Liovando Marciano da Costa

ESTOQUE DE CARBONO DO SOLO SOB PASTAGEM EM ÁREA DE TABULEIRO COSTEIRO NO SUL DA BAHIA

The replacement of forest environments by pastures leads to fundamental alterations in soil carbon stocks and consequently in the global cycle of this element. This study was conducted in the municipality of Itabela, Bahia, and the objective was to evaluate carbon stocks in soils of a natural forest in comparison to degraded and productive pastures with different usage periods. For this purpose, remnants of the Atlantic Forest, productive pastures after different periods of use (2, 9 and 18 years) and an ill-managed pasture (18 years) were selected. All areas were located on a flat terrain of the same soil class (Typic Paleudult). In each area three plots were established and used for soil sampling and subsequent carbon analyses. Results showed no significant difference in soil carbon stocks in the forest and degraded or productive pastures with different use periods and soil layers. Moreover, it was observed that after 28 years of usage an average of the 62 % of organic carbon found in well and ill- managed pastures was still derived from the original forest soil organic matter.

Modificações causadas pelo uso e a formação de camadas compactadas e, ou, adensadas em um latossolo vermelho-escuro textura média, na região do cerrado

O objetivo deste trabalho foi avaliar as modificacoes causadas pelos diferentes usos em atributos de um Latossolo de textura media e a influencia destas na formacao de camadas compactadas e, ou, adensadas de subsuperficie, sob diferentes usos agricolas, na regiao do cerrado. Para tanto, em abril de 1994, nos municipios de Uberlândia e Monte Alegre de Minas, foram selecionados seis locais onde o solo foi amostrado em trincheiras: CC (Fazenda Canada, vegetacao de cerrado); CP (Fazenda Canada, cultivo com uso de pivo central); GC (Fazenda Gaia, vegetacao de cerrado); GPa (Fazenda Gaia, pastagem); GP1 e GP2 (Fazenda Gaia, cultivo com uso de pivo central). O solo foi classificado como Latossolo Vermelho-Escuro, textura media e apresentava camadas compactadas e, ou, adensadas em subsuperficie, incluindo as areas sob vegetacao de cerrado, variando apenas o valor da densidade do solo e a profundidade em que a camada aparece. O cultivo provocou modificacoes em relacao a presenca do cerrado. A area sob pastagem, exceto por um aumento superficial na resistencia a penetracao, apresentou comportamento semelhante ao das areas sob cerrado. O aumento da densidade nas camadas subsuperficiais deveu-se, possivelmente, ao aumento da argila dispersa em agua nas areas cultivadas. O aumento da argila dispersa em agua ocorreu em decorrencia de diversos fatores, tais como: reducao do carbono orgânico, calagem e aumento do PCZ. Ocorreu correlacao positiva e significativa entre o teor de SiO2 e a percentagem de argila dispersa em agua e, consequentemente, com a formacao de camadas compactadas e, ou, adensadas, no solo estudado, sob diferentes usos.

Effects of weed control on physical and micropedological properties of a brazilian ultisol

In the tropical soil environment, raindrop impact is capable of disrupting natural soil aggregation and porosity, thus influencing the amount of infiltrated water and its redistribution. Under such conditions, a vegetation cover of weeds cannot be viewed simply as a crop competitor. This research project was designed to examine, under field conditions, the changes of soil properties, namely soil water content, structure and sealing, resulting from different types of weed management, with the aim of contributing to the establishment of more sustainable agricultural practices. Four weed management types - hoe-weeded, bare soil (combined application of pre-emergence herbicide Arsenal-250® (Imazapir) 2.0 L ha-1 and the systemic herbicide Gliz® (Glifosate) 5.0 L ha-1), cut and cut + herbicide (systemic herbicide Gliz®(Glifosate) 5.0 L ha-1) - were studied on an intensively cropped Kanhapludult in Minas Gerais State, Brazil. In high rainfall periods, the insulating effect of cut and cut + herbicide resulted in higher soil water, as compared to bare soil and hoe-weeded. On the other hand, in dry periods, the bare soil and hoe-weeded covers presented higher soil water content than the cut and cut + herbicide. Based on macro and micropedological observations, a sealing effect up to 15 mm below the surface was observed in bare soil and hoe-weeded covers and was particularly well-sorted and stratified in the latter. It is postulated that microerosional and microdepositional processes are involved in hoe-weeded sealing. These processes result from the breakdown of microaggregates, repacking the soil matrix. In the bare soil, the sealing was associated with physical alterations in the top layer, related to raindrop impact. Cut and cut + herbicide covers showed greater development of algae, bryophytes and worm activity in the soil surface. Based on the results obtained, the use of motorized cutters associated with herbicides appears to be a suitable alternative to hoeing and hand-weeding, reducing soil physical degradation and losses of water and soil in this particular environment.

