bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the lateral and vertical variability of soil organic carbon
Authors: VandenBygaart A J , Gregorich E G , Angers D A , McConkey B G
Published: April 2011

Accurate predictions of changes in soil organic matter are difficult, at least in part, because of the lack of precision in measurements of soil organic carbon (SOC). This lack of precision is mostly due to the spatial variability in SOC that occurs with depth through the profile and laterally across the soil surface. The objective of this study was to assess the lateral and vertical variability of SOC in several pedologically distinct agricultural soils across Canada. Our goal was to determine the effect of different sampling methods on the precision of SOC measurements, namely: the effect of sampling either by fixed depth or by genetic soil horizon, the influence of compositing samples from different depth increments, and the number of cores required for a minimum detectable difference. Soils were sampled in increments down to 60 cm using a 4 × 3 m grid at six sites: two each from Ontario (Gleysol and Melanic Brunisol), Quebec (Humic Gleysol and Humo Ferric Podzol) and Saskatchewan (Dark Brown Chernozem). At four of the six sites, sampling by genetic soil horizon appeared to increase the precision of SOC measurements, but only when the surface 30 cm of the soil profile was considered. At the other two sites (soil types: Gleysol and Melanic Brunisol) sampling by fixed depth increments was more effective for increasing the precision of SOC measurements than sampling by genetic horizon. The effect of compositing samples from different depth increments had little influence on the precision of SOC measurements for all six soil types. These results suggest that sampling more than two depth increments per soil core has limited advantages for increasing statistical power to detect change in SOC. The high background SOC levels in the Gleysol soil would require a large number of soil cores in order to detect a small change in SOC such as that which would occur in a typical monitoring project. The Chernozem soils had lower spatial variability in SOC than the soil types in eastern Canada. Determining a statistically significant change in SOC of 5 Mg ha-1 would be difficult with the sampling design used in this study. Key words: Soil organic carbon, statistical power, sampling design, coefficient of variation, spatial variability, Canada
Application of X-ray computed tomography to soil science: A literature review
Authors: Taina I A , Heck R J , Elliot T R
Published: April 2011

The study of the spatial configuration of soil, in its complexity, requires an understanding of the interrelations and interactions between the diverse soil constituents, at various levels of organization. Investigations of the spatial arrangement of the mineral and organic components of soil have benefited from the development of techniques for structural analysis. X-ray computed tomography (CT) is a non-destructive and non-invasive technique that has been successfully used for three-dimensional (3D) examination of soil. Valuable information has been obtained by the application of CT for the description and quantitative measurements of soil structure elements, especially of soil pores and pore network features. In many studies, X-ray CT has been used to investigate the hydro-physical characteristics of the soil, in a functional and temporal manner. A dynamic approach has also been utilized in the evaluation of the biotic factor influence on soil. The analysis of soil solid phases, by X-ray CT, has been challenging due to the similar X-ray attenuation of different solid constituents. However, the use of multiple X-ray energy levels has facilitated the discrimination of minerals in soil. The aim of this review and synthesis is to offer a perspective on the major issues related to application of the technique, general attempted solutions and possible directions in the utilization of X-ray CT in soil research. Relevant scanning parameters, procedures for CT image reconstruction, algorithms for the quantification of soil characteristics and results are presented for each type of application. Key words: X-ray computed tomography, energy level, spatial resolution, segmentation, soil mineral and organic constituents, soil physical and hydro-physical properties, soil biota
Tillage effects on N2O emission from soils under corn and soybeans in Eastern Canada
Authors: Gregorich E G , Rochette P. , St-Georges P. , McKim U F , Chan C.
Published: April 2011

The ways in which agricultural soils are managed influence the production and emission of nitrous oxide (N2O). A field study was undertaken in 2003, 2004, and 2005 to quantify and evaluate N2O emission from tilled and no-till soils under corn (Zea maysL.) and soybeans (Glycine max L. Merr) in Ontario. Overall, N2O emission was lowest in 2003, the driest and coolest of the 3 yr. In 2004, the significantly larger annual N2O emission from no-till soils and soils under corn was attributed to an episode of very high N2O emission following the application of fertilizer during a period of wet weather. That the N loss by N2O emission occurred only in no-till soils and was large and long-lasting (~4 wk) confirms the strong effect that management has in reducing fertilizer N losses. In 2005, tilled soils had significantly larger N2O emission than no-till soils, most of which was emitted before the end of June. Because the tilled soils were better aerated , nitrification was likely the primary process contributing to the larger emission. Relatively low N2O emission from soybeans suggests biological N fixation does not appear to contribute substantially to the annual N2O emission. Further study of methods to reduce N2O emission in agricultural systems should focus on improving N use efficiency within a particular tillage system rather than looking to differences between tillage systems. Key words: Tillage, corn, soybeans, nitrogen, nitrous oxide, biogenic gas emission, nitrification, denitrification, fertilization
Soil properties related to the spatial pattern of microbial biomass and respiration in agroecosystems
Authors: Dupuis Eartha M , Whalen Joann K
Published: April 2011

