HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Avellaneda, M. O. Articles by Jauregui, M. A. Search for Related Content PubMed Articles by Avellaneda, M. O. Articles by Jauregui, M. A. Agricola Articles by Avellaneda, M. O. Articles by Jauregui, M. A.

Comparing Potassium Soil Tests with a Flexible Function and a Modifier Variable

Fac. de Ciencias Agrarias, Univ. Nacional de Cuyo, Almirante Brown 500, 5505-Chacras de Coria, Mendoza, Argentina

Mario A. Jauregui^*

PRODETEC FINNIDA, NICABOX 115, P.O. Box 52-7444, Miami, FL 33152-7444

*Corresponding author.

ABSTRACT

Selecting the appropriate functional form and using modifier variables are key issues in soil test calibration. Flexible functions capture all the information conveyed by the data, except for stochastic aberrations of local maxima, minima, and inflexion points. The objective of this study was to show that a flexible function can be used for comparing soil tests including the sediment volume (SV) as a modifier variable. Data used in this test were collected from 30 irrigated Torrifluvents in which K availability had been evaluated with the Neubauer method. The dependent variable was total K uptake by ryegrass (Lolium perenne L.). Independent soil K variables corresponded to seven soil test methods: NH₄OAc-exchangeable K; HNO₃-extractable K; H₂CO₃-extractable K; soluble K; resin-extractable K; K potential; and K adsorption ratio. The modifier variable, SV, is a quick, inexpensive, and fairly accurate attribute widely used in western Argentina to appraise soil texture. Data were evaluated using the generalized Cobb-Douglas (GCD) function. Explanation of variability in K uptake using the GCD model, with exchangeable K and SV as independent variables, was highly satisfactory (R² = 0.88). The other six methods of soil testing gave R² values from 0.55 to 0.76. Contribution of SV as a modifier for the interpretation of K availability was significant ( < 0.01) for all soil K indices. The GCD function captured a positive interaction between the independent variables. This indicates that the higher K buffering capacity of the finer textured soils was an overriding factor that favored K absorption by plants.

Received for publication December 21, 1993.