ALBERT

Beschreibung: The objective of this study was to compare the effects of various pretreatments on the X-ray identification and quantification of clay-sized minerals from some podzolic B horizons. After soil samples were treated with H2O2 to remove organic matter, clay fractions were dispersed, separated, and freeze-dried. A portion of each clay sample was subjected to the following pretreatments: ultrasonic bath, extraction by citrate-dithionite, extraction by 0.5 N NaOH, and extraction by Tiron. Oriented slides were used for identification and quantification of clay minerals after each pretreatment. The X-ray patterns for ultrasonically dispersed samples were used as a basis for evaluating the effectiveness of the three chemical pretreatments. Tiron pretreatment was found to be the most suitable method for removal of amorphous material from clay separates of podzolic B horizons. The traditional citrate-dithionite method was not effective in removing amorphous Si from clays. The 0.5 N NaOH method is not recommended because it resulted in significant destruction of phyllosilicates and it was not effective in removing amorphous Fe.

Beschreibung: A single batch application of phosphorus once in several years might be a more economical practice for wheat production in Western Canada than the traditional annual application at seeding time. Annual phosphorus applications and batch applications once every 8 yr were compared. Response functions were estimated for annual applications for two locations in Saskatchewan and two in Manitoba. The response functions were used to determine the optimum application rates at each location. These optimums were compared with the profitability of the batch application to determine the economic optimum phosphorus application strategy. Three wheat/fertilizer price ratios were used in the analysis to examine the effect of changes in relative prices. The 100-kg batch application was economically preferred to annual applications for all three price ratios at three of the four locations. Only at Swift Current, Saskatchewan was the batch application not economically justified. The 100-kg batch application was economically superior to the 200-kg application at all locations studied.

Beschreibung: The effect of labile inorganic phosphate (Pi) status of the soil on the decomposition of added cellulose and on the immobilization, mineralization, and redistribution of native and added P in soils was studied in a greenhouse incubation experiment. Cellulose was added at 765 μg C∙g−1 soil with and without P (9 μg∙g−1 soil) every 30 days under adequate N, H2O, and constant tempreature to two soils of different available P status. Lack of P eventually slowed down decomposition of added C, but this effect was partially compensated for by increased mineralization of organic P (Po) forms. Added P was redistributed to both P, (58–69%) and Po (42–31%) forms; higher amounts of Po were found in the soil with the highest Pi status. The correlation between microbial P uptake and solution P values was significant, and microbial C:P ratios ranged from 12:1 under high available P conditions to 45:1 where P was in low supply.

Beschreibung: A theory is presented for the distribution of load pressures over the different phases in an unsaturated soil. It provides differential and integral relations between the equilibrium liquid pressure, the equilibrium solid pressure and the load pressure. Mechanical and thermodynamic models are presented by which the effective stress in unsaturated soils is defined. The value of the effective stress is then calculated for a certain state of a clay soil.

Beschreibung: It is becoming common for soil surveys to be made of the same area at different intensities and published at different scales. The principles of cartographic generalization are discussed that control the relationships between the map units and delineations on maps made from such surveys. A study of two sets of maps showed that almost no lines were coincident. Up to 20% of the small scale delinations could be ’inliers’ of different soils and about 15% of the large scale delineations would be outside their small scale equivalents. The same discrepancies are to be expected between large scale soil maps and the smaller scale maps of physiography or vegetation that are often used to stratify soils. Reasons for these discrepancies are discussed under the headings of simplification and classification. Recommendations arc made to guide the preparation of maps and legends for different intensities and scales of survey in the same area. These recommendations have practical implications for the planning of surveys and the designs of computer-based autocartography systems.

