Vladia Correchel

Assessment of the retention of sediments by riparian forest by morphological and physico-chemical characterization of soil

This study aimed to assess the efficiency of a riparian forest to retain runoff sediments from cropped areas by means of morphological and physico-chemical characterization of a Typic Haplustox Cerrado soil along a 204 m transect. All soil samples were collected from layers of 0-5, 5-10 and 10-20 cm on the cropped areas, ending on a riparian forest. The studied areas were cropped with cotton under conventional tillage system. For the morphological descriptions of soil profiles in the riparian forest, four trenches were opened. The first two descriptions done at the entrance of the forest showed the presence of non-pedogenic material over the A horizon, originated from sediments dragged off the cropped areas to the forest through erosive processes. Morphological assessment of soil profiles associated to soil analysis shows that intensive cropping changes physical and chemical attributes, especially aggregation indices, as well as organic matter and Ca contents.This study aimed to assess the efficiency of a riparian forest to retain runoff sediments from cropped areas by means of morphological and physico-chemical characterization of a Typic Haplustox Cerrado soil along a 204 m transect. All soil samples were collected from layers of 0-5, 5-10 and 10-20 cm on the cropped areas, ending on a riparian forest. The studied areas were cropped with cotton under conventional tillage system. For the morphological descriptions of soil profiles in the riparian forest, four trenches were opened. The first two descriptions done at the entrance of the forest showed the presence of nonpedogenic material over the A horizon, originated from sediments dragged off the cropped areas to the forest through erosive processes. Morphological assessment of soil profiles associated to soil analysis shows that intensive cropping changes physical and chemical attributes, especially aggregation indices, as well as organic matter and Ca contents.

Riparian forest potential to retain sediment and carbon evaluated by the 137Cs fallout and carbon isotopic ratio techniques

Riparian forests can provide an important service for aquatic ecosystems by sequestering hillslopederived sediments. However, the width of a riparian buffer zone required to filter sediments is not yet wellunderstood. Here are used two complementary tracers to measure sediment retention. The 137Cs technique and the soil carbon isotopic ratios (delta13C) are utilized to investigate sediment deposition and erosion rates on a slope transect cultivated with sugarcane followed by a secondary riparian forest zone in Iracemápolis, State of São Paulo, Brazil. The 137Cs technique and the delta13C analysis showed that the width of a riparian vegetation in accordance to a Brazilian Environmental Law (N masculine4.771/65) was not sufficient in trapping sediments coming from agricultural lands, but indicated the importance of these forests as a conservation measure at the watershed scale. The complementary delta13C analysis together with soil morphology aspects allowed a better interpretation of the sediment redistribution along the sugarcane and riparian forest transects.

Erodibility and critical shear stress on unpaved road soils

The absence of an adequate drainage system in unpaved roads is one of the main factors for their degradation. For adequate planning knowledge of the resistance parameters of soil is necessary. This study had as its objective the determinatiom of the erodibility and critical shear stress of unpaved road soils. For this work, a runoff simulator was directly installed on road channels, under natural conditions. Different flow depths were applied and the soil loss was measured for each depth. The erodibility and the critical shear stress were determined through adjusted curves relating soil disaggregation and flow shear stress. The results showed variations in erodibility and in critical shear stress values of the roads. The erodibility values obtained, when compared with values observed in the literature, evidenced high susceptibility to the erosion for road conditions. These values were higher on silt loam and sandy soils. The critical shear stress values were similar to those observed in other publications.