Soil microorganisms exhibit a high degree of spatial variation, even in homogenously managed agroecosystems. The spatial pattern of microbial biomass and activity may be related to soil properties like hydrology, texture, organic matter and pH. This study took place in a 0.4-ha field with research plots under wheat and maize production. Soil microbial biomass, respiration and extractable nutrient levels were not generally affected by fertilizer treatments (inorganic NP fertilizer, poultry manure), relative to the unfertilized plots. This was probably due to soil heterogeneity; for instance, soil pH (1:2, soil:water) ranged from 5.8 to 7.2 across the field. Exploratory path analysis revealed that soil pH, dissolved organic carbon and total organic carbon concentrations were directly related to the spatial pattern in soil microbial biomass and respiration. This work demonstrates that path analysis could be used to identify independent soil variables and describe relationships between soil properties and microbial indicators in spatially heterogeneous agroecosystems. Key words: Field variability, microbial biomass, mineral fertilizer, organic amendment, soil respiration, spatial dependence
Soil microbial carbon and phosphorus as influenced by phosphorus fertilization and tillage in a maize-soybean rotation in south-western Quebec
Authors: Liu Aiguo , Hamel Chantal , Spedding Tim , Zhang Tie-Quan , Mongeau Rene , Lamarre Georges R , Tremblay Gilles
Published: April 2011

The management of the soil microbial P pool could improve system sustainability. The long-term impact of inorganic P inputs (0, 40 and 80 kg P2O5 ha-1) and tillage (conventional and ridge tillage) on soil microbial biomass P (SMB-P) was defined in the soybean phase of a 10-yr-old maize-soybean rotation, on a Gleysolic clay-loam. Soil microbial biomass C (SMB-C) and SMB-P were determined four times in the growing season. Yearly applications of 40 kg P2O5 ha-1 increased soil organic carbon level, partly explaining the increase in SMB-P measured at this rate. Results suggest that P-mediated modification of soil microbial community structure also contributed to increase SMB-P at this P rate. The increase of application of P rate (80 kg P2O5 ha-1) produced the largest soybean yield, but generally decreased SMB-P. Our results and those of others suggest that balanced soil fertility (corresponding to fertilizer recommendations in our case) promotes soil microbial development. The use of ridge tillage did not increase the soil organic carbon level, but did increase SMB-P. The SMB-P pool was large (equivalent to 24.4kg P2O5 ha-1) in the 0- to 20-cm soil layer, but unrelated to yield. Improving the ability of crops to access this pool of soil P would increase the value of its management. Key words: Conventional tillage, conservation tillage, P fertilization, soil microbial biomass C, P, and C to P ratio
Spatial patterns of forest floor properties and litterfall amounts associated with bigleaf maple in conifer forest of southwestern British Columbia
Authors: Chandler J R , Schmidt M G , Dragicevic S.
Published: April 2011

This study was aimed at detecting the spatial characteristics of forest floor properties and litterfall amounts related to bigleaf maple (Acer macrophyllum Pursh) within conifer forest. Two 36-m × 36-m plots, centered on individual dominant bigleaf maple stems, were sampled at 129 systematic locations and tested for forest floor pH, cation exchange capacity, exchangeable cations, and mineralizable N. Tree stem location, forest floor horizon depths and litterfall amounts were measured. The kriging approach was used to visualize overall spatial patterns, Moran's I was used to give a global measure of spatial autocorrelation over the sampled region, and local indicators of spatial association (LISA) was used to detect and locate significant spatial clustering of similar values at the local scale. Most soil chemical properties had higher values in locations adjacent to the bigleaf maple stem, up to distances of 2.5 m from the stem on both study plots, and all exchangeable cations were positively spatially autocorrelated (P < 0.05) up to distances of 4 m. The majority of bigleaf maple litter (84% on plot 1, 92% on plot 2) was found to be deposited directly beneath the canopy extent. This study provides an understanding of the underlying spatial patterns of bigleaf maple influence on soil properties at plot scale. Key words: Bigleaf maple, spatial analysis, broadleaf species, plant-soil interactions local indicators of spatial association, forest floor
The use of in situ volumetric water content at field capacity to improve the prediction of soil water retention properties
Authors: Al Majou Hassan , Bruand Ary , Duval Odile
Published: April 2011

