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 Allison, L. E. Search for Related Content PubMed Articles by Allison, L. E. Agricola Articles by Allison, L. E.

A Study of Synthetic Aggregate Breakdown Using Logarithmic-Normal Distribution Analysis¹

ABSTRACT

A logarithmic-normal plot of the size distribution of water-stable aggregates has been recommended as a valuable method for studying the mechanism of soil aggregate stability. This system of analysis was applied to a 4-year study of VAMA-treated Pachappa loam soil from 4 field plots in which the initial exchangeable sodium levels varied from 3 to 47%.

The log-normal plotting method for expressing the persistence of soil conditioner effects indicates directly the annual changes in the geometric mean aggregate diameter and the changes in standard deviation for aggregate-size distributions about the mean.

The highest degree of aggregation, due to VAMA treatment, was produced in the presence of moderate to high exchangeable sodium. However, the high-sodium aggregates appeared to breakdown more rapidly than those produced in the presence of low-exchangeable sodium.

For aggregates stabilized with VAMA in field plots of Pachappa loam, it was found that, following treatment, the geometric mean diameter, M in mm., was related to the time, T in years, by the equation M = ae^-T/b, where a = M at T = O and b is the relaxation or time constant, i.e., the years required for M to decrease by 63%. For low exchangeable sodium, a = 2.57 mm. and b = 1.19 years. For moderate to high exchangeable sodium, a = 5.28 mm. and b = 0.88 year.

¹ Contribution from the U. S. Salinity Laboratory, Soil and Water Conservation Research Branch, A.R.S., U.S.D.A., Riverside, Calif., in cooperation with the 17 Western States and the Territory of Hawaii.

² Soil Scientist.

Received for publication July 23, 1955.