bluuebunny/crossref_metadata_2025 huggingface dataset:
Effet de l’herbicide atrazine sur la respiration et l’ammonification de l’azote organique dans un sol agricole au cours d’une incubation
Authors: Lafrance P. , Salvano E. , Villeneuve J. P.
Published: April 2011

The importance of soil microflora and fauna in the breakdown of organic matter and nutrient release for plant growth is well recognized. However, the use of pesticides can affect soil bioactivity in a variety of ways. A long-term incubation laboratory experiment was performed to study the impact of the herbicide atrazine (commercial formulation) on soil respiration and arginine ammonification. The incubation time was lower than the half-life time for atrazine: this allows the presence of significant amounts of residual atrazine in soil throughout the incubation period. Atrazine induced a marked stimulation of cumulative CO2 evolution and the results were analyzed to fit a first-order degradation model for soil organic carbon. In the presence of various atrazine application rates (from 1 to 5 times the agricultural rate), the soil mineralizable carbon content was found to be 1.7 and 1.4 times higher than that of untreated soil. During the incubation, a marked temporal variability occurred in the arginine ammonification rate. Atrazine induced a decrease in ammonification rate, in comparison to the one obtained for the untreated soil. The ammonification rate varied little for atrazine applications greater than three times the agricultural rate, and for incubation times greater than 40 d. The characterization of the relation between the soil CO2 production rate (for 1 or 2 wk) and the ammonification rate (for 3 h) was obtained as a function of incubation time intervals by applying linear regression functions. Results showed that these variables are not significantly related. Key words: Bioactivity, atrazine, respiration, arginine ammonification, agricultural soil
Evaluation of selected factors influencing aggregate fragmentation using fractal theory
Authors: Rasiah V. , Kay B. D. , Perfect E.
Published: April 2011

Two fractal parameters, probability of failure (P) and fractal dimension (D), were used to evaluate the influence of cropping and wetting treatments, and aggregate size on fragmentation of soil aggregates during wet sieving. Five different sizes of aggregates (4–10, 2–4, 1–2, 0.5–1 and 0.25–0.5 mm) from five cropping treatments [conventionally cultivated continuous corn (CCC), CCC underseeded to red clover (CCR), minimally tilled continuous corn underseeded to red clover (CCRM), alfalfa (AL), and bromegrass (BR)] were subjected to two wetting treatments (rapid and slow) before being wet sieved. P increased nonlinearly with increasing aggregate size. The P of the slowly wetted agggregates was always less than that of the rapidly wetted aggregates. The P of larger aggregates, 2–4 and 4–10 mm, increased in the following order of cropping: BR = AL < CCRM < CCR = CCC. The D for the size distribution of 4- to 10-mm aggregates increased in the same order of cropping as that given previously. The D for the rapidly wetted aggregates was higher than that of the slowly wetted aggregates for all cropping treatments except CCC. The values of P predicted from a fractal probability model correlated well with the observed values. The results show that P and D of soil aggregates are strongly influenced by cropping and wetting treatments and aggregate size. Key words: Probability of failure, fractal dimension, wet sieving, wet aggregate stability, prewetting
Acidification adjacent to an elemental sulfur stockpile: II. Trace element redistribution
Authors: Warren C. J. , Dudas M. J.
Published: April 2011

Total concentrations of Ag, As, B, Ba, Co, Cr, Cs, Ga, Hf, Hg, Mn, Mo, Ni, Rb, Sb, Sc, Se, Sr, Ta, Th, U, V, W, Zn, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Yb, and Lu, were determined by instrumental neutron activation analysis (INAA) for samples of elemental sulfur and samples of soil material from selected depths adjacent to a large elemental sulfur stockpile. The objective was to determine the total content of trace elements and examine their redistribution within surficial till material influenced by extreme acidity resulting from the oxidation of elemental sulfur. The elemental sulfur did not contain detectable (by INAA) quantities of other elements to contribute to soil contamination. Elements mobilized within the acidified section were derived solely from the parent till. An Fe-rich indurated layer that formed at the interface of the acidified and calcareous layers acted as a scavenger for As, Co, and Ga. Formation of aqueous sulfate complexes probably inhibited attenuation of Mn, Sc, Th, U, Zn and rare earth elements. Barium and Hf were enriched in the acidified material while B, Rb, Cs, Sb, Sr, Ta, and V displayed no evidence of redistribution. Mercury displayed the unique behavior of volatilization to the atmosphere from the soil surface.Key words: anthropogenic acidification, trace elements, weathering
Changes in ATP content, enzyme activity and inorganic nitrogen species during composting of organic wastes
Authors: Garcia C. , Hernández T. , Costa F. , Ceccanti B. , Ciardi C.
Published: April 2011

