Soil biological responses to biochar amendments

Janice Thies - Associate Professor, Department of Crop and Soil Sciences, Cornell University. Responses of the soil biota to biochar amendments are characterized by high variability. Soil enzyme activities, carbon turnover, nitrogen cycling and availability, greenhouse gas emissions, microbial abundance and diversity have all been reported to increase, decrease or remain unchanged in biochar amended soils. The major drivers of this variability are biochar feedstock and its production conditions, soil type, climate, land use history, soil management, the crops grown and time since biochar was applied. Feedstock and production conditions dictate the quantity and quality of fixed carbon, ash and bio-oils adhering to the biochar surface. Soil type determines the presence and activity of clays and, together with climate, land use, soil management and crops grown, controls soil pH and Eh, the presence of other organic matter, and resulting water and nutrient availability. All of these factors, which also change over time, interact to influence the behavior of the soil microbial community. Synthesis of the diverse findings remains hampered by a lack of standards against which to compare the effects of different biochars on the soil biota in different settings. Thus, our ability to predict how microbial community will respond to biochar amendments in any given setting and what the resulting impacts on crop productivity and environmental quality will be remains somewhat rudimentary. While results reported may seem like a “dog’s breakfast”, some common themes are beginning to emerge.Ope