Changes

For BMPs including: [[bioretention]], [[enhanced grass swales]], [[vegetated filter strips]], [[absorbent landscapes]], [[green roofs]] and, bulk materials including: [[compost]], and [[topsoil]], phosphorus (P) should be measured as extractable phosphorus. Extractable P is the portion that is easily available to organisms like plants and algae i.e. is the measure of immediate concern to water quality.

For BMPs including: [[bioretention]], [[enhanced grass swales]], [[vegetated filter strips]], [[absorbent landscapes]], [[green roofs]] and, bulk materials including: [[compost]], and [[topsoil]], [[phosphorus]] (P) should be measured as extractable phosphorus. Extractable P is the portion that is easily available to organisms like plants and algae i.e. is the measure of immediate concern to water quality.

The quantity of extractable P is determined through acid or base extraction of a sample and testing the concentration in solution by a soil testing laboratory. Commonly used extraction methods on soil samples are the Bray and Kurtz P-1 procedure for non-calcareous soil <ref>Bray, R.H. and Kurtz, L.T. 1945. Determination of total, organic, and available forms of phosphorus in soils. Soil Science, 59: 39-45.</ref>or the Sodium Bicarbonate (Olsen) method for calcareous soil <ref>Olsen, S.R., Cole, C.V., Watanabe, F.S., and Dean, L.A. 1954. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circular 939:1-19. Gov. Printing Office Washington D.C.</ref>.  

The quantity of extractable P is determined through acid or base extraction of a sample and testing the concentration in solution by a soil testing laboratory. Commonly used extraction methods on soil samples are the Bray and Kurtz P-1 procedure for non-calcareous soil <ref>Bray, R.H. and Kurtz, L.T. 1945. Determination of total, organic, and available forms of phosphorus in soils. Soil Science, 59: 39-45.</ref>or the Sodium Bicarbonate (Olsen) method for calcareous soil <ref>Olsen, S.R., Cole, C.V., Watanabe, F.S., and Dean, L.A. 1954. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circular 939:1-19. Gov. Printing Office Washington D.C.</ref>.