Decomposition of vegetable residues of different species of the Caatinga in the region of Patos, Paraíba State

Abstract

The aim of this work was to study the dynamic of decomposition of vegetable residues of different species of the Caatinga and to evaluate the microbial activity in the semi-arid region in the Paraíba State. The study area was located in the city of Patos PB, with climate of the type Bhs, defined as semi-arid hot and dry with dry season well defined, mean temperature of 28,8 ºC, altitude of 270 m and mean precipitation of 400 mm. The soil of the study area was classified as Luvissolo Crômico Órtico planossólico vértico. The experimental design was completely randomized in a 5 x 2 factorial, in referring to residues of the five species, ‘pereiro’ (Aspidosperma pirifolium), ‘favela’ (Cnidoscolus phylacanthus), ‘pinhão bravo’ (Jatropha curcas), ‘gliricídia’ (Gliricidia sepium), ‘canafistula’ (Pithecolobium multiflorum), deposited on soil surface and buried in the soil, with portions subdivided in the time (1, 2, 3, 4, 5, 6, 7 months) with four replications. The rainfall the content of water in the soil, rate of decomposition of the material were evaluted and the microbial activity was measured by the absorption of CO₂, at 07:00 p.m and at 07:00 a.m.for 210 days. The highest rates of microbial breathing independent of plant species occured during night. All the vegetable residues of the species studied presented higher rate of decomposition when buried, and the ‘gliricídia’ presented better results.