Sensitivity of Microbiological Properties of a Rhodic Ferralsol in Response to Management and Environmental Variables in Subtropical Brazil

Management practices and soil environmental variables influence microbiological properties and may cause inaccuracies in the interpretation of the results of these bioindicators. This study evaluated the sensitivity of seven microbiological properties to soil management and environmental variables of a Rhodic Ferralsol from a subtropical region of Brazil. The experimental area was cultivated with crotalaria and corn, followed by a fallow period. Samples were collected monthly for a year to determine soil enzyme activities and heterotrophic bacteria and fungi counts. Soil respiration was evaluated directly in the field. Total hydrolytic activity, cellulases, proteases, dehydrogenases and soil respiration were sensitive to management. Moreover, soil respiration was sensitive to fluctuations in soil temperature (r = 0.75) and pre-sampling precipitation (r = 0.54). Dehydrogenase activity was sensitive to soil moisture (r = 0.72) and total microorganisms (r = 0.61). The bacterial (5.69 +/- 0.37 log10 CFU g soil-1) and fungal (3.99 +/- 0.42 log10 CFU g soil-1) counts showed low sensitivity to soil management and environmental variables. The seven microbiological properties evaluated responded differently to the management and environmental variables. This information must be considered when using soil quality bioindicators to avoid errors in interpreting results.