Most pedotransfer functions (PTF) developed over the past three decades to generate water retention characteristics use soil texture, bulk density and organic carbon content as predictors. Despite the high number of PTFs published, most being class- or continuous-PTFs, the accuracy of prediction remains limited. In this study, we compared the performance of different class- and continuous-PTFs developed with a regional database. Results showed that the use of in situ volumetric water content at field capacity as a predictor led to much better estimation of water retention properties compared with using predictors derived from the texture, or the organic carbon content and bulk density. This was true regardless of the complexity of the PTFs developed. Results also showed that the best prediction quality was achieved by using the in situ volumetric water content at field capacity after stratification by texture. Comparison of in situ volumetric water content at field capacity, with the water retained at different matric potentials as measured in the laboratory, showed field capacity to approximate 100 hPa, whatever the soil texture. Finally, the lack accuracy of PTFs that do not use the in situ volumetric water content at field capacity as predictor did not appear due to the test soils being unrepresentative of the soils used to develop the PTFs, but were instead related to poor correlations between the predictors used and the water retention properties. Key words: Pedotransfer functions, root mean square error, mean error of prediction, standard deviation of prediction, texture, bulk density, organic carbon content
Management strategies to simultaneously reduce ammonia, nitrous oxide and odour emissions from surface-applied swine manure
Authors: Smith E. , Gordon R. , Bourque C. , Campbell A.
Published: April 2011

Surface-applied swine manure has the potential to generate ammonia (NH3), nitrous oxide (N2O) and odour. Field research was conducted in Prince Edward Island to measure the simultaneous emissions of NH3, N2O and odour following the surface-application of swine manure. Manure was applied to a grain stubble field consisting of a sandy loam soil low in pH (5.6–5.9). The effect of manure type (liquid and solid), application rate [conventional/typical rate (1 ×): 30 000-36 000 L ha-1, double (2 ×): 60 000-72 000 L ha-1 and five times (5 ×): 180 000 L ha-1] and rainfall (8–200 mm) before and after liquid manure application were examined. There was no relationship between odour emissions and manure type, application rate and rainfall before and after spreading, due to high variability. Liquid manure (dry matter (DM = 45 g kg-1) reduced NH3 emissions by 32% compared with solid (DM = 350 g kg-1). Increasing application rates enhanced NH3 emissions; increasing the rate by 2 × and 5 × the typical rate increased losses by 62 and 78%, respectively. Applying manure prior to rainfall reduced NH3 emissions by 37%, compared with application after a rainfall. Ammonia and odour emissions were similarly correlated to atmospheric conditions with increased emissions at higher air and soil temperature, net radiation, vapour pressure deficit and windspeed. Nitrous oxide emissions were low in magnitude and showed no correlation to climatic conditions, suggesting that management strategies to reduce both odour and NH3 did not enhance N2O emissions when applied to a moderately acidic soil with low levels of soil nitrate (< 5 mg N kg-1). Our results indicate that for conditions similar to those in this study, there is no trade-off between NH3 and N2O production and more attention should be placed on controlling and reducing odour and NH3 emissions. Key words: Ammonia, nitrous oxide, odour, swine manure, management strategies
Soil and sweet cherry responses to irrigation with wastewater
Authors: Neilsen G. H. , Stevenson D. S. , Fitzpatrick J. J. , Brownlee C. H.
Published: April 2011

Lambert sweet cherry (Prunus avium L.) established on Osoyoos loamy sand in 1983 was subjected to treatments involving all combinations of two types of irrigation (wellwater or municipal wastewater) and three rates of N fertilization (0, 68 and 136 g of N as NH4NO3 tree−1 yr−1), 1984–1987. The zero-N treatment was increased to 34 g N tree−1 in 1986–1987. Wastewater irrigation increased leaf N, P, K, B and Mn concentration, decreased leaf Mg and Ca and had few consistent effects on leaf Fe and Cu. Tree growth was increased after 2 yr but not after 5 yr by wastewater irrigation. Inadequate N and Zn nutrition appeared to limit long-term tree growth. After 5 yr, wastewater-irrigated soils had higher extractable P, K, and B and lower Ca and Mg than well-water-irrigated soils which had higher Ca and Mg to 0.9-m depth. Wastewater irrigation also increased extractable Na throughout the soil but insufficiently to adversely affect tree growth. Soil pH and electrical conductivity also increased during the experiment for both well- and wastewater-irrigated soils, but these increases did not cause alkalinity or salinity problems. Key words: Prunus avium L., wastewater irrigation, leaf nutrition, soil quality
Effect of cropping practices on the initial potential rate of N mineralization in a thin Black Chernozem
Authors: Campbell C. A. , Leyshon A. J. , Zentner R. P. , LaFond G. P. , Janzen H. H.
Published: April 2011

