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Hardwood Biochar Influences Calcareous Soil Physicochemical and Microbiological Status

J. A. Ippolito, M. E. Stromberger, R. D. Lentz, R. S. Dungan
Journal of environmental quality 2014 v.43 no.2 pp. 681-689
Gram-negative bacteria, application rate, biochar, calcareous soils, carbon, community structure, fatty acid composition, fatty acids, hardwood, iron, manganese, microbial communities, nitrate nitrogen, nutrient availability, soil amendments, soil bacteria, soil fertility, soil fungi, soil respiration, stress response, water content, water holding capacity
The effects of biochar application to calcareous soils are not well documented. In a laboratory incubation study, a hardwood-based, fast pyrolysis biochar was applied (0, 1, 2, and 10% by weight) to a calcareous soil. Changes in soil chemistry, water content, microbial respiration, and microbial community structure were monitored over a 12-mo period. Increasing the biochar application rate increased the water-holding capacity of the soil–biochar blend, a trait that could be beneficial under water-limited situations. Biochar application also caused an increase in plant-available Fe and Mn, soil C content, soil respiration rates, and bacterial populations and a decrease in soil NO₃–N concentration. Biochar rates of 2 and 10% altered the relative proportions of bacterial and fungal fatty acids and shifted the microbial community toward greater relative amounts of bacteria and fewer fungi. The ratio of fatty acid 19:0 cy to its precursor, 18:1ω7c, was higher in the 10% biochar rate soil than in all other soils, potentially indicating an environmental stress response. The 10% application rate of this particular biochar was extreme, causing the greatest change in microbial community structure, a physiological response to stress in Gram-negative bacteria, and a drastic reduction in soil NO₃–N (85–97% reduction compared with the control), all of which were sustained over time.