A STUDY OF METHODS FOR THE DETERMINATION OF THE AVAILABLE POTASSIUM OF SOILS

Publisher Website
Google Scholar
Abstract
11 soils from the glaciated part of Wisconsin were examined for avail-able K by means of pot expts., Neubauer tests, and chemical solvents, which included water, citric acid, steam, and n NH4LC1 solution. No consistent relationship between available K as indicated by the different methods was discovered, though in most cases the Neubauer tests and the leaching tests with n NH4Cl gave results in accordance with both pot and field responses to fertilizer. Successive teachings with NH4Cl were more effective than a single extraction. It appeared that in all the soils studied, the K compounds reacted with n NILCl at about the same rate, so that the reaction can be expressed by the laws of heterogeneous equilibrium, thus: dx/dv = K(A [long dash]x) where A is the total K dissolved through leaching, and x is the amount dissolved in a certain volume[long dash]v of leachate. The value of K for different soils varied from 20.02 [image] 10-4 to 25.06 [image] 10-4 over the range of greatest solubility. Integration and substitution of suitable values enables one to eliminate the long leaching processes, by calculation of the total replaceable K from the values ob-tained from the 1st leachate. The total replaceable K was roughly 3 times the amount obtained in the 1st leachate. The results indicate that there is a certain exchange complex of similar composition in all soils which is involved in the determination of the amount of K that is available to plants. For soils of the humid regions, the exchangeable K is believed to be the available K.
Keywords

This publication has 1 reference indexed in Scilit: