A. Farshadirad, E. Dordipour, F. Khormali1 ,
Volume 16, Issue 59 (4-2012)
Abstract
Non-exchangeable potassium (NEK) release is necessary to supply potassium for plant in different soils. A few studies on the NEK release have been done in soils and particularly on its components. This study was intended to investigate the NEK release from soil and the components of clay and silt through successive extractions with oxalic acid (0.01 M) over a period of 1844 (h) in 4 soil series of Golestan province. The amount of NEK release from whole soil, silt and clay fractions after 1844 (h) were 242 to 450, 380 to 550 and 105 to 199 mg kg-1, respectively. The cumulative rates of NEK release after 1844 (h) were well described by simplified Ellovich, parabolic diffusion and power function equations. The rate of K release was high initially, and then decreased gradually in all soils and in their silt and clay fractions. The amount of released NEK (with high rate) consisted of lower percentage of total NEK, but in spite of less amount, this K form plays a vital role in K dynamic and soil fertility.
S. Ghasemi, A. Hosseinpur, Sh. Kiani,
Volume 22, Issue 3 (11-2018)
Abstract
The rate of metal transfer from the solid phase to solution is an important factor governing their concentration in the soil solution and its availability. In this research, the release rate of Zn in contaminated soils from Isfahan was studied using solutions citric acid, oxalic acid and malic acid 0/01 M during the period of 2 - 504 hours and its relationship with soil characteristics was investigated. The results showed that low molecular weight organic acids could release Zn in the contaminated soils. The Zn released by acids was in the order citric acid> oxalic acid> malic acid. Variation range of Zn released a solution of citric acid, oxalic acid and malic acid, which was 38/9 -21173, 25/2 - 26761 and 25/5 – 20650
mg/kg of soil. Zn released in citric acid solution was higher than that of the two acids. Based on the determination coefficient and standard error estimates done by the kinetic equations, the release of Zn of the contaminated soils and three acid solution was described by the first order equation, elovich, parabolic diffusion and power function, with a high coefficient of determination and a low standard error. Correlation results showed that for the Zn release with the index of Zn usability, there was a significant correlation at 5% level. Showed Multivariate regression model showed that Calcium carbonate, pH and EC affected characteristics of Zn desorption.
