ALBERT

Beschreibung: In a previous study a nitrogen mineralization model was developed by combining the potentially mineralizable nitrogen (No) with functions representing the effect of temperature and soil moisture on the mineralization rate constant (k). The model performed well in predicting the amount of net nitrogen mineralized during a growing season when soil was incubated in plastic bags placed in incubators or buried in the field. In the present study a similar model was used to estimate net nitrogen mineralized in situ from Wood Mountain loam an Orthic Brown soil at Swift Current, Saskatchewan under (a) summerfallow, (b) cropped-dryland and (c) cropped-irrigated conditions. Model output showed good agreement to field measurements especially for the first 45–60 d, but thereafter tended to underestimate the measured data particularly under cropped-dryland conditions. During a growing season the cropped-irrigated system predicted 69 kg ha−1 net nitrogen mineralized, but 81 kg ha−1 was measured; the corresponding values for summerfallow were 64 and 86 kg ha−1, and for cropped-dryland 36 and 52 kg ha−1, respectively. The model is not dynamic since it does not allow for No to be replenished continuously by nitrogen derived from decomposition of fresh residues and rhizosphere microbial biomass. Net nitrogen mineralized from this source might explain at least part of the underestimate predicted by the model. Other sources of possible discrepancy could be imprecision in measuring the mineralization of nitrogen and in estimating the parameters in the model. Nonetheless, it was established that one of the main shortcomings of the model was that it underestimated the amount of nitrogen mineralized whenever the soil became very dry and was then rewetted by rainfall. This was probably because the latter process resulted in large flushes in mineral nitrogen in situ while in the laboratory estimate of No and k, this effect is not adequately simulated. Key words: Q10, No, N mineralization, rate constant, temperature function

Beschreibung: The influence of tillage on net nitrogen mineralization out of sod for two toposequences was estimated by several different methods. A field procedure utilizing small rain shelters to prevent leaching was employed to measure N mineralized in no-tillage (NT) and plowed (CT) treatments for six soils. Potentially mineralizable N and autoclavable N were also determined. An intact soil core procedure was developed to measure N mineralization. With the field procedure, mineralized N was generally greater in the well-drained soils but decreased with decreasing drainage. There was a highly significant interaction between soil type and tillage with greater amounts of N mineralized in the plowed well-drained soils but less in the poorly drained soils when compared to the corresponding no-tillage treatment. The standard laboratory estimates were able to predict differences between soils but did not predict the tillage effect. The development of a laboratory intact core procedure allowed for simulation of tillage effects and was correlated to the field estimates (r = 0.76). More importantly, the tillage ratios for mineralized N (NT:CT), which varied from 1.38 to 0.43, were reasonably correlated (r = 0.73) between the field and intact core procedures. Key words: Mineralized N methods, no-tillage, moldboard plow tillage, intact cores

Beschreibung: A survey of the DTPA-extractable Cu levels of approximately 1000 fields representing a large number of soil types in Saskatchewan suggested that, under current cropping systems, Cu deficiencies appear to be concentrated in the Grey Soil Zone. They are especially probable in seven soil associations, which include light Transition of Grey and Brownish-Grey Podzolic soils. Soil criteria for detecting Cu deficiencies in cereal crops cannot be fully documented using conventional calibration tests and techniques. However, data from 21 field trials and a growth chamber study indicated that the critical level of DTPA-extractable Cu in these soils is approximately 0.4 mg∙kg−1 for cereals. Large spatial variability of DTPA-extractable Cu levels has been found to occur in a level field, thus suggesting that the Cu status of a field may not be adequately described by assessing the Cu levels of composite field samples. Key words: DTPA-extractable Cu, soil survey, critical level, spatial variability

Beschreibung: The objective of this study was to compare several methods of estimating the availability of soil nitrogen to plants. Total soil N, organic matter content, mineralized N during a 2 wk incubation at 35 °C, organic N in 6 N HC1, 0.01 M NaHCO3 and 1 N KCl extracts, and finally mineral N extracted by 2 N KCl were evaluated and contrasted with N uptake by sugar beets cultivated on 19 soils in a greenhouse experiment. The relative yield or plant N uptake gave the highest correlation coefficients when both mineral and organic N fractions in soil extract were considered. The incubation methods gave the best correlation coefficient with relative yield (R2 = 0.85**). N contents in NaHCO3 extract were more correlated with relative yield or N uptake than total N, organic matter contents or N extracted by 6 N HCl or 1 N KCl. The UV absorbance values obtained at 205 nm with 0.01 M NaHCO3 extract were also well correlated with relative yield (R2 = 0.78**) and plant N uptake (R2 = 0.66**). At this wavelength, as well as at 220 nm, the absorbance was affected by mineral and organic N contents in the extract. However, at 260 nm, the UV absorbance was only related to organic N in the extract; consequently these absorbance values were less correlated with relative yield (R2 = 0.49**) or N uptake (R2 = 0.27*). Furthermore, the absorbance measured at 205 nm was too sensitive to NO3-N and organic N concentration and this relationship was not linear in the high-N concentration range. The UV absorbance at 220 nm in the 0.01M NaHCO3 extract seemed to be a promising method to evaluate the availability of soil N. Key words: Soil nitrogen, incubation, ultraviolet absorbance, hydrolyzable nitrogen

Beschreibung: A 7-yr study was conducted to determine the effects of repeated annual applications of manure containing softwood shavings (M + S) at 50 t ha−1 on the soil and its productivity, relative to manure without shavings (M) at 50 t ha−1 and nitrogen fertilizer (F) at 67 kg ha−1. The EC, OM, total N and C:N ratio of the soil of the M + S and M + S + F plots to 60-cm depth were not significantly greater than those from the M plots, and in some instances they were significantly less. The NO3-N and total N and available P contents of the soil from the M + S treatment were significantly lower than those from the M treatment. Immobilization of N in the M + S and M + S + F treatments was indicated. Barley (Hordeum vulgare L. 'Gait') straw and grain yields and protein content of the grain were generally greater under the M than under the M + S treatment. When N fertilizer was included in the M + S treatment (M + S + F) the yields were similar to those of M, and the protein content increased. If manure with shavings is used for fertilizer, supplemental N should be applied to offset N immobilization. Key words: Manure disposal, manure, manure with wood shavings, nitrogen, crop yields

Beschreibung: The thermal stability and acidic characteristics of Al interlayered montmorillonite were affected by citric acid which was present during its formation. Perturbation to the formation of Al interlayers by citric acid resulted in more gradual loss of their structural water in the 430 °C to 520 °C region at initial citric acid/Al molar ratios of 0.1 and 0.5. The data clearly reveal that, besides hydroxy-Al polymers, hydroxy-Al-citrate complexes adsorbed on the surfaces of montmorillonite very substantially contribute to the total and third buffer range titratable acidity of the clay. Key words: Hydroxy-Al-citrate interlayers, smectite, organic acid, DTA, third buffer range, organic carbon

Beschreibung: To investigate the content of amorphous forms of Fe, Al and Si in podzolic soils, the B horizons from 54 Humo-Ferric Podzols and 24 Eluviated Dystric Brunisols were sampled in northern Ontario. Dithionite-citrate-bicarbonate (DCB) Fed and Ald, acid NH4-oxalate Feo, Alo and Sio, Na-pyrophosphate Fep, Alp and Cp and NaOH-tetraborate Fet and Alt were determined on all samples. Feo/Fed ratios averaged 0.87 and suggested that most of the extractable Fe was amorphous. Inorganically bound Fe and Al in pyrophosphate extracts were estimated by addition of NH4OH to the extracts. The amount of inorganically bound Fe, expressed as a percentage of that extracted by DCB, was calculated at 79 ± 23%, whereas the corresponding value for Al was 61 ± 20%. (Alo-Alp)/Sio atomic ratios, plus linear correlation analysis of (Alo-Alp) against Sio, suggested the presence of amorphous aluminosilicates with Al/Si ratios approaching 3. (Feorg + Alorg)/Cp ratios averaged 0.10, a figure near the value suggested by other authors for the maximum amount of Fe and Al bound to organic matter. (Cp/(Fep + Alp) atomic ratios did not appear to be useful in differentiating Podzolic from Brunisolic soils. Key words: Podzolic soils, chemical criteria, extractants

Beschreibung: Subsoil moisture accumulation due to cultivation and particularly summerfallowing is considered as an important causative agent of dryland salinity. However, few studies have been conducted to quantify the magnitude of this accumulation. The amount of additional moisture that had accumulated under cultivated land as compared to adjacent native prairie was determined at two sites in Southern Alberta. In comparison to noncultivated sites, a total of 74.0 cm of additional moisture was found under the cultivated area of a Dark Brown Chernozem and 36.2 cm under a Brown Chernozem to a depth of 6 m. Only relatively insignificant changes in salt content were found. Key words: Dryland salinity, soil moisture, soluble salts

Beschreibung: Repeated freezing and thawing of glacial till cores of clay loam texture results in the formation of granic and metafragmic microfabrics. These units of fabric are best developed near the surface of cores kept at moisture levels between field capacity and saturation. Well-sorted lacustrine sediments with fewer voids tend to form banded fabrics. Many of the morphological features such as vesicles, metavughs and desiccation cracks commonly attributed to freeze-thaw processes are evident in all materials tested. Discrete units of fabric observed in this study are very similar to units of fabric observed in the Ah horizons of Black Chernozemic and Cryosolic soils. Results of this investigation strongly support earlier research which suggests that frost processes are major contributors to their microstructural development. Key words: Granic, freeze-thaw, microfabrics

Beschreibung: Response of spring wheat (Triticum aestivum) to varied amounts of broadcast and band-applied phosphorus (P) was examined at soil temperatures of 10, 15, 20 and 25 °C. The research emphasized the response of shoot yields with time and the root proliferation in the band-applied P. A non-destructive technique to measure growth with time was developed. This method allowed interpretation of plant responses even though the temperature treatments markedly changed the rate of physiological development. The relative plant-shoot response to P application did not change with time or developmental stage in this experiment. There was a marked effect of temperature on plant response to band-applied P. Band application was more efficient than broadcast P at 10 °C soil temperature, but less efficient at 25 °C soil temperature. Root proliferation in the fertilizer band was significantly different from the control soil-zone only at 10 °C and was not diminished by concurrent application of broadcast P. The efficiency of band application was confirmed with 32P labelling of the banded P. Banded P accounted for more of the total plant P at lower soil temperatures than at higher soil temperatures, regardless of concurrent application of broadcast P. Temperature had little effect on yield response to broadcast P at the final sampling or throughout the growth period. Tissue P concentrations decreased with increases in temperature and with time. Key words: Temperature, root proliferation, band, broadcast, phosphorus

Beschreibung: Identification of nutritional disorders in crops growing on saline soils may facilitate the development of breeding or agronomic practices that improve yields in saline areas. An investigation was conducted under controlled environment conditions to identify possible cation deficiencies in barley (Hordeum vulgare 'Gait') grown under sulfate-dominated salinity stress. Soil was artificially salinized to produce a factorial of five salinity levels (ranging from approximately 6.5 to 17.5 dS m−1) and five salt types containing various ratios of Na:Mg:Ca. A control treatment (3.1 dS m−1) was also included. Barley was grown for 75 d and harvested for analysis of dry matter yield and tissue composition. Yield response of barley to salinity stress was not differentially affected by the type of salt used in salinization. Concentrations of sodium and magnesium in the plant tissue were generally increased by salinity stress, but these accumulations did not restrict yield since no consistent relationship was found between the concentrations of these cations and barley yield. Potassium concentration in the plants was inversely related to level of soil salinity, apparently because of an antagonistic effect of sodium, but was not consistently related to barley dry matter yield. Calcium uptake was also suppressed by soil salinity. In contrast to the results observed for other cations, a very strong relationship indicative of a yield response curve was observed between yield and calcium concentration in the plant tissue, particularly when the latter was expressed as a ratio of total cation concentration (R2 = 0.94). Furthermore, calcium concentration in the plant tissue and estimated calcium activity in the soil solution in highly salinized treatments were well below those considered adequate. These results suggest that calcium deficiency may have played an important role in restricting yield under salinity stress. The apparent calcium deficiency induced by salinity stress was attributed to reduced activity of calcium in the soil solution because of precipitation with sulfate and high ionic strength. Key words: Calcium, magnesium, potassium, sodium, salinity

Beschreibung: Quantification of calcium carbonates in a light-colored matrix or disseminated calcium carbonates cannot be obtained directly from impregnated blocks by image analysis. A method that combined staining by alizarin red-S with digital image analysis made it possible to identify and quantify soil calcium carbonates including the disseminated form in thin sections. Best results were obtained under reflected light using a tungsten lamp source. Photographic filters did not improve the image quality of stained calcium carbonates. Key words: Image analysis, soil micromorphometry

Beschreibung: Soil water retention data, predicted from texture, organic carbon content and bulk densities, were compared to measured values. Although significant correlations were obtained, the differences between predicted and measured water contents were large, especially at high potentials, and suggest that extreme caution must be exercised in employing the models under conditions other than those for which they were developed. Key words: Soil water retention, modelling, texture

Beschreibung: Although corn (Zea mays L.) stalks contribute to the total quantity of organic material in soil, their direct influence on soil structural stabilization may be small. In a laboratory study 14C-labelled corn stalks were placed on the surface of, or buried at, a 5-cm depth in a sandy loam soil. The soils were incubated at 25 °C for 119 d to determine the extent of organic carbon redistribution. Approximately 70% of the buried stalk carbon and 90% of the surface stalk carbon remained in the soil after incubation. Most of the residual carbon was identifiable as stalk tissue. Less than 5% of the added carbon was intermixed with the soil. Both the lack of C redistribution in the soil and the high loss of the mineralized 14C as CO2 stress the importance of the initial distribution of added organic materials in soils. The results imply that corn stover is a poor source of soil C and that it would be best used as a surface protectant against raindrop impact. Key words: Carbon mineralization, carbon redistribution, corn stalks, soil structure

