Influence of Pecan-Derived Biochar on Chemical Properties of a Norfolk Loamy Sand Soil.

Sandy, Coastal Plain soils in the Southeastern USA are low (0.3 to 2%) in soil organic carbon contents (SOC) due to high soil temperatures, abundant rainfall, and a low physico-chemical protection of organic substances.  Consequently, the soils have poor soil fertility characteristics.   A strategy to enhance SOC content is to add a carbon-rich soil amendment like biochar that is fairly resistant to decomposition and can be physico-chemically protected by sorption to the soil matrix.   Pecan-derived biochar was created by oxidizing ground pecan shells to 700°C.   Elemental and ¹³C NMR analyses revealed that the biochar had 88% OC, 0.4% N (C:N ration 220:1) and that 69% of the C was distributed in polymerized aromatic ring structures.  Incubation of a Norfolk loamy sand soil with 0, 0.5, 1.0 and 2.0% biochar (w/w) for 60 days at 10% moisture resulted in a SOC, pH, Ca, K, and cation exchange capacity increase.  Although FT-IR analyses revealed that structural alteration had occurred, the cumulative CO₂ values were similar to or lower that the control implying minimal oxidative losses of biochar.  A SEM/EDX scan of a biochar treated soil revealed a close association between biochar and sand grain surfaces.  Our results show that some soil fertility characteristics were improved by adding biochar and that the biochar was a stabile source of C.