Carrot, Corn, Lettuce and Soybean Nutrient Contents are Affected by Biochar

Biochar, the carbon-rich material remaining after pyrolysis of cellulosic and manure feedstocks, has the potential as a soil amendment to sequester carbon and to improve soil water-holding and nutrient properties- thereby enhancing plant growth.  However, biochar produced from some feedstocks also could adversely affect crop quality by changing soil pH and reducing nutrients (e.g., Ca, K, Mg, N, Na, and P) in plant tissues.  To evaluate effects of biochar on the nutrient quality of four crops, we conducted a greenhouse study using pots with: carrot (Daucus carota cv. Tendersweet), corn (Zea mays, cv. Golden Bantam), lettuce (Lactuca sativa, cv. Black-Seeded Simpson) and soybean (Glycine max cv. Viking 2265). Plants were grown in one of two South Carolina sandy Coastal Plain soils (Norfolk and Coxville Soil Series), along with biochar (1% by weight) produced from pine chips (PC), poultry litter (PL), swine solids (SS), switchgrass (SG), and two blends of pine chips plus poultry litter (PC/PL, 50/50% and 80/20%). Each of the feedstocks and feedstock blends was pyrolyzed at 350, 500, and 700 ÌŠ C to produce the biochar used to amend the Norfolk and Coxville soils.  Effects of biochar on leaf nutrients (% dry weight) statistically varied with species, soil, feedstock and temperature and nutrient.  For carrot and lettuce, the PL, PL/PC, and SS biochars generally decreased leaf N, Ca, Mg, and P; while PL and PL/PC increased K and Na.  Biochars had little effect on leaf N for corn, but PL, PL/PC, and SS biochars tended to increase N for soybean. Other leaf nutrient responses varied among soils and biochars for corn and soybean. Thus, our results indicate that plant tissue nutrient quality is impacted by the type of biochar and its pyrolysis temperature during production.