Veredas do Triângulo Mineiro: solos, água e uso

Abstract

The veredas ( small valleys where occurs a typic vegetal formation of hydrophilic character, constituted by a tree-shrub set, where the "buritFiMauritia vinifera Mart) palm is outstanding, bypassed bya grass zone, where water seepages), which constitute an importam drainage net ofcerrado region, frequently occur in the Minas Gerais Triangle. However, little is know about their natural resourses. ft is know that they nave a fundamental role in water courses equüibrium and occur at different landscape positions in the cerrado region. This study aimed to characterize the soil, water and use type of natural resourses ofveredas atdifferent geomorphic surfaces, comparing them. Three veredas in each geomorphic surface were selected. For soil characterization, composite samples of soil horizons at each vereda position (inferior, médium and superior part) were collected. For water analysis, samples were collected at veredas inferior part. Theimportance ofveredas andthe use of their natural resources were analysed by field observations and informal interviews with tenfarmers in each geomorphic surface. The veredas present Hydromorphic soils in ali their extension. At the Chapada (high tablelands) veredas, different soil classes were observed: Organosoil (Bog soil), Melanic Gley soil (Humic Gley soil) and Haplic Gley soil (Low-Humic Gley soil), which vary by according to the depth ofwatertable, conditioned byreliefand presence ofimpedance layers. At Bauru veredas, there is a higher homogeneity ofsoil classes, which dominance ofHaplic Gley soils, as a function ofthe contribution ofrecent coluvial material. From the superiorto the inferior part, the drainage gets worse, and the amounts ofclay and organic matter increase as well as the soil natural fertility. Between the veredas' soils, the Bauru ones present better drainage, higher natural fertility, smaller organic matter and claycontents. The mineralogy ofclay fiaction revealed kaolinite and gibbsite dominance, being also identifíed 2:1 clayminerals. TTie waterwas classifíed as class 4, being the colorthe attribute which more depreciated its quality. The water color values foUowed the variations of soil organic matter. The majority ofsoils at chapadas' veredas are not used for agricultural purposes. At Bauru veredas, the soils are frequently used wich native pasture, observing horticulture cukivation in some small farms. At the Chapada área, agricumual activity was verifíed near the veredas. The vereda' water represent an important natural resource for farmers. At Chapada, it is mainly utilized for machinery washing, pesticides application and irrigation, representing high contamination risk. At Bauru veredas, it is common the water dan up for cattle supplying. The increase ofconstruction ofirrigation reservoirs, intetionoffermers, canhave reflexesin reduction ofvolume ofwater bodies and degradation ofveredas, damaging the communities which survive below these systems. TTie blackorgrayish color ofveredas'soils is an easily-identifíable field attribute and it can be used for delimitation ofsuch permanent preservation environments.