The present study investigated the impact of the application of gypsum and of a sulfur-rich source on the microbial and biochemical characteristics of a dark red latossol used for cabbage cultivation. Gypsum was applied in amounts of 134, 268, and 402 kg S/ha. The following controls were included: a treatment with no sulfur; fertilization with ammonium sulfate (402 kg S/ha); and organic matter (20 t/ha lab-lab, dry weight). Application of increasing sulfur doses to the soil led to an increase in total number of bacteria and a decrease in Gram-negative bacteria. The remaining groups of microorganisms, Bacillus spp, actinomycetes and fungi, did not vary significantly or did not present a satisfatory response. The increase in total number of bacteria compared to control was 29 to 60% in the rhizosphere and 15 to 107% in the non-rhizosphere, with the number of microorganisms in the rhizosphere exceeding the number of microorganisms in the non-rhizosphere by 5 to 251%. The microbial biomass of the rhizosphere increased in the treatments with ammonium sulfate and organic matter and was unchanged in the non-rhizosphere. In agreement with microbial count data, the microbial biomass also increased in the rhizosphere compared to the non-rhizosphere. Dehydrogenase and urease activity increased in comparison to the control, although no effect was observed on arylsulfatase activity. Cabbage production on treated soil was 52.2 to 81.1% higher as compared to the control. Increasing sulfur concentrations were observed in the soil and in the cabbage aerial portion.
gypsum; bacteria; fungi; dehydrogenase; urease; arylsulfatase