Changes in several biochemical parameters, exchangeable [Formula: see text] and [Formula: see text] were evaluated during the composting of sewage sludge and city refuse. Except for casein-protease activity, all enzyme activities were higher in sewage sludge than in city refuse, at all times, denoting larger microbial populations; this was also confirmed by a high initial ATP level. In addition to differences in microbial biomass, the lower enzyme activity in city refuse might also depend on inhibition by a high content of heavy metals. Absolute urease and phosphatase activities decreased during composting, showing a minimum at 91 and 65 d, respectively; thereafter they increased slightly. ATP also decreased markedly during the first month, then it stabilized to a low level. The correlation found between urease-phosphatase-ATP and the lack of correlation between proteases, and between both proteases and ATP-urease-phosphatase, confirmed the different synthesis and behaviour of these enzymes. Proteases might partially exist outside living cells, thus playing an important role in composting when microbial activity is low. High levels of ATP and enzyme activity at the beginning of the composting, their sharp decrease and the increase in casein-protease followed by a decrease, characterized the "mineralization" phase, while low levels in ATP and casein-protease and a re-activation of the other hydrolases, characterized the "maturation" phase of the composting. The ammonium content decreased during composting while nitrate increased, indicating that the process evolved exhaustively and under fully aerobic conditions. Key words: ATP, city refuse, enzyme activity, hydrolases, sewage sludge
Formation of swelling clay minerals by sulfide oxidation in some metamorphic rocks and related soils of Ontario, Canada
Authors: Kimpe Christian De , Miles Norman
Published: April 2011

Sulfide minerals are commonly present in the metamorphic and igneous rocks of southeastern Ontario. They are also dispersed in the till that is the parent material for many soils in the area. When sulfides from these rocks are exposed to a humid atmosphere, bacteria (Thiobacillus ferrooxidans) proliferate and acid sulfate weathering proceeds rapidly with the formation of jarosite, for which K+ ions are provided by the alteration of micas and feldspar. Interstratified minerals occur as an intermediate stage during the transformation of micas towards swelling clay minerals, which are major constituents of the clay-size fraction. A similar transformation likely takes place in the soils of the area, in which swelling clay minerals are dominant. This hypothesis may be further supported by the presence of large amounts of goethite, a weathering (hydrolysis) product of jarosite. Key words: Jarosite, goethite, smectite, vermiculite, acid sulfate weathering
Mehlich 3 extractant for determination of available B, Cu, Fe, Mn, and Zn in cryic Alaskan soils
Authors: Walworth J. L. , Panciera M. T. , Gavlak R. G.
Published: April 2011

Field trials were conducted on three cryic soils in southcentral Alaska to determine the local suitability of the Mehlich 3 extractant. Mehlich 3 extractable B, Cu, Fe, Mn and Zn, DTPA-TEA extractable Cu, Fe, Mn and Zn, and hot water extractable B were measured on soils from factorial experiments with variable rates of B, Cu, Mn, and Zn. Additional soil samples from two B rate and liming studies in central Alaska were included in extractable B comparisons. Forage rape, broccoli, and potato tissue samples were collected from the factorial studies to determine relationships between soil- and plant-available micronutrients. Crop yields were not affected by micronutrient applications Neither Mehlich 3 nor DTPA-TEA extractant predicted plant-available Cu or Fe. Coefficients of determination between soil and plant tissue B were comparable for extraction by Mehlich 3 or hot water and ranged from 0.11 to 0.82 Neither the Mn nor Zn tests accounted for more than 39% of the observed tissue nutrient concentration variation. The inclusion of soil PH and organic matter slightly improved estimates of available B, Mn, and Zn. Mehlich 3 extractable Fe was poorly related to DTPA-TEA extractable Fe. Copper extracted with Mehlich 3 was related to that extracted with DTPA-TEA (r2 = 0.73); the inclusion of soil pH improved the relationship (r2 = 0.84). Mehlich 3 extractable Mn and Zn were closely related to DTPA-TEA extractable levels (r2 = 0.91 and 0.94, respectively). The correlation between Mehlich 3 and hot water B (r2 = 0.57) was significantly improved by including soil organic matter content (r2 = 0.71). Key words: Micronutrients, extractant, Mehlich 3, DTPA, hot water
Long-term crop rotation and fertilizer effects on phosphorus transformations: II. In a Luvisolic soil
Authors: McKenzie R. H. , Stewart J. W. B. , Dormaar J. F. , Schaalje G. B.
Published: April 2011

The effects of different cropping systems, fertilizer, and lime on soil phosphorus (P) dynamics in soils developed under forest vegetation have received little attention. The objective of this study was to develop an understanding of P fractions and transformations in long-term rotation plots on a Luvisolic soil at Breton, Alberta. Results have shown that crop rotation and fertilizer application have affected more inorganic soil phosphorus (Pi) and organic phosphorus (Po) fractions, as determined by a sequential extraction procedure. Continuously cropped treatments, which had not received fertilizer, resulted in P drawdown of resin-extractable Pi (resin-Pi), sodium bicarbonate-extractable Pi (bicarb-Pi), sodium hydroxide-extractable Pi (NaOH-Pi), sodium bicarbonate-extractable Po (bicarb-Po), sodium hydroxide-extractable Po (NaOH-Po) and hydrochloric acid-extractable Pi (HCl-Pi) fractions. Only the residual-P fraction (insoluble Pi and stable Po forms) was unaffected. Addition of fertilizer had an effect on all P fractions except the NaOH-Po fraction. Phosphorus fertilizer treatments positively affected the Pi fractions and N fertilizer positively affected the bicarb-Po fraction. Lime application affected soil pH, which lowered NaOH-Pi levels and increased HCl-Pi levels through formation of more stable calcium phosphate compounds. Addition of lime also resulted in lower bicarb-Po levels. Cropping without using phosphate fertilizer has resulted in a 30–40% decline in total-P in the Breton plots in the Ap horizon. Continuous cropping, with a forage crop in the rotation, coupled with modest N and P fertilizer application, had the most positive effects on P cycling and transformations. Summerfallow had no apparent beneficial effects on P transformations. Key words: Soil P transformations, Luvisolic soil, P bioavailability, sequential extraction
Observations on the effect of a soil polysaccharide fraction on boron adsorption by clay minerals
Authors: Gu B. , Lowe L. E.
Published: April 2011

