Dados do Trabalho

Título

LAND-USE SYSTEMS AFFECT THE VARIABILITY OF PHYSICAL ATTRIBUTES OF AMAZONIAN FERRALSOL

Resumo

Studies evaluating soil quality in land-use systems often consider the changes on the levels of soil attributes and overlook eventual alterations in the variability itself. Neglecting heteroscedasticity may lead to mistaken conclusions when different areas are compared by parametric methods. In this study, we aimed to compare the variability of soil physical attributes between land-use systems, through statistical tests with different levels of robustness. The study was carried out at the Campus Ariquemes of the Federal Institute of Rondônia (9°57'11.72"S, 62°56'54.55"W), in an Haplic Ferralsol under three land-use systems, namely: native forest, agroforestry (T. grandifolium and H. brasiliensis), and cultivated pasture. In each system, we collected 35 soil samples distributed in 2500 m2 at depths: (I) 0.0-0.05 m, (II) 0.05-0.1 m, and (III) 0.1-0.2 m. The variances of clay content, bulk density and total porosity in the samples were compared, between the three systems, within each soil layer, by Bartlett's test, Levenne's test and Snedecor's F test (P<0.05). The Bartlett’s test found difference in the variances: of porosity, in layer I; of all attributes analyzed, in layer II; and of clay content and porosity, in layer III. The Levenne’s test indicated different variances of clay content between the systems, in the three soil layers. In pairwise comparisons, the F test found different variances: of clay content and porosity, between native forest and agroforestry; of density and porosity, between native forest and pasture; and of clay content and porosity between agroforestry and pasture. The differences in clay content variability between land-use system indicate that the agroforestry area may have undergone more vertical soil mobilization, since texture is a resilient soil attribute. Our results indicate porosity as the soil physical attribute whose variability is most affected by land-use, and it mus be considered in combined analysis.

Palavras-chave

variability; homoscedasticity; soil management.