Relationship Between Extractable Potassium And Phosphorus Under Two Laboratory Preparations

Abstract

Drying, grinding and sieving are commonly employed to facilitate the handling and storage of soil samples on which chemical analyses are to be done. These laboratory pre-analysis protocols have the potential to alter soil chemical characteristics and may result in unrealistic estimates of in situ chemical processes. The effect of laboratory soil sample preparation on level of extractable Potassium (K) and Phosphorus (P) was studied on various soil types collected at Magoebaskloof pine farm (MPF), Tshiombho irrigation scheme (TIS), Dal water farm (DWF) and Syferkuil experimental farm (SEF). Twenty soil samples were collected at each of the study locations and each sample was split into two halves and used as treatments to represent fresh and laboratory prepared soil. Clay content, and soil pH were the most considered and remarkable variables in modeling the behaviour of analysed extractable P and K from fresh and laboratory prepared soil samples. The laboratory pre-analysis protocols had a negative effect on soil pH in all soils; P and K were also affected negatively in most soils except in Hutton soils of Syferkuil experimental farm (soil pH of 7.73 and Clay content of 15.39 %). It was noticeable from soil of TIS (soil pH of 6.28 and clay content of 24.01 %) and MPF (soil pH of 6.23 and clay content of 24.34 %) that soil with low soil pH and high clay content can be highly affected by pre-analysis protocols. In DWF (soil pH of 6.81 and clay content of 14.41 %), P analysis has shown significant different (P ≤ 0.05) while K did not. The results indicated that soil samples should be kept fresh until pH, K and P analyses are done.

Keywords: Correlations, Extractable K and P, soil conditioning

Journal of Agriculture and Social Research Vol. 7 (1) 2007: pp. 49-55