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Plant-available and water-soluble phosphorus in soils amended with separated manure solids

Gasser, M.O., Chantigny, M.H., Angers, D.A., Bittman, S., Buckley, K.E., Rochette, P., Massé, D. (2012). Plant-available and water-soluble phosphorus in soils amended with separated manure solids, 41(4), 1290-1300.


Physical, chemical, or biological treatment of animal liquid manure generally produces a dry-matter rich fraction (DMF) that contains most of the initial phosphorus (P). Our objective was to assess the solubility and plant availability of P from various DMFs as a function of soil P status. Eight diff erent DMFs were obtained from liquid swine (LSM) and dairy cattle (LDC) manures treated by natural decantation, anaerobic digestion, chemical fl occulation, composting, or mechanical separation. Th e DMFs were compared with mineral P fertilizer in a pot experiment with oat (Avena sativa L.) grown in four soils with varied P-fi xing capacities and P saturation levels. Th e DMFs were added at a rate of 50 mg P kg-1 soil and incubated 14 d before seeding. Soil water-extractable P (PWT) at all water:soil extraction ratios (2:1, 20:1, and 200:1) was slightly higher when DMFs were derived from LDC rather than LSM. Soil PWT at the 2:1 ratio was lower with anaerobically digested LSM. At the 2:1 extraction ratio, DMF P was less soluble than mineral P as P saturation in soils increased. In soils with a lower P-fi xing capacity, DMF P appeared less water soluble than mineral P under 20:1 and 200:1 extraction ratios. Aft er 72 d of plant growth, DMFs produced yields comparable to mineral P fertilizer. Although the plant availability of P from DMFs was comparable to mineral P fertilizer, P from DMFs could be less vulnerable to leaching or runoff losses in soils with a high P saturation level or low P-fi xing capacity. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

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