest land, whereas the soil of cultivated lands had the lowest SOC stock (48.15 ton/ha).These soil fertility parameters were relatively high for plantation forest land and relatively low for soil on cultivated land. Correlation analysis also showed a positive and highly significant relationship between clay and CEC, BD, PWP, and FC but a negative relationship with TP, SOCS, and AP. Additionally, there was a positive and significant relationship between soil OC and CEC, AP, SOCS, and TP, but there was a negative relationship between clay and BD of soil. Misuse of land and improper soil management systems in the study area could be the major reasons for variations in soil properties across land-use types. Therefore, further studies needed to be conducted on the effects of land use change on soil fertility-related properties as well as on integrated soil and water conservation practices to reduce the continuous loss of soil nutrients