Resistência à penetração em Neossolo Quartzarênico submetido a diferentes formas de manejo

The replacement of native forests for agrosystems causes changes in soil structure. The degree of these changes depends on the intensity of use and soil management, climatic conditions and soil physical and chemical properties. The aim of this study was to evaluate the soil bulk density (Bd), soil resistance to penetration and organic matter content of an Ortic Quartzarenic Neosol under four land use systems: native forest, agroforestry, pasture and other area recently converted to agricultural use. In each system seven soil profiles were selected and samples were collected in July 2010 and January 2011. The soil resistance to penetration was determined in 0-40 cm depth using an impact penetrometer, Planasucar Stolf IAA model. The water content in the soil layers was determined in 0-20 and 20-40 cm depth. The organic matter and soil bulk density were deternied in layers 0-5, 5-10, 10-20 and 20-40 cm. Among the evaluated systems, the lowest values of soil bulk density and soil resistance to penetration were found in agroforestry and the highest values were obtained in the pasture. In the area recently converted to agricultural use the results obtained were similar to those obtained under native forest.

Sequências de dias chuvosos: fator de risco à colheita em Goiás

O objetivo deste trabalho foi estabelecer sequencias de dias chuvosos como fator de risco a colheita no Estado de Goias. Para isso, foram utilizadas series historicas pluviometricas, com periodo de base de, no minimo, 17 anos referentes a 36 estacoes pluviometricas localizadas neste Estado. As sequencias de dias chuvosos foram separadas por uma rotina computacional para os meses de dezembro, janeiro, fevereiro e marco. Para o estudo de probabilidade destas sequencias, utilizou-se a Distribuicao Binominal Negativa Truncada (DBNT). A aderencia da distribuicao as sequencias de dias chuvosos foi verificada, utilizando-se do teste de Qui-quadrado (χ2). Os resultados foram espacializados, de modo a facilitar a visualizacao da distribuicao espacial das sequencias de dias chuvosos para os meses estudados. Verificou-se que o risco de chuva na colheita varia localmente. As maiores probabilidades de ocorrencia de sequencias com dois dias chuvosos ocorreram nas regioes centro, sudoeste e sul, e tres dias na regiao central e entorno. Ocorrencia de sequencias com quatro dias chuvosos ou mais apresentou baixa probabilidade.

USO E OCUPAÇÃO DE MICRORELEVO DE MURUNDUS NO SUDOESTE DE GOIÁS: UMA ABORDAGEM SOBRE OS ASPECTOS FISICOS DO SOLO

The increases achieved in agricultural production are due to the use of technology and the advancement of new frontiers. Part of this expansion is the substitution of pastures and natural vegetation. Some of these areas are situated in the floodplains and environmental point of view are of extreme importance, as are areas of recharge and maintenance of water from rivers and streams in the watershed where they are located . The aim of this study was to conduct a review of the origin and significance of microrrelevos of mounds . It was observed that there is still the need for public policies aimed at raising awareness of producers in the region about the ecological and economic importance of these microrrelevos in the region as well as the training of technicians who provide assistance to farmers . Allied policies of awareness on the part of government needs is to foster research on this topic , since little is known about the micro relief of this region . In studies on the physical aspects phytophysiognomies soil must be addressed , as these will be of crucial interest to managers in decision making about the use and occupation of land.

Voçoroca em borda de relevo tabular residual sobre cobertura latossólica, Quirinópolis (GO)

The Confusao do Rio Preto Range, located on the north-central Quirinopolis (GO), present tabular residual hills with elevations about 880 m. In the higher parts of the range occur sizable erosive scars, like rills and gullies. The research aimed to identify the origin, controlling factors and dynamics of the processes responsible by the formation and evolution of a gully in pasture area on the referred range. First, was realized the registration of the erosive feature and the selection of 17 profiles along the banks of the gully to describe, in top sequence, the horizons cut by the erosion. The obtained data allows to state that the gully is developing on an old erosive scar, mainly conditioned by: 1) surface runoff concentrated in cattle trails in the surroundings of the incision; 2) surface runoff concentrated in channels of terraces, that overflows and reaches the borders of the erosive feature; and 3) exfiltration of the subsurface water in the contact of the Bw and Bc horizons with the underlying C horizon in the strongly inclined banks. Before the prevision of fast lateral and backward expansion, is necessary to adopt practices for control and stabilization of the gully.