Teores e distribuição do carbono orgânico do solo sob diferentes usos no âmbito do projeto Carbon-PNLBA, Caxiuanã-Pará

Abstract

The soils of the Caxiuanã region are predominantly of the Latosols group, with the occurrence of other soils, such as Gleys and Terra Preta Arqueológica (TPA). In this work we compared the granulometry and chemical attributes between two soil types: Terra Preta Arqueológica (Manduquinha site): sandy and well drained, and Latossolos Amarelos (LA's). The LA's studied are under different uses: capoeira (CAP), sandy texture and well drained, and dense forest (PA and PB - ESECAFLOR experiment) sandy texture and well drained and LBA Project tower (TOR): clayey texture and poorly drained. Soil samples were collected at depths of 0-5 in, 5-10 in and 20-50 in. After air-drying and sieving (2 mm mesh), soil granulometry was determined and the chemical components (N, P, Ca, Mg,AI,H+AI) and pH value were determined. The results were statistically analyzed by Person's correlation, using the statistical program ESTAT Version 2.0. Among the correlations obtained, the chemical and granulometric characteristics of the soil, referring to the site with Archaeological Black Earth, the most relevant occurred between pH H20, C and Ca2+, which are highly positively correlated with r=0.99 at 1% probability. At the sites in dense forest (PA and PB) and under grassland (CAP), carbon showed positive correlations with the chemical characteristics N, P, Ca, Mg, AI and H+AI, and negative correlations with pH H20. In the LBA tower site (TOR), however, only the associations obtained for the clay fraction and pH H20 are negative. Thus, there is a contrast in the correlations presented by the TPA site in relation to the other sites studied (CAP,PA,PB and TOR), reflecting the better fertility of the TPA, in terms of exchangeable nutrients and organic matter quality.