Beschreibung: Wheat (Triticum aestivum L.) was grown in rotation with maize (Zea mays L.) and soybeans (Glycine max L.) as first crops at the National Irrigation Research Station, Nanga, Zambia. Two nodulating soybean cultivars used in the first season of the rotation were compared for their ability to support symbiotic N2 fixation by Bradyrhizobium japonicum using a nonnodulating cultivar as a reference crop and the 15N isotope dilution technique. All first crops received two levels of P (0 or 30 kg P ha−1). The legumes received a blanket application of 20 kg N ha−1, whereas maize received two rates of N (20 and 60 kg N ha−1). There were no benefits of residual P from the first crops to the succeeding wheat. However, the yields of wheat grown on plots where fixing legumes had been grown the previous season were significantly higher than those where maize had preceded. The superior wheat yield in the soybean-wheat rotation over the maize-wheat rotation was attributed to residual N from biological N2 fixation by the preceding legume crop. The benefits were greater when the lower yielding soybean cultivar preceded wheat in the rotation presumably due to its lower soil N demand. Key words: 15N isotope dilution, B. japonicum, N fixation, residual P, residual N, crop rotation

Beschreibung: A good statistical relationship was obtained between the exchangeable-sodium ratio and the sodium adsorption ratio (SAR) in Brown Solonetzic and associated soils in southern Alberta. Reliable estimates of the exchangeable-sodium status of these sulfate-rich soils may be anticipated when SAR values are less than 20. Prediction of the exchangeable-sodium status of soils on the basis of SAR values is preferable for both Solonetzic soil and irrigation suitability classification. A saturation extract SAR value of five in the B horizon generally corresponds to an exchangeable calcium to sodium ratio of 10. Saturation extract SAR values of five and 12 are recommended as revised soil chemical criteria for Brown Solonetzic soil and irrigation suitability classification, respectively. Key words: Solonetzic soils, exchangeable cations, sodium adsorption ratio, selectivity coefficient, irrigation suitability

Beschreibung: The 0–5 cm depth from Ap horizons of Orthic Brown, Dark Brown and Black Chernozemic soils when recently brought under cultivation, and of unfertilized Dark Brown Chernozemic soils under continuous wheat and a wheat-fallow rotation since 1912 were sampled in early May 1984. The samples were separated into 500- to 1000-μm, 250- to 500-μm, 100- to 250-μm, and

Beschreibung: K deficiency was identified for the first time in British Columbia orchard soils. Greenhouse-grown apple seedlings responded to K in soils low in available K. MacSpur McIntosh (Malus domestica Borkh.) had increased leaf K (above deficiency) and improved initial fruiting after surface applications of KCl in an orchard with low soil K. Key words: Potassium deficiency, apple, leaf and soil potassium

Beschreibung: Field and growth chamber experiments were conducted to evaluate the short-term effects of selected crops on macro-aggregation of a Kamouraska clay soil. Under field conditions, the growth of barley (Hordeum vulgare L.) and alfalfa (Medicago sativa L.) for up to 2 yr resulted in increased macro-aggregate size and stability compared to a fallow control and to initial conditions. Under these two crops, the proportion of water-stable aggregates of the 2- to 6-mm fraction increased from 25% in May 1986 to 40% in September 1987 at the expense of the 0.25- to 1.0-mm fraction which decreased from 37% to 19% over the same period. Macro-aggregation after 2 yr was not different in corn (Zea mays L.) and fallow control. Seasonal variations in aggregate stability were significant but small and less important than the effects of cropping treatments. Results of the growth chamber experiment agreed with those obtained under field conditions suggesting that controlled environment experiments can be used to model cropping effects on the aggregation of this soil. Key words: Aggregation, soil structure, clay soil, corn, barley, alfalfa

Beschreibung: Growth chamber experiments were conducted to investigate the effect of size of fertilizer reaction zone, rate of added zinc and method of placement of added zinc on the dry matter yield, zinc concentration and zinc uptake of blackbeans grown on a calcareous soil. Relationships between zinc concentrations in the plant, zinc utilization by the plant and zinc concentration in the soil reaction zone were obtained. An equation was developed relating zinc utilization to zinc concentration in the fertilizer band, and a figure was derived showing how increasing the size of the fertilizer zone impacts upon the zinc concentration of the plant. The results indicate that inorganic zinc fertilizers must be mixed as uniformly as possible for maximum effectiveness. Key words: Zinc, placement, calcareous, soil, blackbean, Phaseolis vulgaris

Beschreibung: The importance of microrelief in relation to mass loss was studied in a Minnesota ombrotrophic forested peatland. Litter and paper strips placed in hummocks for 1 yr lost significantly more mass (two and three times, respectively) than similar material placed in hollows. Less favorable environmental conditions for decomposition, especially lower temperature, reduced decomposition in the hollows. Key words: Peatlands, ombrotrophic, decomposition, Histosols

Beschreibung: The objective of this study was to evaluate different available P extracting methods in relation with soil properties, oat yield and plant P uptake. Six chemical extractants (Bray-1, Bray-2, new Mehlich, North Carolina DA-4, DA-10, and Olsen) and two anion exchange resins (F− and HCO3−) were compared on 42 acid soils. The DA-4, DA-10, new Mehlich, and HCO3− resin methods showed the best correlation with oat yield and plant P uptake. The Bray-1, Bray-2 methods were significantly less correlated than the other methods. The HCO3− resin was better than F− resin to predict plant P uptake and yield. Available P levels as determined by these eight methods were classified poor, medium and rich by the Cate and Nelson procedure. Oxalate extractable Al, pH (NaF), pH (H2O), exchangeable (Ca + Mg), forms of P, maximum P fixation capacity and soil texture have great influence on the plant P uptake. Soil organic matter content and oxalate-extractable Fe had significantly less important an effect. The Bray-1 and Bray-2 methods were the most affected by soil properties especially oxalate-extractable Al. The P-HCl/P-DAF ratio proposed by Mehlich to identify forms of soil P indicated that seven soils contain predominantly Ca-P and 21 soils with predominantly Al-P and Fe-P. This ratio was related with oxalate extractable Al (r = − 0.32*), pH NaF (r = − 0.59**), pH H2O (r = 0.52**) and exchangeable Ca + Mg (r = 0.55**). The maximum P fixation capacity (M) ranged from 150 to 4200 μg P/g soil and was closely related with oxalate-extractable Al (r = 0.81**), pH NaF (r = 0.74**), pH H2O (r = − 0.36*) and Mehlich ratio (r = − 0.33*). The maximum P buffering capacity (Mb) of soils was also measured and showed the best correlation with oxalate-extractable Al (r = 0.84**) and pH NaF (r = 0.53**). Key words: Soil testing, available P, anion exchange resins, P fixation, oxalate-Al, forms of P

Beschreibung: The influence of birnessite (δ-MnO2) on the precipitation products of iron was studied, in the FeCl2-NH4OH system at different Mn/Fe molar ratios (0, 0.01, 0.1 and 1.0) and in the acidic pH (4.0, 5.0 and 6.0) range, by X-ray, TEM, IR and chemical analyses. The precipitation products formed at pH 5.0 and 6.0 were found to be lepidocrocite (γ-FeOOH) in the absence of birnessite. Birnessite promoted increased precipitation of Fe oxide; the oxidation of Fe(II) by MnO2 was thermodynamically feasible and was confirmed by the presence of Mn(II) in the solution by ESR data. Birnessite also influenced the crystallization processes of hydrolytic products of Fe which range from lepidocrocite through goethite (α-FeOOH), akaganeite (β-FeOOH), to X-ray noncrystalline Fe oxides. The noncrystalline Fe oxides formed at a Mn/Fe molar ratio of 1.0 were characterized by infrared absorption maxima at 1400 and 750 cm−1. Key words: Birnessite, Fe(II) oxidation, ESR, lepidocrocite, akaganeite, noncrystalline oxide

Beschreibung: Organic C, N, P, and S contents in soil are thought to be the result of interactions among soil-forming processes, which occur in all soils but to different degrees. To test this hypothesis, the effect of climate, vegetation and topography on the organic matter composition in cultivated soil profiles was examined along an environmental gradient, from semiarid to subhumid regions in Saskatchewan. This transect encompasses a narrow environmental gradient of decreasing evapotranspiration and increasing precipitation (350–450 mm). Representative catenas selected from Brown, Dark Brown, Black and Gray Luvisol soil zones showed changes in the quantity and composition of organic matter. Concentrations of organic C, N, P and S progressively increased from the Brown to the Black soils and then decreased substantially in the Gray soils. Nutrient concentrations also increased from the upper to the lower slope positions of the catenas and decreased with depth in the soil profile. However, the distribution of organic elements across the soil zones, relative to each other (i.e. C:N, C:P, or C:N:P:S ratios), did not follow the same trends as concentration of the individual elements. The most consistent trends were observed in the lower slope soils, where organic C:N (9.8 to 12.5:1), C:P (48 to 78:1) and C:N:P:S (68:6.9:1.4:1 to 145:11.6:1.8:1) ratios widened from the Brown to the Gray soils. Within any one catena, organic C:N:P:S ratios narrowed with depth in the soil profile, often showing a several-fold decrease relative to the C:N:P:S ratios of the surface horizons. This study demonstrates the value of recognizing integrative relationships among soil processes. It provides a mechanism for better understanding and explaining the patterns of distribution and behavior of various soil chemical, physical and biological properties. Key words: Catenary sequence, Chernozem, Luvisol, hierarchical relationships

Beschreibung: In an 8-yr experiment on an irrigated Dark Brown Chernozemic soil, four rates of N (0, 34, 67 and 101 kg ha−1), applied annually with 45 t ha−1 of manure containing softwood shavings (avg. of 46% dry wt) produced a linear yield response (from 3.5 with the check to 4.3 t ha−1 at the highest rate) of barley grain (Hordeum vulgare L. 'Galt'). There were large differences in yields among years, which could be attributed to weather factors, but there was no significant N × year response. Protein content increased linearly (from 11.2 to 13.5%), and both kernel weights and "test weights" (kg hL−1) decreased slightly but significantly with N applications. There was a pronounced "residual" effect of N rates on both grain yield (from 3.8 to 6.3 t ha−1) and protein content (from 10 to 13%) in the first year after applications of manure and N fertilizer ceased. These effects decreased rapidly and had practically disappeared by the end of the 3rd yr, although yields of all treatments remained high (about 5 t ha−1). Organic matter and N contents of the soil were increased by 70 and 41%, respectively, from the cumulative applications of shavings manure. It is concluded that application of manure containing large quantities of softwood shavings has a negligible effect on the N fertilizer requirements of the crop being grown. Beneficial residual effects of N fertilizer applied with the manure may result because of buildup of NO3-N throughout the soil profile, and likely also because of N release from readily mineralized organic compounds or microbial biomass. However, this effect was not reflected in soil tests for readily mineralizable N by NO3 incubation or KCl digestion methods and the effects were practically dissipated after 3 yr. The recovery of applied N fertilizer by the crops was high at all rates (61–79%), and essentially all of the N applied (fertilizer + manure) was accounted for by crop removal + increased soil N. Key words: Mineralizable-N soil tests, Chernozemic soil, repeated fertilizer applications, residual effects

Beschreibung: In northeastern Saskatchewan on Gray Luvisolic soils, rapeseed (Brassica napus L. and B. campestris L.) grown on many fields does not set seed, possibly because of deficiencies of S and B. Therefore, experiments were begun in 1979 to determine (1) the effect of N, S and B fertilizers on yield and quality of rapeseed; (2) if cultivars (B. napus and B. campestris L.) responded differently to these nutrients; and (3) nutrient and nutrient interaction effects of five rates of N, S and B in a composite rotatable design on yield and quality of the cultivar Regent (B. napus L.). Rates of up to 200 kg N ha−1, 50 kg S ha−1 and 2.8 kg B ha−1 were applied. The experiments were conducted on 13 sites. Nine were in N.E. Saskatchewan on Sylvania f1, Waitville 1 (Luvisolic) and Melfort sicl (Black Chernozemic) soils. Four were in N.W. Saskatchewan on Loon River 1 and Waitville 1, (Luvisolic) soils. In N.W. Saskatchewan there was a significant yield increase because of N (1.00 t ha−1) and S (1.06 t ha−1). In N.E. Saskatchewan on Sylvania f1, rapeseed yields were increased by 0.38 t ha−1 by a combination of S and B and by 0.78 t ha−1 by N. Sylvania f1 soils were lower in soluble B than other experimental sites. At other sites in N.E. Saskatchewan, N but not S increased rapeseed grain yield significantly. Significant response to a combination of S and B was obtained with the cultivar Regent, and both species of rapeseed responded to S fertilizer. Sulphur fertilizer increased the glucosinolate concentration in rapeseed meal at all sites. Sulphur increased oil concentration of rapeseed on all sites except one where frost damaged the crop and increased protein of grain on sites where there was yield response to S. Nitrogen increased protein of rapeseed grown on all sites whereas N combined with B decreased protein and increased oil percentage on all sites except Sylvania f1. The yield response of the cultivar Regent to B was not significantly related to soluble soil B. The combined yield response to S and B in relation to soluble soil S and B was significant (R2 = 0.60). Yield response of rapeseed to S was significantly related to soluble soil S (R2 = 0.35). In conclusion, S fertilizer solved the problem of poor seed set in rapeseed cultivars, but B also enhanced yield by decreasing the number of sterile florets and improving pod development. Key words: Nitrogen, sulphur, boron, rapeseed, oil, protein, glucosinolates

