Resumo

CULCHAC CUARAN, Lubi Yomaira; ESTRADA MARCILLO, Jhon Sebastián  e  ORDONEZ JURADO, Héctor Ramiro. Quantification nitrifying bacteria in a Typic melanudands soil under three land use conditions in Pasto, Nariño, Colombia. Cienc. Tecnol. Agropecuaria [online]. 2021, vol.22, n.2, e1424.  Epub 01-Maio-2021. ISSN 0122-8706.  https://doi.org/10.21930/rcta.vol22_num2_art:1424.

The study was conducted in Pasto, Nariño, Colombia, to estimate the amount of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in three land uses (forest, traditional pasture, and silvopastoral system) at two depths We used a completely randomized design (CRD) with six treatments and three repetitions, resulting in 18 experimental units, and, for estimation, the Most Probable Number (MPN) technique. The analysis of variance showed highly significant statistical differences for land uses and depths in AOB. Traditional pasture exhibited the highest AOB density at a depth of 0-10 cm (8.8 x 104 CFU/g), while the forest showed the lowest density (1.3 x 103 CFU/g). In NOB, the highest population density was found in the pasture (9.4 x 103 CFU/g), while the forest showed the lowest density (3.8 x 103 CFU/g). The highest density of bacteria was found at a depth of 0-10 cm: 3.7 x 104 CFU/g for AOB and 7.3x103 CFU/g for NOB, probably because the most biologically active layer of soil is in the first 5 cm of soil. The highest densities of nitrifying bacteria found in traditional pasture and the silvopastoral system could be related to organic fertilization, i.e., the reincorporation of animal manure and urine, ureic substrates that promote microorganism growth.

Palavras-chave : agroforestry; agroforestry systems; grazing systems; secondary forests; soil microorganisms.

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