Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2008
Publication Date: 2/1/2009
Citation: Novak, J.M., Busscher, W.J., Laird, D.A., Ahmedna, M., Watts, D.W., Niandou, M. 2009. Impact of biochar amendment on fertility of a southeastern Coastal Plain soil. Soil Science 174(2):105-112.
Interpretive Summary: The concentration of carbon dioxide in the earth’s atmosphere has been increasing and scientists have been assessing methods to lower its concentration. Soils hold more carbon than the atmosphere, so it is an important storehouse. Storing carbon in southeastern USA Coastal Plain soils is difficult because fresh plant residues are rapidly oxidized by soil microorganisms causing little to contribute to the soil carbon pool. Recently, scientists in the USA have noticed that carbon in the form of charcoal has lasted thousands of years in South American soils. Charcoal was found to make the South American soils also more fertile; concern was then raised if this technology could be used in USA Coastal Plain soils to replenish carbon as well as nutrients. Our research has examined if charcoal made from pecan shells and incorporated into sandy soils was resistant to breakdown and was able to raise the nutrient level. Charcoal was laboratory incubated in a sandy soil for about 2 months. After this time period, soil carbon, plant nutrient concentrations and pH levels were measured and compared to soil without charcoal. We found that adding charcoal to soil raised carbon levels which remained stable for 2 months. Additionally, soil pH levels and key plant nutrient concentrations like calcium, potassium and magnesium were raised. Our results showed that adding charcoal to sandy soil improved its fertility and resulted in a more stable carbon storage form. This means that charcoal additions to southeastern USA Coastal Plain soils can be an effective counter measure to reduce atmospheric carbon dioxide levels while also improving their soil fertility status.
Technical Abstract: Agricultural soils in the southeastern USA Coastal Plain region have meager soil fertility characteristics due to their sandy textures, acidic pH values, kaolinitic clays, low cation exchange capacities (CEC), and diminutive soil organic carbon (SOC) 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% (w/w) biochar were incubated at 10% (w/w) 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 day 0 and 67, soil samples were collected and analyzed for fertility. The biochar had a pH of 7.6, contained 834,240 and 3,413 mg/kg 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, SOC, Ca, K, Mn, and P, and decreased exchangeable acidity, S, and Zn. Biochar additions did not significantly increase soil CEC. Leachates contained increasing electrical conductivity (EC), K and Na concentrations, but decreasing levels of Ca, P, Mn, and Zn. These effects reflect the additions 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. [GRACEnet Publication]