Complexes formed by coating a soil polysaccharide fraction on illite, montmorillonite and kaolinite, substantially reduced boron adsorption by the clay minerals at approximately neutral pH. This suggests that boron retention in soils is influenced by the occurrence of stable polysaccharide-clay complexes. Key words: boron adsorption, organo-clay complex, soil polysaccharide
Soil structure and crop yield over a 5-year period following subsoiling Solonetzic and Chernozemic soils in Saskatchewan
Authors: Grevers M. C. J. , Jong E. de
Published: April 2011

The effect of subsoiling of Solonetzic and of Chernozemic soils was studied over a 5-yr period under dryland conditions and under irrigation, involving 11 farm sites, and 2 soil zones. Subsoiling reduced soil density for up to 3 yr on most of the Solonetzic soils and on one of the Chernozemic soils. Overwinter soil-water recharge in subsoiled Solonetzic soils was increased for up to 3 yr, but not in subsoiled Chernozemic soils. Under irrigated conditions, subsoiling reduced soil salinity and sodicity at one site; however, under dryland conditions soil salinity and sodicity levels remained unaltered. Crop emergence on one of the Solonetzic soils was decreased in the first year after subsoiling because of poor seedbed conditions. Subsoiling increased crop production on Solonetzic soils in the 1st, 2nd, 3rd and in the 4th years, and at one site in the 5th year. Subsoiling did not affect crop production on Chernozemic soils. Increased crop production resulted from increased soil water depletion with depth, and also from greater crop water-use efficiency. Soil loosening by subsoiling, as indicated by decreased soil bulk density of the B horizon lasted up to 3 yr, during which the largest yield increases were measured. The results suggest that subsoiling may have to be repeated every 5 yr or more. Key words: Subsoiling, amelioration, soil water, crop growth
X-ray diffraction characteristics and related properties of Smectites in some Canadian soils
Authors: Ross G. J. , Kodama H.
Published: April 2011

The X-ray diffraction (XRD) peak intensities of smectites in Chernozemic and related soils of Western Canada are generally low, in contrast to the high peak intensities of smectites in Podzolic soils of Eastern Canada and those of standard smectite samples. Consequently, X-ray quantitative analysis based on standard smectite samples may underestimate the amount of smectite and overestimate the amount of noncrystalline material in western Canadian soils. This study was undertaken to find the reasons for the weak XRD peak intensities of western soil smectites in terms of their purity and crystallinity. The Tiron dissolution method extracted only small amounts of noncrystalline material from the western soil clays and had little effect on XRD characteristics. The cation exchange capacity (CEC) hysteresis (or pH dependent CEC) between pH 3.5 and 11.0 of the western soil clays was also relatively small which confirmed the absence of significant amounts of noncrystalline material in these soil clays. Observed deviations of XRD positions from true basal spacings indicated that the western soil smectite particles were consistently thinner than the eastern soil smectite and Wyoming montmorillonite particles. Electron microscope observations supported these results. Because the diffraction intensity is proportional to the square of the particle thickness, the thinness of the western soil smectite particles appears to be a major factor in reducing their peak intensities. Thus, to obtain comparable peak intensity data from different soil smectites, particle thickness should be taken into account. Since it is often not practical to measure particle thickness, a procedure for quantifying smectite in soils that avoids this measurement is proposed. Key words: Peak intensity, crystallinity, particle size, particle thickness, Chernozemic smectite, Podzolic smectite
A rapid method for measuring dynamic changes in pH of fertilizer microsites
Authors: Fan M. X. , MacKenzie A. F.
Published: April 2011

Nutrient availability from banded fertilizers will depend on the properties of the fertilizer band or microsite. Increased pH from urea hydrolysis may change P fertilizer reactions with the soil. A rapid method is described which allows precise measurement and visualization of dynamic changes in pH near microsites around fertilizer granules or bands. One day after application of urea and triple superphosphate fertilizers into the soil, a 0.75% agar solution containing 0.06% bromocresol purple was poured onto the soil surface. The pH was measured using a combination microelectrode placed on the agar and the pH range was estimated from agar colour 2, 4, 6 and 8 d after placement of the fertilizer mixture. Triple superphosphate reduced and retarded pH increases from urea hydrolysis. The results demonstrate the ability of the agar method to monitor pH changes around fertilizer granules or bands. Key words: pH, agar, triple superphosphate, fertilizer, microsite, urea
Nitrogen partitioning and cycling in barley-soil systems under conventional and zero tillage in central Alberta
Authors: Haugen-Kozyra K. , Juma N. G. , Nyborg M.
Published: April 2011

