Biochar and Herbicide Interactions With Soil.

Three biochars, switch-grass, corn stover, and Ponderosa pine woodchip, were developed using fast pyrolysis at maximum temperatures of 300C. Biochar samples were sorted by size < 2 mm, 2 to 4 mm, and >4 mm.  The pH, and EC characteristics of each biochar and size was determined in water and 0.01 M CaCl2.  Biochar, at 1 and 10% (w/w), at each size grouping, was added to two South Dakota soils with pH and EC determined.  In addition, atrazine sorption was investigated with addition to soil at these same levels in slurry experiments. Electrical conductivity and pH levels in soil were affected at both low and high amendment amounts. pH values of pure biochar, all sizes and types, were significantly higher than both types of soils. For all 1% (w/w) biochar amendment, a decrease in pH was shown. For all 10% (w/w) biochar amendment, a slight increase in sample pH was shown. EC values of pure biochar varied significantly. EC values were more determinate upon size than by type of char. The largest sized biochar (>4mm) for both amendment values had a lessening effect on EC values, whereas smaller biochar sizes (2-4mm, and <2mm) generally increased EC values. About 99% of the atrazine added was sorbed from solution during a 1 d equilibration at either biochar amendment amounts.