ALBERT

Description: Long-term manure application could increase soil earthworm abundance in cultivated soils. The objective of this study was to evaluate the effect of 14 yr (1977–1991) of manure and NPKMg fertilizer on earthworm populations, soil structural stability, N mineralization (NO3) and biological activity (CO2) on a Le Bras clay loam (Humic Gleysol) situated at St-Lambert, Quebec. The field experiment, in a split-plot design, consisted of two manure rates (0 Mg, 20 Mg ha−1) as principal treatments with secondary treatments receiving mineral fertilizer (NPKMg) and a control. These treatments were carried out over a 4-yr crop rotation of silage corn, (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and canola (Brassica campestris L.). Soil and earthworm sampling was done in fall 1991 under corn. Compared to mineral fertilizer treatment, long-term application of manure increased earthworm populations. However the interaction between the treatments of mineral fertilizer and of manure was not significant. Of the earthworms extracted by formalin and hand sorting, Aporrectodea genus was dominant in soil, representing 98–100% of the population. Several Allolobophora chlorotica and Lumbricus juveniles from the genus Lumbricus were found only in manured plots. Soil water stable aggregates and biological activity (CO2) were both increased by manure application. Mineral fertilizer application had no significant effect. A strong correlation was obtained only between earthworm abundance and biological activity (CO2). The results indicate that 14 yr application of solid cattle manure improved soil earthworm populations and diversity, biological activity (CO2) and structural stability compared to fertilizer treatments and the control. Key words: Earthworms, Aporrectodea turgida, manure, mineral fertilizer, organic matter, biological activity (CO2), N mineralization potential (NO3), water-stable aggregates

Description: The availability of fertilizer N to crop under zero tillage (ZT) versus conventional tillage (CT) is affected by immobilization, ammonia volatilization, denitrification or leaching. This study examined the relative importance of those four factors in influencing the availability of N to the crop and the recovery of applied 15N-labelled N in soil and plants. Field experiments were conducted at two sites in central Alberta to determine the influence of tillage, N source, method of N placement and simulated rainfall on the recovery of 15N-labelled fertilizers in spring barley (Hordeum vulgare L.) plants and soil. A first experiment compared four soil surface broadcast N sources [urea, ammonium sulphate (AS), ammonium nitrate (AN) and potassium nitrate (KNO3)]. The N recovery in barley plants was KNO3〉 AN 〉 AS 〉 urea. With the exception of KNO3, plant N recovery was greater under CT than under ZT, particularly for urea. Immobilized N in soil was often less with KNO3 than the other N sources. There was apparently virtually no denitrification loss during the one crop season used in these experiments, and the recovery of KNO3 was complete. In a second experiment, methods of placement were evaluated. The recovery of N in plants was lowest for surface broadcast urea under ZT, particularly when no water was added after urea application. Banding urea beside and/or below the seedrow in comparison to broadcasting markedly increased N recovery in plants, especially under ZT. The differences in N recovery between ZT and CT were greater for broadcast application than for band placement. Method of placement had little effect on N immobilization under ZT, but under CT the amount of immobilized N was less with subsurface banding than incorporation. Simulated rainfall immediately after surface broadcast urea application under ZT increased the N recovery in plants. In conclusion, surface broadcast urea under ZT was less efficient than the other N sources and its recovery improved considerably when placed in bands below the soil surface near the seedrow. Key words: Ammonium nitrate, banding, fate of applied N, 15N-labelled fertilizers, N immobilization, N recovery, surface broadcasting, urea

Description: Spatial variability of soils is a landscape attribute which soil scientists must identify and understand if they are to construct useful soils maps. This paper describes the spatial variability of soils in a forested watershed in the Medicine Bow Mountains, Wyoming, using both conventional statistics and geostatistics. Principle Components Analysis indicated that flow accumulation and aspect were the two terrain attributes that most economically described terrain variability. Thickness of A and B horizons, organic carbon and solum coarse fragments were variable in the study area (CVs of 40 to 58%). Simple correlation and regression analyses suggested there were no statistically significant relationships between soil properties (texture, pH, coarse fragments, organic carbon content) and terrain attributes (elevation, slope gradient, slope shape, flow accumulation, aspect). Geostatistical analysis indicated thickness and coarse fragment contents of the A and B horizons, and solum thickness were spatially independent variables; however, pH, organic carbon content, and solum coarse fragment content were spatially correlated. Spatial variability was described by both linear (pH and organic carbon content) and spherical (solum coarse fragment) models. Use of geostatistics provided insight into the nature of variability in soil properties across the landscape of the Libby Creek watershed when conventional statistics (analysis of variance and regression analysis) did not. Key words: Rocky Mountains, Medicine Bow Mountains, forest soils, spatial variability, principle component analysis, geostatistics

Description: Tillage effects on the soil environment suggest that it may influence rooting depth and root distribution. In this study, corn (Zea mays L.) rooting depth and root mass distribution were compared under conventional and conservation (chisel, ridge, no-) tillage on sandy loam and clay loam soils at Ottawa, Ontario. Root depth and distribution in 0.10-m vertical increments during vegetative growth were estimated using a combination of excavation of the surface horizon (0–0.10 m) and 0.05-m diameter cores obtained in the row and midway between two rows over a 3-yr period. An exponential model was used to fit root mass distribution data normalized with respect to total root density summed over all increments and maximum rooting depth in the profile. Soil moisture, temperature, mechanical resistance and bulk density varied with tillage treatment, but differences were not associated with root mass distribution. Rooting depth varied with soil texture, year and tillage, with increased rooting depth associated with increased tillage and decreased moisture in surface soil layers. In contrast, a common exponential model was found to fit normalized root mass distribution data under all tillage treatments. Our data suggest that simulation of root mass distribution under all tillage practices is possible if rooting depth and root mass density of the surface soil layer are known. Key words: Corn, model fitting, root distribution, tillage, Zea mays

Description: A chemical fractionation scheme for soil boron was investigated by measuring the amounts of B extracted from minerals and synthetic soils amended with B. The scheme fractionated B into five fractions — readily soluble (solution plus non-specifically adsorbed), specifically adsorbed, oxide bound, organically bound and residual. These five fractions were extracted by 0.01 M CaCl2, 0.05 M KH2PO4, 0.2 M acidic NH4-oxalate, 0.02 M HNO3-30% H2O2, and 1:4:5 HNO3-HF-HCl, respectively. The methodology was tested on goethite and clay mica and three synthetic soils containing mixtures of goethite, clay mica, humic acid, calcite, and quartz sand and amended with three levels of B. Specifically adsorbed and oxide bound B were significantly correlated with the content of goethite in the synthetic soils, while residual B was significantly correlated with the content of clay mica. The recovery of extracted B, estimated as the percentage of total fractions over total B content in minerals and synthetic soils, ranged from 85 to 104%, with a mean of 97%. The overall results obtained with the fractionation scheme were deemed satisfactory as to sensitivity and precision for B fractionation. Key words: Boron, soil fractionation, sequential extraction

Description: The possibility of nitrate adsorption in 18 samples representing 11 soil types from the lower Fraser Valley of British Columbia was examined by differential extraction, equilibration and column leaching methods. Contrary to what was expected if nitrate was adsorbed by the soil, more nitrate was extracted by water than by 2 M KCl from some of the samples. Observations in related studies of greater microbial growth in 0.1 and 1.0 than in 2.0 M KCl extracts after more than 1 wk of storage and of different equilibrium results when conducted with and without toluene supported the conclusion that microbial or enzyme activity caused the larger amount of nitrate to be extracted by water than by 2 M KCl. Both equilibration and column leaching methods measured adsorption in some of the soil samples, but the amounts in the various samples by the two methods were not always the same. The equilibration method was analytically more precise than the column leaching method because it was simpler and required fewer measurements, but the column leaching method was considered to match more closely the soil to water ratio that would occur in the field. The equilibrium method found from 0 to 34% adsorption of the nitrate when added at a concentration not exceeding 50 μg N g−1. Further work is required to develop a practical method to meaningfully quantify nitrate adsorption in soils. The presence of nitrate adsorption has important implications for the interpretation of soil nitrogen research data and should possibly be included in nitrogen simulation models. The observation of microbial or enzyme effects on extraction of nitrate from soil shows the importance of using extraction solutions (e.g., those of high salt concentration or that contain a microbial inhibitor) that eliminate that possibility. Key words: Nitrate reactions, anion adsorption, nitrogen process, microbial effect, microbial inhibition

Description: The Versatile Soil Moisture Budget (VSMB), including the background leading to its development in the "early days" meaning around 30 yr ago, is described. National and international efforts before that time created a healthy climate for the development of agrometeorology in Canada and the pioneering work in soil moisture and crop-weather modelling.Events in the early days leading to a concerted endeavour of soil moisture modelling included: (i) a small group of highly qualified professionals from different disciplines, as well as support staff, had been established under the guidance of a team leader at the then Plant Research Institute (PRI); ii) a Canada wide crop-weather study had produced daily climatological and crop data at nine Canada Department of Agriculture establishments over 10 yr (1953–1962); iii) a computer became available to PRI staff (IBM 1620 with 16K); and (v) several sub-models providing the necessary input to the soil moisture model were at various stages of development (e.g. the "latent" evaporation and the biometeorological time scale sub-models).This paper presents an overview of the development of the VSMB using standard climatological data for generating daily soil moisture estimates under crops. Its concept, design and widespread applications in Canada and abroad are discussed. A more detailed analysis is left to the other presentations at this Symposium. Key words: Soil moisture, modelling, applications

Description: The use of conservation tillage management in fallow cropping systems reduces soil erosion and improves soil quality. The economic benefits of these alternate tillage methods are less certain. This study examined the economic returns from reduced tillage methods on fallow using yield and input data from two experiments at the Agriculture and Agri-Food Canada Research Centre at Lethbridge, Alberta. One experiment was long-term study initiated in 1955 with eight treatments, the second was a 5-yr study with 15 treatments. Results from the 5-yr study indicated no difference in net returns between conventional and reduced tillage fallow systems. In contras, the long-term study net returns were highest for tilled systems and lowest for herbicide-only systems. The long-term study had a build-up of weeds that are difficult to control with herbicides alone. The resulting lower average yield and higher herbicide costs of the herbicide-only treatments in the long-term study accounted for most of the contrasting results between the two experiments. An economic evaluation of tillage practices requires the entire system to be evaluated, not just the tillage component. Key words: Economics, tillage, reduced tillage, conservation practices, weed control

Description: Soil organic matter contributes to the productivity and physical well-being of soils. An 11-yr study was conducted on a clay soil in the Brown soil zone in southwestern Saskatchewan to determine the influence of tillage and cropping frequency on soil organic C and total N content. Carbon and N behaved in a similar manner. Cropping frequency did not affect soil organic C or total N content, but soil C and N were greater under no-tillage (NT) than under mechanically tilled continuous wheat (Triticum aestivum L.) (Cont W) and fallow-wheat (F-W) rotations. Effects were apparent in the 0– to 7.5– and 7.5– to 15-cm depths. Over the 11-yr period, F-W (minimum tillage) gained no additional C; Cont W (conventional tillage) gained 2 t C ha−1, and both Cont W (NT) and F-W (NT) gained 5 t C ha−1. Changes in organic C and N were greatest in the final 4 yr of the experiment when crop residue production was greatest. Using data from two similar experiments conducted during the same period on soils differing in texture, we demonstrated that C gains were directly related to clay content of the soils. Thus, when attempting to estimate C storage in soils, we must consider both residue input and soil clay content. Key words: Organic C, total N, organic matter, soil texture, bulk density