Beschreibung: Hydrolysis, immobilization and nitrification of urea-N was measured in samples of Ap horizons of a Black Chernozemic and a Luvisolic soil incubated in the laboratory. Urea was either placed as a nest or mixed throughout the soil. Samples were removed over time to determine the two-dimensional redistribution of urea, [Formula: see text], [Formula: see text], and [Formula: see text]. Localizing urea in a nest reduced both its rate of hydrolysis and subsequent nitrification, and increased recovery of added N in the presence of straw equivalent to 4 t ha−1. In contrast, urea mixed into the soil was nearly completely hydrolyzed and oxidized in 8 d or completely immobilized in the presence of straw. Kinetic studies showed urea hydrolysis was inhibited in a Luvisolic soil sample with increasing substrate concentration beyond 5 mM. The apparent Michaelis-Menten constant (Ka) was 19 mM; the inhibition constant (Ki) was 7 mM; and apparent maximum velocity (Va) was 34.5 μg N g−1 h−1. Urease activity in the Black Chernozemic soil was described by normal Michaelis-Menten kinetics with a Km value of 3.4 mM and Vmax equal to 18.2 μg N g−1 h−1. When urea was localized in a nest, most of the nitrite oxidizers originally present in the soil were killed during the first 24 d of incubation. Factors such as solubilized organics, in addition to [Formula: see text] and [Formula: see text] were considered to be involved. It was concluded that nest placement of urea influenced N transformations in two ways. First, the low surface area:mass ratio reduced exposure of urea to the soil, thereby slowing processes such as immobilization by organisms on decomposing straw. Second, at the microsite level, high concentrations of urea can inhibit urease; and NH3, once generated in such concentrated localized areas, can itself inhibit nitrification through direct toxic effects or possibly through dissolution of inhibitory organics. Key words: Kinetics, Michaelis-Menten, inhibition, nest placement, nitrification, urea

Beschreibung: Three field experiments were undertaken over a 2-yr period to compare the response of winter wheat to fall-applied large urea granules containing a nitrification inhibitor (dicyandiamide, DCD) with that of commercial urea granules (prills) applied as a top dressing in the spring. The objective was to determine the effectiveness of large urea granules coupled with DCD in conserving N when applied at planting or one month after planting. Granules of 1, 2 and 3 g urea as well as 2 g urea + DCD were compared with commercial urea prills at an application rate of 80 kg N ha−1. Large urea granules, as compared with fall-incorporated commercial urea prills, were effective in conserving N over the winter period especially when applied 1 mo after planting and resulted in yields and apparent N recovery similar to those with top dressed commercial prills applied in the spring. Incorporation of DCD into 2-g granules (50 or 100 g kg−1 urea) further increased the conservation of N fertilizer as reflected by higher yields and greater apparent fertilizer N recovery. Uptake of 15N from 2-g urea granules decreased with distance from the granule. However, plants furthest from spaced large granules were able apparently to obtain sufficient N to reach the yield potential dictated by the weather and soil conditions. Yield and N recovery data indicated that N conservation increased with increasing granule size. Crop response and fertilizer N availability decreased as depth of placement exceeded 10 cm. Placement between the 5 and 10 cm depths appeared to maximize fertilizer N availability. It was concluded that a combination of large urea granules and a nitrification inhibitor (such as DCD) can effectively conserve fall-applied N and result in yield responses and N uptake by winter wheat similar to that with commercial urea prills applied as a top dressing in the spring. Key words: Time of application, yield, 15N recovery, apparent fertilizer N recovery

Beschreibung: The effects of application of manure and P fertilizer on wheat yields in a fallow-wheat-wheat rotation on a Black Rego Chernozemic clay soil have been studied for 36 yr. The objective of this study was to identify the effects of manure on soil characteristics that could be related to the reported progressive yield increases over time and an apparent improvement in soil tilth. Soil samples were taken in 1982 from the check (no treatment), and from treatments receiving 13.4, 20.2 and 26.9 t ha−1 of manure applied each fallow year, and 112 kg ha−1 of seed-placed 11-48-0 applied to wheat after summerfallow. Soil physical and P-related parameters were determined for depth increments to 30 cm; the total-N and 15N data to 90 cm; other data were for the 0- to 7.5-cm depth. Manure had no effect on bulk density or hydraulic conductivity. However, it increased the total C and humic acid (HA) content of the soil, the percent of soil C as HA-C, the C concentration in humin, and the percent of total soil N as humin-N. Manure significantly increased the percent of HA-N but not humin-N present as amino acid and amino sugar-N, but increased amino acids and the amino sugars in the humin hydrolysate. The net rate of N mineralization and the available forms of inorganic P were all increased significantly by manure. The natural 15N-abundance technique showed that a significant though small proportion of soil N was derived from manure. Manure had no effect on soil microbial biomass C and N, soil respiration, and the quantity of potentially mineralizable N. Applied P had no effect on N-related parameters measured; its effect on available P was not measured. It was concluded that manure increased crop yields by improving the N- and P-supplying power of the soil, and improving the physical environment of the soil through its effects on the humic colloids. Key words: Humic substances, soil P fractions, soil biological properties, natural 15N abundance, net N mineralization

Beschreibung: The objective of this study was to evaluate the Kelowna multiple element extractant and some EDTA and DTPA modifications for simultaneous determination of potassium and sodium in acid and calcareous soils. To that end, the relationships between K and Na concentrations extracted with 1 N NH4OAc and the Kelowna multiple element extractant (0.25 N HOAc + 0.015 N NH4F) were assessed. However, relationships between K and Na concentrations removed by the modified Kelowna multiple element extractants containing either EDTA or DTPA (KEDTA & KDTPA with NH4F; and AAEDTA & AADTPA without NH4F) were evaluated by comparing values against those obtained with the Kelowna extractant. Addition of these complexing agents was of interest because of their potential in enabling simultaneous extraction of available Zn. The procedures were evaluated by contrasting K and Na concentrations extracted from 100 Canadian soils — half which had pH values between 4.1 and 6.9 (H2O) and a second group with values between 7 and 9.6 — by means of graphing, regression and correlation techniques. Potassium and sodium concentrations removed by the Kelowna extractant ranged from 25 to 510 μg and from 10 to 1420 μg mL−1 soil, respectively. The Kelowna and its EDTA and DTPA modifications extracted K and Na as effectively from acid as calcareous soils. This conclusion was supported by the similar regression slopes obtained when relating concentrations of K and Na removed from these soil groups by the multiple element extractants against those removed by 1 N NH4OAc (r-values ≥ 0.97**). However, the new multiple element extractants removed an average of about 20% less K than 1 N NH4OAc from these soils, though similar Na levels. The lower K levels removed from the Kelowna extractant, or by one of its modifications, may require that soil test interpretation norms be adjusted to compensate for the lower values when using one of these to determine K-availability. A significant correlation was found between extracted Na levels and 1:2 vol/vol water-extract conductivities (r ≥ 0.83**) suggesting that "higher" Na levels may be soluble instead of exchangeable. Some Na test interpretations are discussed in the text. Key words: EDTA, DTPA

Beschreibung: Nitrogen in fallow soil in four field trials was monitored at Agassiz to examine the response of N processes under humid weather conditions of south coastal British Columbia. Inorganic N in the soil profile of control and ammonium-nitrate-treated plots were compared at various time intervals. In two trials (Spring-78 and Spring-81) treatments were applied in late May and in two (Fall-79 and Fall-82) in early November. Leaching of spring-applied N was quite limited during the spring and summer. In the Spring-78 trial, there was negligible nitrate movement until September whereas in the Spring-81 trial there was some movement in June. In the Spring-81 trial, upward movement of nitrate was detected in late August. Nitrate leaching in the summer of 1981 was associated with an unusually high amount of precipitation during June. Leaching of nitrate was significant in late October to December. Nitrogen applied in early November showed extensive leaching by late December. The ammonium appeared to have been nitrified quickly to enable leaching of the applied N as nitrate. Leaching of nitrate appeared to be associated with net water surpluses (precipitation less pan evaporation). Clay fixation of applied ammonium was detected immediately after fertilizer application in the fall but not in the spring trials. The applied ammonium that was fixed by clay was apparently released during the monitoring period. An increase of surface acidity due to ammonium nitrate application was detected in the Fall-79 trial. Comparison of nitrate leaching with long-term precipitation and pan-evaporation records shows that there is low risk of nitrate leaching during the spring and summer but high risk during the fall and winter in south coastal British Columbia. It was concluded that residual inorganic N after the growing season would not be available for crop growth in the spring due to nitrification and leaching over the winter. Development of a soil test for N would have to concentrate on the potential of the soil to mineralize soil N in the spring and early summer. Key words: Nitrogen leaching, nitrogen transformations, clay fixed NH4+, nitrification, fall nitrogen application

Beschreibung: Effects of tillage on soil morphology and porosity were investigated in plots planted to corn (Zea mays L.) for seven consecutive years. Micromorphometric analyses indicated that Ap horizons of no-till plots had approximately half the macroporosity (pores ≥ 200 μm equivalent circular diameter) of those of conventionally tilled plots. Loss of macroporosity was characterized by a decrease in mean pore size and a tendency for pores to become elongated, less tortuous, and oriented parallel to the soil surface. Obvious zoological activity, which consisted mainly of burrowing earthworms, resulted in two to nine times more bioporosity in a no-till pedon than in a conventionally tilled pedon. Earthworm activity also contributed to the formation of 5-cm-thick B & A horizon and a more uniform distribution of organic carbon than in the conventionally tilled pedon. These differences in morphology are reflected in the classification under Soil Taxonomy but not under the Canadian System. We speculate that zoological activity may serve to counteract the reduction in macroporosity in the Ap of the no-till pedon. Key words: Bioporosity, earthworms, micromorphometric analysis, zoological activity

Beschreibung: The effects of crop rotation and fertilization on moisture conserved and moisture use efficiency (MUE) were assessed on a loam soil in the Brown soil zone of southwestern Saskatchewan over the period 1967–1984. Six spring wheat rotations were examined that were either fertilized at soil test recommended rates of N and P, or N or P was withheld according to rotation specifications. MUE in this study was calculated as grain yield divided by sum of 1 May to 31 Aug. precipitation plus soil moisture used between seeding and harvest. In the first fall after harvest 8–11 % of the precipitation received was stored in soil in all rotations. During the first winter 3–5 times as much moisture was stored as was stored in the fall; compared to continuous wheat receiving only P, continuous wheat fertilized with N and P increased moisture storage by 12 mm due to a larger amount of crop residues left in the field. In the first 9 mo of summer-fallow, 33% of the precipitation was stored, but over the entire 21-mo fallow period only 18% was stored. At seeding, fallow-seeded crops receiving P annually had 43 mm more moisture in the 120-cm profile than stubble-seeded wheat that received N and P. Failure to apply P to wheat grown on fallow in the F-W-W rotations reduced spring soil moisture at seeding by about 8 mm. Wheat seeded on fallow retained more moisture in soil compared to wheat seeded on stubble until the shot blade stage, but at harvest and fall sampling there was no difference. At harvest there was no available moisture in the top 90 cm of soil. Wheat made greater use of stored soil moisture in dry years than in wet. Wheat grown on fallow that received P used 102 mm of soil moisture per year; wheat on fallow receiving no P used 93 mm; wheat on stubble receiving N and P used 61 mm and continuous wheat receiving no N used 50 mm. The 18-yr average MUE was as high as 6.9 kg ha−1 mm−1 for wheat on fallow that received P and as low as 5.1 kg ha−1 mm−1 for continuous wheat receiving no N. These values were much greater than those reported 30–40 yr ago for this area and reflect improved crop management and crop varieties now used. The improvement in MUE due to fertilizer was greater in later years due to the cumulative effect of fertilizer on soil quality, crop production and crop residues which enhanced moisture available for use. When efficiency was based on the precipitation received from harvest to harvest continuous wheat receiving N and P had the highest efficiency (3.75 kg ha−1 mm−1) and the 2-yr fallow-wheat rotation the lowest (2.60 kg ha−1 mm−1). Key words: Water use efficiency, WUE, nitrogen, phosphorus and moisture use, summerfallow and moisture conservation

Beschreibung: Numerous techniques for measuring near-surface soil moisture with a neutron probe have been reported. Placing the neutron probe horizontally on the ground surface within a hydrogenous shield has been discussed theoretically, but field adaptations have not. Such a shield was designed and used, yielding measurements of near-surface soil moisture quickly and accurately. Key words: Neutron probe, soil surface moisture, calibration

Beschreibung: Nosema locustae Canning is a potential biological control agent for grasshoppers but some aspects of its environmental impact have not been investigated. This study assessed the impact of N. locustae and the chemical insecticides carbofuran, deltamethrin and dimethoate on microbial activity and nutrient cycling in soil. In a laboratory study, the insecticides were applied to a Haverhill loam at recommended field application rates and 10 times the field rates. There was no adverse effect from N. locustae or the chemical insecticides on any of the measured parameters. Analysis of field soils 6 wk after application of a mixture of N. locustae and dimethoate indicated this treatment had no adverse impact on microbial activity. Key words: Nosema locustae, carbofuran, deltamethrin, dimethoate, microbial activity

