Physical, chemical and structural attributes of soil in agroecosystems in the Brazilian Semiarid region¹

Atributos físicos, químicos e estruturais do solo em agroecossistemas na região semiárida brasileira

ABSTRACT

The soil attributes can be easily changed according to its management and use, compromising the productive capacity of the areas. The objective of this research was to evaluate the variability and interrelationships of soil physical, chemical and structural attributes in agroecosystems in the Brazilian Semiarid region (Rio Grande do Norte State), pointing out the most sensitive attributes in the environment distinction through multivariate analysis. The research was carried out in the rural community of Piracicaba, Upanema municipality, Rio Grande do Norte State, Brazil. Four agroecosystems were selected: Native Forest Area (ANF), Corn Bean Consortium Area (ACBC), Pasture Area (AP) and Cashew Area (AC). Undisturbed and deformed soil samples were collected in the 0.00-0.10, 0.10-0.20 and 0.20-0.30 m layers, and the physical, chemical and structural attributes were analyzed. The data were submitted to multivariate statistical techniques, using the correlation matrix, cluster analysis, factor analysis and principal component analysis. Factorial analysis revealed the most sensitive attributes in distinguishing agroecosystems: microporosity, field capacity (FC), permanent wither point (PWP), available water (AW), sand, clay, flocculation degree (GF), Ca²⁺, Mg²⁺ and sum of bases (SB) (F1) and soil density (SD), total porosity (PT), macroporosity, electrical conductivity (EC) and total organic carbon (TOC) (F2). Cluster analysis formed three distinct groups. The TOC was discriminant to group the native forest and cashew tree areas, showing the influence of soil management. The other environments were grouped according to the texture differentiation, influencing the attributes variability.

Key words:
Inorganic fractions; Multivariate statistics; Total organic carbon; Soil management