Clays are of paramount importance for soil stability, but also in applications ranging from oil recovery to composites and hydrogels. Generically, clays are divided into two subclasses: macroscopically swelling, 'active' clays that have the capacity for taking up large amounts of water to form stable gels, and 'passive' or non-swelling clays; the former stabilize soils whereas the latter are kn...

Visible and near-infrared diffuse reflectance spectroscopy (VIS-NIR) has shown levels of accuracy comparable to conventional laboratory methods for estimating soil properties. Soil chemical and physical properties have been predicted by reflectance spectroscopy successfully on subtropical and temperate soils, whereas soils from tropical agro-forest regions have received less attention, especial...

Improving swine effluent management practices requires understanding of the fate of nutrients derived from swine effluent in soil quality. This study was conducted to evaluate the effects of long-term swine lagoon effluent application on nutrient distribution in an alkaline Okolona silty clay, an acidic Vaiden silty clay, and a Brooksville silty clay loam. Swine effluent has been applied using ...

-A laboratory study of the hydraulic conductivity (HC) of a marine clay with monovalent, divalent and trivalent cations revealed large differences in HC. The exchangeable cations employed in this study are Na, K, NH4, Mg, Ca and AI in order of increasing valency. An interpretation of the results derived from consolidation tests suggests that HC is significantly affected by the valency and size ...

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D miner...

BACKGROUND Metsulfuron-methyl is widely used for controlling many annual grasses and broadleaf weeds in cereal crops. Nonetheless, increasing evidence has demonstrated that even extremely low levels of metsulfuron-methyl residues in soil can be toxic to subsequent crops or non-target organisms. The behavior of herbicides in soils is mostly related to their residual forms. The intent of the pres...

In this study, we examined the influence of different nitrogen (N) application rates (0, 168, 240, 270 and 312 kg N ha(-1)) on soil properties, maize (Zea mays L.) yields and microbial communities of three types of soils (clay, alluvial and sandy soils). Phospholipid fatty acid analysis was used to characterize soil microbial communities. Results indicated that N fertilization significantly dec...

Cadmium (Cd) concentration in soil solution and its bioavailability is controlled by sorption-desorption reactions. The objective of this research was to compare Cd adsorption behavior in six calcareous and four acid soils. Soil samples were equilibrated with 0.01 M Ca(NO3)2 containing 25 to 3200 mg Cd L−1. Results showed that the tendency for adsorption was high at low Cd concentrations (0-400...

Nitrification is a key process in soil nitrogen (N) dynamics, but relatively little is known about it in tropical soils. In this study, we examined soils from Trinidad to determine the edaphic drivers affecting nitrification levels and community structure of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in non-managed soils. The soils were naturally vegetated, ranged in t...

In order to determine the mechanisms involved in the persistence of extracellular DNA in soils and to monitor whether bacterial transformation could occur in such an environment, we developed artificial models composed of plasmid DNA adsorbed on clay particles. We determined that clay-bound DNA submitted to an increasing range of nuclease concentrations was physically protected. The protection ...