Physical and chemical properties of the biochar varied as a function of feedstock selection and pyrolysis temperatures. Biochar additions to acidic soils have the potential to improve soil fertility and crop yield. Biochar materials were produced from coffee husk and corn cob at temperatures of 350 and 500°C and characterized by their physical and chemical properties. These were mixed with acidic soil at the rates of 0, 5, 10 and 15 t haG 1 and were laboratory incubated for 2 months at ambient temperature to examine changes in soil properties. Types of feedstock used at two different pyrolysis temperatures and application rate had no significant effects on soil textural classes but showed highly significant effects (p<0.01) on soil pH, Electrical Conductivity (EC), Cation Exchange Capacity (CEC), Organic Carbon (OC), Organic Matter (OM), Total Nitrogen (TN), exchangeable cations and available phosphorous. Application of coffee husk biochar showed relatively better improvement in soil chemical properties (pH, EC, CEC, OC, OM, TN, exchangeable cations and available phosphorous) than corn cob biochar at all application rates. The highest values of chemical properties were recorded when coffee husk biochar produced at 500°C temperature was applied at a rate of 15 t haG 1 . Therefore, we generated an evidence that application of biochar is very important to improve physical and chemical properties of acidic soil.

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Understanding of phosphorus (P) retention and release mechanisms provides crucial information for the effective management of phosphorus to enhance crop production and sustain soil. In acidic soil, available phosphorus is fixed by aluminum and iron. To overcome this problem, soils are limed to fix aluminum and iron. But this practice is not economical for small scale farmers and also it is not environmentally friendly. This study was conducted to improve phosphorus availability using biochar produced from coffee husk and corn cob to fix aluminum and iron instead of phosphorus. Acidic soil samples were mixed with biochar applied at the rates of 0, 5, 10 and 15 t ha -1 and incubated in laboratory for 2 months at ambient temperature. The results showed significant effects (p<0.01) on selected soil chemical properties by increasing soil pH and reduced exchangeable acidity, exchangeable aluminum, and exchangeable iron in a way that enhanced the availability of phosphorus. Due to the incorporation of biochar the available P level increased to a level ranging 3.64±0.34 -23.21±0.07 mg/kg after an incubation period of 2 months and it increased by 84.3% available phosphorus when coffee husk biochar produced at 500°C temperature was applied at a rate of 15t/ha. Moreover, further field researches are needed to evaluate the effect of biochar on availability, the fate and uptake of available P in soil.

This study was undertaken to evaluate the effect of cultivation, fallow and woody land with and without soil bund on soil physical and chemical properties in Gojeb river basin of Dedo district. Landscape of the basin was divided in to three slope positions as upper (25 to 35%), middle (15 to 25%) and lower (5 to 15%). From each slope position, purposely three land use types (cultivated, fallow and woody) lands conserved with and without soil bund were selected. Accordingly, a total of 54 composited soil samples, from 3 slope positions x 3 land use types x 3 replications x 2 conservation system (with and without soil bund) were considered to collect soil sample for soil physical and chemical properties analysis. For both composited and core sampled soil sample collection systematic random sampling techniques were conducted through considering similarity of slope gradient, soil types and land use cover. Analysis of variance (ANOVA) and mean separation was carried out by Turkey test using Rversion 3.2.2 (2015). Additionally, Pearson's correlation analysis was done by using Statistical Package for Social Sciences (SPSS version 20).The result showed that soil bulk density and sand fraction decreased from upper to lower slope position. In contrast, total soil porosity, gravimetric soil moisture content, fraction of clay and silt were increased from upper to lower slope position. With respect to land use soil porosity, gravimetric soil moisture content, clay and silt proportion of woody land >fallow land> cultivated land. However soil bulk density and sand fraction highest in the cultivated land than fallow and woody land. Similarly, for all land uses conserved with soil bund has highest gravimetric soil moisture content, soil porosity, clay and silt fraction than similar land uses not conserved with soil bund. Soil chemical parameters [pH, EC, Av.P, OM, OC, TN, CEC,[exchangeable cations (K, Ca and Mg), exchangeable sodium percentage (ESP) and percent base saturation (PBS)] were significantly increased from upper to lower slope position while exchangeable sodium was not significantly increased. All soil chemical parameters, mean value of woody and fallow land were highest than cultivated land. Similarly, land uses conserved with soil bund has highest mean value than land uses without soil bund. The result of Pearson's correlation matrix also confirmed that several soil phyisical and chemical parameters have a positive relationship, particularly soil organic matter/organic carbon was strongly correlated with cation exchangeable capacity and clay content. In conclusion, the result affirmed that soil physicochemical property of the study area was strongly influenced by land use and conservation difference in addition to topographic position variation. Therefore, to conserve soil resources it needs highest attention of policy makers as well as land use planners to concentrate their efforts on land management/conservation strategies based on land use system and slope variation.

Application of biochar to soil can improve numerous physicochemical and biological properties of the soil. The method for lead metal (Pb) remediation in soil is a challenge worldwide. The excessive Pb accumulation in the soil can radically reduce the soil quality and fertility. This study was conducted to find out the efficiency of biochar in improving the physicochemical properties of soil and to evaluate its effect on Pb availability in a military camp soil. Soil sample was collected from military camp of Jimma town, southwestern Ethiopia and was incubated for 90 days with different application rates (0, 2.5, 5, 7.5, 10, 12.5 and 15 t/ha) of biochar. The results showed that the addition of biochar improved, pH, electric conductivity (EC), cation exchange capacity (CEC), organic carbon (OC), organic matter (OM), total nitrogen (TN), exchangeable cations and available phosphorous of the soil and had no significant effect on soil texture. Sequential extraction of Pb showed that at 15 t/ha (4.2 g/kg) application of biochar, the exchangeable form of Pb significantly transformed the carbonate bound, Fe/Mn oxide bound, organic bound and residual fractions to 66.79, 100.5, 112.7 and 112.1 mg/kg, which is reduced by 88.6, 88.9, 88.5 and 88.3%, respectively as compared to the control. It is concluded that the application of biochar could not only improve physicochemical properties of the soil but also stabilize Pb in a military camp soil.