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Effect of biochar type on macronutrient retention and release from soilless substrate

Altland, James E., Locke, James C.
Hortscience 2013 v.48 no.11 pp. 1397
Sphagnum, bark, biochar, fertilizer application, fertilizers, greenhouses, growing media, hulls, leaching, mosses and liverworts, nitrate nitrogen, nitrates, nutrient retention, peat, perlite, phosphates, potassium, rice, sawdust, wood
A series of column studies were conducted to determine the influence of three different biochar types on nitrate, phosphate, and potassium retention and leaching in a typical greenhouse soilless substrate. Glass columns were filled with 85 sphagnum peat moss : 15 perlite (v:v) and amended with 10% by volume of three different biochar types including: gasified rice hull biochar (GRHB), sawdust biochar (SDB), and a bark and wood biochar (BWB). Columns were drenched with nutrient solution and leached to determine the impact of biochar on nutrient retention and leaching. Nitrate release curves were exponential and peaked lower, at later leaching events, and had higher residual nitrate release over time with each biochar amendment. The impact of biochar amendment on phosphate retention and release was more variable within and across the two experiments. In both experiments, the GRHB was a net source of phosphate, providing more phosphate to the system than the fertilizer application and hence obscuring any retention and release effect it might have. Potassium release varied by amendment type within each experiment, but within each amendment type was relatively consistent across the two experiments. All biochar types were a source of potassium, with GRHB providing more than SDB, but both providing far more potassium than the fertilizer event. The BWB amendment resulted in more leached potassium than the control substrate, but relatively little compared to GRHB and SDB amendments.