Available phosphorus in the central area of the Argentinean Pampas. 2: Kinetics of adsorption and desorption of phosphorus under different soil and management environments

Abstract

The concentration of phosphate ions in solution is critical in defining the ability of a soil to adequately meet crop demand. That concentration is regulated by adsorption/desorption and precipitation/dissolution processes, particularly its kinetics of reaction. This work was developed in order to find the kinetic model describing the sorption/desorption of phosphate in soils of the Argentinean Pampas region, to describe the processes associated with these reactions and to define the effect of temperature on them. A bi-linear model that adequately describes the data obtained in the adsorption and desorption experiments is proposed. Thus, it was possible to clearly differentiate two different kinetic mechanisms, each characterized by different reaction rates. Two very labile pools of phosphorus were determined in these soils. The rate at which these processes occur indicates the occurrence of chemical reactions of precipitation in highly soluble compounds and surface adsorption reactions with very low binding energy, as P is quickly released into the soil solution in the desorption process. However, since the amounts of P released in the desorption process are very much less than the adsorbed, is possible to infer that both processes occur at non-equilibrium conditions and there is a lack of reversibility of the reaction P-Soil – P-Solution in the soils studied. The intensity of these processes is differentially affected by temperature and, in general, there is a positive effect of phosphorus fertilization history, although the effect of this is not clearly seen in the amounts of extractable phosphorus with the classic Bray & Kurtz N°1 method.

X-ray Diffraction and X-ray Absorption Near-Edge Structure Spectroscopic Investigation of Hydroxyapatite Formation under Slightly Acidic and Neutral pH Conditions

“…However, such a ratio is not relevant in a typical low temperature geochemical environment such as P rich agricultural soils in the Midwestern U.S. The Ca/P ratio in P rich agricultural soils is in a range of 8–86 in the different regions of alfisols in the U.S., which had relatively abundant Ca because of at least 35% base saturation. − In the case of mollisols with >50% base saturation, − the ratio is as high as 226. Since there is no comprehensive data of dissolved Ca and P concentrations in soil pore waters in the literature, it is difficult to assess the actual Ca/P ratio in soil solutions.…”

Determining the optimal application rate of chicken manure for agricultural land through Phosphorus sorption-desorption analyses in Andisols of Wonokitri, East Java, Indonesia

“…P sorption kinetic analysis showed that the soil became saturated with P, thereby affecting the rate of P sorption, specifically at manure application rates above CM20. At higher treatments of CM20-CM40, the rate of P sorption decreased significantly, indicating that the sorption sites were saturated with P. According to Silva Rossi et al (2016), the history of fertilization or P addition significantly affected the rate of P sorption through the binding mechanism of the soil sorption site. Consequently, the rate of P sorption influenced the optimal timing of fertilization (Guppy et al, 2005).…”