Description: Accurate simulation of soil moisture content at any time of the year is important to agriculture in dry regions due to the vital role soil moisture plays in crop production. In certain applications such as drought monitoring, other components of the hydrologic cycle such as runoff, snowmelt runoff, deep drainage and evaporative loss must also be accurately estimated. The goal of this study was to develop a model which accurately accounts for the major components of the hydrological cycle in order to simulate soil moisture content for drought monitoring and crop yield prediction. The versatile soil moisture budget (VSMB) was evaluated and modified to improve the prediction of soil moisture content runoff from rainfall and snowmelt, drainage of moisture out of the root zone and soil surface temperature. The modified components of the model were independently tested and validated using field and published data. The soil moisture output from our modified model correlated well with observed changes in soil moisture during the growing season under wheat, fallow and over the winter. The moisture content of the surface layer was simulated with greater accuracy than that of deeper layers. The soil moisture simulated by the modified model compares better with measured values than that simulated using the original version of the VSMB. The simulation of snow dynamics at Lethbridge, a chinook-dominated region, gave credibility to the snowmelt runoff predicted by the model. Key words: Soil moisture, modelling, runoff, evapotranspiration, snowmelt, Canadian prairies

Description: Proper management of crops on Gray Luvisols requires knowledge of net soil N mineralization during the growing season. Soil samples from a long-term field experiment at Beaverlodge, Alberta, were used to determine the kinetics of net N mineralization in soil samples from different crop rotations. The cropping systems established in 1968 consisted of (i) continuous barley (Hordeum vulgare L.) (CB); (ii) barley–forage (BF) [bromegrass (Bromus inermis Leyss.) and red clover (Trifolium pratense L.)]; (iii) continuous bromegrass (CG); and (iv) continuous legume (red clover) (CL.). The BF rotation was generally alternated every 3 yr, and each phase of the rotation (BF and BF) was present in every year. Soil samples from each cropping system were sampled to a depth of 15 cm in 1984. Net N mineralized during a 20-wk laboratory incubation at 30 °C and optimum moisture ranged from 32 to 207 mg kg−1 soil and followed the trend BF 

Description: Nutrient imbalances of declining sugar maple (Acer saccharum Marsh.) stands in southeastern Quebec have been associated partly with high soil exchangeable acidity and low base saturation on. A greenhouse experiment was set up to determine how growth and nutrient status of sugar maple seedlings can be influenced by soil acidification and the presence of an endomycorrhizal fungus. The experiment consisted of five levels of soil base saturation (from 12 to 50%) and two levels of soil inoculation by an endomycorrhizal fungus (inoculated and control) in a complete factorial arrangement Sugar maple seedlings were grown for 3 mo in the treated soil substrates. Seedling shoot elongation rate, growth [dry matter (TDM) mass, stem diameter, and total leaf area], and K, Ca and Mg concentrations in foliage and roots decreased with soil acidification with base saturation used as an indicator of the soil-acidification status. Foliar K and Ca level reached values below critical thresholds when soil base saturation was reduced to 12%. Under the experimental conditions, seedling growth was not significantly affected by endomycorrhization, except for root DM mass, which was reduced by 24% compared with the control treatment. For mycorrhizal seedlings, foliar Al concentration increased linearly from 113 mg kg−1 to 210 mg kg−1 with the reduction of soil base saturation from 50% to 12%, while, for non-mycorrhizal seedlings, foliar Al concentration remained at a high level (195 mg kg−1) independently of the soil acidification level. Sugar maple seedling growth was not related to accumulation of Al in foliage. The results of this experiment support the hypothesis that a causal relationship exists between the level of soil base saturation and the growth decrease and associated nutrient disorders observed in declining sugar maple stands in Quebec. Key words:Acer saccharum, nutrient status, seedling growth, soil base saturation, endomycorrhizae

Description: Humic acids (HAs) from major horizons of a Gleyed Black Chernozem and a set of soil and sediment samples were examined to understand the influence of the structure a composition of organic substances on sorption of organic pollutants. Solid state 13C cross-polarized/magic angle spinning (CP/MAS) NMR results indicated that the aromaticity of HAs increased with soil depth. The aromaticity of organic substances in bulk soils and sediments varied with the degree of geological diagenesis. Sorption experiments showed a linear relationship between the carbon normalized partition coefficient (Koc) of α-naphthol and the aromaticity of HAs and non-extracted organic substances in whole soils and sediments. The Koc values of α-napthol had a log-linear relationship with the atomic mass ratio (N+O)/C of the organic substances in soils and sediments. Correlation analysis for the literature data further revealed that the compositional and structural properties of organic substances were related, suggesting possibilities of predicting Koc with either compositional or structural parameters Measured Koc values demonstrated considerable deviations from those calculated with prediction models using Kow. The prediction models may not be accurate because they do not account for the compositional and structural differences in organic substances of sorbents. Key words: sorption, organic substances, aromaticity, Koc, α-naphthol

