Investigation of Biochar for Amendment of a Disturbed Urban Soil
Dr. Brian Bodenbender
We examined the influence of biochar in amending a disturbed urban entisol that is sandy, quartz rich, and very low in organic matter. We assessed short term (2–3 week) plant growth by comparing dry plant mass among varying treatments of biochar and/or inorganic fertilizer and a control. Biochar has high porosity and specific surface area (Bagreev et al., 2001). Biochar has been reported to increase water holding capacity, improve retention of soil nutrients, and enhance beneficial microorganism growth. We hypothesized that biochar would improve short term growth by enhancing nutrient and water retention in the high drainage, sandy soil. We tested three species in a greenhouse experiment and measured pH and water retention. The sandy soil had a pH of 6.85; commercial biochar had a pH of 6.40. Vigna radiata (mung bean) and Avena sativa (common oat) were planted in control (original) sandy soil, soil intermixed with 1%, 3%, 7%, 10%, and 20% (by mass) commercial biochar, the same percentages of biochar with full fertilizer, and soil without biochar containing ¼, ½, full, 2x, and 4x recommended fertilizer dosage. All biochar-only treatments for Vigna radiata yielded greater above-ground biomass than the control, but fertilizer-only and combined biochar-fertilizer treatments were variable relative to the control. In Avena sativa most fertilizer treatments yielded higher biomass than the control whereas biochar treatments were variable. None of these results, however, were significant at a 5% confidence level. Brassica rapa was not tested for fertilizer treatment and showed no significant difference from the control among biochar treatments. Data suggested that increasing biochar and increased water retention correlate, but not significantly. In the early stages of plant growth, biochar does not produce significantly different results than fertilizer. This suggests that biochar could potentially serve as a lower input, alternative remediation medium in urban soils.
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