Beschreibung: The objectives of this study were to find ways to improve the accuracy of soil fertilizer recommendations by taking into account the variation in bulk density (BD) of organic soils. To achieve this end, field BD values of 30 organic soils (0.100–0.504 g/mL) were used to evaluate methods of measuring the BD in the laboratory by means of correlation and regression techniques. A simple and rapid procedure using the reconstituted BD of field-moist soils was the most accurate means of determining the average field BD in the laboratory, as indicated by the correlation coefficient obtained between the BD values obtained by this method and those in the field (r = 0.975**). The second most accurate method relied upon the exponential relationship between the water content of soils and their BD (R2 = 91.1 %). The least exact method of correcting for BD variations was to scoop a volume of dried (65 °C) and sieved (2-mm) soils, as is done in some soil test laboratories. Although the values obtained by this method were related (r = 0.502**) to the field data, drying caused shrinkage of soils, thereby increasing their BD about twofold. Soil pH (r = 0.716**) and percentage ash contents (r = 0.851**) were also related to the field BD of soils. These tests could be used to estimate the BD of soils when the preferred method cannot be used. Regression equations are provided for relating appropriate test values to the BD of organic soils.

Beschreibung: In a recent cooperative study, in which four laboratories participated, organic matter in a large number of Canadian soil samples was characterized by relatively simple methods. As result of this work we are proposing a procedure for the extraction, separation and characterization of soil organic matter. The procedure includes determinations of organic C and total N in initial soils, followed by the isolation from the soils of humic and fulvic acids. Total C and N and E4/E6 ratios are then determined in the latter fractions. From these data, proportions of extractable soil-C and soil-N and HA/FA ratios are computed.

Beschreibung: The objective of this study was to determine the magnitude of biologically immobilized and/or chemically fixed N (N retained) resulting from N addition to soils under laboratory conditions. Urea (200 μg N/g of soil) tagged with 21.0 atom % 15N was added to 11 Manitoba soils. The relationship between microbial immobilization and/or chemical fixation of added N and soil characteristics was determined using forward stepwise and multiple linear regression analyses. Three to 32 ppm of added N was immediately retained by the soils after urea was added. Biological immobilization and/or chemical fixation was virtually completed within the first 4 wk of incubation with only one soil showing continuous increase in the retention of applied N during the remainder of the experiment. Amounts of urea N retained in soils during the 12-wk incubation period ranged from 16 to 91 ppm. The initial retention of N was positively correlated with sand + silt fraction and negatively correlated the pH of the soil, the R2 value being 0.86**. Correlations between, 15N retained and organic matter (OM) content for 4 and 8 wk of incubation were positive (R2 = 0.40* and 0.53*, respectively). After the 12 wk of incubation, the retention of added N by soils was positively correlated with OM and negatively correlated with soil pH (R2 = 0.74**). The retention of N with pooled data of 4, 8 and 12 wk of incubation was positively correlated with OM and negatively correlated with both pH and CEC of the soils (R2 = 0.73**). Mineralization of soil N and retention of added N for 4, 8 and 12 wk of incubation were found to be positively correlated, the r2 values being 0.42*, 0.52* and 0.42*, respectively. Gaseous losses of applied N appeared to be appreciable in only one soil. Ten of the eleven soils showed no or little N interchange, suggesting that a significant proportion of the applied urea N appeared to be truly immobilized and/or fixed in soils.

Beschreibung: Rounding of the lands in a field involves changes in the surface horizons. The thickness of Ap horizons at various sites in corn fields varied from 15 to 41 cm. In these horizons, the organic matter content that ranged between 10 and 250 t/ha influenced the real density of the particles, the bulk density of soils with similar texture, and also the shape of the water retention curves at tensions from 0 to 1.5 MPa. Maximum available water in the Ap horizons between 33.3 kPa and 1.5 MPa varied from 0.5 to 4 cm H2O. Yield differences reached 74% while the standard deviations were generally lower than 15%. Higher yields were observed at higher, intermediate and lower sites of the fields. The differences in the yield were not entirely accounted for by the variations in the chemical and physical properties of the soils.

Beschreibung: A loamy soil amended with sewage sludges chemically treated with Ca(OH)2, Al2(SO4)3 or FeCl3 was used for P adsorption studies. Phosphate adsorption was increased by sludge application in the order: Ca-sludge 〉〉 Al-sludge = Fe-sludge 〉 untreated soil, and was associated wtih the increase in CaCO3 and hydrous iron and aluminum oxide countents resulting from sludge application.