Description: We propose a conceptual model based on our results from rhizospheric studies of a Norway spruce stand growing on a nutrient poor Podzol in Southwest Sweden. We assume that dynamic linkages exist between three soil fractions: bulk soil, rhizosphere (Rhizo) and soil root interface (SRI). The soil fractions were characterized by organic matter content, electrical conductivity, pH, and soluble and exchangeable cations. Analyses showed great differences among the three soil fractions, especially the properties of the SRI. Cation exchange capacity and base saturation were higher in the rhizosphere and SRI than in the bulk soil. We attribute this to accumulation of organic matter (OM) in the rhizosphere and SRI. Moreover, the rhizosphere and SRI fractions had lower pH and higher titratable acidity than the bulk soil. Any possible negative effects of Al to the roots could be offset by accumulated organic matter and base cations (BC). The calcium-aluminum balance followed a consistent trend: bulk 〈 rhizo 〈 SRI. The results suggest that soil around the roots exhibits a different chemical composition than that of the root-free (bulk) soil, indicating more favorable conditions for roots. We suggest that trees growing on nutrient-poor acid soils invest their energy around roots to create a favorable microenvironment for both roots and microorganisms. Our results suggest that existing models which attempt to connect tree growth to soil acidification need modification. Such modification would include horizontal variation (bulk soil, rhizo and SRI) besides the vertical ones normally emphasized. It is possible that the conceptual model may enable a better understanding and description of naturally existing relationships between soil and plants under normal and stressed conditions. Key words: Conceptual model, organic matter, rhizosphere, soil root interface, acidification and growth models, Norway spruce

Description: Soil fertility may vary considerably within a field. The effects of variable soil fertility on the relationships among average crop yield response, average soil test, and fertilizer applied evenly to a field have not been examined. This paper develops stochastic equations to describe the average yield gain on a field basis from the application of a single constant rate of fertilizer, in fields with variable soil fertility. The equations are solved numerically for the specific case of nitrogen fertilizer on corn (Zea mays L.) in Ontario, Canada. The results suggest that since the relationships among yield response, soil test, and applied fertilizer are non-linear, a single soil test calibration cannot exist for fields with different spatial variability. Soil test calibrations obtained from sites with low variability (for example small plots) will not hold for sites with higher variability (for example farm fields). Calibrations obtained from sites with low variability will under-predict the optimum economic fertilizer rate for sites with low variability will under-predict the optimum economic fertilizer rate for sites with high variability. The results do not invalidate soil test calibration relationships per se. The challenge is to combine these calibrations with additional knowledge about the spatial distribution and field-scale variability of soil test values in order to maximize economic benefit. Key words: Spatial variability, soil test, fertilizer recommendation, yield, corn, field scale

Description: The herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-tnazine) is widely used in the production of corn and several other crops. It is moderately mobile in soil and is frequently detected in surface water and groundwater. The objective of this study was to determine if incorporating manure into a soil cropped to corn influenced the rate or pathway of atrazine dissipation. Soil cores (0–60 cm) were taken from two field plots in continuous corn one unfertilized the other receiving an annual application of 100 t manure ha−1 for each of the last 4 yr. The cores were sectioned into 20-cm increments, and subsamples used to prepare soil slurries amended with 2.5 to 25 μg atrazine mL−1 slurry. These were incubated with shaking at room temperature for up to 2 mo. Chemical analysis of extractable atrazine revealed that the herbicide was completely and rapidly degraded after a variable lag period of as short as about 18 d. Samples from each of the three depths degraded atrazine. [U-Ring-14C]atrazine was quickly and completely converted to carbon dioxide through the intermediate of hydroxyzine by activated soil slurries. The lag period prior to atrazine removal was significantly shorter in soil from the manure-treated plot. Stable enrichment cultures transferred at weekly intervals continued to mineralize atrazine confirming that atrazine-metabolizing microorganisms were responsible for atrazine degradation in this soil. Key words: Soil atrazine dissipation, herbicide biodegradation, manure incorporation

Description: During the past decade, a number of developments have improved the possibilities for real-time, in situ monitoring of soil water content, providing potential for much improved testing and validation of soil water models Brief reviews of the principles and procedures are presented for the gravimetric and gamma ray attenuation methods. A summary of the developments of time-domain reflectometry (TDR) demonstrates its high capability for continuous monitoring of soil water content. Portable dielectric probes (PDP) and capacitance instruments also use the high dielectric constant of water as an indicator of soil water content. Commercially available TDR instruments offer a choice of options that allow this method to be fitted to a variety of specific measurement requirements. The ease of use and portability of TDR instruments and the flexibility of design for the TDR probes has made possible the rapid measurement of surface and near surface water contents on a field scale. Multiplexers and data loggers now allow the efficient monitoring of water content to record both spatial and temporal patterns not previously detectable. Fine resolution and analyses within the electric field of a TDR probe has allowed us to measure and record the diurnal patterns of water uptake from, and its release to, relatively dry sod adjacent to growing corn roots Water distribution calculations show that the water measured as moving in and out of roots daily is sufficient to hydrate and stabilize the sheaths of soil that surround the root growing in dry soil. Key words: Soil water content, TDR, root uptake, root exudation, field measurement, water balance

Description: The forms, amounts and distribution of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) were assessed in soil profiles under trembling aspen (Populus tremuloides Michx.) stands in the southern boreal forest of Saskatchewan, Canada. The total mass of organic C storage in the LFH horizon and mineral soil to a depth of 1 m ranged from 95 352 to 103 430 kg ha−1, with an average of 99 220 kg ha−1. Organic C and N in the LFH horizon accounted for the greatest proportion of the total storage (47.3% of C and 34.2% of N), followed by the B horizon (22.4% of C and 32.7% of N) the A horizon (17.3% of C and 18.3% of N) and the C horizon (13.0% of C and 14.8% of N). Unlike C and N, more than 96% of the total P was found in the mineral soil and only 3.5% in the LFH horizon. Much of the P stored in the mineral horizons is contained in non-labile primary minerals forms. The greatest proportion (36.5%) of organic S was found in the C horizon with 26.6% in the LFH horizon. The contribution of the LFH horizon to total organic C and N stored in boreal forest soils should not be neglected in global nutrient cycling models. Key words: Forest floor, litter, nutrient storage, organic matter

