The effectiveness of surface application of lime to soils under a no‐till (NT) system, particularly with regard to subsoil acidity, is uncertain, and long‐term data is needed to determine optimum surface liming rates in this cropping system. A field experiment was performed in the period from 1993 through 2003 in Paraná State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate the extent of the downward movement of surface‐applied lime in a NT system, and the effect on grain yields under crop rotation. The treatments consisted of dolomitic limestone at the rates of 0, 2, 4, and 6 t ha−1, calculated to raise the base saturation in the topsoil (0–20 cm) to 50, 70, and 90%. Surface‐applied lime under NT was effective in alleviating soil acidity below the point of placement, and increased the cumulative grain yield of the crops. The effects of surface liming on all three acidity‐related variables (pH, Al, and basic cations) were significant at 0‐ to 5‐ and 5‐ to 10‐cm depths from 1 yr onward, and also at the 10‐ to 20‐cm depth from 2.5 yr onward, remaining consistent for a period of up to 10 yr after liming. The maximum economic yield was obtained at 4 t ha−1 of limestone, showing that the lime rate estimated by the soil base saturation method at 70% in the 0‐ to 20‐cm depth was appropriate for surface liming recommendation in a NT system.

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The application of sewage sludge or biosolids on soils has been widespread in agricultural areas. However, depending on their characteristics, they may cause increase in heavy metal concentration of treated soils. In general, domestic biosolids have lower heavy metal contents than industrial ones. Origin and treatment method of biosolids may markedly influence their characteristics. The legislation that controls the levels of heavy metal contents in biosolids and the maximum concentrations in soils is still controversial. In the long-term, heavy metal behavior after the and of biosolid application is still unknown. In soils, heavy metals may be adsorbed via specific or non-specific adsorption reactions. Iron oxides and organic matter are the most important soil constituents retaining heavy metals. The pH, CEC and the presence of competing ions also affect heavy metal adsorption and speciation in soils. In solution, heavy metals can be present either as free-ions or complexed with organic and inorganic ligands. Generally, free-ions are more relevant in environmental pollution studies since they are readily bioavailable. Some computer models can estimate heavy metal activity in solution and their ionic speciation. Thermodynamic data (thermodynamic stability constant), total metal and ligand concentrations are used by the GEOCHEM-PC program. This program allows studying heavy metal behavior in solution and the effect of changes in the conditions, such as pH and ionic strength and the application of organic and inorganic ligands caused by soil fertilization.

The conversion from forest to grassland is drastically changing soil characteristics in Amazon, leading to land degradation when it is poorly managed. Chemical and physical changes of a Typic Hapludox were evaluated as a function of the conversion (by means of fire) from forest to Brachiaria brizantha cultivation. Samples from the remaining forest were also sampled. Treatments were made to pastures eight (P8), thirteen (P13) and fifteen (P15) years after conversion, and to land under continuous grazing, and to a remaining forest area (control). The forest soil was more acidic than the pasture soils. Soil density and Ca+2 increased after the conversion, regardless of the period of grazing. Carbon stocks varied from 31·2 t ha−1 in the forest soil to 37·4 (P8), 33·5 (P13) and 30·7 t ha−1 (P15). Copyright © 2011 John Wiley & Sons, Ltd.

Animal production is a leading economic activity in Brazil and antibiotics are widely used. However, the occurrence, behavior, and impacts of antibiotics in Brazilian soils are still poorly known. We evaluated the sorption behavior of four fluoroquinolones (norfloxacin, ciprofloxacin, danofloxacin, and enrofloxacin) and five sulfonamides (sulfadiazine, sulfachloropyridazine, sulfamethoxazole, sulfadimidine, and sulfathiazole) in 13 Brazilian soils with contrasting physical, chemical, and mineralogical properties. Fluoroquinolone sorption was very high (Kd≥544 L kg(-1)) whereas sulfonamide sorption ranged from low to high (Kd=0.7-70.1 L kg(-1)), consistent with previous reports in the literature. Soil texture and cation exchange capacity were the soil attributes that most affected sorption. Cation exchange was the most important sorption mechanism for the fluoroquinolones in highly weathered tropical soils, although cation bridging and ion pairing could not be ruled out. Hydrophobic partition played an important role in the sorption of the sulfonamides, but sorption was also affected by non-hydrophobic interactions with organic and/or mineral surfaces. Sorption for both compound classes tended to be higher in soils with high Al and Fe oxihydroxide contents, but they were not correlated with Kd values. No direct effect of soil pH was seen. The fluoroquinolones are not expected to leach even in worst-case scenarios (soils rich in sand and poor in organic carbon), whereas soil attributes dictate leaching potential for the sulfonamides.

Gypsum application and ionic speciation of the solution from an Oxisol under no-till system RESUMO O baixo teor de Ca e a toxicidade por Al são importantes limitações à produtividade das culturas em solos ácidos brasileiros. É possível aumentar o teor de

RESUMOOs resíduos de plantas de cobertura podem mobilizar cátions no solo e beneficiar a ação da calagem superficial, por meio da liberação de ácidos orgânicos de baixo peso molecular da fração solúvel dos resíduos. Entretanto, faltam estudos no campo que comprovem tais efeitos em sistema plantio direto. Para avaliar as alterações químicas do solo e a resposta do milho e da soja com a aplicação de doses de calcário dolomítico na superfície (0,0, 2,5, 5,0 e 7,5 t ha -1 ), na ausência e na presença de cobertura de aveia preta, foi realizado um experimento em um Latossolo Vermelho distrófico textura argilo-arenosa, há cinco anos no sistema plantio direto, em Ponta Grossa (PR) .

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