Modified method for measuring acid phosphatase activities in forest soils with high organic matter content

The acid phosphatase activity (APA) is a key factor in phosphorus (P), mine ralization, P nutrition of plants, and P cycling. However, the widely used method of Tabatabai and Bremner for APA determinations is seriously restric ted in soils with high organic matter contents, owing to interference in ph otometric detection by dissolved organic matter. The objectives of this stu dy were: a) to modify the procedure of Tabatabai and Bremner with a view to its application to forest soils rich in organic carbon, b) to determine AP A contents in forest soils of the Sierra de Gata mountains, and c) to estab lish relationships between the APA with different soil parameters. The modi fied procedure was well adapted to forest soils with high organic matter co ntents and had good reproducibility, while maintaining the relative simplic ity and accuracy of the original Tabatabai and Bremner procedure. APA in th e forest soils studied was high but did not correlate with labile P. The AP A in the soils studied depended principally on availability of readily degr adable energy sources and soil nitrogen(N).