Cropping systems which conserve soil, water and nutrients are needed on the Canadian prairies. The objectives of this study were: (1) to assess the effects of urea injection on N partitioning in barley-soil systems under conventional (CT) and zero tillage (ZT); and (2) to measure the dynamics of fertilizer and soil N over the growing season. Twelve microplots were installed in each of CT and ZT plots located on a Black Chernozemic soil and were fertilized (59 kg N ha−1) with 15N urea solution, sown to barley (Hordeum vulgare (L.) 'Empress') and destructively sampled at the fifth leaf, ear emergence, grain filling and ripening growth stages. Distribution of 14N and 15N in shoots, roots, mineral N, microbial N, and soil organic N were measured. The recovery of fertilizer N in the soil-plant system was not different between treatments. Microbial N and non-microbial organic N accounted for > 80% of residual 15N in both treatments. Nitrogen budgets showed that grain removal from CT was 76 kg ha−1 and 56 kg ha−1 in ZT. Our study suggests that more 15N from injected urea was converted to organic N under ZT than CT; thus ZT systems have the potential of conserving N. Tillage practices affect the fate of added N. Key words: Typic Cryoboroll, 15N, organic matter, Hordeum vulgare, N recovery, zero tillage
The effects of tillage systems and crop sequences on soil bulk density and penetration resistance on a clay soil in southern Saskatchewan
Authors: Grant C. A. , Lafond G. P.
Published: April 2011

Concern has been expressed that reduced tillage systems may lead to excess soil compaction, negatively impacting on crop growth. The objectives of this study were to determine the effects of tillage systems zero (ZT), minimum (MT) and conventional tillage (CT) and crop rotations on soil bulk density and penetration resistance after 4 yr on an Indian Head heavy clay soil, in southeastern Saskatchewan. Moisture content was similar among tillage systems, except for slight differences in the lower soil depths with crop rotation. Penetration resistance and bulk density of a heavy clay soil were increased in the surface 10 cm of the soil by ZT as compared to CT management. However, in the deeper soil zones, tillage system did not consistently influence either bulk density or penetration resistance. Inclusion of peas in the crop rotation had a moderating effect on bulk density and penetration resistance, while inclusion of flax in a continuous rotation increased bulk density and penetration resistance in the surface soil profile. At the 30- to 45-cm depth, ZT had a lower bulk density than CT or MT in the rotation which included fallow, possibly because the tillage operations associated with the cultivated fallow led to compaction in the deeper soil zone. Penetration resistance was great enough in the deeper soil zone in all tillage systems to restrict rooting, but difference due to tillage treatment or cropping rotation was not sufficient to markedly influence crop production. Key words: Penetration resistance, bulk density, crop rotation, tillage
Effects of lignosulfonate-fertilizer applications on soil respiration and nitrogen dynamics
Authors: Meier J. N. , Fyles J. W. , MacKenzie A. F. , O'Halloran I. P.
Published: April 2011

Lignosulfonate (LS) has been used as a carrier for micronutrients and has the potential to improve macronutrient fertilizer efficiency, but little is known about the behaviour of LS fertilizer mixtures in soil. A laboratory study was conducted using ammonium lignosulfonate (2.67% wt wt−1) in combination with diammoniumphosphate (DAP), urea (U) and U+DAP incubated in a silty clay loam soil. The experiment monitored CO2 evolution and NH3–N volatilization for 69 d and extractable soil N periodically for 38 d. Addition of LS initially increased CO2 evolution, but only a small proportion (10–22%) of the LS-C was evolved as CO2. Lignosulfonate decreased urea hydrolysis slightly and reduced the proportion of added N volatilized from the LS+U treatment. Lignosulfonate treatments accumulated N in the form of [Formula: see text], suggesting that LS may inhibit nitrification. A larger proportion of added inorganic N was recovered in the LS + fertilizer treatments, indicating that LS may increase fertilizer N availability. Key words: Lignosulfonate, urea, diammonium phosphate, ammonia volatilization, nitrification, fertilizer efficiency
Nitrate leaching as influenced by fertilization in the Brown soil zone
Authors: Campbell C. A. , Zentner R. P. , Selles F. , Akinremi O. O.
Published: April 2011

The possibility of nitrates being leached into groundwater supplies from improper use of fertilizers is a concern to society. Two experiments were conducted on a loam soil in the Brown soil zone at Swift Current, Saskatchewan. In the first experiment, continuous wheat (Triticum aestivum L.), grown under various fertilizer-N management systems and with and without cereal trap strips (tall stubble, 0.4–0.6 m) to capture snow and enhance soil-moisture storage, was compared with short stubble cut at the standard height (0.15–0.2 m). Prior to seeding in spring 1991, tall stubble had stored 14.7 ha-cm of soil moisture at 0–1.2-m depth compared with 10.9 ha-cm under short-stubble treatment. Because growing-season precipitation in 1991 was much higher than normal (302 mm from 1 May to 31 My), considerable NO3-N was leached below the rooting zone of wheat (1.2 m), particularly in the tall-stubble treatment. Leaching patterns were as expected in short stubble, with major leaching occurring only at the highest N rate (125 kg ha−1), where yield and N-uptake response had levelled off. However, in tall stubble, the amount of NO3-N leached beyond the root zone under the 0 and 25 kg N ha−1 rates was similar to that under the 125 kg N ha−1 rate. This result was attributed to poor tillering obtained at low N rates, which contributed to lower evapotranspiration, thereby permitting more moisture to be leached and enhancing N mineralization. When we used a leaching model (NLEAP) to simulate our results, it gave lower estimates of NO3 leached and did not reveal the interaction of NO3-N leaching with N rates that was observed under tall stubble. The second experiment measured soil NO3-N distribution to 2.4 m under two fallow–wheat–wheat systems after a 24-yr period. One system received only N, the other, N + P fertilizer. The results corroborated those obtained under tall stubble in the first experiment: the poorly fertilized system had the most NO3-N below the root zone. The results of this study suggest that the key to reducing nitrate leaching is the adoption of proper fertilization practices, since too little fertilization may potentially be as detrimental to groundwater pollution as too much. Key words: Fertilizer N, N uptake, snow management, crop rotations, NO3 leaching
Effect of ground covers and tillage between raspberry rows on selected soil physical and chemical parameters and crop response
Authors: Zebarth B. J. , Freyman S. , Kowalenko C. G.
Published: April 2011

