bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane and carbon dioxide fluxes from poorly drained adjacent cultivated and forest sites
Authors: Lessard R. , Rochette P. , Topp E. , Pattey E. , Desjardins R. L , Beaumont G.
Published: April 2011

Methane and carbon dioxide fluxes at the soil surface were measured from April to November 1992 in Ottawa, on adjacent cultivated (corn) and forest (temperate woodland) sites using closed chambers (10 chambers per site). The objectives were to quantify the spatial and temporal variability of gas exchange rates, and to determine the effects of soil temperature and moisture on the fluxes. On the forest soil, rates of CO2 emissions and CH4 uptake ranged from 2.27 to 14.82 g m−2 d−1 and from 0.04 to 1.10 mg m−2 d−1, respectively. On the cultivated soil, the measured CO2 fluxes varied from 0.27 to 7.07 g m−2 d−1 while methane uptake ranged from 0 to 0.13 mg m−2 d−1. There was a positive correlation between soil surface CO2 fluxes and soil temperature for the forest (R2 = 0.74, s(ŷ) = 1.77 g m−2 d−1) and the cultivated (R2 = 0.48, s(ŷ) = 1.10 g m−2 d−1) sites. Temperature had little effect on methane uptake by the forest soil suggesting that gas diffusion was rate limiting. This was further substantiated by the observation that methane uptake showed a strong negative correlation with soil water content (R2 = 0.79, s(ŷ) = 0.12 mg m−2 d−1). The spatial variability for methane uptake in the forest soil was found to be much larger than that previously observed for soil carbon dioxide production but is lower than that reported for nitrous oxide production. For fluxes larger than 0.15 mg m−2 d−1, the number of sites necessary to estimate the average flux with a precision of 10% (α = 0.05) ranged from 7 to 452. Key words: Greenhouse gas, methane oxidation, soil respiration, spatial variability
Corn yield, nitrogen uptake and nitrogen use efficiency as influenced by nitrogen fertilization
Authors: Liang B. C. , MacKenzie A. F.
Published: April 2011

Improving efficient use of applied nutrients in crop production is a desirable agronomic, economic, and environmental goal. Field experiments with corn (Zea mays L.) were carried out at two sites with contrasting soil textures in southwestern Quebec from 1988 to 1990. Objectives were to establish an optimum N fertilization rate for grain production, and to study fertilizer N use efficiency on a Chicot sandy clay loam (Grey Brown Luvisol) and a Ste. Rosalie clay (Humic Gleysol). Under favourable heat units and rainfall, yields of grain corn were quadratic functions of fertilizer N rates on both soils. Maximum grain yields of corn were calculated to require from 300 to 350 kg N ha−1 fertilizer application. However, large amounts of N fertilizer at both 285 kg ha−1 and 400 kg ha−1 were not recovered by the crop. Optimum economic grain yields at a price ratio of 10:1 N:grain were found at 273 kg N ha−1 on the Ste. Rosalie site in 1990, and 286 and 179 kg N ha−1 for 1989 and 1990, respectively, on the Chicot site. A normal fertilizer rate (170–44–141 kg N–P–K ha−1) and a high fertilizer rate (400–132–332 kg N–P–K ha−1) were used in 1989 and 1990 for 15N microplot experiments. Grain and stover fertilizer N recovery (FNR) varied with N rate and year from 9 to 58%. Favourable climatic conditions substantially increased crop yield, and thus crop FNR. Residual FNR the second year was less than 5% of the initial applied N. Key words:15N, grain yield, Zea mays L., nitrogen use efficiency, fertilization
Evaluation of sulfur mineralization potential of meadow soils and availability to alfalfa
Authors: N’dayegamiye Adrien , Delisle France , Simard Régis R.
Published: April 2011

