Influence of Pecan Biochar on Physical Properties of a Norfolk Loamy Sand.

Because the southeastern Coastal Plain has high temperatures and abundant rainfall, its sandy soils have poor physical characteristics and low carbon contents. To increase soil C, we added switchgrass and non-activated recalcitrant pecan biochar. Biochar was developed by pyrolyzing ground pecan shells at temperatures that ramped up to 700°C. The biochar had 88% C, 0.4% N (C:N ration 220:1); 69% of its C resided in polymerized aromatic ring structures. Biochar treatments were 0, 5, 10 and 20 g/kg of the soil. Switchgrass was ground to a fine powder and added to the biochar treatments at rates of 0 and 10 g/kg. Treatments were incubated for 60 days at 10% (w/w) water content. Biochar decreased soil penetration resistance; adding switchgrass generally decreased it more. Biochar and switchgrass affected aggregation, infiltration, and water holding capacity; but results were mixed. Biochar and switchgrass increased soil C; the biochar C is expected to be more recalcitrant. The non-activated Biochar (and switchgrass) improved some soil physical characteristics; it is possible that activating the charcoal will improve its affect on more soil characteristics.