The use of inter-row ground covers has been suggested to reduce soil degradation in raspberry (Rubus idaeus L.) production. The effect after 6 yr of consistent inter-row management of ground covers or roto-tillage in raspberry on soil wet aggregate stability (WAS), bulk density, organic C and total N, and mineralizable nitrogen in the Fraser Valley of British Columbia was studied. Management treatments included no cover crop or cover crops of barley (Hordeum vulgare L.), sheep's fescue (Festuca ovina L.), perennial ryegrass (Lolium perenne L.), and white clover (Trifolium repens L.). A general pattern of perennial grasses > legume and barley > control was observed for soil WAS. Some quantitative and qualitative differences in the organic component of the soil profile to 30 cm were detected among management treatments. The differences were not statistically strong because the changes were small relative to the large pool present, but were relatively consistent overall. The white clover treatment tended to have more organic carbon, particularly in the subsurface, than the other treatments. The four treatments that included inter-row vegetation tended to have a greater amount of total and mineralizable N than the clean-tilled control. Crop vigour, as indicated by cane diameter, was reduced by the perennial grasses, but the inter-row management had only limited effects on berry yield. White clover appears to provide the best compromise between improving soil quality and minimizing competition with the berry crop. Key words: Wet aggregate stability, barley, sheep's fescue, perennial ryegrass, white clover
Influence of legumes and fertilization on deep distribution of available phosphorus (Olsen-P) in a thin Black Chernozemic soil
Authors: Campbell C. A. , Biederbeck V. O. , Winkleman G. E. , Lafond G. P.
Published: April 2011

Inorganic phosphorus (P) is generally believed to be relatively immobile in Chernozemic soils. However, available P (e.g., Olsen-P) has been found at depth in some soils and this has been postulated to be either the result of leaching or of transportation by plant roots. Lagumes, in particular, are believed to be involved in the latter mechanism. A long-term (34-yr) crop rotation study conducted on a heavy clay, thin Black Chernozemic soil at Indian Head, Saskatchewan, was sampled to a depth of 4.5 m in May and September 1991, to determine the influence of fertilization, cropping frequency, legume green manure and legume-grass hay crops on Olsen-P distribution in the soil profile. The results indicated that Olsen-P may indeed leach in Chernozemic soils, especially when fallow-containing cropping systems are fertilized. It also appeared that deep-rooted legumes, such as sweetclover Melilotus officinalis L.) green manure and alfalfa-bromegrass (Medicago sativa L. — Bromus inermis Leyss) hay crops do increase Olsen-P in the subsoil, possibly through root decomposition in situ. Key words: Rotations, bicarbonate-soluble Pi, legumes, green manure, fertilizers
Soil aggregation as influenced by cultural practices in Saskatchewan: I. Black Chernozemic soils
Authors: Campbell C. A. , Curtin D. , Moulin A. P. , Townley-Smith L. , Lafond G. P.
Published: April 2011

The impact of cultural practices on soil aggregate characteristics which determine the susceptibility of the soil to wind and water erosion was studied at two long-term (> 30-yr) crop rotation sites on Black Chernozemic soils at Indian Head and Melfort, Saskatchewan. Surface soil (top 5 cm) taken in spring and fall, 1991, was air-dried and sieved by rotary sieve to measure aggregate size distribution. The water-stability of soil aggregates (1–2 mm) was determined after: (i) slow wetting, and (ii) fast wetting. Both rotation studies employed conventional tillage management until 1990 when the Indian Head experiment was converted to zero-tillage. Summerfallowing increased the wind-erodible (< 0.84-mm) fraction of soil and decreased the geometric mean diameter (GMD) of aggregates. One year of cropping was sufficient to significantly reduce the proportion of wind-erodibile aggregates. Fertilization and legume green manure and hay crops reduced the wind-erodible fraction at Indian Head, but had no effect on the higher organic matter soil at Melfort. In monoculture wheat systems at Indian Head there was an inverse relationship between the wind-erodible fraction and cropping frequency; this was credited to the positive influence of cropping frequency on crop residue production. The wind-erodible fraction (Y) was related to GMD at Indian Head: Y = 11.8 + 117/GMD (r2 = 0.80***), and at Melfort, Y = 11.9 + 91/GMD (r2 = 0.82***). When subjected to rapid wetting, both the difference between cropped and native grassland soils, and the influence of cultural practices on water stable aggregates were pronounced. Aggregate stability was more closely related to the long-term management than to recent (< 1 yr) cultural treatments. Frequent cropping, fertilization, and use of legumes increased water stable aggregates, particularly at the Indian Head site with its lower organic matter content. Key words: Wet sieving, dry sieving, legumes, fertilization, geometric mean diameter, wind erosion
Soil aggregation as influenced by cultural practices in Saskatchewan: II. Brown and Dark Brown Chernozemic soils
Authors: Campbell C. A. , Curtin D. , Zentner R. P. , Brandt S.
Published: April 2011