With the reduction in S inputs through atmospheric deposition and high analyses fertilizers, soil organic S will become a more important source of S to crops. Sulfur mineralization in 20 meadow soils was investigated using a long-term aerobic incubation and a greenhouse bioassay with alfalfa (Medicago sativa L.). The cumulative S mineralization (Sm) was linear with time for 13 soils whereas 7 soils showed an exponential phase over the first 10 wk followed by a linear release phase. Podzolic soils dominated the latter group. The data were described by an incremental zero-order model where an initial flush was accounted for. The total amount of mineralizable S (Sm), the amount of S mineralized in the first 1.4 wk (Se), the S mineralization potential (So) and the rate constant (k) were all very closely correlated to the N mineralization potential and to the amount of N mineralized in the first 1.4 wk of incubation (r = 0.64–0.85; P < 0.01). The S mineralization parameters were not significantly correlated to soil pH, total C, N, and S, C:S and N:S ratios and extractable P content. The Se and So mineralization parameters were significantly correlated to the soil sand content (r = 0.51 and 0.53; P < 0.05) suggesting the possible involvement of particulate organic matter as a pool of mineralizable S. Alfalfa yield response to S addition was observed only on seven soils with lowest cumulative S. Total S uptake of alfalfa represented, on average, 10% of Sm and was strongly correlated to Sm (r = 0.81**) and k (r = 0.78**). The effect of S fertilizer on plant S uptake was observed only for the third cut (P < 0.01), this being probably due to mineralizable S depletion in soils. The results of this study suggest that the initial potential of N mineralization is a good indicator of Sm and that a short term incubation could measure the S supplying power of Québec soils. Key words: S uptake, organic C, nitrogen and sulfur, texture, incremental zero-order equation
Comparison of immiscibly displaced soil solutions and saturated paste extracts from saline soils
Authors: Kohut Connie K. , Dudas M. J.
Published: April 2011

Soil solutions from four salt-affected soils in Alberta were extracted by immiscible displacement from field moist soils and saturated pastes after air-drying to examine the implications of using saturated paste extracts as a proxy of soil solutions. Solutions ranged in pH from 7.8 to 10.6 and in electrical conductivity (EC) from 6 to 45 dS m−1. Sodium dominated the cation suite, with Mg and K concentrations varying by several orders of magnitude between sites. Calcium was the major cation in lowest abundance at all sites. Sulfate was the predominant anion. Phosphorus concentrations ranged from 1 to 247 ppm. Considerable variation was seen between the properties of saturated paste extracts and immiscibly displaced solutions, with the saturated paste extracts having lower conductivities and Na, Mg, K and anion concentrations. The differences in composition between the two extraction methods resulted in differences in ion speciation, SAR and ESP values and mineral stabilities. Saturation indices for evaporite minerals were poor predictors of minerals formed in evaporated soil solutions. It was also found that even in chemically similar solutions, different minerals precipitated, and therefore the prediction of evaporite mineral formation from extracted soil solutions is not recommended. Key words: Salinity, saturated paste extracts, soil solutions, evaporites, mineral stability
Seed banks: Memory in soil
Authors: Cavers Paul B.
Published: April 2011

Approaches used to study seed banks and early publications on them are summarized. Current areas of interest are described, including the balance between herbicide-susceptible and herbicide-resistant seed populations, the effects of reduced tillage, the genetic structure of the seed bank, the role of desiccation, the impact of nutrients, oxygen and ortho-dihydroxyphenols, and methods of sampling seed banks and processing the data.
SHORT COMMUNICATION: Stimulation of elemental sulphur oxidation by sewage sludge
Authors: Cowell L. E. , Schoenau J. J.
Published: April 2011

Sewage sludge and elemental sulphur (S°) were combined and incubated under controlled conditions. Sulphur oxidation was enhanced by sewage sludge, though acidification of the mixtures prevented more than 4% of the S° from being converted to sulphate. When introduced to the soil environment, over 50% of the S° from these mixtures oxidized within 6 wk, compared with about 20% oxidation of S° applied without sewage sludge. Key words: Elemental sulphur, sulphur oxidation, sewage sludge
Spatial and temporal variability in chemical properties of a podzolic B horizon of an old-growth maple forest
Authors: Godbout Christian , Brown Jean-Louis
Published: April 2011

A Podzolic soil from an old-growth maple hardwood forest in eastern Canada was systematically sampled from a 16.5-m-long trench in 1975. In 1986, the upper 10 cm of the B horizon was resampled from two sampling lines located on each side and parallel to the 1975 trench, one at a distance of 1 m downhill and the other at a distance of 4 m uphill. Total N, organic C, pH, and exchangeable Ca, Mg and K were measured. The objectives were to evaluate the change in the chemical status of the B horizon from 1975 to 1986 and to characterize the spatial variability of the horizon. No significant change was found in the soil chemical properties tested during this 11-yr period. No significant autocorrelation was observed between soil samples 60 cm apart, except for the downhill sampling line, which was located 1 m from the trench. For most properties, the magnitude of the difference between two soil sampling units was not proportional to the distance separating them over the range of 0.6–4.2 m. Except for pH, a difference in soil properties of more than 30% was observed in 37–56% of sample pairs 60 cm apart. Resampling near (1 m) an old soil pit may not be valid because of possible local modifications of soil properties created by the pit, even when it is filled in. Key words: Podzol, soil variability, acidic deposition, soil changes
Soil microbial and biochemical properties after ten years of fertilization with urea and anhydrous ammonia
Authors: Biederbeck V. O. , Curtin D. , Bouman O. T. , Campbell C. A. , Ukrainetz H.
Published: April 2011