Beschreibung: The relationships among the spatial variations of soil water content, soil texture, soil solution electrical conductivity, and bulk soil electrical conductivity were examined for a field characterized by net drainage and low concentrations of dissolved electrolytes. Bulk soil electrical conductivity was measured over various depths at 52 locations within a 1.8-ha field using noncontacting electromagnetic inductive meters. Soil water content (0–0.5 m depth) was measured at the same locations using the time domain reflectometry method. Measurements of soil texture and soil solution conductivity were obtained from core samples from 37 of the sampling locations. Soil water content at the site ranged from 0.06 to 0.36 m3 m−3. Clay content ranged from 2.5 to 44% percent and bulk soil electrical conductivity ranged from 0.0 to 0.21 S m−1. Significant correlation existed among almost all of the measured variables. Regression analysis indicated soil solution conductivity had no effect on measured bulk soil electrical conductivity for soil water contents less than 0.25 m3 m−3. Bulk soil electrical conductivity explained 96% of the spatial variation of soil water content independent of a wide range of soil texture. Autocorrelations of soil water content were similar to autocorrelations for bulk soil electrical conductivity. Under conditions similar to those in the study area, it should be possible to infer spatial variations in soil water content quickly by measuring bulk electrical conductivity using noncontacting electromagnetic inductive meters. Key words: Spatial variability, soil water, electrical conductivity, soil texture

Beschreibung: Amounts and turnover rates of biomass and water-soluble organic C (WSOC) were measured at the Breton plots where records of long-term management of a Gray Luvisolic soil are available. Plots (control, manure, and NPKS) which had been cropped to either a wheat-fallow or a wheat-oats-barley-forage-forage rotation for 50 yr were sampled 13 times during 1981 and 1982. Biomass C and flush of microbial N were measured using the chloroform fumigation technique. Long-term crop yields were used to derive C supply to the plots. Regression analyses were used to relate seasonal fluctuations in environmental conditions to biomass and WSOC dynamics. Reinoculation with soil was unnecessary but Lysobacter sp. formed a greater proportion of isolates following incubation of fumigated soil than of unfumigated samples. Reinoculation with Lysobacter sp. is suggested to provide a more standardized biological assay. The 5-yr rotation contained 38% more N but 117% more microbial N than did the 2-yr rotation, and manured treatments contained twice as much microbial N as did NPKS or control plots. A management effect on soil organic matter quality is indicated. Averge turnover rates of biomass were 0.2–3.9 yr−1; being 1.5–2 times faster in the 2-yr rotation than in the 5-yr rotation. Replenishment of the WSOC component would have to occur 26–39 times yr−1 to supply microbial turnover. Most of the biomass must be dormant because annual C inputs are two orders of magnitude less than maintenance energy requirements. Seasonal variations in biomass were most consistently related to losses during desiccation and regrowth upon moistening. Regrowth appears to be at the expense of native soil organic matter. Management practices and environmental conditions therefore affect amount of organic matter by controlling both input of C and biomass turnover. Key words: Crop rotations, Luvisol, organic matter, biomass, soluble C, Breton plots

Beschreibung: Mean annual rates of calcium carbonate removal from soils in a subarctic climate estimated from data on two chronosequences of calcareous storm ridges, appeared to be relatively constant through time. Concentrations of dissolved calcium carbonate in the soil solution in the study sites calculated from the rates of weathering of CaCO3 and of water drainage are in the range expected for equilibrium with calcite. The same conclusion could be drawn from published studies elsewhere. Over a wide range of conditions, the dissolution rate of calcite appears to be high enough to maintain equilibrium concentrations in water percolating calcareous soils and rocks. Consequently, the rate of calcium carbonate weathering can be predicted from (1) the solubility of CaCO3 and (2) the water drainage rate. Key words: Calcium carbonate weathering, soil chronosequence, subarctic soils

Beschreibung: A soil chronosequence near Cox Bay, on the west coast of Vancouver Island, British Columbia was investigated. Soils in the sequence have developed on sandy beach deposits, which are advancing toward the ocean at a rate of 0.26 m per year. Dendrochronology and geomorphology established surface ages ranging from 127 to 550 yr for seven selected pedons across these deposits. With soil age, there was progressive deepening and differentiation of genetic horizons, resulting in soil classification that ranged from an Orthic Dystric Brunisol at the youngest site (site 1) to an Orthic Humo Ferric Podzol at the oldest site (site 7). Organic matter increased from a maximum value for mineral horizons of 1.1% in the Bm of site 1 to 4.7% in the Ae of site 7. Oxalate-extractable Al in the uppermost B horizons of the soils increased from 0.12% at site 1 to 0.30% at site 6. Available Mg and K from the lowermost horizons sampled decreased from 35 and 25 mg kg−1 to 4 and 5 mg kg−1, respectively, when moving from sites 1 to 6. Accumulations of organic matter, Fe and Al, and losses of available Mg were plotted against soil age and yielded chronofunctions with exponential solutions. Key words: Soil chronosequence, soil genesis, Podzol development, chronofunctions

Beschreibung: Successful reduced tillage systems depend on suitable soil types and the maintenance of optimum soil structure. Studies were conducted to assess the tillage requirement of some well-drained Podzolic and Luvisolic soils in Prince Edward Island and their suitability for direct drilling. Relatively high amounts of silt and fine sand indicated that the soils were structurally unstable with a propensity for compaction. Compactability was inversely related (r2 = 0.90) to concentrations of soil organic carbon over a range of 0.2–2.0%. In the Ap horizons, where organic carbon exceeded 1.6%, the level of macroporosity (equivalent pore diam. 〉 50 μm) was generally greater than 10%. The B horizon and lower level of the Ap horizon, generally, had low porosity and organic matter, although pore continuity was adequate. Macroporosity was closely related to soil bulk density (r2 = 0.81). Penetrometer resistance down the soil profile indicated a relatively shallow rooting depth potential of 25–40 cm. A 3-yr direct drilling study with spring cereals illustrated that some degree of soil loosening is required to maintain optimum soil structure. Soil limitations for direct drilling were mainly low resistance to compaction combined with low potential for regeneration of soil structure. The possible implications of the soil physical properties are discussed in relation to the use of direct drilling within the short-term rotational mixed farming systems of Prince Edward Island. Key words: Soil structure, macropores, Podzolic soils, Luvisolic soils

Beschreibung: A micropenetrometer with a diameter similar in magnitude to that of a root is capable of measuring variations in tip resistance over distances as small as 0.1 mm. Measurements at this scale offer the potential of characterizing zones of high resistance to penetration and the frequency of occurrence of zones of low resistance which could be exploited by a growing root. Spectral analysis provides a new approach to characterizing soil structure and has been applied to the micropenetrometer tip resistance profiles obtained from beds of aggregates. Nine different aggregate size ranges were considered; the aggregate diameters varied from less than 0.36 mm to 6.4–12.8 mm. The analyses indicate that larger aggregates are more resistant to penetration. In addition, comparison of variance spectra among several of the aggregate sizes reveals information on the structural make up of soil aggregates, namely that larger aggregates are made up of smaller "component" aggregates which offer higher resistance when they occur in large aggregates than when they occur individually in loose packing. The use of spectral analysis also appears to provide information on the spatial separation of zones of low resistance which correlate with aggregate size if the aggregate diameters are larger than 1.6 mm. Key words: Soil strength, soil resistance to penetration, micropenetrometer, aggregate size

Beschreibung: The effects of wheat straw incorporation on denitrification, immobilization of N, and C mineralization were investigated at H2O contents of 60, 90 and 120% saturation. Incorporation of increasing levels of straw consistently increased the rate of denitrification for the first 4–8 d, followed by negligible N losses thereafter. In a total period of 96 d, the addition of 1.0% straw increased N losses from 2.5 to 10.1, and from 61.6 to 83.9 μg g−1 in the 60 and 120% water saturation treatments, respectively. The pattern of CO2-C evolved was practically identical to that of the denitrification rate for the initial period when sufficient [Formula: see text] was present. This study has confirmed that in flooded soils, high rates of denitrification will persist only when C is supplied by native or applied organic C sources, provided adequate [Formula: see text] is present. When [Formula: see text] was low, denitrification rates rapidly decreased, even with a sufficient supply of C. Immobilization of fertilizer N (50 μg N g−1 as K15NO3) was very rapid. Around 90% of the total immobilization of applied N occurred within 4 d. Incorporation of 1.0% straw increased the immobilization of fertilizer N from 8.4 to 42.8, and from 1.0 to 7.6% in the 60 and 120% water-saturated treatments, respectively. Remineralization of recently immobilized fertilizer N was observed after 32 d in the 60% saturation treatments only. Key words: Denitrification, wheat straw, mineralization of N

Beschreibung: Information on rates of change of the structure of different soils under different cropping systems is vital to research in soil conservation. Much data on soil structure cannot be used to provide information on rates of change because of an inability to relate measurements at a given time to cropping history. A conceptual model is presented which facilitates quantification of cropping history in relation to soil structure. The model relates structural form, structural stability, stabilizing materials, biological factors and forces which may be exerted on the soil. Soil and crop management practices influence the nature and magnitude of forces involved, biological factors, and the level of stabilizing materials. The model is applied, for illustrative purposes, to five different cropping treatments involving the production of corn and bromegrass grown for different lengths of time over a 15–yr period. Functions to describe the accumulation or loss of stabilizing material under the two different cropping systems are assumed and functions describing the relations between calculated levels of stabilizing materials and structural stability, and between structural stability and structural form are then presented. The model provides a framework for expressing the impact of soil and crop management practices on soil structure and includes variables which could be used for assessing the "quality" of soil under current conditions. It also provides a method for characterizing the susceptibility of soils to structural change arising from soil and crop management practices. Extensive research is required to evaluate the model, however potential applications justify the effort which will be required. Key words: Tensile strength, wet aggregate stability, compaction index, corn, bromegrass, soil conservation

Beschreibung: Six Manitoba soils of varying physical and chemical compositions were used to determine the efficiency of nitrate analysis by high-performance liquid chromatography (HPLC). The nitrate was extracted with distilled water and the extract was analyzed with a reverse phase column using a mobile phase of 1:1 methanol-water, pH 3.0. In five soils, the HPLC method of nitrate analysis resulted in near 100% recovery of added nitrate. An average 90.2% recovery was obtained with the hydrazine sulfate method using sodium bicarbonate, pH 8.5, as the soil extractant. Variable recoveries were obtained with the phenoldisulfonic acid method using a silver sulfate-copper sulfate extractant. Key words: HPLC, nitrate analysis, soil

Beschreibung: Low recovery of recently added [Formula: see text] fertilizer as [Formula: see text] was observed in a Bainsville (Orthic Humic Gleysol) and a Dalhousie (Gleyed Eutric Brunisol) soil, whereas a Brookston (Orthic Humic Gleysol) and a Conestogo (Gleyed Melanic Brunisol) soil had a high recovery. The former two soils had higher vermiculite contents than the latter two soils. Therefore, [Formula: see text] fixation was believed to be responsible for the low recovery. Between 18 and 23% of added [Formula: see text] was fixed after 15 d in the Bainsville and Dalhousie soils whereas only 1–3% of added [Formula: see text] was fixed in the Brookston and Conestogo soils. Potassium pre-addition (with/without air drying) increased the apparent recovery in the Bainsville and Dalhousie soils but did not affect the actual recovery. Potassium pre-addition did not block subsequent [Formula: see text] fixation, rather it resulted in a release of native 14N. Gamma irradiation was used to inhibit biological activity. Between 1 and 7% of added 15N was immobilized in these soils after 15 d. Key words: Ammonium fixation, immobilization, vermiculites, 15N gamma radiation, potassium, native N, ammonium exchange

Beschreibung: Field experiments were conducted during 1982–1983 at two locations (Rimbey and Ellerslie) in north-central Alberta to determine the influence of date of application (mid-October, late October and spring), method of placement (incorporation, banding and nesting) and straw (0 and 3.4 t ha−1) on the recovery of 15N-labelled urea in plants and soil at harvest. The rate of N was 50 kg N ha−1. The recovery of 15N in mature barley plants at both locations was greater with spring application as compared to fall application, and greater with banding or nesting compared to incorporation. At Rimbey, the average recovery, in plants plus soil, of incorporated urea N was lower with October applications (43% for mid and 55% for late) as compared to spring application (89%). Banding or nesting increased the N recovery of October applications. With spring application, there was more immobilization of applied N when incorporated into soil as compared to band or nest placement. Also there was more immobilization of applied N when straw was added to the soil, but banding or nesting tended to overcome the immobilization effect of straw so that the plant N recovery was greater with banding or nesting as compared to incorporation. At the Ellerslie location, there was heavy rain with consequent saturated topsoil in late June and early July. Recovery of fall-applied N in plants was low, and even with nesting the recovery was only 13%. There was substantial immobilization of applied N at Ellerslie. With spring application, nesting overcame the large immobilization effect and produced normal recovery of applied N in the plants. Addition of straw resulted in more immobilization of applied urea N, particularly when urea was incorporated. The 15N recovery in plants plus soil of spring-applied N indicated N losses during the growing season and the losses were much greater at Ellerslie than at Rimbey. Key words: Band placement, fall application, immobilization of N, incorporation, 15N, N losses, nest placement, spring application

Beschreibung: A natural-rainfall erosion plot study was conducted during three consecutive growing seasons (May to September) on a tile-drained sandy loam with a 9% slope to evaluate differences in soil and nutrient losses (NO3-N, P, K) from conventional (C-T) and no-till (N-T) silage corn systems. For the N-T system, corn was seeded directly into an alfalfa-timothy sod that had been treated with atrazine at 4.5 kg ha−1 a few days prior to seeding to kill the sod. The conventional system involving continuous cultivation consisted of fall moldboard plowing, spring disking with a 2.2 kg ha−1 of atrazine applied to control weeds, and seeding. When compared with the C-T system, the N-T system reduced rainfall loss as runoff by 63.6% and soil losses by 92.4%. The 3-yr total soil losses amounted to 3.87 t ha−1 for N-T and 50.68 t ha−1 for C-T. The N-T system reduced K losses by 72.6% and P losses by 93.5% with respect to C-T. NO3-N losses were significantly lower for the C-T treatment as compared to the N-T treatment. Lower percentage nutrient loss occurred in solution from C-T corn because of better incorporation of the fertilizer into the soil. Yield and percent ear were not significantly different between the two systems. Key words: No-till corn, nitrogen, phosphorus, potassium, soil erosion, surface runoff