The size distribution and stability of aggregates are important characteristics influencing tilth, erosion, water infiltration and nutrient dynamics in soil. We need to understand how soil management influences agregation so that we may make suitable modifications to farming practices to enhance soil stability. Two long-term crop-rotation experiments in southern Saskatchewan were used to examine the effects of management on aggregation. In 1991, soil was collected three times during the summer from the top 5 cm of soil as part of a 25-yr experiment at Swift Current (Orthic Brown Chernozemic soil) and twice as part of a 27-yr experiment at Scott (Orthic Dark Brown Chernozemic soil). The two medium-textured soils were dry-sieved by rotary sieve and then wet-sieved after (i) slow wetting and (ii) fast wetting of the 1–2-mm size fractions. The wind-erodible fraction (<0.84 mm) of soil and geometric mean diameter (GMD) of aggregates varied with antecedent precipitation. Thus, wind-erodible aggregates increased at both sites, even in cropped rotation phases, when conditions were dry during the last 6 wk of the 1991 summer. However, the presence of crops and management practices that increased crop residues (e.g., fertilizers) tended to reduce the wind-erodible fraction and increase GMD. A very close relationship existed between the wind-erodible fraction (y) and GMD at the two sites: y = 16.2 + 105/GMD, (r2 = 0.95***) for the pooled data for the two sites. In contrast to results for the wind-erodible fraction, dry growing-season weather conditions tended to increase the water stability of aggregates. Fast wetting was more effective than slow wetting in delineating management effects on aggregate stability. Aggregate stability was increased by frequent cropping and by adequate fertilization, presumably as a result of increased production of crop residues. At Swift Current, chemical fallow increased aggregate stability, likely as a result of reduced soil disturbance. Key words: Wet sieving, dry sieving, crop rotations, erodibility, geometric mean diameter, meteorological conditions
Quantitative characterization of nutrient regimes in some boreal forest soils
Authors: Klinka Karel , Kayahara Gordon J. , Wang Qingli
Published: April 2011

In order to assess to what extent soil nutrient properties support differentiation of field-identified soil nutrient regimes, composite samples from each forest floor and 0–30 cm of the mineral soil were collected from 116 forest stands in central British Columbia. The samples were analyzed for acidity, total carbon (tC), total nitrogen (tN), mineralizable-N (min-N), and extractable Ca, Mg, K, P, and SO4-S (eCa, eMg, eK, eP, eSO4); and the results were expressed as concentrations on a dry-mass basis. Mineralizable-N of the mineral soil showed (1) the largest amount of variation in the population of sampled soils, (2) significant differences (P < 0.01) among field-identified soil nutrient regimes, and (3) strong correlations with tC, tN, and eCa, eMg, and eK. Using mineral soil min-N as a differentiating characteristic, the following limiting values (mg kg−1) were proposed to provide an objective means of defining soil nutrient regimes: < 2 for very poor, 2–8.9 for poor, 9–27.4 for medium, 27.5–110 for rich, and > 110 for very rich. Site index (height at 50 yr breast height age) of lodge-pole pine (Pinus contorta Dougl. ex Loud) and interior spruce [Picea engelmannii Parry ex Engelmann × P. glauca (Moench) Voss] increased from very poor to very rich soils; however, the differences among site indices of contiguous soil nutrient regimes were largely insignificant. Regression analysis indicated that (1) soil moisture accounts for the largest proportion of the variation in site index, (2) models using C:N ratio of the forest floor and 0–30 cm of the mineral soil had a stronger relationship with site index (0.38 ≤ R2 ≤ 0.43, standard error < 3.0 m) than those using min-N. These results gave further evidence that min-N in the 0–30 mineral soil is a good single measure representing soil nutrient conditions, and justify the use of the existing field procedure for estimating soil nutrient regimes in montane boreal soils. Key words: Boreal soils, soil nutrient regime, quantitative classification, mineralizable-N, site index
Kinetics of potassium chloride-induced Mn release from selected Mn-toxic soils of Indonesia and the United States of America
Authors: Krishnamurti G. S. R. , Huang P. M.
Published: April 2011

The Mn release by M KCl from two Oxisols from Indonesia and one Inceptisol from Oregon, USA was studied at different temperatures (25, 35 and 45 °C) to understand the kinetics and mechanism of Mn release from these soils, which were reported to have a Mn toxicity problem. The Mn release by M KCl continued to increase with time up to at least 772 h without reaching equilibrium. The kinetics of Mn release followed a parabolic diffusion model during the 0.25–772 h reaction period. The activation energy of Mn release, calculated from the overall diffusion coefficients, varied from 34 to 47 kJ mol−1. Even after removing the exchangeable Mn from the soils with M calcium nitrate, significant amounts of Mn were released by M KCl. Data presented indicate that ionic strength effect coupled with Cl complexation was the main mechanism governing the KCl-induced Mn release. The Mn release from the soils during the initial reaction period (0.25 h) was fast and accounted for 34–39% of the total amount of Mn released during the 772 h reaction period. The significantly high Mn release during the initial 0.25 h reaction time, the high overall diffusion coefficients of Mn release, and the high values of the pre-exponential factor (calculated from the Arrhenius equation) of Mn release from Mn-toxic soils apparently contributed to the KCl-induced Mn toxicity in these soils. Key words: Potassium chloride-induced Mn toxicity, pre-exponential factor, ionic strength, complexation
Sensitivity of total, light fraction and mineralizable organic matter to management practices in a Lethbridge soil
Authors: Bremer E. , Janzen H. H. , Johnston A. M.
Published: April 2011

