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Title: Biochar affects macronutrient leaching from a soilless substrate

item Altland, James
item Locke, James

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2012
Publication Date: 8/14/2012
Citation: Altland, J.E., Locke, J.C. 2012. Biochar affects macronutrient leaching from a soilless substrate. HortScience. 47(8):1136-1140.

Interpretive Summary: Modern pyrolysis systems are used to extract liquid and gas petroleum products from biomass for fuel or other chemical products. Biochar is the charred organic matter that remains after pyrolysis of biomass or manure. The remaining biochar is being studied for its utility in greenhouse and nursery substrates. The specific objective of this research was to determine if biochar amendment to a greenhouse substrate would affect the primary plant nutrients, nitrogen, phosphorus, and potassium. We found that nitrogen and phosphorus were retained by the biochar and more slowly released into the substrate solution. This could result in more efficient uptake of these nutrients in a greenhouse production system, with less losses to irrigation runoff. This is important in reducing nitrogen and phosphorus loads in runoff water that could potentially pollute ground and surface waters. Potassium levels were increased by biochar amendments.

Technical Abstract: Byproducts of pyrolysis, known collectively as biochar, are becoming more common and readily available as ventures into alternative energy generation are explored. Little is known about how these materials affect greenhouse substrates. The objective of this research was to determine the effect of one form of biochar on the nutrient retention in a typical commercial greenhouse substrate. Glass columns filled with 85 : 15 sphagnum peat moss : perlite (v:v) and amended with 0, 1, 5, or 10% biochar 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 increasing biochar amendment rate. Peak phosphate concentration decreased with increasing biochar amendment rate, while time of peak release, girth of the peak curve, and final residual phosphate release all increased with increasing biochar amendment. Potassium levels in substrates with 0% or 1% biochar increased linearly across leaching events, while substrates with 5% or 10% biochar exhibited an exponential release similar to nitrate and phosphate. Implications on greenhouse fertility management with regards to how biochar affects nitrate, phosphate, and potassium release are discussed.