The influence of nitrogen (N) fertilizers, especially anhydrous ammonia, on soil quality has been questioned frequently by proponents of organic farming and low input sustainable agriculture. A 10-yr experiment was conducted on an Orthic Dark Brown Chernozemic loam, at Scott, Saskatchewan, to examine the influence of urea and anhydrous ammonia, at rates of N up to 180 kg h−1, on yields of cereals and oilseeds. In the 10th yr, we sampled soil from the 0- to 7.5- and 7.5- to 15-cm depths of each treatment 3 d before and 6 and 26 d after fertilization to assess the impact of applied N on microbial populations and soil biochemical properties. The long-term residual effects of N fertilization on soil properties were evident prior to the 10th annual N application. The short-term effects were most pronounced 6 d after the 10th N application. Generally, effects were greater in the 7.5- to 15-cm depth, where N was placed. The soil, which was already acidic (pH = 5.2 in 0.01 M CaCl2), decreased in pH in proportion to N rate and more so for anhydrous ammonia than urea. Generally, fungal and bacterial populations (plate counts) were positively related to N rate and were greater in soil treated with anhydrous ammonia than in urea-treated soil. In contrast, the actinomycete population was inversely related to N rate and was less for anhydrous ammonia than for urea. Nitrifier counts were increased by low rates of N (added substrate) but were similar to the check at high N rates (high acidity). There were no significant effects of N treatment on denitrifiers or yeasts. In contrast to the plate count results, microbial biomass decreased with increasing rates of N and was lower for anhydrous ammonia than for urea. However, the authenticity of this response is questionable because the fumigation-incubation method of biomass determination is compromised under acid conditions. Carbon mineralization was unaffected but N mineralization and nitrification tended to decrease at the 180 kg N ha−1 rate of anhydrous ammonia. Significant nitrification occurred at pH < 5.0 suggesting possible adaptation of nitrifiers in this acid soil. Wet aggregate stability (WAS) was unaffected by N treatments. We concluded that, if producers in the Dark Brown soil zone apply fertilizers at rates less than 90 kg N h−1, deterioration of soil quality should be minimal. Key words: Anhydrous ammonia, microbial biomass, nitrification, mineralization, soil microflora, urea
Net nitrogen mineralization from a Gray Luvisol under diverse cropping systems in the Peace River region of Alberta
Authors: Broersma K. , Juma N. G. , Robertson J. A.
Published: April 2011

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 < CB = CG = BF < CL. The potentially mineralizable N (N0) ranged from 29 to 364 mg kg−1 soil; the mineralization rate constant (k) ranged from 0.04 to 0.26 wk−1; and the ratio of N0 to total N (active fraction) ranged from 1.1 to 11.4%. The net N mineralization rate of CL soil was 10-fold greater than that of the other cropping systems at the end of 20 wk of incubation. This suggests that the CL cropping system provides more N than other cropping systems during the growing season. Results support the observation that forages improve the N-supplying power of Gray Luvisols. Key words: Gray Luvisol, Typic Cryoboralf, N mineralization potential, cropping rotations, active N fraction
Soil infiltration and hydraulic conductivity under long-term no-tillage and conventional tillage systems
Authors: Azooz R. H. , Arshad M. A.
Published: April 2011

Long-term tillage practices may affect crop growth, in part by changing soil hydraulic properties. The hypothesis that long-term no-till (NT) and conventional tillage (CT) practices affect soil infiltration and hydraulic conductivity was evaluated on silt loam and sandy loam soils (both Gray Luvisols). Ponded soil infiltration, water content and marric potential were measured in the field during 1992 and 1993. In most cases, the ponded soil infiltration rates (i) were significantly lower (P ≤ 0.05) under the CT than under the NT for both soils. Total volume of soil pores with radii < 14 μm (micropores) were significantly greater in NT than in CT. Differences in volume of soil pores with radii > 14 μm (macropores) between CT and NT were not significant. For the initial soil moisture conditions ranging from dry to field capacity, the i values were greater by 0 24 to 3 01 cm h−1 in NT than in CT for the silt loam and by 3.30 to 4.13 cm h−1 for the sandy loam. Saturated hydraulic conductivity values were significantly greater in NT (range from 0.36 to 3.0 cm h−1) than in CT (range from 0.26 to 1.06 cm h−1). Unsaturated hydraulic conductivity increased more with increasing matric potential (less negative) in NT than in CT. Long-term NT practices kept soil pore structure and continuity undisturbed, which contributed to significantly greater hydraulic conductivity and infiltration rates in NT than in CT for both soils. Key words: Infiltration, hydraulic conductivity, macroporosity, microporosity, tillage systems
The effect on earthworm abundance and selected soil properties after 14 years of solid cattle manure and NPKMg fertilizer application
Authors: Estevez Bernard , N’Dayegamiye Adrien , Coderre Daniel
Published: April 2011

