Cation-exchange properties of some acid soils of california

does not appear. First page follows. Most soil acidification experiments are conducted in laboratory or greenhouse over short periods of time, and there is always some uncertainty concerning the application of the data to the field where soils are acidified over a much longer period. Thus, the data presented in this report, part of a study of acid soil samples from the field, provide a background against which to compare the results of short-term experiments. This report is not intended to be a complete survey of acid soils of California because too few samples have been included. But there are a sufficient number to provide a wide range in such properties as clay and organic C content, cation-exchange capacity (CEC), clay mineral content and pH. The samples also represent a variety of acid soils found in central and southern California. (Cole (1949))4 reported the acidity and alkalinity of soils of California that had been previously surveyed. Soil Samples Data on county location, pH, clay and organic C contents of 31 samples are presented in table 1. The clay content was measured by a pipette method and the organic C by a modified Walkley-Black method (Pratt et al. 1957). With the exception of samples 27, 29 and 31, all were taken from the surface soil of cultivated fields or from the A1 horizon of undisturbed soils. Samples 27, 29 and 31 were taken from the horizon immediately below the plow layer of the same soils as samples 26, 28 and 30, respectively. All samples were air-dried and then ground to pass a 2 mm screen. Subsamples ground to pass a 60-mesh screen were used where small portions were taken for analysis. Sixteen of the samples were taken from central California and fifteen came from Kern and San Diego counties. Data on the relative abundance of various minerals in the clay fractions of a number of soils are presented in table 2. The clay in twelve of these samples was dominantly illite and montmorillonite, and in seven samples there were mixtures, with montmorillonite constituting only a small portion.