Abstract:
Soil acidity is one of the main factors affecting agricultural productivity in the highlands of Ethiopia. It is one of the problems that decrease the potential of arable lands for crop growth because of high rainfall in highland areas. The purpose of this study was to assess and quantify the extent of soil acidity under different land use systems and to determine the amount of lime required for neutralizing soil acidity in the study area. Three land uses (cultivated, grazing and natural forest lands) and two soil depths (0-20 and 20-40 cm) of dominant Cambisol were considered for this study. A total of 36 composite samples were collected for laboratory analysis. The samples collected from the different land use systems were analyzed and the recorded data were subjected to GLM (General Linear Model) procedure using SAS. The results revealed that the soil textural classes of the study area were sandy loam and sandy clay loam with high contents of sandy fraction. The soil pH (H2O) of the study area was in range 4.56-6.45 with very strongly acid, strongly acid, moderately acid and slightly acid. The OM was significantly (p<0.05) affected by land uses and soil depths. Exchangeable bases were affected by both land uses and soil depths. Exchangeable Ca had the highest value of 1.54 cmol(+)kg−1while the lowest value of 0.06 cmol(+)kg−1. Mg had highest value of 0.25 cmol(+)kg−1 and lowest value of 0.02 cmol(+)kg−1 exchangeable Ca and Mg categorized under very low and Exchangeable K had the highest value of 1.32 cmol(+)kg−1 was and the lowest value of 0.15 cmol(+)kg−1, and in the categories of very low, low, moderate and high. The highest value of exchangeable acidity in the study area was 1.82 while the lowest 1.04 cmol(+)/kg. Exchangeable Al was ranging from 1.36 - 0.43 cmol (+)/kg. Exchangeable H was in between 0.78 and 0.13cmol (+)/kg. Acidity indicator parameters were higher as compared with exchangeable bases. Available P and total N were high for the surface soil. Soil of the selected kebeles of the study area has the highest (27.94) and the lowest (6.13) C: N ratio which is directly related to SOM contents. From the incubation study, 42.4t/ha was determined to neutralize the acidity of the soil of cultivated land to the target pH of 6.0. In the selected kebeles of the study area, high rainfall and the nutrient uptake by crop might have caused soil acidity and lime rates of 42.4 for cultivated land and 28.2 t/ha for grazing and forest lands by incubation. The lime rats of 22.75- 23.6 for cultivation land, 18.7- 23.6 for grazing land and 16.3- 17.1 t/ha for forest land by SMP method were recommended.
