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Designing relevant biochars to revitalize soil quality: Current status and advances
Citation:
Novak, J., K. Centrell, D. Watts, AND M. G. JOHNSON. Designing relevant biochars to revitalize soil quality: Current status and advances. Presented at 16th Meeting of the International Humic Substances Society, Hangzhou, CHINA, September 09 - 14, 2012.
Impact/Purpose:
Biochars chemical and physical properties can be designed to improve specific soil quality issues. In order to make appropriate selections, evaluations are required of different feedstocks, pyrolysis conditions, and gross biochar particle sizes.
Description:
Biochars chemical and physical properties can be designed to improve specific soil quality issues. In order to make appropriate selections, evaluations are required of different feedstocks, pyrolysis conditions, and gross biochar particle sizes. We conducted laboratory soil incubations using a Norfolk loamy sand (fine-loamy, kaolinitic, thermic Typic Kandiudult) mixed with biochars made from two different feedstocks processed into two different particle sizes. Switchgrass (Panicum vigatum L.) and Loblolly pine (Pinus taeda) were individually made into (1) hammer milled (HM) chips (< 6-mm) and (2) >6-mm diameter pellets. These prepared feedstocks were pyrolyzed into biochar for 2 hrs at 350°C. For each treatment (n = 4), a 1% (w w-1) biochar loamy sand mixture was incubated in triplicate pots at 10% moisture content (w w-1) for 78 days. Untreated Norfolk soil (no biochar) served as a control comparison. On incubation days 32 and 67, each pot was leached with 1.2 pore volumes of deionized water and the leachate collected. Thereafter, we gravimetrically determined each pot’s daily % soil moisture content (w w-1). On days 1, 5 and 11 after both leaching events, HM switchgrass biochar had the most significant moisture storage improvement (≈ 6%). The HM pine chip biochar showed mixed results with a longer time period required to demonstrate improvement (day 11). Pelletized biochars caused lower to no significant improvement in soil moisture contents. Our results indicate that, in addition to feedstock choice, biochars processed into different particle sizes impacts their ability to improve soil moisture contents.