Description: The retention of Cd by selected Ontario soils with a range of soil properties was investigated. Batch adsorption experiments were carried out at the actual (unadjusted) PH of the soil and at a range of PH values adjusted by the addition of acid or base. For all soils, Cd adsorption increased with increasing pH and with increasing Cd solution concentration. The adsorption data was fitted, by a linear least squares technique, to the Langmuir adsorption isotherm. Maximum adsorption, qmax, at unadjusted soil pH values ranged from less than 8 mmol kg−1 for the Fox sandy soil to 64.8 mmol kg−1 for the Hanbury heavy clay soil. Calculated Cd adsorption maxima were regressed against measured soil properties to determine the most important properties involved in the adsorption of Cd. Multiple linear regression analysis revealed the best model to be qmax = 8.33 + 0.67 (organic carbon) + 4.37 (inorganic – poorly crystalline Fe, Fepc). Surface complexation modeling indicates that humic surfaces account for adsorption at pH values beginning at approximately 3.5 and that hydrous ferric oxide surfaces account for Cd adsorption at pH values greater than 7. Key words: Cadmium adsorption, Langmuir isotherm, surface complexation, soil contamination

Description: Studies about Pb variability in contaminated soils, especially in the case of fallout from smelters or facilities, are few and the relevance of geostatistical technique for studying contaminated soil as well as the surface area required for investigation are unclear. Few studies have been conducted on short-range variability of trace elements in soils, and some of them have shown these elements to be randomly distributed while others pointed out the spatial dependence between sample locations. Therefore the main objective of this study is to document the short-range variability of Pb in an area contaminated by fallout, using a case study in France. Soil lead in this site arises from a history of industrial use. No other metals were detected in Pb emissions. On this site, we conducted a statistical and a geostatistical study of Pb content in soil, and of soil characteristics that may affect it. The aims of this work are (i) to separate the spatial structure due to high Pb fallout from a content and diffuse pollution, (ii) to separate the variability due to analytical measurements from ones related to spatial variations, (iii) to point out the soil characteristics correlated with Pb, (iv) to optimize sampling design for monitoring the long-term changes following remedial action. Results demonstrated that in this highly contaminated soil, fallout Pb was mainly located in the surface layer (0–0.2 m depth). The geostatistical study suggested that the study of the spatial structure may help in discriminating fallout Pb from Pb coming from diffuse pollution or geochemical content. However, the large spatial variability of Pb, partly due to microheterogeneity made the monitoring of this toxic element very difficult, and required a larger surface for sampling. Using correlation techniques to detect causations appeared not to be relevant. Therefore, other statistical techniques such as path analysis should be tested. Additionally, microanalysis, mobility and bioavailability studies, as well as lab or bench scale remediation studies should be conducted. Key words: Contaminated soils, fallout Pb, short-range variability, geostatistics

Description: There is an increased use of no-tillage (NT) methods in soils of the Peace River region of Alberta–British Columbia where a good proportion of acid soils exist. There is little information, however, on how crops, soils, and weeds respond to liming under different tillage intensities. A Hythe clay loam (Gray Luvisol; initial pH in CaCl2 ≈ 5) was limed (7.5 t ha−1) in May 1991. Field pea (Pisum sativum L.) yield, soil properties, and weed populations under conventional tillage (CT) and NT were monitored during three growing seasons (1993–1995). The pH of limed soil in the 0–10 cm layer ranged from 6.0 to 6.3. Liming slightly increased NO3-N, P and bulk density of soil, lowered exchangeable Al concentration and wet aggregate stability, and had no effect on NH4-N and penetration resistance. Liming increased the grain yield by 0.50 (22%) t ha−1 yr−1 in CT and by 0.55 (18%) t ha−1 yr−1 in NT. Aboveground dry matter (DM) increase of 1.37 (27%) t ha−1 yr−1 in CT and 1.72 (25%) t ha−1 yr−1 in NT was obtained due to liming. Populations of annual broadleaf, annual grass and perennial weeds were not affected by either liming or tillage. Reduced soil acidity and exchangeable Al in conjunction with increased NO3-N and P contributed to increased crop yield by liming under both CT and NT. Higher soil moisture in the NT contributed to increased yield in comparison to CT system, as other soil properties and weed population were not significantly affected by tillage. Key words: No tillage, Pisum sativum L., exchangeable aluminium, wet aggregate stability

Description: The application of the herbicide Roundup (glyphosate), and subsequent death of a predominately bromegrass (Bromus inermis Leyss.) and blue grass (Poa pratensis L.) sward, resulted in a 20- to 30-fold increase in denitrification rate 14 and 49 d after application compared to herbicide-untreated and fallowed soil treatments. The regulation of denitrification by O2, carbon and NO3− availabilities was assessed by measurement of various soil variables. The regulation of denitrification by C and NO3− availabilities was further studied in a laboratory experiment in which denitrification was measured following NO3− and glucose-C addition to soil from the field treatments. Elevated denitrification in the herbicide-treated soil was attributed to increased soil moisture and NO3− contents resulting from the death of vegetation. The death of the grass sward did not increase available C to denitrifiers, whereas the absence of vegetation in the fallowed soil 1 yr following herbicide application reduced available C. This study indicates that herbicide application to a grass sward increases denitrification and hence may contribute to greater nitrous oxide emission and N loss from soil. Key words: Denitrification, herbicide, plants, nitrate, regulation, soil moisture