Crop management influences the quantity and quality of organic matter in agricultural soils. A crop rotation study established at Lethbridge, Alberta in 1951 was sampled in September 1992 to determine the effect of crop management on total, light fraction and mineralizable (10-wk) organic matter contents. Spring wheat was the dominant cropping system; treatments examined include fallow frequency, forage hay production in rotation, manure amendment, N fertilizer application, and native grass. The two latter treatments were introduced in 1985. Total and light fraction organic matter did not vary among phases of the rotation whereas mineralized C tended to be lowest during and shortly after a fallow phase. When averaged across rotation phases, total, light fraction, and mineralized organic matter were enhanced by reduced fallow frequency, manure additons, hay production and native grass. Highest concentrations of total and labile organic concentrations in the 0- to 7.5-cm soil depth were generally found in the continuously-cropped wheat and native grass treatments. Hay production significantly increased soil organic matter in the 15- to 30-cm soil depth. Nitrogen fertilization did not increase soil organic matter in this study, likely because of minimal yield response over the treatment period. Sensitivity of the various indicators to treatment [(highest–lowest)/lowest] was 0.2 for total, 2.5 for light fraction, and 1.5 for mineralized soil organic C. Light fraction organic matter was the most robust indicator of management-induced effects on soil organic matter. Key words: Labile organic matter, fallow frequency, forage hay production, manure, native grass
Short-term nitrogen dynamics in soil amended with fresh and composted cattle manures
Authors: Paul J. W. , Beauchamp E. G.
Published: April 2011

The amount of available nitrogen in fresh and composted manures is required to adjust inorganic fertilizer applications for crops when using manures and composts. Corn (Zea mays L.) plants were grown for 8 wk at temperatures of 17–27 °C and 12–18 °C in soil amended with two rates of fresh and composted solid beef cattle manure. Apparent N uptake of corn grown in soil amended with fresh solid beef cattle manure, composted beef cattle manure and (NH4)2SO4 at the higher temperature was 2, 8, and 36%, respectively, during this 8-wk period. Nitrogen uptake by corn in fresh solid beef cattle manure-amended soil at low temperature was affected by factors other than N availability. A 12-wk laboratory experiment was performed in which 15NH4+ was added to fresh and composted manure-amended soil to determine the fate of the inorganic N in the manure and to measure N mineralization rates. Net immobilization of inorganic N occurred with all manures; however, after 3 wk, net mineralization occurred with the solid and composted beef cattle manure. Immobilization of 15N continued with all manure amendments as a result of mineralization-immobilization turnover. The amount of unrecovered 15N after 12 wk was 10.5, 2 and 1% of the added 15N in soil amended with solid beef cattle manure, composted beef cattle manure and manure composted with bark, respectively. Key words: Composted manure, nitrogen availability, 15N, immobilization, remineralization, temperature
Structural stability of Chernozemic soils as affected by exchangeable sodium and electrolyte concentration
Authors: Curtin D. , Steppuhn H. , Selles F.
Published: April 2011

The stability of soil structure in the presence of exchangeable Na is an important factor determining the success of irrigation developments using sodic waters. Our objective was to determine the effects of sodium adsorption ratio [SAR = Na/((Ca + Mg)/2)0.5, where concentrations are expressed in mmolc L−1] and electrolyte concentration on saturated hydraulic conductivity (K) and on macroscopic swelling in a range of Brown Chernozemic soils from southern Saskatchewan. All soils showed the same general response to sodicity (SAR) and electrolyte concentration of the leaching solution, i.e., K decreased as SAR increased and as salt concentration decreased. However, major differences existed between the soils in their susceptibility to Na-induced structural deterioration. For example, at SAR 20, the electrolyte concentration needed to maintain stable structure ranged from about 5 to 30 mmolc L−1. Our results indicated that use of a generalized threshold concentration curve to partition stable from unstable structure would not be satisfactory for all irrigated prairie soils. Texture was a major source of variation between soils; the limits on acceptable irrigation water SAR should generally be decreased as clay content increases. Swelling and dispersion of soil clays both contributed to sodicity-induced K decline. Soil clays swelled appreciably when soil exchangeable Na percentage exceeded about 10. In contrast to swelling, which was relatively insensitive to electrolyte concentration, clay dispersion was only observed at low salt concentrations (≤ 20 mmolc L−1. In implementing irrigation water:soil compatibility guidelines, it will be necessary to identify soils which deviate substantially from general or average behavior because of their propensity to disperse or swell. Key words: Sodicity hazard, threshold concentration curves, clay swelling
Comportement mécanique d’un sol argileux. Effets de la taille des agrégats, de la teneur en eau et de la pression appliquée
Authors: Derdour H. , Laverdière M. R. , Angers D. A.
Published: April 2011

