ALBERT

Description: Lepidocrocite occurred in B and C horizons of several poorly drained, acid soils; it was determined by X-ray diffraction, electron optical, and chemical dissolution methods. A comparison of X-ray diffraction results obtained by diffractometer, Debye-Scherrer and Guinier-de Wolff methods showed the latter method to be superior in providing the more distinct and complete evidence of lepidocrocite in soil clays. Dithionite-soluble aggregates commonly had a dumbbell-like shape characteristic of lepidocrocite but their electron diffraction patterns were similar to those of maghemite. This suggested the topotactic dehydroxylation of lepidocrocite in the electron microscope. Amounts of lepidocrocite estimated from X-ray diffraction intensities agreed fairly well (within 2.5%) with amounts calculated from iron dissolved by dithionite and oxalate treatments. Lepidocrocite concentrations in soil clays of 1–2% gave distinct X-ray diffraction evidence.

Description: Soil water properties were estimated in the field, using guidelines established in Canada, for five volcanic-derived soils in Tanzania. Many of the estimates for horizons near the surface were satisfactory but those for water retained at − 1500 kPa by horizons below a depth of 1 m were far too low. These low estimates combined with underestimates of air porosity at − 10 kPa for many of the samples resulted in very poor estimates of available water capacity. The guidelines were not directly applicable for estimating water properties of most of the soils studied. The samples had bulk densities of 0.9–1.3 Mg m−3, air porosities at − 10 kPa ranging from 3 to 27%, and available water capacities of 280–116 mm to depths of 140 cm or to a petrocalcic layer. X-ray analysis indicated weakly crystalline clays in all of the soils. Tiron extracted from 7 to 38% of the material from the

Description: The K release characteristics of surface samples from five Quebec soils were investigated. Each soil was fractionated by size into six separates. Each separate was extracted with 1 M ammonium acetate (NH4OAc), with 1 M nitric acid (HNO3) and with sodium tetraphenylboron (NaTPB) and the K extracted was determined. The clay separates contained most of the HNO3 and NaTPB-extractable K. The average amounts of K removed by 1 M HNO3 and NaTPB from the clay was up to 16 times more than that released from silt or sand fractions. The strong relationship between extractable K and clay content was probably due to the similarity in mineralogical composition and degree of weathering of these soils. Clay-sized chlorite and vermiculite were destroyed by the HNO3 extraction but not by the NaTPB extraction. Crop response to K fertilizer was generally reduced as clay content and extractable K increased. Key words: Extractable K, NaTPB-K, HNO3-K

Description: The mineralogical variability of the clays from the Ap and BCg horizons of 20 pedons in a delineation of Brandon soil near Ottawa was measured. The soil has level topography, is dominantly poorly drained, and has developed from marine clay during the past 8000 yr. Smectite, vermiculite and mica were the dominant clay minerals, whereas quartz, feldspars and amphiboles were generally present in smaller amounts. The coefficients of variation (CV) among pedons were generally less than 20% indicating that the lateral distribution of minerals in the clay was relatively uniform. This was supported by the low variability (CV of 10% or less) of the chemical properties of the clay, such as cation exchange capacities and K contents, which are generally related to clay mineralogy. There were more significant differences in clay mineralogy between Ap and BCg horizons. Differences appear to have resulted from pedogenic weathering. The clay from the Ap horizon contained a higher proportion of smectite and lower proportions of mica, albite and amphiboles. Presumably, some mica had expanded to form smectite and some primary mineral grains had weathered. Decreased total amounts of Na, K and Ca in the Ap clay also reflected this weathering. The lateral uniformity of the clay mineralogy was accounted for by the relatively uniform soil forming factors and processes in this map unit. The confidence limits for variations from means of mineral contents in replicated clays as well as other results indicate that the determination of spatial variability of clay mineralogy is limited by the precision of analytical methods for mineral quantification. Key words: Mineralogical variability, map delineation, Brandon soil