In pursuit of identifying sustainable agricultural production practices, there is an urgent need to develop or identify parameters that effectively describe and differentiate changes in the quality and quantity of soil organic matter resulting from crop management or cultural practices. The effectiveness of the potentially mineralizable nitrogen (No) concept for this purpose was examined using data from a 30-yr crop rotation study, carried out on a Rego thin Black Chernozem at Indian Head, Saskatchewan. Although Kjeldahl N and hydrolyzable soil amino-N are effective for demonstrating the beneficial influence of fertilizers, legumes and continuous cropping on total soil organic N content, they are less effective in identifying changes in organic matter quality. We have shown that a parameter which we called the "initial potential rate of N mineralization" [potentially mineralizable N (No) × rate constant (k) at time = 0] was effective in distinguishing both the absolute and qualitative changes in soil organic N due to various cultural and management practices. The results showed that fertilizers can be as effective as legumes, used either for green manure or for hay, in increasing the quantity and improving the quality of soil organic matter. A 6-yr rotation including 1 yr of fallow, 2 yr of spring wheat (Triticum aestivum L.) and 3 yr of bromegrass (Bromus inermis Leyss) and alfalfa (Medicago sativa L.) hay had a greater quantity and improved quality of soil organic N relative to that of unfertilized continuous wheat (Cont W), but they were equivalent to that of fertilized Cont W. Key words: Soil quality, potential mineralizable N, crop rotations, legumes, fertilizer effects
Distribution and plant availability of soil copper fractions in Saskatchewan
Authors: Liang J. , Stewart J. W. B. , Karamanos R. E.
Published: April 2011

Growth chamber and laboratory studies were conducted to investigate the distribution and plant availability of copper (Cu) fractions in Saskatchewan soils. These studies included an examination of the distribution of Cu fractions in 27 soils and an evaluation of plant availability of native and added Cu fractions in beans (Phaseolus vulgaris L.) grown in seven soils. The soils in these experiments were selected to give a wide variation in physical and chemical properties. Total Cu content of the 27 soils ranged from 6.5 to 39.0 μg g−1 with an average of 21.0 μg g−1. A seven-step sequential fractionation showed that most of the total Cu (49.0–78.0%) was present in the residual fraction (Res-). The percentages of soil Cu in the exchangeable (Ex-), Pb-displaceable (Pb-), acid soluble (Aci-), Mn oxide bound (MnO-), organically associated (OM-) and Fe, Al oxide bound (FeO-) fractions averaged 2.2, 1.5, 2.0, 4.8, 7.9 and 11.1%, respectively. Amounts of Cu in MnO-, FeO-, Res- fractions and total Cu were interdependent and varied directly with DTP A- extractable Cu and clay content. The growth chamber experiment showed that the most of the applied Cu was accumulated in MnO-, OM-, FeO-, and Res- fractions. Therefore, sesquioxides and organic matter are the major components responsible for the adsorption of added Cu. The concentration of Cu and its uptake into navy beans were positively correlated with DTPA-extractable Cu, MnO-Cu, FeO-Cu and total Cu, which in turn were correlated with clay content. Plant Cu concentration and uptake can be predicted by an equation which includes DTPA-extractable Cu and clay content. These results showed that DTPA-extractable Cu is a good predictor of Cu availability in prairie soils. Key words: Cu fractions, distribution, availability, DTPA-extractable Cu, clay content, navy beans
Spatial and temporal variability of soil respiration in agricultural fields
Authors: Rochette P. , Desjardins R. L. , Pattey E.
Published: April 2011

Chamber measurements of CO2 evolution were made on bare soil, and in maize (1988) and wheat (1989) crops in order to study the spatial and temporal variability of soil respiration (Rsoil). Semivariograms showed no definite structure of spatial autocorrelation on bare soil when measurements were made along transects. Spatial variability was shown to occur at a scale smaller than 15 cm. In a maize crop, Rsoil in the row was significantly higher (P = 0.05) than in the interrow when the soil surface was dry. Under wet soil conditions, Rsoil in the interrow compacted by the tractor wheel was lower (P = 0.05) than on noncompacted soil and no significant difference was found between rows and interrows. These observations were attributed to the contribution of plant roots to Rsoil in dry conditions. In wetter soil, the role of microbial activity was dominant except in the compacted interrow where lower airfilled porosity caused lower Rsoil. Random measurements in a wheat crop over the growing season showed that the number of samples needed to estimate the Rsoil of a 1 ha area within 10% (P = 0.05) of its mean value decreased from 190 at the time of seeding to 30 at the end of the season. The maximum Rsoil during the growing season coincided with the period of maximum growth of both crops. A post-rainfall Rsoil burst is also described. Immediately after a 2-h rainfall event, when soil was at field capacity, Rsoil was nine times higher than its level prior to the rainfall and gradually decreased with time. Key words: Soil respiration, variability, chamber measurements, CO2 flux
The effect of time and rate of N application on the yield and N uptake of wheat, barley, flax and four cultivars of rapeseed
Authors: Nuttall W. F. , Malhi S. S.
Published: April 2011

