Resumo

FERNANDEZ, Leticia Andrea; SAGARDOY, Marcelo Antonio  e  GOMEZ, Marisa Anahí. Study of acid and alkaline phosphatase in soils of the Pampean North Region from argentine soybean area. Cienc. suelo [online]. 2008, vol.26, n.1, pp.35-40. ISSN 1850-2067.

Transformation of organic phosphorus (Po) into soluble inorganic phosphorus (Pi) is called mineralization and is carried out by phosphatase enzymes. The present research focuses on the study of the phosphatase activity of five soils from the soybean area of the Northern Pampean region, by evaluating the phosphatase activity in soil samples and the number of bacteria and fungi with that activity. Soil samples were collected and the total number and phosphatase activity of cultivated heterotrophic aerobic bacteria (CHAB) and cultivated fungi (CF) was assessed. No significant differences were observed in the numbers of CHAB and CH between the studied soils. The number of bacteria with acid phosphatase activity was 6.85 10⁵ CFU g^-1 soil, while alkaline activity was 5.80 10⁵ CFU g^-1 soil. In contrast, the number of fungi with acid phosphatase activity was 1.78 10³ CFU g^-1 soil and with alkaline activity was 1.77 10³ CFU g^-1 soil. No significant differences were observed in the number of bacteria and fungi with both enzymes. However, acid activity was higher than alkaline activity in soil samples. Alkaline phosphatase activity ranged from 5.72 to 15.5 mg p- nitrofenol kg^-1 soil h^-1 while acid activity varied from 27.4 to 10⁵ mg p-nitrofenol kg^-1 soil h^-1. There were significant differences in phosphatase activity between the soybean soils. Our results show that the mineralization activities of Po sources are in agreement with other cultivated soils. On the other hand, the number of bacteria and fungi complements the information on soil phosphatase activity. Clearly, both methods allow the study of alkaline and acid phosphatase activity in soil and give information about the soil potential to mobilize Po.

Palavras-chave : Microbial counts; Acid phosphatase; Alkaline phosphatase.

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