Description: Field microplot studies were conducted under zero-till conditions on a fine sandy loam (Orthic Black Chernozem) to determine the effect of the urease inhibitors N-(n-butyl) thiophosphoric triamide (NBPT) and ammonium thiosulphate (ATS) on volatile losses of NH3 from urea and urea ammonium nitrate (UAN). Two studies were conducted, one in late May and one in early August. Losses of NH3 were measured on days 1, 2, 4 and 7 after fertilizer application, using ammonia traps. Ammonia losses were higher in the second study due to the higher soil temperatures and lower soil moisture later in the growing season. Total NH3 losses increased in the order Control 〈 UAN + NBPT = Urea + NBPT 〈 UAN + ATS = UAN 〈 Urea. Total loss of NH3 during the 7 d after fertilizer application was higher from urea than from UAN, particularly in the first study. Use of NBPT was effective in reducing NH3 volatilization from both UAN and urea during 7 d after fertilizer application while use of ATS had little influence on NH3 loss from UAN. The NBPT may delay losses by slowing the hydrolysis of urea, but volatilization may persist for a longer duration. The delay in urea hydrolysis could allow time for rainfall to carry the urea into the soil, thus reducing total volatilization losses from surface fertilizer application. Key words: N-(n-butyl) thiophosphoric triamide, zero tillage

Description: With growing pressure to reduce pesticide use, fruit growers require an alternative to herbicidal control of weeds. One option is the use of mulches or permanent vegetative ground covers, which in turn may have advantages in promoting soil physical properties and improving growth. This study examined the short-term effects of ground cover management in two newly established dwarf apple orchards in Quebec. Effects of cultivation, composted manure mulch, straw mulch, grass cover crops, a cover crop mixture of lupin and wild carrot (mixed flora) and geotextile were determined, comparing soil aggregate stability, bulk density, temperature, volumetric water content and tree growth. Straw and geotextile mulches resulted in higher soil water contents and tree growth relative to soil under grass or mixed flora ground cover. Ground cover maintained soil aggregate stability. Soil temperatures were highest under cultivation and geotextile treatments in spring and summer months, and apple yields and growth rates were greater than for ground cover treatments. Straw mulch buffered soil from temperature variation. Little effect of mulch treatments on soil bulk density was observed. Given that soil water content was the primary factor related to optimum orchard production straw and geotextile mulches promoted soil water retention and could be considered superior management options for growers, depending on costs of establishment and maintenance of the mulches. Key words: Mulches, ground cover, bulk density, aggregate stability, soil temperature, volumetric water content

Description: A by-product of phosphate fertilizer production is phosphogypsum (PG). Relatively high F concentrations occur in the solid phase and in the highly acidic process water (PW) that initially fills its pores. The present research addresses the fate of F and the effects on mineral stability as phosphogypsum leachate (PGL) interacts with calcareous (Ck) soil and non-calcareous (Bt) soil. In a sequential batch equilibration, soils were exposed to fresh PGL during 30 d-long extractions. Major ions, pH and electrical conductivity (EC) were monitored. At 28 d, F concentration decreased from 31 mg L−1 in the PGL to 11 mg L−1 in the Bt-PGL mixture and 22 mg L−1 in the Ck-PGL mixture. Saturation indices (SIs) for fluorite ranged from 2.1 to −3.6. Extracts were closer to saturation with fluorite than with the other F minerals studied. Using alternative geochemical constants, fluorapatite was predicted to be stable in Bt-PGL extracts. The day 28 Bt-PGL extract was also near equilibrium with alunite, basaluminite, jurbanite, gypsum, amorphous silica, and quartz. Of the phyllosilicates in the soil-PGL mixtures at day 28, only kaolinite was predicted to be stable in only the Bt-PGL mixture. The potential for clay mineral instability and accelerated dissolution in F-rich PGL needs to be considered m the design of PG repositories. Key words: Fluoride, phosphogypsum, waste management, leachates, geochemical modeling, mineral stability

Description: Modeling simultaneous response to multinutrient fertilization to take advantage of element interactions is a promising approach in fertilizer prescription, but the practice is relatively unexplored in forestry applications. This paper demonstrates that simultaneous prescription of nitrogen (N) and phosphorus (P) fertilizer for tree seedling culture can be facilitated by response surface models generated from a multi-level factorial experiment designed to quantify growth, nutritional response and N × P interactions in white spruce [Picea glauca (Moench) Voss]. Seedlings grown from seeds in potted soil were tested in a 6 (N) × 4 (P) × 3 (replicates) factorial experiment in a greenhouse. Analysis of variance indicated significant quadratic trends in treatment responses and significant N × P interactions, hence quadratic response surface models were generated from the total biomass database. However, model accuracy (R2 = 0.56) was low and the N × P interaction was underestimated when luxury to toxic N levels were included. Since the positive N × P interaction was enhanced by N additions at lower (deficient) levels but diminished at higher (luxury to toxic) levels, a model constructed from a data subset which excluded high N treatments markedly improved accuracy (R2 = 0.88) and significantly increased the regression-coefficient estimate for the interaction term. Verification in a nursery field trial for a 3-yr rotation confirmed that this refined model improved fertilizer prescription by increasing acceptable seedling numbers and fertilizer recovery by plants in bare-root stock production. Key words: Nutrient interaction, modeling, forest nursery, fertilization efficiency

Description: Cultivation of oxisols of the Niari Valley (Congo) leads to considerable decline in the soil organic carbon content and structural stability in a few years. The objective of this study was to estimate the very short-term effects of cultivation on organic status and macroaggregate (〉 0.2 mm) stability of a soil which had been under savanna for 20 yr. Another objective was to identify the determinants of macroaggregate stability.On one hand, after 5 mo of manual or mechanized cultivation, stable macroaggregate content MA decreased significantly in the 0- to 10-cm layer (7% on average); soil organic carbon stock S did not (6% on average), whereas the decrease in soil organic carbon content C was significant only under mechanized cultivation (13.5% on average, vs. 7% under manual cultivation). On the other hand, the influence of cultivation on MA, S and C was not significant in the 10- to 20-cm layer (variations