Field experiments were conducted for 3 yr on a Black Chernozemic soil at Melfort in northeastern Saskatchewan to determine the yield response and N uptake of seven crop/cultivars to autumn and spring applied N. The crop/cultivars were, rapeseed (Brassica napus L. 'Midas' and 'Target'; Brassica campestris L. 'Torch' and 'Echo'); wheat (Triticum aestivum L. 'Manitou'); barley (Hordeum vulgare L. 'Conquest') and flax (Linum usitatissimum L. 'Noralta') (main plots). Ammonium nitrate fertilizer treatments consisted of three rates of autumn broadcast N, 0, 34 and 67 kg N ha−1 (subplots), combined with N at 0, 11, 22, 45, 67 and 134 kg N ha−1 side-banded with seed in the spring (subsubplots). At the 67 kg N ha−1 rate, autumn application was inferior to spring application in increasing grain yield and N uptake for three of the seven crops (Torch and Echo rapeseed and Manitou wheat). Nitrogen fertilizer applied at 134 kg N ha−1 in spring produced grain yields that were not significantly higher than the split application of 67 kg N ha−1 applied in autumn and 67 kg N ha−1 applied in spring. All crops responded to spring applied N and continued to increase in yield up to the high rates of 67 or 134 kg N ha−1. Key words: Time of N application, N, crops, cultivars
Effect of crop rotations and fertilization on soil organic matter and some biochemical properties of a thick Black Chernozem
Authors: Campbell C. A. , Zentner R. P. , Bowren K. E. , Townley-Smith L. , Schnitzer M.
Published: April 2011

The effects of crop rotation and various cultural practices on soil organic matter and some biochemical characteristics of a heavy-textured, Orthic Black Chernozem with a thick A horizon were determined after 31 yr at Melfort, Saskatchewan. Treatments investigated included: fertilization, cropping frequency, green manuring, and inclusion of grass-legume hay crops in predominantly spring wheat (Triticum aestivum L.) systems. The results showed that neither soil organic C nor N in the top 15 cm of soil, nor hydrolyzable amino acids, nor C mineralized in 14 d at 20 °C were influenced by fertilization. However, the relative molar distribution (RMD) of the amino acids reflected the influence of fertilization and the phase (Rot-yr) of the legume green manure rotation sampled. Some characteristics assessed increased marginally with increasing cropping frequency but differences were less marked than results obtained earlier in a heavy-textured Black Chernozem with a thin A horizon at Indian Head, Saskatchewan. The relationship between soil organic matter or C mineralization versus estimated crop residues, residue C, or residue N returned to the land over the 31-yr period, were not significant in the Melfort soil. This contrasts with our findings for the thin Black soil. We speculate that the lack of soil organic matter response in the Melfort soil was due to its very high organic matter content (about 64 t ha−1C and 6.5 t ha−1N in the top 15 cm). We also hypothesized that the amino acid RMD results, which differed from most of those reported in the literature, may be reflecting the more recent cropping history of the soil. This aspect requires further research into the composition and distribution of the humic materials in this soil. Key words: Amino acids, relative molar distribution, C respiration, green manures, fertilization
Quantifying denitrification on a field scale in hummocky terrain
Authors: Elliott J. A. , Jong E. de
Published: April 2011

In this study a landscape classification and daily climatic data were used to extrapolate from a number of discrete denitrification rate measurements to an annual field average. Denitrification rates were calculated from modelled daily moisture contents and observed daily temperature using regression equations. Different regression equations were used for crop and fallowed fields, and for three distinct landscape groups; depositional, intermediate, and erosional. Good correlations were found between predicted and measured denitrification rates. Annual denitrification losses were greatest under fallow, ranging from 50.5 kg N ha−1 on the low level landscape element to 3.1 kg N ha−1 on the diverging blackslope. Losses from cropped soil ranged from 12.8 kg N ha−1 on the diverging footslope in 1988 to 0.7 kg N ha−1 on the diverging backslope in 1986. Field average denitrification losses were estimated to be 3 kg N ha−1 in 1986 (wheat), 16 kg N ha−1 in 1987 (the fallow year) and 4 kg N ha−1 in 1988 (canola). Key words: Denitrification, annual field averages, landscape elements, soil properties, simulation model
Acidification adjacent to an elemental sulfur stockpile: I. Mineral weathering
Authors: Warren C. J. , Dudas M. J.
Published: April 2011

Soil pH values below 3.0 are measured in soil material located adjacent to stockpiles of elemental sulfur on sour gas plant sites. The objective of this study was to examine the influence of extreme acidity on the changes and redistribution of major chemical and mineralogical components in soil along the side of a 25-year-old elemental sulfur block. Soil samples, obtained from pits located 2 m from the side of the sulfur block, were analyzed for total content of Al, Fe, Ca, Mg, Na, K, and Ti. Sand and clay separates were analyzed by X-ray diffraction, and physical and chemical methods to identify and quantify mineral phases. Carbonate, Fe-containing primary minerals, chlorite, smectite, and plagioclase feldspars were either partially or completely dissolved in soil having pH values of about 2.1. Clay-sized mica and kaolinite were apparently not affected by the acidity. Calcium carbonate and Ca-feldspars dissolved in the presence of H2SO4 to form gypsum. Iron dissolved from minerals in the acidified surface layer was deposited primarily as oxyhydroxides at the interface of acidic and calcareous materials to form an indurated layer about 10–15 cm thick. Jarosite precipitated within the acidic material just above the indurated layer. Key words: Elemental sulfur, anthropogenic acidification, mineral weathering, acid soils
Effect of crop rotations and rotation phase on characteristics of soil organic matter in a Dark Brown Chernozemic soil
Authors: Campbell C. A. , Biederbeck V. O. , Zentner R. P. , Brandt S. A. , Schnitzer M.
Published: April 2011

