September 30, 2020
Soheila sadat Hashemi

Soheila sadat Hashemi

Academic rank: Assistant professor
Education: Ph.D in agri
Phone: 08132233448
Faculty: agriculture


Title Potassium release from sand, silt and clay fractions in calcareous soils of southern Iran
Type Article
soil fractions; K release; kinetic models; calcareous soils; mica
Journal Archives of Agronomy and Soil Science
Researchers Soheila sadat Hashemi


The release of non-exchangeable potassium from 24 calcareous soils of divergent mineralogy, from southern Iran, was examined. Sand, silt and clay particles were fractionated after dispersion with an ultrasonic probe. Samples were extracted with 0.01 M CaCl2 for 30 successive 2-h periods. The clay fraction released the largest amount of K in each soil. Cumulative K released ranged from 175 to 723, 35 to 128, and 71 to 146 mg kg71 contributing 20–90, 4–39 and 2–54% for clay, silt and sand fractions, respectively. The lower proportion of K released from sand and silt fractions can be explained by the presence of a high content of CaCO3 and quartz in these fractions. The release kinetics for the nonexchangeable K data showed that parabolic diffusion and power function were the best fitting kinetic models. This indicated that slow diffusion of K from the mica interlayer positions is the main rate-controlling process. Cumulative K released and constant b values of parabolic diffusion model correlated significantly with the mica content of the clay fraction.