Beschreibung: The response of grain corn (Zea mays L.) to applied K was studied for 10 yr on three southern Ontario soils. On a Conestogo L, the most profitable rate of K application was 2.5 times higher than expected and the critical concentration of NH4OAc-K, above which no response occurred to either applied K or increasing NH4OAc-K concentrations, was higher (2 ×) than expected, based on 1 M NH4OAc-extractable K and interpretation by the Ontario Ministry of Agriculture and Food soil test. All soils fixed substantial quantities of applied K, but the amount fixed by the Conestogo L was not greater than that fixed by the other two soils. When no K was applied, corn removed less nonexchangeable K (NEK) from the Conestogo L than from the other two soils. A greenhouse experiment was conducted to determine if either the availability of NH4OAc-K or NEK to alfalfa (Medicago sativa L. 'Banner') was lower on highly responsive soils than on less responsive soils. By the end of the experiment, soils on which crops were very responsive to applied K (Guelph L, Conestogo L, and Teeswater SiL) had supplied less K to alfalfa than had soils (Brookston L and Fox SL) on which response to applied K in field trials was similar to that predicted by the soil test. Total K uptake was related to NEK uptake suggesting that differences in the K-supplying capacities of the soils were associated with the availability of NEK to alfalfa. It was concluded that the responses to higher rates of applied K than expected in field trials were due to lower uptake of NEK. The clay mineralogy of the soils was dominated by illite with lesser amounts of vermiculite. No appreciable differences in mineralogy were found between the two groups of soils and NEK uptake was not significantly related to the amount of clay nor to the illite content of the coarse clay and fine clay fractions. Key words: NH4OAc-K, nonexchangeable K, illite, vermiculite, alfalfa, corn

Beschreibung: The Ap horizons of two conservation tillage studies on Dark Brown Chernozemic soils in southern Alberta were sampled in 1986 following the fallow year. The first study, started in 1967, consisted of a wheat-fallow rotation under either no-till chemical fallow, blade-cultivate, or chemical fallow + blade-cultivate management. The second study, started in 1977, consisted of continuous winter wheat, winter wheat-barley-fallow, and winter wheat-fallow rotations under either no-till or conventional tillage management. Nine years of no-till continuous wheat and 19 yr of no-till in a wheat-fallow rotation both led to 40% of the dry aggregates being 〉 0.84 mm in diameter. The parameters selected helped to characterize differences in organic matter between soil tillage systems. Dehydrogenase and phosphatase activities were twice as high under no-till as under the blade-cultivate treatment. No-till also led to the largest monosaccharide accumulation in the soil. Carbohydrates, solvent-extractable organic matter, and chitin N were significantly higher in the 〉 0.84 mm diameter dry aggregates from the no-till treatment. The monosaccarides under the blade-cultivate regime were generally of microbial origin whereas those under the no-till regime were generally of plant origin. Key words: Water-stable aggregates, dry aggregates, enzyme activities, organic carbon, monosaccharides, fallow

Beschreibung: The mineral N flush, a measure of microbial biomass N, and the N mineralization potential (No) were determined in eight representative agricultural soils (Humo-Ferric Podzols and Gray Luvisols) of Prince Edward Island. The acidic (pH 5.0–5.8) soils, varying in texture from loam to loamy sand had an organic C range of 0.75–2.74%. Both mineral N flush (4–38 μg N g−1 soil) and the percentage soil organic N in the mineral N flush (0.4–2.0%) were relatively low compared to other studies. This observation was related to the generally low pH range of these soils. Potentially mineralizable soil N (No) ranged from 44 to 247 μg N g−1 and accounted for 4.5–13.3% of the total soil organic N. The No was closely related to the mineral N flush (r2 = 0.94) but poorly related to percent organic matter (r2 = 0.26) or organic N (r2 = 0.38). The results indicate that for these soils of similar properties, with low levels of residual mineral N, the mineral N flush could be utilized as an indirect measure of the soil N mineralization potential. Key words: Biomass C, mineral N flush, N mineralization potential, Podzolic soil, Luvisolic soil

Beschreibung: The effect of soil temperature on urea hydrolysis and subsequent nitrification in an acid Podzolic soil was investigated under laboratory conditions to determine the transformation rate parameters. More than 90% of applied urea was hydrolyzed within 5 d at temperatures between 9 and 18 °C. Subsequent nitrification rates were more temperature dependent and increased from 4 up to 18 °C. Nitrification was limited at 4 °C, was extensive at 9 °C, and it was essentially complete after 48–68 d at 18 °C and 90% complete after 92 d at 9 and 13 °C. The nitrate-N produced during the cropping season from a spring application of urea was predicted, with a model based on the laboratory determined transformation rates, for field conditions at normal soil temperatures. Following spring-applied urea (20 May), the model indicated that nitrification would be virtually complete by 31 July. In a field experiment, total N uptake by Kennebec potatoes (Solanum tuberosum L.) from applied ammonium nitrate was 95% complete within the same period and with a similar seasonal pattern to that predicted for nitrate N produced from urea. It was concluded that urea can be a suitable source of nitrogen fertilizer for the production of potatoes. Key words: Urea hydrolysis, nitrification, potatoes, modelling, prediction

Beschreibung: This study compared the surface morphology of quartz grains from A and C horizons of a Chernozem, Luvisol and a Solonetz. Observations and chemical determinations were based on scanning electron microscopy and energy dispersive X-ray analysis of fine sand separates. Features indicative of glacial and eolian transport, physical weathering by low energy subaqueous impact, and chemical dissolution and silica precipitation dominated surface characteristics. Most surface morphological features were of an inherited origin since they were common to solum and parent material samples. Quartz dissolution features were not uniquely associated with solum samples and apparently not of pedogenic origin. Key words: Scanning electron microscopy, quartz, pedogenesis, surface morphology, weathering classification

Beschreibung: Ground, sieved forest floor material, collected from an interior Alaskan white spruce (Picea glauca (Moench.) Voss) stand was incubated in polyethylene bags of three thicknesses (0.015, 0.020 and 0.032 mm) at three temperatures (5, 15 and 25 °C) for periods of up to 28 d. Temperature and length of incubation proved to be more important factors affecting nitrogen mineralization than thickness of bag over the range of thicknesses tested. Regardless of temperature and time of incubation, all thicknesses of bags remained permeable to CO2. All bag thicknesses remained impermeable to H2O loss, thus ensuring constant moisture content over the duration of the experiment. An additional experiment which utilized a urea-amendment to stimulate CO2 production indicated that, even under circumstances of high CO2 evolution, the bags remained well oxygenated. Key words: Spruce (white), soil incubation, polyethylene bags, nitrogen mineralization

Beschreibung: Surface soil samples taken from two long-term crop rotations at Lethbridge, Alberta were used to assess the influence of fertilizer N and P on total and mineralizable concentrations of organic C and N in a Dark Brown Chernozemic soil. Rotations sampled were continuous wheat and fallow-wheat-wheat initiated in 1912. In 1967 and 1972, N fertilizer and P fertilizer treatments, respectively, were superimposed over the rotation treatments (which had received no previous fertilizer) to produce a factorial of two N rates (0 and 45 kg N ha−1) by two P rates (0 and 20 kg P ha−1). After 18 yr of application, N fertilizers increased organic C content in both rotations by approximately 14% over that observed in soil receiving no N fertilizer. Organic N contents, similarly, were increased by 15 and 11% in the continuous wheat and fallow-wheat-wheat rotations, respectively. As well, N fertilization increased relative N mineralization potential by 22% in the continuous wheat rotation and by 44% in the fallow-wheat-wheat rotation. Phosphorus fertilization had no significant influence on either total or mineralizable C and N concentrations. Soil pH (measured in dilute CaCl2) was reduced, on average, from 7.2 to 6.9 by 18 annual N applications. These results demonstrate that N fertilization can make significant contributions to the replenishment of organic matter in soil and to the maintenance of indigenous soil N fertility. Key words: Organic matter, nitrogen, carbon, mineralizable nitrogen, mineralizable carbon, pH

Beschreibung: Soil carbon and nitrogen were determined by a LECO CHN-600 determinator; precision and rate of analysis by the new method were compared with those by two other methods. Precision of total carbon data as expressed by the range of standard deviations of seven values for each of 10 samples with carbon contents of 0.1–11% were: CHN-600, 0.01–0.13; LECO induction furnace 0.02–0.86; and wet oxidation 0.04–0.96 Standard deviations of nitrogen data by the CHN-600 ranged from 〈 0.01 to 0.02 for samples with total nitrogen of 0.01–0.95%. Rate of determination of carbon and nitrogen by the CHN-600 was more than double that of either of the other carbon methods combined with nitrogen by Kjeldahl. Key words: Soil, carbon, nitrogen, precision, rate of analysis

Beschreibung: Seven chemical methods (Bray-II, Bray-I, North Carolina DA-4, DA10, Mehlich II, Mehlich III and Olsen) and two anion exchange resins (F− and [Formula: see text] forms) were evaluated on 43 soils with pH varying from 6.4 to 7.88. A greenhouse experiment was carried out with ryegrass receiving two treatments (without P fertilization and 150 mg kg−1 soil) on these soils. The Olsen's method and the two anion resins used as reference ones were effectively the better correlated with P uptakes (r = 0.83**–0.87**) and relative yield (R2 = 69.3–70.2%). The Mehlich II, Mehlich III and to a lesser extent Bray-I methods showed good correlations with these reference methods (r = 0.77**–0.83**) and with plant P uptakes (r = 0.73**–0.79**) or relative yields (R2 = 48.9–55.1%). The Bray-II, DA-4 and DA-10 methods may dissolve some calcium phosphates such as apatites or tricalcium phosphate in some soils and thus overestimated their available P content. The P amounts extracted by these methods were less correlated with P uptakes (r = 0.57*–0.67**) or relative yields (R2 = 14.4–31.4%). On the other hand, the DA-4 extractability was diminished in soils containing more than 3% of carbonates. Although the Ca-P was the predominant form in these soils, the P fixation capacity (M) and maximum P buffer (Mb) capacity were mostly related with Al and Fe-oxalate contents. However, the low Mb values obtained from these soils indicated that the P concentration in soil solution is more favored with respect to adsorbed P. Organic matter and clay contents, pH (H2O), exchangeable Ca and carbonate contents had some effects on the extraction capability of some methods without affecting plant P uptakes. Key words: Available P, soil testing, anion exchange resins, soil properties, P fixation

Beschreibung: The effects of humus on plant metabolism are conditioned by the release of the hormone-like activities contained in HEf bound to HSp. HEf and HSp are both humic fractions that can be separated from each other by acidification with acetic acid or other organic acids. HEf is composed of small molecules and shows hormone-like activities; HSp possesses higher molecular weight and works as a support for HEf. The molecular sizes of the separated HEf and HSp are both low enough to permit root absorption. The dispersion and solubilization of humic molecules are essential to the release of cytokinin-like activity from HSp, but are only preliminary to the release of auxin- and gibberellin-like activities. These can be released by a partial acidification of the humic extracts that do not result in complete depolycondensation. The process appears to regulate the delivery of the hormone-like substances and is influenced by their particular arrangement in the humic aggregate. Key words: Humus fractions, biological effect, nitrate uptake, hormone-like activity

Beschreibung: In a 4-yr study, root growth in the upper 50 cm of a silt loam soil (Gleyed Melanic Brunisol) was equal to or greater than that in a low-density artificial medium (soil:peat:perlite) in spite of a high bulk density in the soil (1.5 Mg m−3 in the 15-to 45-cm depth). We suggest that, due to the natural structure of the Bm horizon, the resistance to root growth is much less than would be expected from bulk density or penetrometer resistance measurements. Marked increases in P and K fertility in the surface soil had only minor effects on either the total length or distribution of roots although the shoot growth was markedly increased. Neither total root length nor root distribution were altered by irrigation during 1981, the only year a moisture variable was included. During a 2-wk dry period in July, prior to anthesis, soil water potential on the nonirrigated plots decreased to −1.5 MPa in the upper 15 cm and to −0.5 MPa in the 15- to 30-cm layer. Leaf water potential, stomatal conductance and rate of growth during the period were lower on the nonirrigated treatment although final dry matter production was not. The results indicate that corn root growth and distribution in the field are not as sensitive to environmental factors as one would expect from short-term laboratory studies. Key words: Corn, root growth, soil bulk density, fertility, soil water

Beschreibung: Soil-erodibility indices were investigated in two regions of Ontario to evaluate their seasonal variation and differences between soil types. Shear strength and water-stable aggregates 〉0.5 mm were strongly negatively correlated with gravimetric soil water content for a Guelph sandy loam soil in southwestern Ontario. Similar variation of shear strength was estimated in three other southwestern Ontario surface soils as a result of seasonal changes in moisture content. Shear strength and aggregate stability increased as four eastern Ontario soils, ranging in texture from loamy sand to clay, dried and warmed following spring thaw. Laboratory incubation at constant temperature and water content showed that shear strength increased in two fine-textured soils with increasing degree days but changed very little in two coarse-textured soils. At the point-of-thaw in the field, all of the eastern Ontario soils exhibited very high values of the indices 1/shear strength and 1/aggregate stability, averaging approximately 15 times those of early July. During spring fallow and seed-bed to 10% canopy periods, the mean values of these indices were 3.7 and 1.4 times, respectively, those in early July. For winter-thaw conditions in the three southwestern Ontario soils, the index 1/shear strength averaged 17 times greater than in the summer. Spring values of this index averaged approximately twice those of summer. Results suggest that Ontario soils are much more susceptible to erosion under thaw and spring conditions than later during the growing season. Soil water content and soil warming may affect the re-establishment of resistance to erosion in soils rendered erodible by freezing, thawing, and saturation. Key words: Erodibility, shear strength, aggregate stability