The influence of five crop rotations and the rotation phases (i.e., rotation-yr) on some soil organic matter characteristics was investigated in a long-term (23 yr) study carried out on an Orthic Dark Brown Chernozemic soil at Scott, Saskatchewan. The cropping systems included different cropping frequencies and crop types (cereals, oilseeds, and legume-hay). Soil samples were taken from the 0- to 7.5- and 7.5- to 15-cm depths in mid-September 1988, 2 wk after harvest of the grain crops (i.e., 2 mo after hay harvest and plowdown). Most effects of rotations, and rotation phases, on soil biological characteristics assessed, were significant primarily in the top 7.5-cm soil depth. Increasing the cropping frequency did not increase soil organic matter. Excessive preseeding tillage of stubble plots may have masked any potential advantage provided by frequent cropping. Including alfalfa (Medicago sativa L.) hay crops in rotation with grain crops decreased soil organic matter in the fallow and grain crop rotation phases of rotations. This was likely due to increased moisture stress depressing associated cereal production in this semiarid environment. As expected, rotation phase did not influence soil organic C, but alfalfa under-seeded into barley (Hordeum vulgare L.) increased soil organic nitrogen. We believe this was due to crop residue inputs from the seedling alfalfa. Microbial biomass C and N, C mineralization, the specific respiratory activity (ratio of CO2-C respired/microbial biomass C) and hydrolyzable amino acids were also greater in the rotation phases in which barley was underseeded with alfalfa. Carbon mineralization and specific respiratory activity were directly related to estimated crop residue-C returned to soil, but not residue-N. However, both were increased by including alfalfa in the rotation. Carbon mineralization and specific respiratory activity were more sensitive indexes of soil organic matter quality than biomass C and N per se. Hydrolyzable amino acids and amino sugars responded to the treatments in a manner similar to total soil organic N. Relative molar distribution of amino acids was unaffected by crop rotation or rotation phase. Potentially mineralizable N in this soil was low compared to other Canadian prairie soils, even though the total soil organic N of the Scott soil was relatively high. We concluded that (i) all soil biochemical characteristics studied are useful for assessing soil quality changes; (ii) when studying soil changes, thin (0- to 7.5-cm) soil slices are more likely to reveal treatment effects than thicker slices; (iii) all rotation phases should be analyzed whenever forage legumes are constituents of crop rotations. Key words: C mineralization; microbial biomass, amino acids, N mineralization, specific respiratory activity
An assessment of the single-head analysis for the constant head well permeameter
Authors: Reynolds W. D. , Topp G. C. , Vieira S. R.
Published: April 2011

An in-situ constant head well permeameter (CHWP) method employing three or more ponded heads per well was used to establish relationships between field-saturated hydraulic conductivity (Kfs), matric flux potential [Formula: see text], the alpha parameter (α*), soil texture, and soil structure. The relationships were then used to evaluate a single-head CHWP technique which employs representative mean α* values in the determination of Kfs and [Formula: see text]. The measurements were made at several depths on four soils which ranged in texture from loamy sand to silty clay, and in structure from single grain to strong, fine subangular blocky. The Kfs and [Formula: see text] results obtained from the multiple-head CHWP measurements were found to be highly variable within and between soils, yielding within-soil ranges as high as 3.5 orders of magnitude and standard deviation factors (SDF) as high as 5.1. The geometric mean (GM) Kfs and [Formula: see text] values were also highly variable between soils, but they were controlled primarily by soil structure rather than by soil texture or other factors. The α* values, on the other hand, were relatively consistent both within and between soils, yielding an overall SDF of only 1.2 and an overall GM of 11 m−1. Use of α* = 11 m−1 in the single-head CHWP technique yielded Kfs and [Formula: see text] values which were usually accurate to within a factor of 2, and often accurate to within ±25%. These levels of accuracy are within acceptable limits for a field method, considering the many potential sources of error and the extreme range and variability of Kfs and [Formula: see text] normally encountered in the field. Key words: Constant head well permeameter, hydraulic conductivity, matric flux potential, alpha parameter, soil texture, soil structure, single-head analysis
Response of some vegetable crops to soil-applied halides
Authors: Sheppard S. C. , Evenden W. G.
Published: April 2011