Description: Naturally compacted subsoils, as a result of geogenic and/or pedogenic processes, are a common phenomenon in soils formed on medium textured basal tills in the Maritimes. This study was conducted to determine whether soil loosening following tile drainage could improve the long-term physical condition of naturally compacted subsoils and consequently improve soil permeability and crop productivity. The effects of subsoiling at various soil depths (35 to 70 cm) perpendicular to tile lines on soil structural form, and crop biomass yield and root growth were investigated over a 4-yr period (1989–1993) on sandy loam to loam Luvisolic, Gleysolic, and Brunisolic soils, at three sites in Nova Scotia. For two of the sites, soil bulk density measured using gamma ray attenuation showed a significant decrease immediately after subsoiling, and soil hydraulic conductivity determined using a constant head well Guelph permeameter was increased, relative to the non-subsoiled control. At one of the sites, subsoil loosening increased crop winter survival and productivity. Subsoiling did not appear to significantly improve the long-term permeability or environment for root growth below the 45-cm soil depth. Evidence of subsoil reconsolidation was found at each site within the three year period. Key words: Subsoiling; drainage; Luvisolic, Gleysolic and Brunisolic soil; soil physical properties

Description: The suitability of soil-test analyses for fertilizer recommendations for hazelnuts was assessed by detailed examinations of correlations with corresponding leaf-tissue concentrations in an orchard survey study. Correlations were examined only where optimum leaf-tissue nutrient concentrations had previously been established (i.e. N, P, K, S, Mg and Ca). Soil nitrate concentrations tended to increase substantially and relatively consistently in orchards where leaf N concentrations were greater than the optimum range, showing that soil and leaf analyses can be used for fertilizer recommendations for conservation and environmental as well as production considerations. Since most of the trees of the orchards in the study had P that was at or above adequate amounts, only limited conclusions could be made for soil P tests. Data from this survey and other literature showed that hazelnut trees can obtain adequate P from soils that have relatively low Bray-1 extractable P. Ammonium acetate extraction provides a reasonably good estimate of the K and Mg that are available to hazelnuts, and, for both nutrients, K and Mg fertilizer should be recommended for hazelnut (compared with many other crops) when soil-test analyses are relatively high. Ammonium acetate extracted considerable Ca from the soil and the amount extracted was not correlated with the concentration of Ca measured in the leaves. Calcium chloride (which extracts only unadsorbed sulphate) was a relatively poor extractant for available S because of the occurrence of sulphate adsorption in these soils. A surface 15-cm soil sample was adequate for most of the nutrients measured, but supplementation with subsurface analyses would improve nitrate, and possibly subsurface S should be included in the development of a soil test for S Soil testing is necessary to determine whether nutrients are building up in the soil. Also, only soil testing can be used for analysis-based recommendations prior to tree planting. Key words: Hazelnuts, Corylus avellana, filbert, nitrogen, phosphorus, potassium

Description: We assessed a method for extraction of plant-available potassium using a cation exchange membrane (CEM) burial technique. The study compared the amounts of K extracted by CEM burial with three reference chemical-based extractants for 19 soil samples representing a wide range of soil types in Saskatchewan, Canada and the People’s Republic of China. The three reference extractants were (1) 1 M NH4OAc, (2) a mixed solution of 0.01 M EDTA, 0.25 M NaHCO3 and 0.01 M NH4F and (3) 1 M HNO3. Potassium extractable by 1 M NH4OAc ranged from 37 mg kg−1 to 1889 mg kg−1 among the 19 soils. The K availability as predicted by CEM was significantly correlated with the reference methods with the strongest relationship (r2 = 0.94, P 

Description: Mulches are an alternative to herbicidal control of weeds in orchards. Mulches may affect soil nutrient levels and consequently alter tree growth, fruit yield, and quality. The objective of this study was to determine the effects of cultivation, straw mulch, geotextile mulch, grass cover, a cover crop mixture of lupin and wild carrot, and manure compost mulch on extractable soil nutrients in two newly established dwarf apple orchards in Quebec. In 1992, manure compost and straw mulches resulted in higher soil NO3−-N and K relative to those levels under ground cover. Levels of soil NO3−-N were related to soil water content under any particular mulch. Straw mulch resulted in high July NO3−-N levels and low September levels of soil NO3−-N. Geotextile and cultivation treatments resulted in higher September NO3−-N levels relative to July. Soil under manure compost tended to have higher P levels than soil under other treatments. There was little or no effect of mulch treatments on extractable levels of soil NH4+-N, Ca, or Mg. Key words: Orchard, apple, mulches, geotextiles, straw, nutrients, manure compost, grass sod

Description: Several pilot projects have demonstrated that estimation of soil moisture over a large area can be done using remote sensing. Three main methods have been tested with some success: thermal inertia, passive microwave and synthetic aperture radar (SAR). The advantages and limitations of each approach were summarized. Most Canadian research has focused on SAR data. It has shown that several parameters can affect the accuracy of soil moisture estimation using radar such as incidence angle, roughness, polarization and frequency. The data collected during the SIR-C/X-SAR experiment in Altona, Manitoba, were used to evaluate the impact of incidence angle on soil moisture estimation accuracy. Incidence angle was the most significant factor to explain the signal variations over time. The effect of incidence angle (38° to 58°) on the signal was linear in October. Correlation between soil moisture and the signal was higher with surface (0–2.5cm) measurements in the wet period (April) but there was no significant correlation during the dry period (October). A statistical model using soil moisture and incidence angle in April showed that an increase of 1° in incidence angle could decreased the C-HH signal by 0.25 dB and the L-HH signal by 0.30 dB. Such variation would generate a change of 2% (C-HH) and 5% (L-HH) in soil moisture estimation. Key words: Radar, remote sensing, soil moisture, microwave