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
Forms, amounts and distribution of carbon, nitrogen, phosphorus and sulfur in a boreal aspen forest soil
Authors: Huang W. Z. , Schoenau J. J.
Published: April 2011

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
Dairy manure incorporation stimulates rapid atrazine mineralization in an agricultural soil
Authors: Topp Edward , Tessier Laurent , Gregorich Edward G.
Published: April 2011

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
Economics of reduced tillage fallow-crop systems in the Dark Brown soil zone of Alberta
Authors: Smith E. G. , Blackshaw R. E. , Lindwall C. W. , Larney F. J. , Peters T. L.
Published: April 2011

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
Effect of seeding rate on seed production of perennial ryegrass after establishment with a grain companion crop in the Peace River region of north-western Canada
Authors: Fairey N. A. , Lefkovitch L. P.
Published: April 2011

A field study in the Peace River region of north-western Canada evaluated the effect of seeding rate on the seed yield and quality of perennial ryegrass (Lolium perenne L.) in the year after establishment with a grain companion crop. Each of two sites was sown with 70 kg ha–1 barley (Hordeum vulgare L.) and under-sown, in 30-cm rows, with three cultivars (All*Star, Barclay and Repell) of diploid perennial ryegrass at seeding rates of 150, 300, 600, 1200, 2400 and 4800 viable seeds m–2. During the establishment year of the perennial ryegrass, the grain yield of the barley companion crop was comparable to commercial yields for the region. Time of seed maturity, seed yield and thousand-seed weight of perennial ryegrass were not significantly (P ≤ 0.05) affected by the seeding rate, but were by cultivar. There was a significant (P ≤ 0.01) seeding rate × cultivar interaction for fertile tiller density and specific seed weight. Seed dockage differed significantly (P ≤ 0.001) among cultivars (16.7–27.9%) and increased with seeding rate (19.8–24.2%), and the germination capacity of the harvested seed was unaffected by seeding rate or cultivar. Grass seed yield was positively associated with fertile tiller density for each cultivar (r = 0.454***, n = 72 for All*Star; r = 0.364***, n = 72 for Repell; and r = 0.719***, n = 72 for Barclay). Compared with the other cultivars, Barclay matured 13 –15d later, had the lowest density of fertile tillers (1330 m–2), the highest seed dockage (27.9%) and the lowest seed yield (345 kg ha–1). All*Star had the highest seed yield (774 kg ha–1), the lowest seed dockage (16.7%), and the highest thousand-seed weight (1.55g). Repell was intermediate in seed yield (633 kg ha–1) but similar to All*Star, rather than Barclay, in other characteristics. The later maturity, creeping habit and prostrate stature of Barclay may have reduced its ability to produce fertile tillers and seed as efficiently as the other two cultivars at this northern latitude. In the Peace River region, there is potential for under-seeding a spring grain crop with perennial ryegrass for the production of successive harvests of grain and grass seed, provided the cultivar of perennial ryegrass is adequately adapted for seed production. The seeding rate for the perennial ryegrass is not particularly critical and 150–300 viable seeds m–2 should be adequate for diploid perennial ryegrass grown in rows with a grain companion crop. Key words: Perennial ryegrass, Lolium perenne L., grass seed production, grass seed quality, seeding rate, grain companion crop
A novel technique for evaluation of apple (Malus × domestica Borkh.) cultivars for susceptibility to powdery mildew
Authors: Sholberg P. L. , Lane W. D. , Haag P. , Bedford K. , Lashuk L.
Published: April 2011

A technique for the evaluation of apple cultivars for susceptibility to powdery mildew caused by Podosphaera leucotricha (Ell. & Ev.) E. S. Salmon (anamorph Oidium farinosum Cooke) was tested at the Pacific Agri-Food research Centre (PARC), Summerland, BC. Shoots of test cultivars [Braeburn, Creston, Elstar, Empire, Fuji strain BC2, Gala strain Royal, Jonagold, McIntosh, Delicious red strain Bisbee, Shamrock, Silken, Sunrise, and one breeding selection (11w-17-85)], approximately 6 cm in length, were grafted on to branches of mature Jonagold trees in the spring and evaluated in the summer of the same year and in subsequent years after growth on the host tree. Incidence and severity of powdery mildew were evaluated in 1994, 1995, 1997, and 1998. They were not evaluated in 1996 because approximately half the grafts from the previous year did not grow and had to be replaced. The highest incidence of powdery mildew averaged 84% for Gala, compared with only 15% for Bisbee Delicious with the lowest incidence. Gala had the highest number of P. leucotricha conidia per cm2 of leaf area (4.9 × 104) compared to Bisbee Delicious (1.2 × 104). Some of the grafted cultivars were also evaluated for primary powdery mildew and fruit russetting in 1998 after the growth for three seasons. Jonagold had the highest numbers of primary infections and russetted fruit. Key words: Podosphaera leucotricha, breeding, cultivar resistance, pest management
Soybean nodule hydrogen metabolism affects soil hydrogen uptake and growth of rotation crops
Authors: Dean Cheryl A , Sun Wenchang , Dong Zhongmin , Caldwell Claude D
Published: April 2011

