Who Benefits from Biochar: Microbes, Weeds, or Conifer Seedlings?.

Biochars are porous charcoal like materials that have shown great potential for enhancing soil health and plant growth in a small number of soil and ecosystem types. To fully use biochars for promotion of soil health and plant growth in a variety of systems, we must expand our understanding of how biochars interact with more soil types, and their resident soil microbial communities. Our objective was to expand upon this understanding by establish in a long-term fully factorial field experiment in the sandy soils of Michigan, USA, with two species of conifer seedlings, and biochars from two suppliers, Biogenic Reagents (BGR) and US Biocarbon (USB). In May 2016 we applied both biochars at rates of 0 Mg ha^-1, 25 Mg ha^-1, and 75 Mg ha^-1. We hypothesized biochar treatments would increase soil water availability, nutrient availability, soil microbial activity and plant growth. We collected soil samples and measured plant biomass in both early and late summer. We analyzed soil pH, water, carbon, nutrient contents, and the activity rates of the hydrolytic soil enzymes leucine aminopeptidase (LAP), acid phosphatase (AP), β-D-glucosidase (BG), and β-N-acetyl glucosaminidase (NAG). Biochars increased soil moisture contents, soil nutrient availabilities, and enzyme activity rates. For example, 25 Mg ha^-1 BGR application doubled plant biomass, whereas 75 Mg ha^-1 biochar treatments doubled BG, AP and LAP rates. These results show the abilities of multiple biochar treatments to increase soil water contents, nutrient availabilities, and to stimulate activity in microbial communities in sandy soils, within four months of biochar applications. Continued work with this experiment will show if observed first year responses to biochar treatments are persistent, or if they are nullified via weathering of biochars, and by adaptations from plants and soil microbial communities to biochar presence, during the course of this multi-year experiment.