Beschreibung: The rapid increase in anhydrous ammonia use in Western Canada has created concerns about possible detrimental soil effects, particularly solubilization of organic matter. Anhydrous ammonia was injected at rates of 0.206, 0.416 and 0.834 g NH3-N into undisturbed soils taken in 20-cm-diameter cylinders. Both field capacity (FC) and permanent wilting point (PWP) moisture contents were used. Samples were taken at 0–2.5, 2.5–5.0, 5.0–7.5 and 7.5–10.0 cm from the injection point, 1 day after injection. For the 0.416 g NH3-N rate samples were also obtained 35 days after injection. Soluble organic carbon (SOC) was measured in a 1:15 soil:water extract. The SOC was closely related to the NH4+-N concentration (r2 = 0.79 to 0.99; P 

Beschreibung: The effects of N placement and organic matter amendments on plant uptake and immobilization of N from 15N-labeled urea were investigated in a growth chamber employing two successive crops of rapeseed (Brassica napus L.). Immature barley (Hordeum vulgare L.) (C:N ratio 20.9) and fababean (Vicia faba L.) (C:N ratio 21.8) plant residues, and sucrose were mixed throughout the soil at 10 g material kg−1 soil. Urea enriched with 20.2 atom % 15N was either mixed throughout the soil, or placed as a point in the center of the soil at 100 mg N kg−1 soil. The soil was incubated at field capacity for 30 d before the seeding of first crop and 60 d before the second crop. For the first crop of rapeseed, there was a net mineralization of N from the added barley and fababean materials regardless of N application. For total N uptake and dry matter yield of rapeseed, the mixed treatment of urea was superior to the point placement where barley and fababean residues were added. However, due to considerable biological interchange of N with added plant residues in the mixed treatment, 15N uptake was greater for the point placement of added urea (47.3 vs. 26.7%). Sucrose led to considerable net immobilization of N with the result that the point placement of N was superior to mixing for N uptake and 15N recovery. Added N remaining in the soil at harvest time after removal of the first crop's roots varied between 20.0 and 48.8% for the point placed N and between 27.5 and 79.2% for the mixed placement and was largest where sucrose was added. In spite of the large variation in 15N remaining in the soil, plant recovery of residual 15N in the second crop ranged from only 11.3 to 13.8%, except for the point placement of urea with sucrose where the value was 19.3%. Key words: N immobilization, organic residues, residual 15N, tagged urea

Beschreibung: In the early 1980s, an internal Agriculture Canada review, carried out as a result of a request from the Province of Saskatchewan, indicated a need to determine whether there were any sites in the Province that posed a possible B toxicity problem. The soil and irrigation water quality (SAR, pH, EC, B concentration) and the B content of alfalfa (Medicago sativa L.) were assessed at 29 irrigation projects in Saskatchewan. Langmuir and Freundlich B adsorption equations were determined for another 13 soils that allowed assessment of the effect of soil zone and texture on these relationships. It was found that, except for a few locations where crops sensitive to B may experience some problems, water quality with respect to B was acceptable for most projects. The survey showed that salinity posed more of a threat to production under irrigation than did B toxicity. Boron toxicity was closely associated with salinity problems. Freundlich equations described the data for the 13 soils best; K values ranged between 0.24 and 2.04. These values were not affected by soil zone; coarse-textured soils had K values less than 0.5 and fine-textured soils values greater than 1.5. Data presented in our study can be used to determine where the irrigation practice of individual irrigation projects in Saskatchewan is appropriate for maintaining proper salt balance in the soils so as not to impede plant growth. Key words: Boron toxicity, alfalfa, SAR, Freundlich isotherm

Beschreibung: A kinetic process was investigated by which H+ ions interact with soil surfaces giving rise to a positive electric charge distribution. A two-step process took place in the range of time examined. A first rapid step was always followed by a relatively slower step, and a first-order kinetic equation was applied to describe this second step of the process. The values of specific rate, calculated at different initial H+ ion activities and two different amounts of soil, indicated that a diffusion-controlled mechanism was governing the rate of the slower step and consequently the overall rate of the process. Protonation and deprotonation specific rates were also calculated in the presence of varying concentrations of supporting electrolytes. It was found that the specific rate was dependent on either the structure of the electric double layer formed on soil surfaces in the presence of electrolyte, or on the particular surface electric charge distribution of the examined soil. Key words: Protonation kinetics, specific rate, diffusion phenomena, permanent charge, pH-dependent charge, diffuse double layer

Beschreibung: Atmospheric deposition rates of 90Sr and analysis of soil samples from non-eroded sites indicated base levels of total soil 137Cs were approximately 2700 Bq m−2 in southern Ontario in 1985. Measured 137Cs losses (1965–1976) from long-term runoff plots were significantly correlated to measured soil losses during the same period. Monitoring temporal changes in soil 137Cs should be an accurate method of estimating soil loss in southern Ontario. Key words: Soil loss, 137Cs, Ontario, runoff plots

Beschreibung: An undisturbed site under forest cover near Breton, Alberta, was chosen to study the dynamics of a Gray Luvisol. Soil moisture and temperature were monitored at selected depths over a 2-yr study period. Canopy drip collectors and gravity lysimeters were used to study soil solution transport and the process of lessivage. The order of cation concentration for canopy drip, LFH and Ae lysimeter samples was K+ 〉 Ca++ 〉 Na+ 〉 Mg++. The lysimeter samples from the Bt showed Na+ 〉 Ca++ 〉 K+ 〉 Mg++. Lysimeter studies further indicated that micaceous clays were being illuviated into the upper Bt horizon. Water movement into the Ae horizon was found to be regulated by the LFH horizon; ice lensing in winter appeared to enhance the formation of the platy structure. The major processes in this soil are the translocation of Fe, Al and organic constituents both in solution and in colloidal form; the concentration of these elements was a function of the rate of water movement. The concentration of other cations was independent of the rate of water movement. Key words: Genesis, pedogenesis, Gray Luvisol, dynamic pedology, clay migration, lessivage, illuviation

Beschreibung: The [Formula: see text] status of sandy, podzolic soils from central Ontario was examined. Water-soluble [Formula: see text] was positively correlated with soil organic C concentrations but not with Fe and Al oxides (citrate-dithionite-bicarbonate minus pyrophosphate extractable Fe and Al). For adsorbed [Formula: see text] the reverse was true. Surface horizons were high in soluble [Formula: see text] and low in adsorbed [Formula: see text] whereas B horizons containing high levels of Fe and Al oxides contained large amounts of adsorbed [Formula: see text] and little soluble [Formula: see text]. Successive distilled water extractions of some samples indicated the removal of almost all soluble [Formula: see text] from surface horizons in one or two extractions. Sulphate, however, remained present in the B horizons after five extractions. The amount of soluble [Formula: see text] extracted was dependent on horizon type and amount of water used for extraction. This makes evident the importance of moisture status, residence time and hydrologic pathways in determining [Formula: see text] release from the soil, and demonstrates the need for in situ studies. Plastic Lake B horizons adsorbed added [Formula: see text] in the laboratory but it was not determined whether this is occurring in the field. Key words: Soluble [Formula: see text], adsorbed [Formula: see text], sulphate, iron oxide, aluminum oxide, podzol

Beschreibung: Horizontal Ksat was estimated as one of eight classes according to guidelines based on soil morphology and then measured by a piezometer method in soils of the Ottawa area that differed widely in texture and structure. The Ksat class estimated by two observers was either the same as, or one class different from the measured class for 14 and 16 of 18 layers tested (average 83%). Measured horizontal Ksat exceeded vertical Ksat by a factor of 9 in some sandy layers with strata of relatively coarse material. Measured vertical Ksat exceeded horizontal Ksat by a factor of more than 3 in some layers having numerous more-or-less vertical earthworm channels. Horizontal Ksat of the layers measured ranged from 0.3 to 14 m∙day−1 and vertical Ksat values for those layers ranged from 0.1 to 27 m∙day−1. Guidelines for estimating horizontal Ksat were revised on the basis of results from this study to give more emphasis to stratification. The results support the view that adequate estimates of vertical and horizontal Ksat can be made rapidly from the observation of soil morphology if specific guidelines are followed. The guidelines are based on relationships between soil morphology and measured Ksat values. Key words: Horizontal Ksat, vertical Ksat, soil morphology

Beschreibung: Linear equations were developed for converting electromagnetic induction readings (ECa) from EM38 meters to saturated paste electrical conductivity values (ECc). To correlate EM38 readings with measured ECe values, field sites representing a range of salinity conditions were sampled in 0.30-m increments to a depth of 1.5 m. Adapting a weighting procedure based on the EM38 meter's response to depth, ECe values were condensed into a single weighted value. The weighted ECe values were linearly correlated with temperature-corrected ECa readings. Equations were designed for soils of various textures under varying temperature and moisture conditions. For accurate ECa to ECe conversions, soil temperature correction of ECa is essential. When a frozen layer is present, EM38 readings are unreliable. EM38 horizontal and vertical modes show different ECa readings for the same depth-weighted ECe. Variability of ECa to ECe conversion was greater on coarse-textured than medium- or fine-textured soils. Available soil moisture should be above 30% for accurate ECe determinations from ECa readings. Key words: Salinity methods, soil salinity, saturated paste extract method, electromagnetic inductance meters, soil temperature

Beschreibung: The influence of three cropping treatments on the quantitative and qualitative composition of the carbohydrate fraction of a silt loam soil and its water-stable aggregates was assessed. Three cropping treatments were considered: bromegrass (Bromus inermis Leyss.) grown continuously for 15 yr (B15), grain-corn (Zea mays L.) grown continuously using conventional tillage for 15 yr (C15), and grain-corn grown continuously for 13 yr followed by 2 yr of bromegrass (B13C2). Six water-stable aggregate size fractions ranging from 8.00–4.70 to 0.25–0.10 mm in diameter were separated from the soil by wet sieving. The carbohydrate fraction was extracted by acid hydrolysis, reduced, acetylated to alditol acetates and analyzed by temperature-programmed capillary gas chromatography. Total carbohydrate content was not significantly influenced by cropping treatment but was observed to increase as aggregate size decreased irrespective of cropping treatment. The carbohydrate content in the different aggregate size fractions was positively correlated with both organic carbon and clay contents. With the exception of xylose and mannose, the monomeric sugars behaved similarly to total carbohydrates. Based on the magnitude of the ratio of the content of mannose to that of arabinose plus xylose, the contribution of plant carbohydrates to the total carbohydrate fraction increased as aggregate size decreased in the B15 treatment, but decreased in the C13B2 and C15 treatments. No significant correlations existed between either the total carbohydrate content or the content of individual sugars, and the stability of aggregates in the soils from the different cropping treatments. Key words: Wet aggregate stability, soil organic matter, soil structure, crop rotation, corn, bromegrass

Beschreibung: A field experiment was conducted to examine the interaction of fertilizer placement and moisture level on barley (Hordeum vulgare 'Gait') utilization of urea-N during early growth. The 15N labelled urea (50 kg ha−1) was either deep-banded or broadcast-incorporated, and plant samples were taken from the two-leaf stage until anthesis, then again at maturity. Five moisture regimes were created using rain shelters, with 0, 10, 15, 20 and 25 mm water applied per week until anthesis. A natural precipitation treatment was also included. All barley plants were unsheltered from anthesis to maturity. Weekly fertilizer recoveries by the crop with no water additions were much less for broadcast-incorporated N than deep placement. The differences narrowed with increasing rates of water additions. Apparently, broadcast-incorporated fertilizer N remained in dry surface layers of the no-water treatment, and was positionally unavailable for absorption by the crop. Compared to deep-banded N, broadcast-incorporated N resulted in 37% less grain when drought stress occurred from seeding to anthesis. Broadcast-incorporated N was more susceptible to immobilization by the soil than was deep-banded N. Key words: Barley, drought stress, 15N-urea, fertilizer positional unavailability, N immobilization

Beschreibung: Nutrient availability in different forest soils must be known before increased wood production can be sustained either by adding supplemental nutrients or by judicious silvicultural operations to optimize the linkage between the variable nutrient requirements of forest crops. This is complicated by the variable availability of nutrients on forest sites during crop development. Forest crops unlike agricultural crops have long rotation periods which make it difficult to apply agricultural methods of estimating potentially available nutrients directly to forest soils. Presented in this review are (i) various approaches used in forestry to estimate the nutrient supplying potential of different sites, (ii) factors affecting nutrient availability, and (iii) evidence to suggest that nutrient cycling processes in forest ecosystems are important factors affecting tree growth. It is suggested that data from chemical analyses of soil samples collected at specific times and sites should be used with caution for both practical decision making and simulation modelling purposes. Key words: Nitrogen, phosphorus, litterfall, throughfall, stemflow, mineralization

Beschreibung: This research examined the effects of soil environment on the decomposition of cereal crop residues and stabilization of microbial products in the field. Microplots at semi-arid and subhumid field sites were amended with 14C-, 15N-labelled wheat straw and with 14C-labelled glucose plus 15N-labelled NH4NO3 and the fate of the residual C and N was monitored over 10 yr. Mineralization of C and N derived from wheat straw was greater at the site in the more moist environment in the short term (2 yr). In the long term (up to 10 yr), however, the residual C and N at this site decayed at a slightly slower rate, providing evidence of stabilization of organic material in chemically resistant forms, as compared to possible physical protection in the semi-arid clay-textured soil. The total recovery of labelled N was 22.5–24% in the harvested crops with 13.4–16% remaining in the surface soil by the end of the study. Mineralized labelled organic N was used with an efficiency ranging from 32 to 51%. However, after summer fallow the crop apparently used mineralized labelled N with an efficiency of only 7%. This study showed that moistness of the soil environment has a considerable effect on residue decomposition. Stabilization of humic material derived from residues relates more to the recalcitrance of microbial products and their interactions with soil mineral colloids than to the nature of the original residue. Key words: Mineralization rates, crop residues, microbial turnover, chemical recalcitrance, physical protection, plant N use-efficiency

