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Landsat multispectral scanner data for Brazos County, Texas, were evaluated in terms of effectiveness for classifying soils on vegetated landscapes at three times during the year: a time of normally adequate soil water, a time of expected soil water deficit, and a time when soil water is normally being replenished. Six test sites were used to evaluate LARSYS supervised and unsupervised classification of vegetated soil landscapes. Open grassland soils were best separated in the fall during a period when soil moisture was being replenished after the summer period of soil water deficit. Woodland soils were separated by Landsat data in late spring when adequate moisture was available. However, a high degree of accuracy was not achieved using Landsat for separating soil map units. Accurate separation of soil mapping units on vegetated landscapes was not possible during late summer when soil water was deficient. Selected soil properties important to plant growth were separable on the test sites using June and October Landsat data. Particle size and soil moisture regime were separated at both dates. Soils with argillic horizons were separated from soils without argillic horizons.

Interfingering of albic material into the upper part of argillic horizons in Udalfs of New York is interpreted as evidence of degradation by loss of clay proceeding from the top of the horizon downward and from the surfaces of peds inward. These conclusions are based on: (i) albic material lacking oriented clay surrounding ped centers that contain oriented clay; (ii) the volume of albic material decreasing with depth; and (iii) the albic interfingering being least in soils in which high carbonate content is believed to have delayed clay translocation or weathering. The absence of clay skins in the degrading zone—in contrast with thick clay skins rich in fine clay at the Bt‐C horizon boundary—suggests that part of the clay removed at the top is translocated to the bottom of the B horizon. Smaller amounts of inherited mica clays and larger amounts of vermiculite, intergradient clays, and amorphous material in the clay fractions of degraded zones than in the remainder of B horizons indicates some weathering, but losses by this mechanism are believed small.

Mineralogical analyses of samples from 16 surface soil horizons and 9 subsoil horizons, representing 15 soil series, revealed that differences in the content of clay sized mica were closely related to the wide differences in the content of exchangeable K in ovendried samples before and after cropping. The specific surface of mica in the clay fraction was significantly correlated with the content of exchangeable K in oven‐dried samples before cropping (r= 0.63), after cropping (r= 0.74), and after fertilization and cropping (r= 0.68). After being cropped and oven dried, for example, a sample of Wabash silt loam surface soil contained 466 pp2m exchangeable K, but a sample of Bates silt loam surface soil contained only 78 pp2m exchangeable K. These samples had 3.3 m2/g and 0.5 m2/g, respectively, of mica specific surface area. No significant relationship occurred between the content of exchangeable K in field moist samples and the content of mica in the soils. The wedge‐zone concept of mica weathering in crystal edges and in crystallographic (hk0) fractures normal to (001) crystal faces was used to explain the relationships between specific surface of mica and content of exchangeable K in oven‐dried samples. The existence of an equilibrium between exchangeable K in the open part of the wedge with nonexchangeable K at the mica weathering side of the wedge was indicated.

Some physical, chemical, and mineralogical properties of compacted and adjacent soil layers, which were selected from cultivated and virgin Willacy fine sandy loam soils in the lower Rio Grande Valley of Texas, were studied to attain a better understanding of the compacted zone and its development. Hydraulic conductivity measurements and field studies substantiated the presence of a hardpan layer, which was first encountered at a depth of 3½ to 7 inches and ranged to a depth of 7½ to 12 inches, at each of the five sites sampled. Clay content increased with depth, while sand content decreased. The fine (0.25 to 0.1 mm.) and very fine sand (0.1 to 0.05 mm.) fractions, for all samples, comprised at least 95% of the total sand and more than 60% of the total soil. Soil reaction (pH), organic matter content, cation‐exchange capacity, exchangeable cations, and extractable silica, aluminum, and iron were determined. Extractable cementing materials were not found in important quantities in any of the layers. Mineralogical analyses of the samples showed that quartz and lesser amounts of feldspar composed the sand and silt fractions, while illite and poorly ordered, weathered micaceous materials dominated the clay fraction. No pronounced differences in the chemical and mineralogical properties of the hardpan layers as compared to the layers above and below the hardpan were found.