The halide elements are environmentally important and share some common attributes. The heaviest, I, and the lighest, F, are quite toxic and are important industrial pollutants. They are also effectively retained in soils. The others, Cl and Br, can be accumulated to high concentrations in plants, are used in agriculture and are highly mobile in soils. This study investigated the behaviour of the halides in plots, outdoor lysimeters, and laboratory sorption and excised-root experiments. Sorption on soil was ordered as F > I > Br > Cl. Concentrations in plants were generally ordered as CI ≥ Br > > F ≥ I, the inverse of the sorption ordering, as expected. Older tissues, which were also closest to the soil surface, had higher concentrations, and sequestered tissues, such as corn kernels and cabbage heads, had lower concentrations. There was evidence of competitive interaction among the halides and with soil anions such as phosphate and sulfate. This competition reduced the toxicity of I and modified tissue concentrations of the halides, P and S. Another interesting interaction was an increase in Cl and I sorption on soil solids when there were elevated levels or the other halides. Overall, the study of the halides in combination enhanced our understanding of their individual behaviours. Key words: Fluoride, chloride, bromide, iodide, vegetable
Comparison of static and dynamic closed chambers for measurement of soil respiration under field conditions
Authors: Rochette P. , Gregorich E. G. , Desjardins R. L.
Published: April 2011

The objective of this study was to compare the dynamic closed and static chamber techniques for the measurement of soil respiration under field conditions. The static chamber method consistently produced lower soil respiration values than did the dynamic closed system and the difference was larger at higher CO2 fluxes. A negative exponential model describes the relation between CO2 fluxes measured by both techniques. A good fit was obtained for measurements on a sandy loam soil (R2 = 0.61) and an organic soil (R2 = 0.74) but parameter estimates were different for each soil. Key words: Carbon dioxide, enclosure, gas flux measurement
Cobalt content of forages and cereals grown on Prince Edward Island
Authors: Gupta Umesh C.
Published: April 2011

Field studies were conducted on Prince Edward Island (PEI) at two locations over a period of 2 years on the effect of soil and foliar applied Co on Co concentration in forages and cereals. Application of Co did not affect crop yields, although the yields varied considerably from location to location (data not reported). The Co concentration in cereal grain ranged from 10 to 25 μg kg−1 in the control plots. With foliar-applied Co, maximum Co concentrations in wheat, barley and oat grain were 101, 70 and 29 μg kg−1, respectively, in the three crops. In forages, large increases in Co were found in the first cut using foliar sprays but in the second cut the Co increases were small and significant only in one-half of the cuts. Soil applications of Co at 150 g ha−1 were ineffective in raising the grain Co but in forages Co was significantly increased in about one-third of the cuts. The mean Co concentration in forages and cereals from various fields in PEI ranged from 13 to 28 μg kg−1; such levels are considered deficient for livestock. In the case of suspected Co deficiency, 60 and 100 g Co ha−1 applied as a foliar spray to forages and cereals, respectively, should raise the feed crop Co concentration in the sufficiency range for livestock. Key words: Cobalt, wheat, barley, oats, alfalfa, timothy
Comparison of humus horizons from two ecosystem phases on northern Vancouver Island using 13C CPMAS NMR spectroscopy and CuO oxidation
Authors: deMontigny L. E. , Preston C. M. , Hatcher P. G. , Kögel-Knabner I.
Published: April 2011

Much forested land in the wetter zones of northern Vancouver Island is characterized by thick humus layers, with two distinct ecosystem phases: the younger "HA" phase arising from disturbance is productive after clearcutting, but in the old-growth "CH" phase, seedlings suffer growth check after 5–8 yr, with reinvasion of the ericaceous shrub salal (Gaultheria shallon Pursh.). We used solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and CuO oxidation to examine whether chemical differences in the humus might be associated with difference in forest productivity after clearcutting. NMR spectra of woody horizons, which were similar for CH and HA sites, were dominated by signals from lignin of decomposed wood. Non-woody humus types were typical of forest litter layers, and were dominated by signals in the O-alkyl region. The differences between CH and HA sites were: (i) higher tannin content in the CH sites, most likely from salal inputs and (ii) higher ratio of carbohydrate to lignin C, indicating less effective decomposition in CH sites. Oxidation with CuO also showed more advanced decomposition in the non-woody horizons of HA than of CH sites. Less effective decomposition possibly due in part to tannin accumulation could contribute to the lower forest productivity on salal-dominated CH sites in this region. Key words: 13C NMR, CuO oxidation, decomposition, humus, tannin, salal
Early changes in water-stable aggregation induced by rotation and tillage in a soil under barley production
Authors: Angers D. A. , Samson N. , Légère A.
Published: April 2011