Soil compaction has been the subject of intense research in recent years, but the mechanisms involved in the compaction process remain poorly understood. The objective of this study was to characterize these mechanisms for a Kamouraska clay (Orthic Humic Gleysol) using beds of aggregates (1–2 mm and 2–3.4 mm) compressed into a uniaxial compression device. Changes in structural void ratio were monitored as a function of aggregate size, applied load and soil water content. Measurements of tensile strength and shrinkage were also made on the larger aggregates (2–3.4 mm) to investigate the involvement of the structural units in the soil compaction process. Aggregate size had little effect on the shape of the compression curves. Compression of the aggregate beds was mainly a function of applied load and water content. The compaction sensitivity threshold was about 0.20–0.22 g g−1 at compression loads of less than 200 kPa. This threshold water content corresponds to the air entry point and to the upper limit of the brittle domain of the aggregates during crushing. These results suggest the existence of a threshold water content above which the soil becomes susceptible to compaction even at low applied stress. Key words: Compression, shrinkage, aggregate tensile strength, threshold water contents
Spatial variability of wheat yield, soil properties and erosion in hummocky terrain
Authors: Moulin A. P. , Anderson D. W. , Mellinger M.
Published: April 2011

The spatial distribution of soil properties, erosion and crop yield was studied along a cultivated transect and an adjacent transect in virgin grassland. The mapping unit was in hummocky moraine in the Dark Brown soil zone of central Saskatchewan. Erosion was affected by an interaction between elevation and surface curvature which affected the spatial and statistical distribution of soil properties and yield in the landscape. For the cultivated transect, percent sand was higher on knolls than in depressions, furthermore several soil properties were nonlinearly related to elevation. Decreases in grain yield on convex or planar lower slopes were correlated with erosion and high carbonate contents. Carbonate concentrations were high in lower slope positions in the cultivated transect, particularly at a relative elevation of 1 m, and appeared to be an important soil property influencing yield. Future studies of soil properties and yield on hillslopes may require careful evaluation of both elevation and microtopography in order to elucidate the effects of erosion. Key words: Erosion, yield, spatial variability, topography
Decreasing amounts of extractable phospholipid-linked fatty acids in a soil during decline in numbers of pseudomonads
Authors: Janzen R. A. , Raverkar K. P. , Rutherford P. M. , McGill W. B.
Published: April 2011

The hypothesis that phospholipid-linked fatty acid methyl ester (PL-FAME) analysis of a soil characterizes lipids from within microbial cells (cellular) as distinct from lipids stabilized in soil organic matter (extracellular) was tested by measuring the sensitivity of PL-FAME analysis to numbers of bacteria in samples of a soil. Autoclaved samples from the Ap horizon of a soil having a sandy loam texture were inoculated with suspensions of a Pseudomonas sp. (day 0) to form bacterial microcosms. On day 2, half of the microcosms were inoculated with an Acanthamoeba sp., a protozoan that grazes on pseudomonads.The numbers of bacteria in the soil samples without or with Acanthamoeba sp. increased about five-fold between days 2 and 4. Between days 4 and 7, the numbers of pseudomonads in grazed microcosms decreased 10-fold and the numbers of Acanthamoeba sp. increased 10-fold, relative to those in nongrazed microcosms. The 10-fold relative difference in numbers of pseudomonads between nongrazed and grazed samples persisted through day 12. Cluster analysis grouped PL-FAME profiles from grazed with those from nongrazed microcosms on day 4. On days 7 and 12, PL-FAME profiles from grazed or nongrazed microcosms clustered separately. The PL-FAME profiles from sterile samples of soil on days 2, 4, 7, and 12 clustered with profiles on day 2 from microcosms inoculated with Pseudomonas sp.We infer that PL-FAME analysis is selective for cellular lipids in the sandy loam soil with the limited range of active organisms used here. Further extension of PL-FAME analysis to a wider range of soils and soil conditions is warranted. Key words: Phospholipid-linked fatty acid, PL-FAME, soil lipids, Pseudomonas, Acanthamoeba
Soil salinity mapping with electromagnetic induction and satellite-based navigation methods
Authors: Cannon M. E. , Lachapelle G. , McKenzie R. C.
Published: April 2011

This project was undertaken to develop a system to map salinity with a towed electromagnetic induction meter (EM) and to position the meter with the Global Positioning System (GPS). The characteristics of the GPS are reviewed and the differential GPS (DGPS) mode of positioning, as applied to the EM meter positioning case, is explained. An EM38 salinity meter was time synchronized to GPS through a field portable personal computer (PC) and mounted on a non-magnetic toboggan for this purpose. The PC was also used to record all data for post-processing and analysis. The system was towed at velocities of up to 25 km h−1 during the field measurements. Continuous positioning of the system was achieved with an accuracy of 1–3 m. Salinity and GPS measurements were integrated and recorded on a field portable PC laptop. The results from a 30-ha site near Brooks are presented as well as those from a 100-ha site near Stettler, AB, which was surveyed in 3 h yielding 6000 salinity measurements. In order to test the repeatable accuracy of the system, the survey at Stettler was repeated the following day. The agreement is of the order of 1 dS m−1 which is satisfactory for most applications. The effect of measurement spacing on accuracy is also analysed using various scenarios. Key words: Soil electrical conductivity, salinity, satellite navigation, Global Positioning System, positioning, precision farming