Arquimedes Lavorenti

Glyphosate sorption and desorption in soils with distinct phosphorus levels

A sorcao do glifosato no solo ocorre devido a formacao de complexos de esfera interna com os metais dos oxidos, o que esta relacionado a capacidade dos solos em adsorver fosfatos. Isto sugere que haja competicao entre o herbicida e os ions fosfato pelos sitios de adsorcao especifica do solo. Com isso, o presente trabalho teve o objetivo de verificar a extensao do efeito de niveis crescentes de fosforo no solo na sorcao e dessorcao do glifosato em solos com diferentes atributos mineralogicos. Os solos foram Nitossolo Vermelho eutroferrico, Latossolo Amarelo acrico e Gleissolo. Amostras dos solos foram incubadas com KH2PO4, por 30 dias, nas doses equivalentes a 0; 1000; 5000; 20000 e 50000 kg ha-1 de P2O5, que sao muito altos do ponto de vista agronomico, mas necessario para estudos de sorcao e dessorcao. O delineamento experimental foi do tipo inteiramente casualizado, em arranjo fatorial 3 (solos) X 5 (niveis de fosforo no solo), com tres repeticoes. No estudo da sorcao foram utilizadas cinco concentracoes do herbicida: 0,42; 0,84; 1,68; 3,36 e 6,72 mg L-1, com radioatividade (14C) de 0,233 kBq mL-1. Apenas para a concentracao 0,84 mg L-1 foram feitas quatro dessorcoes com CaCl2 0,01 mol L-1 e uma extracao com extrator Mehlich 3. Posteriormente, aliquotas do solo foram oxidadas em oxidador biologico para o fechamento do balanco de radioatividade. O glifosato compete com o fosforo pelos sitios de sorcao especifica no solo, mas essa competicao somente e importante quando os niveis de P atingem valores superiores a 1000 mg dm-3. A extracao do glifosato foi muito baixa e foi acrescida com aumento dos niveis de P no solo.

Degradação e sorção de ametrina em dois solos com aplicação de vinhaça

Resumo€Œ€Este trabalho teve o objetivo de avaliar os efeitos da adicao de vinhaca nos processos dedegradacao e sorcao do herbicida ametrina em solos das classes Terra Roxa Estruturada (TR) e LatossoloVermelho-Amarelo (LV). No estudo da degradacao foi instalado um experimento, em delineamentointeiramente casualizado arranjado em fatorial 2€(solos)€x 3€(doses de vinhaca: 0, 100 e 200€m

INFLUÊNCIA DA MATÉRIA ORGÂNICA NA SORÇÃO E DESSORÇÃO DO GLIFOSATO EM SOLOS COM DIFERENTES ATRIBUTOS MINERALÓGICOS

The aim of this study was to evaluate the effects of soil organic matter on the sorption and desorption of glyphosate in three soils with different mineralogical attributes. The experiments were carried out at the Laboratorio de Ecotoxicologia of the Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba, SP (Brazil). The soils were classified as: Rhodic Kandiudalf (NVef), Anionic Acrudox (LAw) and Typic Humaquept (G). In order to evaluate the influence of organic matter on the ghyphosate sorption, the soils were oxidized with H2O2 (30%). The design was completely randomized with a 2 x 3 factorial experiment. For the sorption experiment, five gliphosate solutions were employed with concentrations of 0.42, 0.84, 1.68, 3.36 and 6.72 mg L-1 and radioactivity of 0.233 kBq mL-1. The desorption experiments were performed at concentration of 0.84 mg L-1. The results showed that glyphosate was extremely sorbed to all soils, regardless of the presence of organic matter. The glyphosate sorption was related mainly to the mineral fraction of the soils, i.e., to the Fe and Al oxides. However, the organic fraction only played a secondary role. It was not observed glyphosate desorption, mostly forming soil bound residues.