To test the beneficial effect on the following crop of hydrogen released by Hup− soybean nodules, soybean was inoculated with either a Hup− (JH47) or a Hup+ (JH) strain of Bradyrhizobium japonicum. These isogenic strains differ only in that JH47 has a Tn5 inserted in the gene coding for the small hydrogenase subunit which eliminates hydrogenase activity; thus when present in soybean nodules, hydrogen is released into the rhizosphere. Inoculated alfalfa plants were used as the positive control as no hydrogenase activity has ever been found in alfalfa nodules. Soil adjacent to hydrogen releasing (Hup−strain) legume nodules had a significantly higher hydrogen uptake rate than that around the nodules containing the Hup+ strain. Barley grown following soybean inoculated with the Hup− strain exhibited an increased grain yield under field conditions. Key words: Soil, hydrogen oxidization, rotation benefit
Metribuzin residues in lentil following postemergence application
Authors: Cessna Allan J.
Published: April 2011

In a study involving two sites in western Canada, residues of the herbicide metribuzin in lentil were monitored by gas chromatography following postemergence application at 0.28 kg a.i. ha−1. On the day of spraying, initial residues in lentil green foliage were of the order of 1 mg kg−1. Metribuzin residues in the green foliage continually decreased with time to non-detectable levels (< 0.02 mg kg−1) at 42 d after application. No metribuzin residues were detected in the straw or mature seed. Key words: Metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio-1,2,4-triazin-5(4H)-one; lentil, Lens culinaris Medic., residues, residue analysis, gas chromatography
Control of established alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) in a no-till corn (Zea mays L.) cropping sequence
Authors: Swanton C. J. , Chandler K. , Shrestha A.
Published: April 2011

Evaluation of several herbicides for the control of alfalfa and red clover in a legume-corn no-till system showed that spring burn-down of the legumes may be preferred to fall burn-down. Spring application gave similar or greater control of these species than fall applications. Treatments with dicamba (3,6-dichloro-2-methoxybenzoic acid) at 0.6 kg ha−1 were the most effective in controlling red clover and alfalfa. Key words: Weed control, perennial legumes, spring application, fall application
Adopting zero tillage management: Impact on soil C and N under long-term crop rotations in a thin Black Chernozem
Authors: Campbell C A , Selles F. , Lafond G P , Zentner R P
Published: April 2011

Society’s desire to sequester C in soils, thereby reducing the net loss of CO2 (a greenhouse gas) to the atmosphere, is well known. It is also accepted that the choice of appropriate agricultural management practices adopted by producers will affect this goal. However, quantification of the extent and rate at which it can be achieved is uncertain. A crop rotation experiment that was initiated in 1957 on a thin Black chernozemic clay soil at Indian Head, Saskatchewan, was managed using conventional tillage until changed to zero tillage in 1990. Soil was sampled (0- to 7.5- and 7.5- to 15-cm depths) in May 1987 and 1997 to determine the effects of treatments on soil organic C (SOC) and total N. The rotations were: fallow-wheat (Triticum aestivum L.) (F-W), F-W-W, continuous wheat (Cont W), legume green manure (GM)-W-W, and F-W-W-hay (legume-grass)-hay-hay (F-W-W-H-H-H). The monoculture cereal rotations were either fertilized with N and P based on soil tests or unfertilized, while the legume systems were both unfertilized. There was also a F-W-W (N+P) treatment in which the straw was baled and removed. When the experiment was changed to zero tillage management in 1990, the fertilizer protocol was changed to satisfy the “moist soil” criteria. Consequently, higher rates of N and P were added thereafter to the fallow crop, resulting in a positive yield response of wheat grown on fallow, where before there was no response to fertilizer. Over the 10-yr period (1987-1997) fertilized soil gained C and N, but unfertilized soil did not. For example fertilized F-W, F-W-W and Cont W gained about 4, 5 and 2 Mg C ha–1 in the 10-yr period. During this period, C emissions from manufacture and transportation of N fertilizer was 0.28, 0.53 and 0.90. Mg ha–1 for these three rotations, respectively. These results suggest that without adequate fertility, conversion to zero tillage may not always result in an increase in soil C or N. By 1997, fertilizer increased soil C and N in F-W-W and Cont W, and soil C and N were greater in F-W-W-H-H-H than in GM-W-W and lowest in F-W-W (all unfertilized). Straw removal had no significant effect on C or N. The analysis showed that C inputs from crop residues was the main factor influencing SOC changes. Key words: C sequestration, crop rotation, fertilizer, grain yields, total N, tillage
Spring wheat (Triticum aestivum) yield and grain protein responses to N fertilizer in topographically defined landscape positions
Authors: Walley F. , Pennock D. , Solohub M. , Hnatowich G.
Published: April 2011

