The Effects of Biochar and Compost Applications on Respiration Rates and Carbon Cycling on a Northern Californian Row Cropped Soil in an Incubation Experiment.

Biochar as a soil amendment has high levels of variable behaviors and characteristics depending on the feedstock and processing methods. This study aims to understand the exact behaviors and characteristics of a locally produced (Premier Mushroom, Colusa, CA) walnut-hull based based biochar in California’s Sacramento Valley. By measuring soil respiration rates using a LICOR LI-8100A unit in a 10-week soil incubation experiment, this study has found significant differences between the various treatments. Applications of biochar only, responded with respiration rates that were similar but also lower than the control treatment (p-value > 0.99), biochar and compost (BC) applied together responded with respiration levels that differed significantly between application rates (p-value < 0.01) as well as differed significantly from the control (p-value < 0.05), and pre-mixed biochar (MBC) and compost responded with respiration levels that were the greatest and most significantly different than any other of the 9 treatments (p-value < 0.05), when contrasted to the control. This study indicates an interaction effect between biochar and compost when they are applied together. The treatments increased soil respiration rates, and decreased C mineralization, via altering and increasing the soil’s microbial activity. This locally produced walnut-hull based biochar requires further study into its ability to mineralize C at higher application rates. This conclusion is based on the significant difference that was found between application rates in the BC and MBC treatments (p-value < 0.05). Further investigation into the application rate effects of this specific biochar will provide greater insight into its application in Northern California’s agricultural communities as a source of C mineralization and nutrient retention.