Cinza e carbonato de cálcio na mitigação de drenagem ácida em estéril de mineração de carvão

SUMMARY : COAL ASH AND CALCIUM CARBONATE ON ACID DRAINAGEMITIGATION IN COAL MINING OVERBURDEN Acid drainage is an environmental problem, not exclusive, but commonly associated tocoal mines. It arises from the oxidation of sulfides, like pyrite, in overburden and miningtailings. The use of ashes from coal combustion is still limited in Brazil, but such residueshave a potential use as neutralizing agent for acid mine drainage. This study intended toevaluate the interaction between the use of coal ash and CaCO 3 to neutralize acid drainagefrom pyrite oxidation in coal mining overburden from Candiota (RS) - Brazil. Samples ofoverburden material containing pyrite were treated with increasing CaCO 3 doses and coalash in leaching flasks. The treatments were disposed in a completely randomized design in4 x 4 factorial scheme (4 doses of CaCO 3 and 4 doses of coal ash) with three replications.The flasks were submitted every two weeks to leaching with distilled water during eightmonths. The leached solutions were analyzed for pH, free acidity and S, Si and Fe contents.Results showed that the use of ash was impractical not only due to its low neutralizingcapacity, but also because it reduced the CaCO

Modelagem da retenção de herbicidas em zonas ripárias

This work aimed to investigate the retention of atrazine and picloram, carried by surface flow, in riparian zones. The surface flow, containing a mixture of both herbicides and kaolin, was then simulated within riparian zones established in pine plantations in north-eastern Georgia, USA. Five plots were established within riparian zones, each with a different slope (2, 5, 10, 15 and 20%). The influence of the initial moisture and of the O horizon condition in herbicide retention was analyzed. An exponential model, commonly used for the estimate of biochemical demand of oxygen (BOD) and nutrients attenuation in overland flow treatment, was used to estimate the attenuation of kaolin and herbicides in riparian zones. The model allowed an accurate estimate of the attenuation of kaolin and atrazine from the surface runoff mixture along 10 m of riparian zone. Generally, slope showed the best correlation with retention of the pollutants presented in the runoff mixture within the riparian zone. The O horizon present in the steeper slopes improved the sedimentation of kaolin and the atrazine adsorption.

Influência da qualidade da água de irrigação na dispersão da argila de Latossolos

The phenomenon of dispersion of soil clay can be caused by the quality of irrigation water. This study investigated the effect of irrigation water with different electric conductivities (EC), combined with different Sodium Adsorption Relation (SAR) values on clay dispersion in soil commonly found in the state of Minas Gerais, with different mineralogies. The samples were collected from the B horizon of three soils (Oxisols) in Vicosa, Belo Horizonte and Barroso, respectively, with high levels of the clay minerals kaolinite, hematite, and gibbsite, and are classified as Yellow-Red Latosol, Red Latosol and dystroferric Red Latosol. The physical, chemical, and mineralogical properties of the soils were characterized. The treatments corresponded to percolation, through the three soils, of NaCl and CaCl2 solutions with six different EC values (20; 50; 100; 200; 400, and 800 mS m-1) and five SAR values (0, 5, 10, 20, and 40 mmolc L-1), in a randomized block design with three replications. The solutions were applied in vertical column and constant load permeameters. The solution was applied until the EC of the effluent approached that in the applied solution (C/C0 = 1.0). To evaluate the effect of the solutions applied to the soil structure, the contents of clay dispersed in water (CDW) were quantified. The values of CDW in the soil materials percolated with the different sodic-saline solutions (CDW-S) were related to EC and SAR of the percolated solutiona. The soil behavior was distinct regardint clay dispersion, which was ascribed to its mineralogy as well as to the degree of weathering. The Yellow-Red Latosol showed a non-dispersive pattern in all treatments. In general, all percolation solutions, especially those with highest EC, regardless of the SAR value, indicated reduced dispersed clay (CDW-S) in the Red Latosol and dystroferric Red Latosol.

MÉTODOS DE ANÁLISE DE SULFETOS EM AMOSTRAS DE ROCHAS E SEDIMENTOS

O presente trabalho foi realizado no periodo de agosto a dezembro de 1998, com o objetivo de comparar metodos de analise de sulfetos, visando obter uma tecnica rapida, exata e reprodutivel para avaliar o potencial de drenagem acida em rochas e sedimentos. As amostras foram submetidas a digestoes oxidativas com H2O2 e agua regia. Nos extratos, foram determinados o S por gravimetria, por meio do Ba remanescente por espectrofotometria de absorcao atomica (EAA), por turbidimetria e por colorimetria. Os teores de Fe e Pb foram determinados por EAA. Nos extratos de H2O2, determinou-se, tambem, a acidez por titulacao com NaOH. A tecnica mais indicada para avaliar o teor de sulfetos foi a digestao das amostras com agua regia, seguida da determinacao indireta do S, por meio do Ba remanescente por EAA. A digestao com H2O2 nao foi eficiente para a oxidacao total dos sulfetos presentes nas amostras, devendo subestimar o potencial de geracao da drenagem acida em amostras de rochas e sedimentos.

Uso de opalas biogênicas na identificação de sedimentos lacustres e marinhos

This study aimed to identify lacustrine or marine sediments based on biogenic opals (also known as spicules). The layers and horizons of a Humic Gley Thiomorphic soil in the Riacho catchment area, Aracruz, state of Espirito Santo, Brazil, were analyzed. Each soil sample was specifically treated to isolate the spicules, which were then identified by an electronic microscope. It was possible to verify the presence of lacustrine as well as marine spicules. Moreover, the shape of the opals provided information on the conditions of the geochemical environment and transport distance of the sediments.