THE EFFECTS OF BIOCHAR AGE AND CONCENTRATION ON SOIL RETENTION OF PHOSPHORUS AND INFILTRATION RATE A Senior Project

ii ACKNOWLEDGEMENTS The laboratory research and completion of this senior project report would not have been possible without the help of many faculty members of Cal Poly, San Luis Obispo. First, I would like to thank Dr. Burgoa for presenting me with the opportunity to conduct a senior project on this topic. Second, a sincere thank you is due to Craig Stubler, the laboratory technician of the NRES department. The research for this project required numerous laboratory procedures of preparation and analyses that used a variety of equipment and instruments, none of which would have been possible to complete without his assistance. Next is a thank you to Dr. Appel, Soil Chemist and professor of the NRES department, for offering helpful guidance with methods of analysis. Lastly, many thank is owed to all others who contributed to make this project possible. ABSTRACT Changes in land use and land management practices are regarded as one of the main factors in altering the hydrogeological system, causing changes in runoff, surface supply yields, and the quality of receiving water (Tong and Chen, 2002). Phosphorus is a significant contributor to accelerated eutrophication of fresh water and is largely sourced from agricultural runoff (Sharpley et al., 1994). The dominant processes controlling solution composition in agricultural soils are primarily 'chemical' for P (i.e. adsorption/desorption and dissolution/precipitation) (Edwards and Withers, 1998). Biochar has chemical characteristics that have the potential to adsorb P or influence precipitation of P insoluble pools (DeLuca et al., 2009). However, there is limited knowledge about changes in this behavior in soil over time. To determine the effects of biochar on P adsorption and percolation rate, soil columns containing a sandy loam were amended with 0, 1, 2, and 5% (wt/wt) biochar and incubated at field capacity for zero and nine months. Columns were leached with four pore volumes of a 5ppm P solution (Burgoa, 2011). Phosphorus concentration in the leachate was determined using an ICP-AES. Aging of biochar for nine months resulted in an insignificant increase of phosphorus retention in the soil columns. The highest increase in P retention was observed in the columns amended with 1% (wt/wt) biochar at time zero. Potential absorption capacity of biochar and other chemical influences that affect P in the soil environment seem to improve with time. Further aging of biochar would likely result in a significant increase in P adsorption capacity in soil, due to abundant …