Location: Integrated Cropping Systems ResearchTitle: Phosphorus sorption and availability from biochars and soil/biochar mixtures Author
Submitted to: Clean (Soil Air Water)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2013
Publication Date: 10/17/2013
Citation: Chintala, R., Schumacher, T.E., Mcdonald, L.M., Clay, D.E., Malo, D.D., Papiernik, S.K., Clay, S.A., Julson, J.L. 2013. Phosphorus sorption and availability from biochars and soil/biochar mixtures. Clean Soil Air Water. doi: 10.1002/clen.201300089. Interpretive Summary: There is great interest in generating energy from biomass. When biomass is treated under high temperature without oxygen, bio-oil and biochar are produced. Bio-oil can be used as a liquid fuel. Beneficial uses of the biochar by-product are being sought, including soil application of biochar to improve crop production. For this to be successful, we need a better understanding of the influence of biochar on the behavior of plant essential nutrients and potential water contaminants such as phosphorus (P). This study was conducted to measure P retention and release in biochar and biochar-treated soil. We used three biochars produced from corn stover, Ponderosa pine wood residue, and switchgrass. Biochar produced from Ponderosa pine wood residue had very different chemical characteristics than corn stover and switchgrass biochars. Biochar made from corn stover and switchgrass removed more than 75% of the P from water solution, whereas Ponderosa pine wood residue biochar averaged only 31% removal. Phosphorus associated with Ponderosa pine wood residue biochar was more easily removed compared to P associated with switchgrass and corn stover biochar. When biochar was added to acidic soil, P retention and release was different, depending on the type of biochar and especially on the soil pH. Biochar effects on soil P were consistent with their chemical and surface characteristics. These results suggest that biochar effects on P availability may be able to be predicted by these biochar properties. Other scientists and extension personnel can use these results to develop recommendations for biochar application to soils.
Technical Abstract: In an energy limited world, biomass may be converted to energy products through pyrolysis. A byproduct of this process is biochar. A better understanding is needed of the sorption characteristics of biochars which can influence the availability of plant essential nutrients and potential water contaminants such as phosphorus (P) in soil. Knowledge of P retention and release mechanisms when applying carbon-rich amendments such as biochar to soil is needed. The objectives of this study were to quantify the P sorption and availability from biochars produced from the fast pyrolysis of corn stover (Zea mays L.), Ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue, and switchgrass (Panicum virgatum L.). We determined the impact of biochar application to soils with different chemical characteristics on P sorption and availability. Sorption of P by biochars and soil-biochar mixtures was studied by fitting the equilibrium solution and sorbed concentrations of P using Freundlich and Langmuir isotherms. Biochar produced from Ponderosa pine wood residue had very different chemical characteristics than corn stover and switchgrass. Corn stover biochar had the highest P sorption (sorbed an average of 79% of the initial solution P concentration) followed by switchgrass biochar (average of 76%) and Ponderosa pine wood residue biochar (average of 31%). Ponderosa pine wood residue biochar had higher bicarbonate extractable (available) P (average of 43%) followed by switchgrass biochar (33% of sorbed P) and corn stover biochar (25% of sorbed P). The incorporation of biochars to acidic soil at 40 g kg-1 (4%) increased the equilibrium solution P concentration (reduced the sorption) and increased available sorbed P. In calcareous soil, application of alkaline biochars (corn stover and switchgrass biochars) significantly increased the sorption of P and decreased the availability of sorbed P. Biochar effects on soil P was aligned with their chemical composition and surface characteristics.