The efficiency and balance of nitrogen from one year's application was studied in a long-term fertigation experiment. Enriched nitrogen fertilizer, K~SNO3, was applied to a 22-year-old Shamouti orange tree with a history of high N applications (N3) and to an N-starved tree (N I ). The distribution of N in the different parts of the trees and in the soil was determined after the experimental trees were excavated.Similar total recovery of the labeled fertilizer N was found in the trees and soil in both treatments (N~ -61.7% N 3 -56%). However, the distribution between tree and soil was different. The amount of recovered residual fertilizer in the soil was much larger in the N 3 treatment than in N~.The highest percentage of fertilizer N was found in the new organs, i.e. fruits, twigs and leaves. The roots and branches took up only 6-14% from the labeled fertilizer.Only 20.9% of the leaf N and 23.4% of the fruit N in the N 3 tree originated in the labeled fertilizer, indicating translocation of N from older parts of the tree to new growth.Evidence was found of storage of N in the wooded branches, while the roots contained a surprisingly small part of labeled fertilizer.
The study of ion‐exchange kinetics on soils and soil constituents has attracted much interest throughout the last decade. The introduction of a stirred‐flow method to study these reactions, as well as other adsorption‐desorption phenomena, has stimulated this interest. However, the manner in which rate data are interpreted using this technique and other flow methods has been questioned. Accordingly, a numerical solution for various instantaneous equilibrium and kinetic models is presented. It was found that rate data that could be described using an instantaneous equilibrium model could also be interpreted using a kinetic model. Therefore, the validity of kinetic rate coefficients obtained by flow methods is questionable. An analytical approach was developed to outline experimental methods that could be used to distinguish between instantaneous equilibrium and time‐dependent reactions and to differentiate between solution‐concentration‐dependent kinetic models vs. those that are independent of solution concentration. By using this approach, and employing various flow rates and influent concentrations, as well as using a stopped‐flow technique, it is easy to decide whether rates of reactions can be measured using the stirred‐flow method for specific experimental conditions.
The rate of release of K and structural cations from three micas (biotite, phlogopite, and muscovite) was measured in two‐particle size ranges (5 – 20µm and 20 – 50µm), in dilute electrolyte solutions (0.001N), and at pH 3.0 and 7.0. The rate of K release from phlogopite and biotite was similar to the rate of release of structural cations under acidic conditions and significantly higher under neutral conditions. These findings indicate that structural decomposition of phlogopite and biotite is dominant in acidic conditions, and that the role of interdiffusion increases in neutral conditions. Decomposition was more sensitive than interdiffusion to particle size.The rate of K‐release from muscovite was about 5 and 15% that from biotite and phlogopite, respectively. The rate of K release from muscovite was higher than the rate of Al release. This indicates that muscovite is the most stable of the three micas and that the decomposition mechanism for K‐release in muscovite was less important.
Simultaneous K exchange with Ca, Mg, and Na occurs in soils, but most of the published information is obtained from binary systems. The theoretical question of whether selectivity coefficients obtained in binary systems are valid for ternary systems has not yet been clarified; however, no significant difference has been found between selectivity coefficients in binary and ternary systems. Potassium exchange with Mg plus Ca was studied in two calcareous soils with variable concentrations of Na, using batch and miscible-displacement methods. Preference for K over the divalent cations was found in both soils, regardless of Na concentration and the experimental methods. Modified Gapon (k c) and Vanselow (ft v) selectivity coefficients were calculated for each cation pair in binary and ternary systems. In both soils, the k v and the k c decreased with increasing K fraction in the solution, but the k G value was less affected than the k v. A simple mathematical solution of the Gapon binary equations, K-(Mg + Ca) and Na-(Mg + Ca), in combination with an assumption of constant cation-exchange capacity (CEC), was used to predict the amount of exchangeable K as a function of solution composition in a ternary system. The high correlation of predicted exchangeable K with the directly measured values shows that binary selectivity coefficients can be used in multicationic systems on calcareous montmorillonitic soils. "DOTASSIUM EXCHANGE REACTIONS with each of the A cations Ca, Mg, or Na on clay minerals and soils have been investigated intensively (Bolt, 1979; Sparks and Huang, 1985). Irrigation water, especially sewage effluents and brackish waters, may contain considerable quantities of Na, K, Ca, and Mg. These cations undergo simultaneous exchange reactions with each other on soil surfaces. The possible reactions involving K-Ca-Mg, K-Na-Ca, and K-Na-Mg in soils and the study of their effect on K distribution between the solution and the solid phases is extremely important in plant nutrition. Theoretical understanding of the relationship between ternary and binary exchange systems in clays and soils has been enhanced in the last decade. Chemical and geochemical models were adapted to soils for predicting cation exchange in a ternary system using binary-exchange data (Elprince and Babcock, 1975; Elprince et al, 1980). Chu and Sposito (1981), using data obtained from experiments with pure clays and with careful analytical methods, found that the effect of ternary systems on binary-exchange coefficients was not greater than experimental error. In subsequent studies on ternary cation exchange on clay minerals and soils, Sposito and others (
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.