Zur Phosphatfixierung in sächsischen Verwitterungsböden auf den Ergussgesteinen Nephelinbasalt, Phonolith und Diabas

Abstract

Investigated Saxonic brown soils (Cambisols) on nephelinbasalt, phonolith and diabase in a considerable extent are able to remove water soluble phosphate to a form, which is not double lactate soluble and not available for plants. With regard to this property these soils show a strong phosphate fixation. However, measure of phosphate fixation of soils–ratio of hydrochloric acid soluble phosphorus (P-HCl) and double lactate soluble phosphorus (P-DL) – is different depending on specific weathering rock. Soils on nephelinbasalt are marked by very high ratios and reach values of 36 to 166. They distinguish from soil on phonolith with ratio 15 and soils on diabase with ratios in the range of 9 – 21. Differences between intensities of phosphate fixation possibly can be caused by different mineralogical compositions of weathering rocks and soils and their specific ability of weathering depending on their crystal structure and resulting in different intensities of weathering by soil minerals. Correlation between phosphate fixation and intensities of weathering by soil minerals especially is demonstrated by soils on nephelinbasalt showing strong phosphate fixation and simultaneously higher contents of weathering products of oxalate and dithionite soluble iron and “free” aluminium (by Foster). For minimizing phosphate fixation, arable soils should be regulated to optimal pH and manuring of phosphate should be given each year and, if possible, nearby the roots of plants.