Description: A number of animal licks, representing dry earth exposures, muck licks, and rock face licks, were sampled and analysed for 12 elements by using a sulphuric acid-hydrogen peroxide method to simulate digesta. The various types of licks may serve different needs. Sodium, magnesium, manganese, iron, and copper may draw animals to specific sites. Key words: Salt licks, ungulates, landscape management, Rocky Mountains

Description: A spring application of dairy cattle slurry (300 kg total N ha−1) on high- and low-fertility sites resulted in higher microbial biomass C during the growing season than on a control soil or a soil receiving 100 kg N ha−1 as urea. Microbial biomass C was also significantly higher on the high-fertility site and was reflected in greater N mineralization and N uptake by corn. There was no greater net N mineralization in the manured soil than in the control or fertilized soil as would be expected as a result of higher microbial biomass C and significant organic N contribution from the manure. Key words: Animal manure, nitrogen mineralization, corn, grain yields, soil fertility

Description: Lime-amended acid soil (a single application in 1963 at rates of 4.5 and 6.7 t ha−1) at Scott, Saskatchewan had pH of 0.5 and 1.1 units higher, respectively, than unlimed soil, when measured more than 30 yr later in 1994. However, no differences in soil-available phosphorus levels and crop yield were detected. Key words: Soil acidity, lime, phosphorus, Brassica rapa L., Triticum aestivum L.

Description: The use of urea in corn (Zea mays L.) production is common. Under current N fertilizer recommendations for corn, urea may have adverse effects on corn growth when applied in a band. The effects of ammonium lignosulfonate (LS) on corn growth and on N uptake from the banded application of urea and diammonium phosphate (DAP) mixtures were investigated on two soils from eastern Quebec. Field experiments were initiated in the first week of May 1991 on an Ormstown silty clay and a Ste. Rosalie clay soils (fine, mixed, nonacid, mesic Typic Humaquepts). Treatments were two rates of urea (30 and 90 kg urea-N ha−1) in combination with DAP (14 kg N ha−1), with or without banded fertilizer solutions of LS (8 kg N ha−1) applied at planting 5 cm to the side and 3 cm below the seed. A no treatment control was included. The low rate of urea and DAP (no LS added) resulted in a 19 and 24% increase in grain yield at the Ste. Rosalie and Ormstown, respectively, when compared with the unfertilized plots. When compared with the unfertilized treatment, the high rate of urea and DAP (no LS added) caused 10% increase in grain yield. However, addition of LS to the high rate of urea and DAP increase grain yield by band 20%. In general, LS significantly increased corn N uptake from urea on both soils. Separate 15N field experiments were initiated in June 1991. Mean recovery of 15N in total dry matter (grain and stover) was 51.9% in Ormstown and 47.9% in Ste. Rosalie soil. Denitrification estimates, calculated as 15N not accounted for, were not affected by LS and the rate of banded urea-N. Immobilization of 15N ranged from 17.8% to 30.9% of the applied labelled urea. The rate of urea-N banded had no significant effect on immobilization, but LS resulted in significantly less 15N immobilized. These observations suggest that LS can reduce the biological immobilization of urea-N and increase the efficiency of urea fertilizer by reducing the negative effects of banding high levels of urea, while attaining benefits of band placement. Key words: Lignosulfonate, corn, urea, 15N

Description: Zinc (Zn), copper (Cu) and molybdenum (Mo) concentrations of potatoes, cabbage, cauliflower, carrot, turnip, corn and lettuce grown commercially in three important agricultural regions of the Lower Fraser Valley of British Columbia were surveyed. Zinc and Cu concentrations in the edible portions of the various vegetables were within and frequently at the lower range of concentrations reported for corresponding vegetables grown in other non-contaminated areas of the world. It was concluded that there is more concern about low levels than about toxic Zn and Cu concentrations for vegetables grown in the Lower Fraser Valley. Molybdenum concentrations tended to be greater than those reported elsewhere in the world. Instances of high concentrations were quite site specific. At one location, the concentrations of Zn, Cu and Mo in potato tubers were considerably higher than in potatoes at other locations but it was not possible to determine whether this was due to the cultivar grown, the characteristics of the soil or management practices. The concentrations of the three metals in non-edible parts of the vegetables frequently varied more than the part normally consumed showing that extrapolation of the survey data to other types of vegetables regarding human nutrition quality must be made with caution. There were few correlations between concentrations of the elements in plants and in the corresponding soils, limiting extrapolation to other locations by soil analyses. A comparison of adjacent sites showed greater total soil Cu and Mo, and extractable P and K, concentrations under cultivated than under virgin conditions. Key words: Copper, zinc, molybdenum, survey

Description: A modified version of the irrigation scheduling model SimISP (Simulating Irrigation Scheduling in Potatoes) was evaluated in terms of its ability to simulate the potato crop root zone soil water content through the growing season. The model uses daily radiation, temperature, humidity, windspeed, precipitation and seasonal crop and soil parameter inputs to estimate evaporation, transpiration, canopy expansion and dry matter accumulation. Recent cultivar-specific characteristics incorporated into the model allow for more precise simulations between cultivars.Simulations were conducted for rainfed, irrigated and artificial shelter-imposed stress conditions during four growing seasons on two soil types in Colchester County, Nova Scotia. Generally strong agreement between simulations and field measured (TDR) available soil water content in the top 15 cm of the soil profile was achieved with an average error within ± 4.7 mm and a relative error within ± 0.26. Larger errors were obtained for the 15- to 30-cm soil layer with average errors within ± 7.3 mm and the relative error within ± 0.52. Differences between model simulations and field measurements indicate the need for an improved root growth sub-model that is soil water sensitive and more precise estimates of soil water recharge after rain. Key words:Solanum tuberosum L., SimISP, simulation model