Beschreibung: From the surface horizon of an organic-rich mountain soil, humic and fulvic acids, and organo-mineral compounds including clay and hydroxy-metal colloids, were separated and purified. Each of these fractions was hydrolyzed in 3.0 M HCl under reflux, then the reaction parameters related to the solubilization of carbon and nitrogen and to the kinetics of hydrolysis were calculated. Acid hydrolysis was interpreted as the result of two successive steps: first a rapid electrophilic attack of heteroatomic C-O and C-N bonds by protons, then a slow nucleophilic hydration of the protonated bonds. Electron delocalization in these bonds, which increased with the polycondensation degree of organic compounds, and with their adsoprtion on mineral surfaces, resulted in an increase in their stability to hydrolysis. Fulvic acids were found to be the less stable material, and lead to predominantly anionic hydrolysis products. Clay-sized humin was the most stable material and yielded mainly cationic hydrolysates. The stability to hydrolysis and the humification degree of organic matter in the fractions generally coincided, and decreased in the following order: fine clay-sized humin 〉 alkali dispersible organo-mineral colloids 〉 〉 humic acids 〉 hydroxy-ferric organic colloids 〉 hydroxy-aluminium organic colloids = fulvic acids. Key words: Organo-mineral complex, humic substances, acid hydrolysis, carbon, nitrogen

Beschreibung: This study describes a number of different preparation techniques for recording solid state 13C NMR spectra of whole mineral soils. Removal of paramagnetic Fe3+ improves the quality of 13C NMR spectra of whole soils and of particle size fractions. The C:Fe ratio appears to be an important indicator for obtaining satisfactory 13C NMR spectra of whole soils and fractions separated from them. If the C:Fe ratio is 〉〉 1, the quality of the spectrum will be good; if the ratio is 〉 1, a reasonable spectrum will be obtained, but if the ratio is

Beschreibung: Crop yields and heights and soil chemical properties on and immediately adjacent to an oil pipeline right-of-way (ROW) were monitored over a 10-yr period. Effects of soil mixing on chemical properties were still apparent despite good crop management. With the exception of alfalfa, field crop yields on the ROW were reduced by an average of 28% 10 yr after installation. Key words: Soil mixing, degradation, crop heights

Beschreibung: The spatial variability of soil strength, porosity, and microbial biomass was determined under 4-yr continuous direct-planted silage corn (Zea mays L.) on Prince Edward Island. All soil properties changed relative to the row position. Microbial biomass C and N were lower in the in-row compared to the between-row position. Positional and depth differences for soil bulk density and volume of macropores (EPD 〉 50 μm) were only evident at the soil surface (0–8 cm). Temporal and spatial variations in soil strength indicated the extent of the rooting potential within the soil profile, the depth to compacted soil layers, and the degree of soil structure regeneration during the winter period. Key words: Spatial variability, soil strength, soil porosity, microbial biomass, direct-planted corn, Zea mays L.

Beschreibung: Sulfate sorption and desorption as a function of pH were measured for six podzolic horizons from two forested watersheds of the southern Laurentians. The results showed a rapid increase in sulfate sorption with decreasing pH to a maximum sorption capacity at pH values between 3.8 and 4.2 depending on the horizon considered. Below this pH retention decreased except for the Coniferous (Con) B horizon where sorption remained almost constant. This drop in the sorption capacity of the soils is related to the partial dissolution of Al, and possibly Fe, surface coatings. Levels of up to 15.9 mmol L−1 of total dissolved Al were measured at pH 3.0 for the Herminc (Her) B horizon. The amount of sorbed and total native sulfate and the maximum sorption during the experiment are positively correlated (R2 = 0.986, 0.982 and 0.800) with the oxalate extractable Al content of the soils. Except for the Con B horizon, amorphous plus crystalline Fe make up the bulk of the inorganic coatings in all six horizons. For the Con B horizon, which has the highest sorption capacity of the horizons tested, the composition of these coatings is dominated by Al materials. In all soils, the variations in sulfate sorption as a function of solution concentration are best described by the Gunary equation in the range of pH values tested. Key words: Sulfate, pH-dependent sorption, dissolution, Podzol

Beschreibung: The objective of this study was to compare the values, statistical characteristics and relationships of partition coefficients (Kd) computed from a short-term study of 54Mn sorption with those computed from DTPA extractions of soil Mn. Of particular interest were the frequency distributions, which must be very well known for use in stochastic modelling of environmental impacts. The study used 69 soils. Sorption of 54Mn, applied with stable 54Mn carrier, was measured after 24 h equilibration in suspension. The Kd for 54Mn was based on the single measurement of 54Mn in solution. Total soil Mn and DTPA + NaHCO3-extractable Mn were also measured and used to compute a Kd from two measurements. The frequency distributions of Kd values measured by either method were strongly skewed and conformed to lognormal, regardless of the statistical properties of the underlying measurements. The geometric mean Kd for 54Mn was 44 L kg−1 and was highest for high pH, high clay content and high organic matter content soils, as expected. The geometric mean Kd for DTPA-extractable Mn was 1070 L kg−1 and was not related in the same way to the soil properties. Clearly, the two Kd measurements were quite different. A significant correlation (r = 0.54, P 

Beschreibung: A tracer (15N) study using fallowed field microplots was conducted at Agassiz Research Station to examine the fate of applied N over an entire year. The tracer confirmed nontracer (difference between fertilized and control treatments) observations that applied N does not leach beyond the rooting zone (45 cm) during the growing season, despite the considerably more than average precipitation that occurred in July, but that all residual [Formula: see text] is leached over the winter. The tracer did, however, show that net immobilization of applied N occurred late in the fall resulting in 17% of the N recovered in the 75-cm profile 1 yr after application even though the nontracer method showed that none of the applied N remained. There was significant net mineralization of soil N over the summer (100 kg N ha−1 from early May to late August) and nitrification of the applied [Formula: see text] (120 kg ha−1) was essentially complete within 14 d of application. Tracer analyses suggested that 36% of the applied [Formula: see text] was immediately fixed by the clays but after 14 d in the field it decreased to less than 1%. The fixed [Formula: see text] remained at this level throughout the rest of the year. The apparent large decrease in fixed [Formula: see text] within the first 14 d may have been an analytical artifact which resulted when the initial soil was air dried. Negligible denitrification was observed during the growing season despite the soil remaining quite moist throughout most of the year. Delta 15N measurements of total N, fixed [Formula: see text] and extractable inorganic N fractions showed only enrichment of total N. The delta 15N results support the observation that denitrification tends to be low under Agassiz soil and weather conditions. Comparisons and contrasts to previously reported similar tracer studies in Ottawa were made. Key words: Leaching, clay fixation, N mineralization, N immobilization, nitrification, denitrification, delta 15N

Beschreibung: In the Black soil zone of the Canadian Prairies seedbed preparation is important for handling crop residues from high yields and for incorporating herbicides and fertilizers into soil in the fall or prior to seeding in spring. There are numerous tillage implements available to the producer for this operation. The question often arises as to the relative merits and demerits of using these implements, especially with respect to their effect on yield and on soil quality. A 25-yr (1959–1983) continuous spring wheat study was carried out at Melfort, Saskatchewan, in a split-plot design. The main plots were: four fall tillage implement treatments (plow, heavy duty cultivator, one-way disc and double disc), chopped straw in the fall and spring burn of straw. Four rates of fertilizer (0/0, 5/10, 22.5/10 and 45/10 kg ha−1 N/kg−1 ha−1 P) were subplots from 1959 to 1977; the fertilizer rates were doubled for 1978 to 1983. The results showed that there was no significant effect of tillage on yield but there was a significant fertilizer by tillage interaction. The spring burn treatment gave the highest yield (2073 kg ha−1) and the plow treatment the lowest yield (1963 kg ha−1). Fertilizer increased yields when moisture was adequate and either had no effect or depressed yields when precipitation was low. Only the plow treatment caused a loss of organic C and N. All tillage treatments increased the erosive fraction of the soil (fraction

Beschreibung: Ten soil properties, including texture, pH, available phosphorous, cation exchange capacity, exchangeable cations and organic carbon, were determined from the Ap horizons of 91 map units of two Montreal Lowlands counties. Multivariate analysis techniques were used to classify the soils into fertility groups. Nine fertility groups were derived from cluster analysis. Principal component analysis yielded two components which accounted for more that 75% of the variance. These principal components were related to soil texture and fertilizer management factors. They confirmed the grouping obtained by cluster analysis. Multiple discriminant analysis distinguished these fertility groups and allocated new soil mapping units to one of them using discriminant functions. Clay content, pH, exchangeable Ca and available P were selected as the more potent and significant variables in descriminating groups. This work demonstrated that multivariate analysis has considerable promise in deriving meaningful interpretive grouping from selected soil parameters. Key words: Fertility, interpretive grouping, soil quality, multivariate analysis

Beschreibung: Aggregates (1–2 mm) from a soil under continuous corn management were subjected to a mild shaking treatment and ultrasonic energy levels ranging from 100 to 1500 J mL−1 water to determine the degree of aggregate disruption and dispersion. More clay- and fewer sand-size particles were recovered with greater amounts of applied energy indicating greater aggregate disruption and dispersion with higher energy levels. Most of the breakdown of sand-size aggregates occurred between energy levels of 300 and 500 J mL−1. Ultrasonic energy levels of 500 J mL−1 or greater were more effective than using 20% hydrogen peroxide plus 16 h of shaking in dispersing sand-size microaggregates. Surface area measurements of the clay indicated no severe fragmentation or alteration of primary particles had occurred. With increased applied ultrasonic energy and more complete dispersion, the amount of organic C recovered increased in the clay- and decreased in the sand-size fractions. At complete dispersion, there was no evidence of redistribution of organic matter by ultrasonification and the sand-, silt- and clay-size fractions contained 5, 30 and 60% of the soil organic C. Results of this study suggest that ultrasonic dispersion techniques can be used as a physical method to separate microaggregates from soil and thereby study the nature of organic matter within them. Key words: Ultrasonic dispersion methodology, aggregates, organic matter distribution, particle size fractions

Beschreibung: Soil ammonium and nitrate in the top 15 cm of soil were monitored after application of ammonium nitrate and ammonium sulfate to plots at 14 PF (previously fertilized) and 12 NF (never fertilized) lowbush blueberry (Vaccinium angustifolium Ait.) stands representing a range of soil types and management histories. Overall, nitrate values in unfertilized and ammonium sulfate plots were higher at PF than at NF sites, suggesting greater nitrification at PF sites. In laboratory incubation studies, nitrification proceeded immediately in soil from a PF site, but only after a 4-wk lag in that from an adjacent NF site. Nitrification rates were low compared to that in a garden soil (pH 6.6). N-Serve inhibited nitrification in both soils. In ammonium nitrate plots, "excess" N values (N values in fertilized plots minus values in unfertilized plots) were higher for PF than for NF sites, suggesting greater immobilization, plant uptake or loss of N at NF sites. There was no evidence, in laboratory studies, of immobilization of added N by soil from either type of site. Rhizome N concentration increased significantly in response to fertilization at an NF site, but not at a PF site. Key words: Blueberry (lowbush), fertilizer and soil nitrogen

Beschreibung: Changes in cropping practices can alter soil structural characteristics. The purpose of this study was to assess the extent and rate at which bromegrass (Bromus inermis Leyss) and continuous grain-corn (Zea mays L.) influence soil aggregation and various soil binding agents. Five cropping treatments ranging from 15 yr of continuous grain-corn to 15 yr of continuous bromegrass production were investigated. Soil aggregation and the nature of soil binding agents were determined by measuring the water-stable aggregate size distribution subsequent to the application of six chemical pretreatments — control, distilled water, 0.08 M sodium azide, 0.08 M sodium chloride, 0.08 M sodium periodate, and 0.02 M sodium pyrophosphate. A simple power function was used to describe the relationship between the cumulative percentage by weight of water-stable aggregates and aggregate diameter. The exponent in the power function provided a measure of the influence of cropping treatment and chemical pretreatment across the whole range of aggregate sizes. The size and stability of aggregates increased with increasing domination of bromegrass in the cropping history. Materials resistant to soaking in water contributed to the increased stability under bromegrass. Materials sensitive to periodate and pyrophosphate anions contributed to the stabilization of aggregates from all cropping treatments. However, these materials did not appear to account for the differences in structural stability observed across cropping treatments. The rate of structural deterioration induced by grain-corn production under conventional tillage appeared to be faster than the rate of structural enhancement promoted by bromegrass production. Key words: Polysaccharides, periodates, pyrophosphate, corn, bromegrass, aggregate stability