Comportamento do diclosulam em amostras de um latossolo vermelho distroférrico sob plantio direto e convencional

The aim of this study was to evaluate the dissipation, effects on microorganisms, and sorption/desorption of 14C-diclosulam in Rhodic Hapludox soil samples, cultivated for 10 years under no-till (NT) or conventional tillage (CT) systems. We carried out three individual experiments. In the dissipation and sorption/desorption experiments, diclosulam was applied to soil samples of both management systems. The microbial activity experiment tested diclosulam application and non-application on the soil samples. The degradation experiment was carried out in Bartha flasks, weekly evaluating herbicide mineralization by radiorespirometry. In a parallel evaluation, the herbicide and its metabolites were extracted in other flasks, and the remaining fraction in the soil (bound-residue fraction) was quantified after oxidation in a biological oxidizer. The microbial activity was evaluated by the 14C-glucose technique. In order to obtain the sorption/desorption isotherms, we employed five herbicide concentrations, with four desorptions each. Diclosulam dissipation in the soil was accelerated by the no-till system, due to a higher microbial activity as well as a higher bound-residue formation, compared to the conventional system. The herbicide extraction decreased with time, due to metabolization and the increase in the bound-residue formation. Diclosulam presented a low sorption rate, independently of the management system. Diclosulam application was no hindrance for microbial soil activity, but the management systems did interfere with the dissipation of diclosulam in the soil.

CO2, CH4 and N2O fluxes in an Ultisol treated with sewage sludge and cultivated with castor bean

Organic residue application into soil alter the emission of gases to atmosphere and CO2, CH4, N2O may contribute to increase the greenhouse effect. This experiment was carried out in a restoration area on a dystrophic Ultisol (PVAd) to quantify greenhouse gas (GHG) emissions from soil under castor bean cultivation, treated with sewage sludge (SS) or mineral fertilizer. The following treatments were tested: control without N; FertMin = mineral fertilizer; SS5 = 5 t ha-1 SS (37.5 kg ha-1 N); SS10 = 10 t ha-1 SS (75 kg ha-1 N); and SS20 = 20 t ha-1 SS (150 kg ha-1 N). The amount of sludge was based on the recommended rate of N for castor bean (75 kg ha-1), the N level of SS and the mineralization fraction of N from SS. Soil gas emission was measured for 21 days. Sewage sludge and mineral fertilizers altered the CO2, CH4 and N2O fluxes. Soil moisture had no effect on GHG emissions and the gas fluxes was statistically equivalent after the application of FertMin and of 5 t ha-1 SS. The application of the entire crop N requirement in the form of SS practically doubled the Global Warming Potential (GWP) and the C equivalent emissions in comparison with FertMin treatments.

Produtividade e nutrição de mamona cultivada em área de reforma de canavial tratada com lodo de esgoto

The use of sewage sludge (SS) in agricultural soils is one of the most viable forms of recycling this residue. The purpose of this study was to investigate the effect of SS application on castor bean yield and nutrition in a clayey dystrophic Ultisol following a rotation of sugarcane. The treatments tested were four sewage-sludge rates (0, 5, 10, and 20 t ha-1, dry matter) calculated to supply plants with N at amounts of 0, 37.5 kg ha-1, 75 kg ha-1 and 150 kg ha-1; mineral fertilization with N-P2O5-K2O (75-40-80, respectively) and a control without fertilization. Castor bean, cultivar IAC-Guarani, was grown for 180 days, from November 2004 to May 2005. There was a significant (p<0.05) increment of castor bean yield due to SS application. the application of 10 t ha-1 SS resulted in an agronomic efficiency index of 85 %, compared to mineral fertilization. Nitrogen was the most limiting nutrient concerning yield and plant growth and the nitrogen mineralization rate used underestimated the N supplied by SS under field conditions. Applying SS a the studied rates led to an increment of soil Cu and Zn contents, but metal contents in soil and plant tissues still were within the limits established by the environmental legislation.