Description: Five Okanagan Valley soil series that had been in orchard for from 12 to 40 yr were studied to determine the effect of orchard practices on chemical and mineralogical soil properties. The soils were coarse-textured with relatively low organic C contents. Acidification produced by fertilization, irrigation and herbicide use had lowered soil pH values from between 5.0 and 6.0 in the alleys between the trees to about 3.0–3.5 near the trees and had greatly decreased permanent-charge cation exchange capacities, base saturation percentages, and ratios of exchangeable Ca/Mg, Ca/K, Mg/K. The pH-dependent or variable charge increased with organic C content and thus originated mainly from the organic matter of these coarse-textured soils. The proportional losses of exchangeable bases during acidification followed the order Ca 〉 Mg 〉 〉 K. Acidification had also released large quantities of plant-available Al and Mn. The soil clays from both the higher and lower pH sites were relatively poorly crystalline with X-ray amorphous constituents and mica as major components. Acidification appeared to have decreased mineral crystallinity as well, as indicated by consistently higher levels of extractable oxides of Si, Al and Fe in the clays from the acidified soils. These effects of orchard practices on chemical and mineralogical properties developed rapidly and were evident in one soil within 12 yr. Practical implications of these results for improving the management and fertility of orchard soils are discussed. Key words: Acidification, chemical and mineralogical changes, Okanagan soils, apple orchards

Description: Six soil profiles on a transect orthogonal to the Hudson Bay coast of Ontario are shown to be of increasing age from approximately 100 yr near the coast to 〉 5000 yr 70 km inland. The stages of Podzolic soil development from calcareous parent materials are documented. The Ah horizons required at least 750 yr to develop. The Ae-Bh horizon sequence required at least 1893 yr to form. The Ae-Bf horizon sequence required at least 2300 yr to develop. The depth of carbonate leaching and vermiculite formation in the A horizons are very closely correlated to soil age. Key words: Vermiculite, Podzolic B horizon, carbon dating, carbonate leaching

Description: Data for 22 samples from 17 pedons were analyzed for relationships of specific surface area and amounts and kinds of clay to coefficient of linear extensibility, as determined by the paste method (COLErod), and to free swelling index (FSI). The soils were divided into three main groups according to their clay mineralogy. The clay of the first group was micaceous, that of the second group kaolinitic, and that of the third group montmorillonitic. Both clay contents and specific surface areas of the combined first and second groups of soils were closely related to COLErod (r2 = 0.81 and r2 = 0.91) with specific surface area giving the higher correlation. The correlation of clay content with COLErod decreased markedly, however, when the montmorillonitic soils were included (r2 = 0.56). In contrast, the correlation of specific surface area with COLErod remained high (r2 = 0.97), indicating that for the soils used in this study, specific surface area was more basic with respect to shrink–swell potential than was clay content. Specific surface area was also highly correlated with FSI (r2 = 0.96) which was expected from the close relationship between COLErod and FSI (r2 = 0.95).

Description: Nine soil profiles from a 52-km-long transect orthogonal to the coast of Southern James Bay range in age from 1000 to 3000 yr. The depth of carbonate leaching, mass of vermiculite clay formation, profile organic matter and amorphous material (Fe, Al and Si) accumulation were determined. Rates of these pedogenetic processes were calculated, and compared to rates in a cooler, drier area on the Hudson Bay Coast. The rates are about twice as rapid in the southern James Bay area as in the Hudson Bay Coastal zone. These differences in rates are explained on the basis of mean annual temperature and precipitation. Key words: Vermiculite, carbonate leaching, rates of pedogenesis

Description: The X-ray diffraction (XRD) peak intensities of smectites in Chernozemic and related soils of Western Canada are generally low, in contrast to the high peak intensities of smectites in Podzolic soils of Eastern Canada and those of standard smectite samples. Consequently, X-ray quantitative analysis based on standard smectite samples may underestimate the amount of smectite and overestimate the amount of noncrystalline material in western Canadian soils. This study was undertaken to find the reasons for the weak XRD peak intensities of western soil smectites in terms of their purity and crystallinity. The Tiron dissolution method extracted only small amounts of noncrystalline material from the western soil clays and had little effect on XRD characteristics. The cation exchange capacity (CEC) hysteresis (or pH dependent CEC) between pH 3.5 and 11.0 of the western soil clays was also relatively small which confirmed the absence of significant amounts of noncrystalline material in these soil clays. Observed deviations of XRD positions from true basal spacings indicated that the western soil smectite particles were consistently thinner than the eastern soil smectite and Wyoming montmorillonite particles. Electron microscope observations supported these results. Because the diffraction intensity is proportional to the square of the particle thickness, the thinness of the western soil smectite particles appears to be a major factor in reducing their peak intensities. Thus, to obtain comparable peak intensity data from different soil smectites, particle thickness should be taken into account. Since it is often not practical to measure particle thickness, a procedure for quantifying smectite in soils that avoids this measurement is proposed. Key words: Peak intensity, crystallinity, particle size, particle thickness, Chernozemic smectite, Podzolic smectite