A 3-yr field study was initiated in 1996 to examine the different grain yield and grain protein responses of wheat to varied N fertilizer rates in a typical glacial till landscape in Saskatchewan, Canada. Our objective was to assess the agronomic and economic feasibility of variable rate fertilizer (VRF) N application for wheat. Results suggest that spring soil water status largely determined the yield and the protein content of wheat both within different years of the study and between different landscape positions within a given year. Although grain yield was strongly related to spring soil water and was predictable on that basis, the grain yield response of wheat to fertilizer N additions was highly variable due, in part, to the dual role that N played in determining both grain yield and grain protein content. As a consequence of the unpredictable nature of the varied response of wheat to N fertilizer additions, there was little economic rationale for using VRF strategies in the 3 yr of this study. However, in the long-term, we believe that VRF N application strategies can be employed to manage N inputs from the perspective of managing and replacing harvested N. Key words: Variable rate fertilizer application, precision farming, nitrogen application, N fertilizer, Saskatchewan
Mobility of heavy metals in soils amended with sewage sludge
Authors: Morera M T , Echeverría J C , Garrido J J
Published: April 2011

Sewage sludges added to arable land can improve soil fertility and physical properties. However, the concentrations of heavy metals commonly found in sludges limits their application to soil. The purpose of this paper is to evaluate the mobility of heavy metals (Cd, Cu, Ni, Pb and Zn) in four soils amended with different rates (0, 80, 60 and 320 t ha–1) of anaerobically stabilized urban sewage sludge. Total metal content in the sewage sludge was Zn >> Cu > Pb > Ni >> Cd. Sludge, soils and sludge-soil mixtures were fractionated by the Tessier sequential extraction procedure. The fractions extracted by H2O2/HNO3 and NH2OH.HCl were the most abundant pools for metals under study. The apparent mobility of metals in the sludge was Zn ≈ Cd ≈ Ni > Pb > Cu. The addition of sewage sludge in soils increased the percentages of metal extracted in non-residual fractions. ANOVA showed that the most significant increases were those of Zn, followed by Cu and Pb; there were no statistical differences (P < 0.05) for Ni and Cd. Exchangeable Zn from sludge was immobilized in basic soils. The other trace metals showed no fraction redistribution. The soils and sludge-treated soil samples were also extracted with EDTA and DTPA. Extraction with EDTA was more sensitive to soil type, whereas extraction with DTPA showed wider variation with metals. Both chelates seemed to be more effective to assess the mobility of metals added with the sludges at low concentrations than the Tessier’s chemical partitioning. Key words: Soils, sewage sludge, heavy metals, mobility
Short-term C and N dynamics in a soil amended with pig slurry and barley straw: a field experiment
Authors: Chantigny Martin H , Rochette Philippe , Angers Denis A
Published: April 2011

Interactions between animal slurries and crop residues can impact on soil N availability during decomposition. Our objective was to study the short-term decomposition of pig slurry and barley straw incorporated alone or in combination. A field experiment was conducted on a sandy loam unamended (control) or amended with 60 m3 ha–1 pig slurry (PS) or 4 Mg ha–1 barley straw (BS), or both (PSBS). Surface CO2 and N2O fluxes, soil water content and temperature, microbial biomass C, and NO3− and NH4+ contents were monitored during 28 d in the 0- to 20-cm soil layer. Large CO2 fluxes occurred during the first 4 h of the experiment in slurry-amended plots that were attributed to carbonate dissociation when slurry was mixed to the soil. Specific respiration activity (ratio of CO2-C fluxes-to-microbial biomass C) was increased in slurry-amended soils for the first 7 d, likely due to the rapid oxidation of volatile fatty acids present in slurry. After 28 d, 26% more C had been evolved in PSBS than the sum of C released from PS and BS, indicating a synergistic interaction during decomposition of combined amendments. Adding straw caused a net but transient immobilisation of soil N, especially in PSBS plots where 36% of slurry-added NH4+ was immobilised after 3 d. Slurry-NH4+ was rapidly nitrified (within 10 d), but N2O production was not a significant source of N loss during this study, representing less than 0.3% of slurry-added NH4+. Nevertheless, about twice the amount of N2O was produced in PS than in PSBS after 28 d, reflecting lower soil N availability in the presence of straw. Our study clearly illustrates the strong interaction existing between soil C and N cycles under field conditions as slurry mineral N appeared to stimulate straw-C mineralisation, whereas straw addition caused a net immobilisation of slurry N. Key words: Animal slurry, crop residues, C-N relationships, organic amendments
Predicting nitrogen fertilizer requirements of potatoes in Atlantic Canada with soil nitrate determinations
Authors: Bélanger G. , Walsh J. R. , Richards J. E. , Milburn P. H. , Ziadi N.
Published: April 2011

