Impact of Biochar Amendment on Fertility of a Southeastern Coastal Plain Soil

Abstract

Agricultural soils in the southeastern U.S. Coastal Plain region have meager soil fertility characteristics because of their sandy textures, acidic pH values, kaolinitic clays, low cation exchange capacities, and diminutive soil organic carbon contents. We hypothesized that biochar additions will help ameliorate some of these fertility problems. The study objectives were to determine the impact of pecan shell-based biochar additions on soil fertility characteristics and water leachate chemistry for a Norfolk loamy sand (fine-loamy, kaolinitic, thermic typic Kandiudults). Soil columns containing 0, 0.5, 1.0, and 2.0% (wt/wt) biochar were incubated at 10% (wt/wt) moisture for 67 days. On days 25 and 67, the columns were leached with 1.2 to 1.4 pore volumes of deionized H2O, and the leachate chemical composition determined. On days 0 and 67, soil samples were collected and analyzed for fertility. The biochar had a pH of 7.6, contained 834.2 and 3.41 g kg−1 of C and N, respectively, and was dominated by aromatic C (58%). After 67 days and two leaching events, biochar additions to the Norfolk soil increased soil pH, soil organic carbon, Ca, K, Mn, and P and decreased exchangeable acidity, S, and Zn. Biochar additions did not significantly increase soil cation exchange capacity. Leachates contained increasing electrical conductivity and K and Na concentrations, but decreasing levels of Ca, P, Mn, and Zn. These effects reflect the addition of elements and the higher sorption capacity of biochar for selective nutrients (especially Ca, P, Zn, and Mn). Biochar additions to the Norfolk soil caused significant fertility improvements.