Beschreibung: A field was artificially eroded by levelling in 1957 and then continuously cropped to barley for 7 yr. Subsequently, a wheat-fallow experiment was conducted from 1965 to 1979 to determine the effects of four fertilizer treatments and green manure (yellow sweet clover) on restoring the productivity to soil that had been "eroded" to various depths. After 22 yr and 14 crops, the productivity of the land from which soil was removed has been improved but not fully restored. Although green manuring with yellow sweet clover improved soil structure, wheat yields were not improved because of competition for soil moisture and poorer in-crop weed control in this part of the rotation. The addition of 45 kg N plus 90 kg P2O5 per hectare in each crop year to sites from which 8–10, 10–20, or 46 + cm of soil had been removed resulted in yield increases of 18, 46, and 70%, respectively, over the unfertilized check of each treatment; the average yields were 104, 91, and 70%, respectively, of the undisturbed, unfertilized (check) treatment. On "erosion" treatments where only 8–10 cm of soil were removed, 45 kg N plus 22 kg P2O5 per hectare were sufficient to restore the productivity. Precipitation apparently had a greater effect than fertilizer application on wheat yields. The loss of organic matter and associated soil structure characteristics seemed to be critical factors contributing to yield losses associated with soil erosion. These results show that it is more practical to use management practices that prevent soil erosion than to adopt the practices required to restore eroded soil. Key words: Soil erosion, topsoil loss, water-stable aggregates, soil organic matter, green manure, precipitation

Beschreibung: Application of the seed-applied fungicides captan, DL-Plus, Evershield, thiram and Metalaxyl reduced nodulation in the field bean cultivar Lancer (Phaseolus vulgaris L.) in the field. Captan, Evershield, B3 and Thiram also lowered the acetylene reducing activity under the same conditions. Captan, DL-Plus, and B3 resulted in significant yield reductions of field bean inoculated with commercial multi-strain rhizobial inoculant. Since captan or captan-containing fungicides were the most potent inhibitors of symbiotic N2 fixation in field bean, spontaneous mutants of Rhizobium phaseoli strains 3644 and 8215 were selected on the basis of ability to grow in microbial medium containing 100 ppm of Captan 50 W. Controlled environment chamber and field evaluations indicated that all mutants were less sensitive to commercial rates of Captan 50 W (2.0 g per kilogram seed) than either parent strain or commercial multi-strain inoculant. Inoculation of captan-treated seed with these mutants 24 h prior to seeding did not affect nitrogenase activity or yield. Assessment of the effect of captan on the N2-fixing symbiosis and the captan tolerance of R. phaseoli strains by the acetylene reduction assay or 15N isotope dilution at levels of 15N natural abundance gave similar results. The existence of mutants of R. phaseoli tolerant to seed-applied captan but unaltered in symbiotic properties makes the combined use of captan as a seed protectant and seed-applied rhizobial inoculation fully compatible. Key words: Phaseolus vulgaris L., Rhizobium phaseoli, captan, N2 fixation, 15N isotope dilution, acetylene reduction

Beschreibung: The effects of rhizobium inoculation, vesicular-arbuscular mycorrhizal (VAM) fungi and seed-applied captan on field bean growth and N2 fixation were studied under greenhouse conditions. 15N isotope dilution methods were used to measure N2 fixation in a soil containing indigenous Rhizobium phaseoli. Inoculation of rhizobia onto host plants increased N2 fixation by 50 – 82 mg N per plant compared with uninoculated controls. The incidence of nodulation was also increased by R. phaseoli inoculation. Addition of VAM to the soils increased bean dry matter production by 9 – 54% over plants not receiving VAM, and increased the N2 fixed by rhizobially-inoculated plants by 4 – 27 mg N per plant. VAM addition resulted in greater uptake of soil N by the plants. Inoculation of captan-treated field beans with inoculum derived from a captan-tolerant strain of R. phaseoli did not result in improved N2 fixation rates compared with inoculation with the nontolerant parent strain. Seed-applied captan reduced the proportion of nodules formed by both strains of added rhizobia, but did not result in decreased amounts of N2 fixed by the root systems. Captan did not reduce the effectiveness of VAM. Key words: Rhizobium phaseoli, captan, VA mycorrhizae, N2 fixation, 15N

Beschreibung: Molybdenum, Co and B concentrations in, and uptake by, corn and bromegrass were measured over a period of several years from three field experiments in which sewage sludge was applied and compared with ammonium nitrate as a source of N. There was little effect of sludge on B and Co concentrations in the crops grown. Slight increases in uptake were apparently due to yield increases due to sludge. A lime-treated sludge increased Mo concentration in plant tissues after several years of sludge application. The increase in plant Mo concentration was highest in the eighth and last year of the experiments, although lime-sludge application had ceased 1–3 yr previously. The soil-sludge interactions contributing to increased Mo uptake are discussed. Key words: Molybdenum, cobalt, boron, sewage sludge, corn (Zea mays L.), bromegrass (Bromus inermiss Leyss).

Beschreibung: The rate of release of plant-available sulfur (S) from two soluble sources (thiosulfate, and sulfate) and four elemental S forms (S powder, S-coated urea, S suspension, and S-impregnated urea) was determined in a growth chamber study, using five successive harvests of rapeseed as the test crop. The soluble S sources were plant-available shortly after application. Thiosulfate was rapidly oxidized, and was comparable to sulfate in its short-term release pattern. The elemental S forms, however, showed widely different rates of release, apparently related to the initial particle size of the product and the dispersion of the particles within the soil. Finely-divided S suspension was rapidly oxidized, and the product was completely converted to sulfate by the third harvest. Relatively coarse S powder was oxidized more slowly and in some cases was not completely converted to sulfate even after 124 days. S-impregnated urea, which yields a pocket of finely divided S particles upon urea dissolution, showed negligible initial oxidation but rapid oxidation after the soil was mixed. S-coated urea produced minimal amounts of sulfate over the five harvests and could not be considered a viable fertilizer S source. Key words: Sodium sulfate, sodium thiosulfate, S-coated urea, S-impregnated urea, S oxidation, elemental S

Beschreibung: Fertilizer P was applied annually (0, 15, 29 and 44 kg P ha−1 yr−1) for 26 yr to an acidic loam cropped to timothy (Phleum pratense L.). Some fertilizer P was translocated into the 30- to 45-cm depth of soil when 15 kg P ha−1 yr−1 was applied and into the 45- to 60-cm depth when 44 kg P ha−1 yr−1 was applied. The amount of P translocated increased with increasing rates of applied P. Key words: Fertilizer, phosphorus, leaching, translocation, movement

Beschreibung: The Versatile Soil Moisture Budget (VSMB) and the Soil-Plant-Air-Water (SPAW) model were compared and tested against soil-water content data from a long-term experiment in which wheat was grown on fallow land in the semi-arid zone of Saskatchewan. Both models were driven by daily air temperatures and precipitation data. At the expense of requiring more detailed soil and crop information, the SPAW model simulated the water balance and its components in greater detail than the VSMB. Predictions of soil-water contents throughout the growing season with either model corresponded very well with the measured data. The overall mean absolute difference in total soil-water content to a depth of 120 cm was 1.5 cm for the VSMB and 1.2 cm for the SPAW model. Predictions of water distribution in the profile were also satisfactory. A choice between the two models, to be used under semi-arid growing conditions, will depend on the availability of input data and the required level of output. Key words: Soil-water movement, modelling, evapotranspiration

Beschreibung: Changes in soil phosphorus (P) forms, as determined by a sequential fractionation procedure, were used to assess the influence of soil texture and management practices on the forms and distribution of soil P in a Brown Chernozemic loam soil at Swift Current, Saskatchewan. Significant proportions of the variability of all P fractions except residual-P could be attributed to changes in sand content. Changes in the forms and distribution of soil P with decreasing sand content followed patterns similar to those associated with a weathering sequence. The proportion of total soil P in inorganic and organic extractable forms that were extractable sequentially with anion exchange resin (resin-Pi), sodium bicarbonate (bicarb-Pi and -Po), and sodium hydroxide (NaOH-Pi and -Po) increased with decreasing sand content. Acid-extractable inorganic P (HCl-Pi) was the only P fraction positively correlated with sand content. The presence of a crop increased the proportion of soil P present as the more labile organic-P fractions (bicarb-Po and NaOH-Po) but not as total soil organic P (soil-Po). The presence of a crop also increased the proportion of soil P present as the labile inorganic fractions (resin-Pi and bicarb-Pi), possibly due to a decrease in soil pH. Application of inorganic-P fertilizer caused significant increases in the proportion of soil P as these labile inorganic-P fractions (resin-Pi and bicarb-Pi) and as total soil organic-P (soil-Po), but did not affect the more labile organic-P fractions. Key words: P fractionation, labile P, organic P, inorganic P, texture, management practices

Beschreibung: Available water-holding capacity (AWC) maps of Alberta, Saskatchewan and Manitoba were derived from Soil Landscape maps (1:1 million scale) by substituting AWC classes for soil textural classes. The maps provide information required for the geographical interpretation of soil water and crop modelling analyses. Key words: Available water-holding capacity, maps, texture

Beschreibung: Natural radionuclides of the uranium (U) and thorium (Th) decay series contribute to the radiation dose received by humans. In the context of U mining and refining, it is important to accurately assess the pathway for these radionuclides from soils to food plants. The Canadian Standards Association model of this pathway for dose estimation is based on the plant/soil concentration ratio (CR). In a controlled outdoor lysimeter setting, we measured CR values for experimentally applied U at 100 mg kg−1, 230Th at 8 kBq kg−1 and 210Pb (lead) at 20 kBq kg−1 using a sand, a loam, a clay and an organic soil in 12 soil and crop combinations. The overall geometric mean CR values were 0.013, 0.0022 and 0.0050 for U, 230Th and 210Pb, respectively. A second experiment using one soil and crop showed CR to be dependent on soil concentration for U, but not for Th and Pb. The final two experiments dealt with uptake of U, Th, Pb, Ra (radium), Cs (cesium), Po (polonium), and As (arsenic) from soils contaminated by a former Ra processing facility, both in a controlled lysimeter setting and in uncontrolled home-garden settings. The results generally agreed with those of the initial experiment, although the overall geometric mean CR for Th was higher at 0.02. Most of the recommended Th CR values for dose estimation are tenfold below those for U; our garden-setting results suggest they should be equal or higher. The effects on soil properties and crop type on CR values are discussed. Key words: Concentration ratio, uranium, thorium, lead

Beschreibung: A previous study showed that large differences in K uptake by alfalfa (Medicago sativa L.) grown in the greenhouse occurred on soils which had similar ammonium-acetate-extractable K (NH4OAc-K) concentrations at seeding. Differences in total K uptake appeared to be closely related to the uptake of nonexchangeable K (NEK). The objective of this study was to determine what fractions or forms of NEK in the soils were responsible for the large differences in total K uptake noted in the greenhouse experiment. The total amount of NEK extracted in seven sequential extractions with boiling 1 M HNO3 (Mactotal) varied widely among soils and was significantly related to the total amount of K (r = 0.69; P 

Beschreibung: In a field experiment in which heavy applications of liquid dairy manure were added annually for 6 yr to a vermiculite-containing corn-cropped sandy clay loam soil (Mountain series), fixation potential and X-ray diffraction analyses were done to determine if fixation of added K+ and NH4+ had occurred and clay mineralogical changes could be detected. Of the 850 kg K+ and the 460 kg NH4+ added per hectare each year, approximately 28% of the K+ and 24% of the NH4+ remained fixed. This caused a marked increase in the 1.0-nm peak at the expense of the 1.4-nm peak due to collapse of vermiculite layers to form pedogenic mica. Thus, changes in soil management, specifically in fertilizer practices, can result in significant changes in clay mineralogy within a short period of time. Such changes are agronomically important and should be taken into account in the interpretation of clay mineralogical data. Key words: Potassium and ammonium fixation, vermiculite to pedogenic mica transformation, liquid manure application

Beschreibung: Humic acid (HA) and alkali-insoluble residue fractions (Residue) were isolated from four types of peat from the Fraser River Delta area. The peat fractions were characterized with respect to sulphur forms and response to acid hydrolysis. Total S content of HA fractions ranged from 0.3 to 5.5% on an ash-free basis, with 69–83% in C-bonded S form. Nitrogen: sulphur ratios varied between 0.64 and 5.9. The highest S contents and lowest N:S ratios were associated with peats formed under the influence of brackish water. Similar patterns were observed for the Residue fractions. Only small proportions of S (7.9–17.3%) were recovered in soluble form from the peat fractions after acid hydrolysis, and hydrolysis was accompanied by S losses attributed to volatilization. On average 4% of the initial C-bonded S was recoverable in that form in the hydrolysates, whereas 46% of the initial organic sulphate appeared in the hydrolyzate in sulphate form. The low recovery of S in hydrolyzates indicated a correspondingly small contribution of S-amino acids to the C-bonded S fraction. The large proportions of sulphur and carbon resistant to hydrolysis indicated a rather high degree of chemical (and perhaps biological) stability. Key words: Sulphur forms, hydrolyzable-S, peat humic acid, gyttja, peat fractions

Beschreibung: Distilled water leaching of new alundum/ceramic plate lysimeters removed considerable amounts of Ca, Mg, Na, K, SO4, Cl and Zn. After washing with 3 L of distilled water, levels were still of sufficient magnitude to interfere with the analysis of solutions with low solute concentration. Washing the plates with 2 L of 1 N HCl extracted considerable amounts of Ca, Mg, Na and K, and higher amounts of Fe, Zn, Al and Mn, but further distilled water washing resulted in rapid equilibration with a spike solution. Rinsing new lysimeters with progressively more acidic solutions indicated residual zinc contamination when the solution pH was below 6.0. There was virtually no iron or manganese contamination from the lysimeters at a solution pH between 3.0 and 5.0. Aluminum was leached from the plates at solution pH of between 3.5 and 4.0; however, the high Al concentration in the soil solution at these pHs may mask this interference. Although Al poses a considerable contamination problem at solution pHs of 3.0, soil solutions at this pH level are unlikely except in unusual situations (e.g. soils developed on acid mine tailings). The pumping of 2 L of 1 N HCl followed by large volumes of distilled water through the lysimeters is recommended for most field studies. Prior testing of the plates is required if low solute concentrations are expected or if elements other than those mentioned here are of interest. Key words: Lysimeters, ceramic samplers, soil water collection, alundum lysimeters, soil solution