UC Merced

Biochar is a form of pyrolyzed biomass utilized strictly for human created systems. It has been recognized as a plausible method to address issues related to atmospheric carbon increase and global change, in addition to food insecurity. This research explores the effectiveness of biochar as a soil amendment. This knowledge is necessary because the effects of drought have strengthened, flagging the necessity to develop sustainable methods that will address (1) water shortage and (2) the increasing use of groundwater, which has generated poorly infiltrating, saline-sodic soils. Previous biochar studies have emphasized its increased cation exchange capacity, surface area, and porosity, qualities of which can improve the soil water retention and infiltration rate of soils experiencing drought. Here we investigate the hydraulic and physical impacts of amending an arable loamy sand soil with almond residue biochar of different temperatures, size, and rates. Our biochar was observed to increase in carbon (C) content and stability with temperature of pyrolysis; size was inversely related to C concentration. Additionally, biochar cation exchange capacity and surface area increased with increasing temperature and decreasing size. While these attributes may suggest enhanced aggregate stability and water retention, our findings showed that aggregate stability decreased with biochar addition alone, but increased with wetting/drying cycles; water retention was reduced with increased rates of biochar application, regardless of temperature. Infiltration was observed to increase upon initial application, but reduced with time, regardless of biochar size, temperature, or rate. These findings suggest that almond residue biochar may only be beneficial for retention purposes at low temperature and low application rates, while infiltration increases will likely only be observed for the first few days of application. The results of this study contribute to the growing body of biochar literature, and will be useful in tailoring management practices in improving the infiltration of arable sandy soils if using biochar is of interest.