The effects of biochars produced from the residues of locally grown crops on soil quality variables and indexes

Recently biochar has attracted attention as a soil amendment and soil organic carbon source which can be used to modify soil quality. Although the effects of biochar on individual soil quality parameters are well established, the impacts on soil quality indexes are rather limited or less known. Soil samples were collected from a two year controlled experiment treated with various levels of biochars (0, 4 and 8 Mg ha(-1)) obtained from three locally available materials (cotton straws, pistachio shells and corn cobs) and two different irrigation regimes 100% (FC100) and 65% of field capacity (FC65). Soil samples were collected and analyzed for important soil quality indicators; soil organic matter, aggregate stability, bulk density, porosity, available water content, hydraulic conductivity and total nitrogen. A Soil Quality Index (SQI) of multiple measured soil parameters for each parcel was obtained using both linear and non-linear scoring functions. Biochar application improved all soil quality parameters investigated and soil quality indexes and these improvements were more prominent in FC65 parcels than those in FC100 parcels. Soil quality indexes were significantly increased with a synergistic impact of biochar applications with a range from 3.9% to 138.5% depending on treatments and scoring function used. The results from these field studies showed that carbon rich biochars obtained from locally available plant residues can be applied to improve soil qualities on the degraded, low organic matter soils of the Harran Plain.