Nitrogen greatly affects potato ( Solanum tuberosum L.) yield, but excess N can result in environmental degradation. In this study soil nitrate (NO3-N) content was determined pre-plant to predict fertilizer N requirements of potatoes in Atlantic Canada and in mid-season to adjust N fertilization during the growing season. Soil NO3-N contents were measured to a 0.30-m depth in spring prior to planting at four on-farm sites in each of 3 yr (1995 to 1997) in the upper St. John River Valley of New Brunswick, Canada. Mid-season soil NO3-N contents at a 0–0.30 m depth were also determined (32–47 days after planting) at two sites in three N treatments in 1995 (0, 50, and 250 kg N ha-1) and in four N treatments in 1996 and 1997 (0, 50, 100, and 250 kg N ha-1). The yield response of potatoes to six rates of N fertilization (0–250 kg N ha-1) with and without supplemental irrigation was used to determine the economically optimum N application (Nop). The pre-plant spring soil NO3-N test alone could not adequately predict the N requirements of potatoes in Atlantic Canada; the Nop and relative yield were poorly correlated (0.07 < R2< 0.52) with spring soil NO3-N content. The mid-season soil NO3-N test, however, could be used to determine the need for supplemental N fertilizer; NO3-N content correlated well (0.44 < R2< 0.68) with the relative yield for total and marketable yield. We suggest a critical mid-season value of 80 mg NO3-N kg-1 soil for marketable yield, above which additional N application might not be necessary. Key Words: N fertilizer, nitrate, Nop, relative yield, Solanum tuberosum, critical value
Topographic influence on the variability of soil properties within an undulating Manitoba landscape
Authors: Manning G. , Fuller L G , Eilers R G , Florinsky I.
Published: April 2011

As soil properties influence productivity, it is of interest to characterize their distribution for the purpose of intensified agricultural management in variable landscapes. Soil properties (soil organic C content, soil pH, A horizon thickness, solum thickness and depth to carbonates) were studied in 10 intensively sampled transects in a gently undulating glacial till landscape near Miniota, Manitoba. Using a landform description model, the study site was delineated into upper, mid and lower elevation landform element complexes (LEC). The program used a digital elevation model created from relative elevation data collected on a 10-m grid. Sample points were also stratified by soil series; Newdale (Orthic Black Chernozem), Varcoe (Gleyed Rego Black Chernozem) and Angusville (Gleyed Eluviated Black Chernozem) soils of the Newdale association were identified. Landform element complexes were ranked lower > mid > upper with respect to convergent landscape character. The eluviated Angusville profiles occurred under more convergent landscape character than the Newdale or Varcoe series. There was a consistent rank of lower > mid > upper with respect to depth to carbonates, A horizon thickness, solum thickness and soil organic C content. Relative ranking of the pH in the Ap horizon was the opposite. In all cases, the lower LEC emerged as most clearly distinct. There was substantial variability in soil profile development, and, therefore, soil series membership, within individual LEC. This indicated that the scale at which LEC are delineated is broader than that at which soil series variability occurs. Nonetheless, LEC were useful in capturing gross variability in soil properties within the landscape at a scale that would allow unique agricultural management practices. Key words: Soil-landscape, solum thickness, depth to carbonates, organic carbon, soil pH
The effect of temperature on tight metal binding by peat and soil derived solid humic acids
Authors: Ghabbour Elham A , Davies Geoffrey , Ghali Nadeem K , Mulligan Matthew D
Published: April 2011

