BIOMASSA E ATIVIDADE DE MICRORGANISMOS DO SOLO: REVISÃO METODOLOGICA

Resumo

There is some general concern on the need for evaluating microbial populations in soil, and their contribution to soil productivity. In this aspect, microbial biomass and activity are pursued as important parameters to be evaluated. The suitable methods for determining soil microbial biomass are: direct observation (using vital stains, under fluorescency microscopy) and the biochemical ones (ATP extraction,fumigation, and respiration rate in response to substrate addition). In the direct observation method the biovolume is determined, using special graticules and based on density and water content of microbial cell. ATP is ubiquitous and decays quickly when not in living cells. Fumigation-incubation method (Fl) and its recent variation, fumigation-extraction (FE), is problaby one of the most useful and possible to be applied in a large variety of soils and experimental conditions, although some tests in tropical soils still seem to be necessary. A critical summarized analysis is made here on all these methods, and on other ones that estimate soil microbial activity, such as respiration, substrate decomposition rate, and enzyme activities. Researches on microbial biomass and activity in Brazil is listed here. Comments on the best suitable methods for measuring these agroecological parameters are also presented. FE and Fl, and ATP have been appointed by many researchers as the most reliable methods. There is some general agreement on applying more than one method for quantifying biomass and estimating activity in soil, as also recomends the author of this review.