Water saturation and cation exchange capacity are the most significant parameters used to calculate a hydrocarbon zone potential. In clean formations, by applying the famous Archie model, which assumes that in the formation the only electric conductor is the formation water, the water saturation can be calculated. Additionally, in shaly sand formations this assumption may not be true as the ion...

Variable-charge (v-c) and permanent-charge (p-c) soils differ fundamentally with regard to many nutrient-cycling processes. Variable-charge soils are more common in the tropics than in temperature zones because their formation requires desilication, which proceeds fastest in warm, moist climates. The dynamics of nutrient mobility tend to be more complex in v-c than in p-c soils. For example, th...

experiments were conducted in 1998 and 1999 to study the effects of different levels of potassium and irrigation intervals on yield and water use efficiency of two genotypes of sugar beet (a37.1 and 12681) in khorasan agricultural research center (torogh, iran). potassium levels were; no potassium application, increasing potassium to 5% of soil cation exchange capacity (cec) and second treatmen...

Three soil types with different physicochemical properties were selected to evaluate their effect on lead and cadmium bioavailability toxicity in the land snail Helix aspersa. In 28-day ecotoxicity tests, H. aspersa juveniles exposed increasing concentrations of Pb or Cd. EC50s, reducing growth by 50%, differed between soils so did Cd uptake snails. For lead, EC50s 2397–6357 mg Pb/kg dry soil, ...

ABSTRACT- Paddy soils make up the largest anthropogenic wetlands on earth. Present study was performed to investigate and compare soil formation of paddy soils with long-term rice cultivation history with non-paddy soils and study the effect of waterlogging on soil pedogenesis. Soil samples were taken from paddy and non-paddy soils derived from the same calcareous parent materials. Some pedogen...

The structural and bleaching properties of nitric acid-activated Nteje clay was studied to investigate its ability to serve as an alternative to the high cost imported bleaching earth. The clay was mined, sun-dried, grinded, and reacted with different concentrations of nitric acid, ranging from 2 mol.L-1 to 15 mol.L-1. The un-activated and activated samples were characterized to study the struc...

Clay-mineral composition is one of the factors that determine physical and engineering behaviours finegrained soils; however, it usually ignored in soil investigations, because determination clay-mineral necessitates using sophisticated instruments which are time-consuming require skilled personnel. Many correlations exist for faster prediction properties from its index properties, but quicker ...

field study was conducted at five villages of Botswana namely, Tsabong, Tshane, Mathathane, Motlhabaneng and Tsetsejwe during the periods of June to August 1999 and June to August 2000. The objective of the study was to assess and compare the soil physicochemical properties of soils at the five villages and to study the effect of cultivation on some soil physical properties. Parameters measured...

Abs t rac t -The exchange reactions of Na, Ca and Mg on montmorillonite are revisited employing recently developed analytical and theoretical approaches. The fractional adsorption of the cations has been determined by displacing them from the adsorbed state in one step, using a low concentration of an organic cation of large binding affinity. The analysis of displaced and solution cations emplo...