Effects of Biochar On Soil Properties and Corn and Wheat Yield.

Biochar is the charcoal remains of incomplete combustion of biomass such as woodchips, brush, crop residues, or green waste. It can also be produced when biomass is heated (torrefied) to extract biofuels. Biochar created via ‘slash and smolder’ is believed to be the cause of the high productivity of the terra preta (dark earth) soils of South America. When added to soil, biochar may: sequester C, slow nutrient leaching, increase nutrient availability, decrease fertilizer requirements, improve water relations, and stimulate beneficial soil fungi. In 1- by 1-m microplots, we tested the effects of five rates of biochar (0, 10, 20, 40, and 80 t ha^-1) and two rates of fertilizer N-P-K (0 and 146-34-34 kg ha^-1) on corn (Zea mays L.) and winter wheat (Triticum aestivum L.) yield and soil chemical properties on a Noboco-Goldsboro loamy sand (fine-loamy, siliceous, subactive, thermic Aquic Paleudults) in Duplin County, NC. Biochar at 10 and 20 t ha^-1 had no effect on routine North Carolina soil-test parameters; at 40 and 80 t ha^-1, biochar increased soil pH; CEC; base saturation; and available K, Ca, Mg, S, and Mn.  There was no biochar by fertilizer interaction for corn stover or total (grain + stover) yield nor for wheat straw or total (grain + straw) yield, but some evidence of an interaction for corn and wheat grain yield (p = 0.15 and 0.18, respectively). There was little or no yield response to fertilizer, but biochar ≥ 40 t ha^-1 without fertilizer increased wheat grain yield while corn grain yield was unaffected. These preliminary results suggest that biochar’s agronomic value depends on pre-existing soil conditions including management. We planted soybean (Glycine max L. Merr.) following wheat and plan to assess the effects of biochar on grain yield and soil properties at harvest in October 2009.