Many studies have shown the importance of the soil microbial biomass, mainly as source/sink of carbon (C) and nitrogen (N) in forest stands. However, there are few studies focused on microbial P (MPH), especially in relation to the determination methods of MPH in these ecosystems. For an evaluation of the methods used to determine microbial P (MPH) in soils, three methods were evaluated: fumigation-extraction (FE); radiation with microwave-extraction (RE); and radiation by microwave-extraction with a membrane for anionic exchange (EMAE). Samples of a very clayey dystrophic Red-Yellow Latosol (LVAd) were collected at depths of 0-5 cm and 5-10 cm in soils under pine (Pinus taeda), eucalypt plantations (Eucalyptus grandis), and native forest, in Viçosa, state of Minas Gerais. In general, lower MPH contents were obtained by the RE than by the FE method. The MPH contents established by the three methods in the areas with eucalypt and native forest varied significantly in the surface layer. Under pine, only the RE method was significantly different in the 5-10 cm layer. The lowest coefficients of variation (CV) were obtained by FE, expressing the greater precision of this method. Under the studied conditions, however, where a large-scale analysis of samples is required, the RE method turned out to be, in terms of functionality, most adequate for the MPH determination. In relation to the stands, none of the three tested methods could be indicated as uniquely most precise method for the evaluation of the MPH, due to the great variability in the CV for each forest type.
microbial phosphorus; precision; acid soils
