Method for water extractable phosphorous in saline-sodic soils.

Soil phosphorous dynamics in saline-sodic soils is not well understood and lack of applicable methods for saline-sodic soils is a major problem. One method used for soluble-P measurements in saline-sodic soils includes using anion exchange resins. Water addition to dry saline-sodic soils may cause reactions and fluxes in the pH which can result in inaccurate measures of soluble-P. A low-molar salt solution can be used to stabilise the pH for extraction. Six mixes of a saline-sodic soil were extracted with a low-molar salt solution and compared with the standard deionised water extraction using the anion exchange resin method. Two further extracts were undertaken on all the soils, following the Hedley procedure. The first fraction of P was shown to be significantly less (p>0.005) with a salt extraction, compared to water extraction. Subsequent P was not recovered in the second and third extraction. Further research is being undertaken on the recovery rates of soluble-P with low-molar salt extractants; through recovery rates, full-fractionation of different saline-sodic soils; and determining correction factors.