Remaining phosphorus and sodium fluoride pH in soils with different clay contents and clay mineralogies

The remaining phosphorus (Prem) has been used for estimating the phosphorus buffer capacity (PBC) of soils of some Brazilian regions. Furthermore, the remaining phosphorus can also be used for estimating P, S and Zn soil critical levels determined with PBC-sensible extractants and for defining P and S levels to be used not only in P and S adsorption studies but also for the establishment of P and S response curves. The objective of this work was to evaluate the effects of soil clay content and clay mineralogy on Prem and its relationship with pH values measured in saturated NaF solution (pH NaF). Ammonium-oxalate-extractable aluminum exerts the major impacts on both Prem and pH NaF, which, in turn, are less dependent on soil clay content. Although Prem and pH NaF have consistent correlation, the former has a soil-PBC discriminatory capacity much greater than pH NaF.

Mineralization and degradation of glyphosate and atrazine applied in combination in a Brazilian Oxisol

The aim of this study was to investigate the behavior of the association between atrazine and glyphosate in the soil through mineralization and degradation tests. Soil treatments consisted of the combination of a field dose of glyphosate (2.88 kg ha−1) with 0, ½, 1 and 2 times a field dose of atrazine (3.00 kg ha−1) and a field dose of atrazine with 0, ½, 1 and 2 times a field dose of glyphosate. The herbicide mineralization rates were measured after 0, 3, 7, 14, 21, 28, 35, 42, 49, 56 and 63 days of soil application, and degradation rates after 0, 7, 28 and 63 days. Although glyphosate mineralization rate was higher in the presence of 1 (one) dose of atrazine when compared with glyphosate alone, no significant differences were found when half or twice the atrazine dose was applied, meaning that differences in glyphosate mineralization rates cannot be attributed to the presence of atrazine. On the other hand, the influence of glyphosate on atrazine mineralization was evident, since increasing doses of glyphosate increased the atrazine mineralization rate and the lowest dose of glyphosate accelerated atrazine degradation.

Simulação do transporte e da sorção de imazaquin em colunas de solo

SUMMARY : SIMULATION OF IMAZAQUIN TRANSPORT AND SORPTIONIN SOIL COLUMNS This experiment aimed at the evaluation of imazaquin sorption and transport in soilswith different chemical, physical and mineralogical characteristics using batch and miscible-displacement techniques. The experiment was carried out with Neossolo Quartzarenico (RQ),Latossolo Vermelho-Amarelo (LVA) and Latossolo Vermelho distroferrico (LVdf) soils whichwere air-dried, passed through a 2 mm sieve and followed by chemical, physical andmineralogical characterization. A CaCl 2 solution was applied in the miscible displacementexperiment for the establishment of a Cl - elution curve that was used as tracer. The curveswere adjusted to a model based on the convection-dispersion equation for ideal transport.Then a 14 C-imazaquin solution was applied and the elution curves for this molecule obtained.The curve was adjusted to a bicontinuum model that considers non-equilibrium during thetransport. In order to obtain the isotherms adjusted by Freundlich equation in the sorptionexperiment through the batch method, a radiolabel imazaquin solution was used withconcentrations varying from 0.67 to 10.72 mmol L

Degradation and formation of 14C-atrazine bound residues in soils of the São Paulo state

The objective of this study was to evaluate the degradation and formation of 14C-atrazine bound residues in two soils of the Sao Paulo State, Brazil. Hapludox and Umbraquults soils were incubaded for 63 days in 500 cm3 glass vessels with 14C-atrazine at 10.38mg a.i. g-1 of soil. The 14CO2 evolution was mensured weekly. Acetonitrile and water (4:1 v/v) was used as extractor solution of the herbicide residues and the organic matter fractionation was based on the solubility of the humic frations of acids and bases. The extracted residue were analyzed for radioactivity by using the Thin Layer Chromatography (TLC) method. The mineralization process (0.1% at 63 days after incubation) was insignificant for the atrazine detoxification in the Umbraquults soil. Hidroxyatrazine (HA) was the main metabolite of atrazine found in both soils and bound residue formation was an important process in that molecule dissipation, especially in the Umbraquults soil.