The brown biomaterials called humic acids (HA) in peats and soils retain water and bind metal cations and other solutes. Studies of the interactions of purified solid peat and soil-derived HA from different countries with metal cations in water probe HA microstructures and help to characterize the metal binding sites. Labile cations such as Caaq2+, Co aq2+, Cu aq2+, Fe aq3+, Mg aq2+ and Mn aq2+ tightly bind to solid HAs in sequential steps. The isotherms A vs. c are well fitted with the Langmuir model and plots of 1/A vs. 1/c are linear for each step. Here, A is mmol bound metal g–1 HA and c is the equilibrium cation concentration (M). This paper compares the stoichiometric site capacities vi and equilibrium constants Ki for tight binding of Ca aq2+, Co aq2+, Cu aq2+, Fe aq3+, Mg aq2+ and Mn aq2+ at different solid HA sites. Measurements at different temperatures give linearly correlated metal binding enthalpy and entropy changes, indicating that conformational changes and cation/HA hydration/dehydration are important factors in metal binding and release by solid HAs. Key words: Humic acids; metal binding; isotherms; thermodynamics
Composting organic residues: Trace metals and microbial pathogens
Authors: Dumontet S. , Dinel H. , Schnitzer M. , Paré T. , Scopa A.
Published: April 2011

Industrialized societies are responsible for increasing environmental pollution by trace metals, and pathogenic micro-organisms associated with products and wastes of industrial processes and agricultural production, as well as household activities. The objective of this paper is to discuss the effect of composting on the behavior of trace metals and pathogenic micro-organisms, and to present the latest finding on sanitizing and stabilizing organic fractions and trace metals in composted biosolids. Evidence provided by long-term scientific studies in North America and Europe on toxic effects of trace metals on soil micro-organisms and on pathogenic micro-organisms suggests that revisions of the current guidelines on sludge applications on agricultural soils are needed to protect long-term soil fertility. In addition, the antagonism between harmful characteristics of biosolids and their usefulness for agriculture and land reclaiming purposes could be mitigated by using efficient composting treatments. The production and use of harmless organic wastes should be one of our highest priorities in order to protect our health and environment, and to hand over a sustainable agriculture to future generations. Key words: Composting, biosolids, pathogenic micro-organisms, trace metals, sanitization
Wind erosion and surface stability in abandoned milled peatlands
Authors: Campbell Daniel R. , Lavoie Claude , Rochefort Line
Published: April 2011

Peatlands exploited for their peat by the method of milling are poorly recolonized by plants after the cessation of extraction activities, in part due to unstable peat substrates. Wind erosion has been suspected to play a role in this instability. Four studies were conducted to investigate the role of wind erosion on abandoned milled peatlands. A wind tunnel experiment was performed to evaluate the erodibility of dry, loose peat as a function of its degree of decomposition. A second wind tunnel experiment was conducted to determine how crusted peats differ in their resistance to erosion as a function of their degree of decomposition, without the input of abraders. Third, wind profiles were measured in milled, revegetated and natural peatlands in southeastern Québec to determine their aerodynamic roughness length. Finally, field measurements were made at three abandoned milled peatlands through two field seasons to characterize substrate stability and particle movement. In the wind tunnel, the erodibility of loose surface peat decreased with increasing decomposition and was predicted by their equivalent diameter to mineral particles 0.84 mm in diameter. However, once surface crusts formed, peats were all resistant to erosion. Surfaces of abandoned milled peatlands were aerodynamically smooth; therefore, exposed surface elements are subject to strong erosive forces during wind events. The greatest subsidence on abandoned milled peatlands occurred in the spring, prior to the surface movement of particles. Erosion during the summer could not be clearly detected. The instability of the peat surface remains a constraint for the restoration of abandoned milled surfaces. Key Words: Peat, cutover peatland, wind erosion, soil crust, roughness length, soil stability
Influence of soil texture on snowmelt infiltration into frozen soils
Authors: Zhao Litong , Gray D. M. , Toth B.
Published: April 2011

This paper describes the influence of soil texture on snowmelt infiltration into frozen soils. Field data collected on frozen, unsaturated agricultural soils of the Canadian Prairies during snow ablation demonstrate: (a) poor association between the amount of infiltration of meltwater released by the seasonal snowcover and soil texture, and (b) small differences in cumulative amounts among soils of widely different textures. A physics-based numerical simulation of heat and mass transfers with phase changes in frozen soils is used to study the mechanics of the infiltration process in representative clay, silty clay loam, silt loam and sandy loam soils. The results of the simulations show that the differences among cumulative snowmelt infiltration into clay, silty clay loam and silt loam soils after 24 h of continuous infiltration are small. Infiltration into a lighter-textured sandy loam after 24 h was on average 23% higher than in the other three soils with most of the increase occurring in the first 5 h of the simulation. Key Words: Soil texture, snowmelt, infiltration, frozen soils