Crop rotations and tillage practices can alter the structure of die soil through their effects on soil disturbance and mixing and on organic matter (OM) accumulation and mineralization. The objective of this study was to determine the changes in soil water-stable aggregation induced by 4 yr of different rotation and tillage practices on a Kamouraska clay at La Pocatière, Quebec. The influence of soil water content (WC) at time of sampling and of different biological and biochemical properties on soil aggregation was also examined. Two rotations (continuous barley (Hordeum vulgare L.) vs. a 2-yr barley–red clover (Trifolium pratense L.) rotation) and three tillage treatments (moldboard plowing (MP) chisel plowing (CP) and no-tillage (NT)) were compared in a split-plot design. Measurements of the size distribution of water-stable aggregates were made on surface (0–7.5 cm) soil samples taken periodically during the 4-yr period. Rotations had no effect on soil aggregation. The mean-weight diameter (MWD) of water-stable aggregates did not vary significantly with time under the NT treatment during the study but decreased significantly under the MP and CP treatments. In the fourth growing season, MWD values in NT plots were on average 40% higher than in MP and CP plots, which were both similar. The larger values in MWD under NT were attributable to a larger proportion of aggregates > 2 mm at the expense of smaller ones (< 1 mm). The MWD data showed important temporal fluctuations, which could in part be explained by the effects of WC at time of sampling. This effect of WC on MWD was less apparent under NT, which suggested that these aggregates were less susceptible to slaking. Among different OM fractions, the proportion of organic C present as hot-water-soluble carbohydrates was best correlated with MWD. Key words: Soil management, aggregation, slaking
The effect of sample grinding on extractable iron and aluminum in soils
Authors: Neary A. J. , Barnes S. R.
Published: April 2011

Pyrophosphate-, dithionite- and acid ammonium oxalate-extractable Fe and Al are often measured on a finely ground aliquot of soil. Grinding provides a homogeneous sample from which a representative subsample can be obtained at sampling aliquots of less than 1 g. When a significant portion of the unground soil is greater than the sieve mesh size used when grinding, abrasion of primary minerals may cause increased levels of extractable Fe and Al. This study examined the distribution of extractable Fe and Al in some sandy soils and compared their levels in samples ground to < 500 μm and < 150 μm with those in unground < 2-mm soil. Samples ground to < 150 μm yielded the highest amounts of extractable Fe and Al. This effect was most prevalent when a motorized mortar and pestle was used. Samples ground to < 500 μm, which were frequently re-sieved to avoid over-grinding, contained similar amounts of extractable Fe and Al as the unground < 2-mm sample. If less than 1 g of soil is used for analysis, a sample manually ground to < 500 μm (35 mesh) is advisable and a protocol for sample grinding is recommended. Key words: Iron, aluminum, pyrophosphate, dithionite, oxalate, grinding
Risk simulation of the economics of manure application to restore eroded wheat cropland
Authors: Freeze Brian S. , Webber C. , Lindwall C. W. , Dormaar J. F.
Published: April 2011

The economics of hauling manure as an amendment for restoring the productivity of artificially eroded wheat cropland was investigated using a simulation model. The model incorporated data on the long-term variability of wheat price, growing season precipitation and manure moisture content, and data from manure application experiments conducted on land where topsoil had been removed in levelling. Results showed that on average over the long term, the value of manure as an amendment for restoring the productivity of slightly eroded wheat cropland (< 20 cm soil lost/removed) is sufficient to allow manure to be hauled 3–5 km further than would be the case on non-eroded soils. On heavily eroded wheat cropland (> 80 cm soil lost/removed), hauling distance can be extended approximately 20 km. The disposal market for feedlot manure can be expected to extend to a distance of about 55 km from its source. Results are applicable to the dryland wheat areas of the dark brown soil zone of the Canadian prairies. Key words: Feedlot manure, fertilizer economics, eroded soil, animal wastes
Estimating total soil mass, nutrient content, and trace metals in soils under a low elevation spruce-fir forest
Authors: Fernandez Ivan J. , Rustad Lindsey E. , Lawrence Gregory B.
Published: April 2011

The concentration, contents, and distribution of nutrients, metals, and soil materials were quantified at the Howland Integrated Forest Study (HIFS) site in eastern Maine. The site is a mature, low-elevation spruce-fir forest on Podzolic soils developed from dense basal till. Standard morphologically based soil sampling and quantitative soil pits were both used to characterize the soil component of this ecosystem. Vertical trends in nutrient concentrations at the site were largely governed by the distribution of organic matter. Standard morphological soil sampling techniques tended to overestimate soil pools of labile cationic nutrients and C, and underestimate trace metals and P, as a result of underestimations of coarse fragment content. These discrepancies can be critical if extrapolations for nutrients, metals, and C are made using existing databases to regional or global scales.Key words: Forest soils, spruce-fir, quantitative pits, sample size
Determination of the most efficient phosphorus placement for field-grown maize (Zea mays L.) in early growth stages
Authors: Lu S. , Miller M. H.
Published: April 2011

Field experiments were conducted in 1988 and 1989 to determine the most efficient phosphorus (P) placement for P absorption by maize (Zea mays L.) in early growth stages. The treatments consisted of four rates of applied P (0, 25, 50 and 100 kg P ha−1) mixed with 3, 6, 12 and 25% of the soil volume in the row. Shoots and roots were sampled at 3- to 4-leaf, 6-leaf, and 8- to 9-leaf stages. The roots inside and outside the zone of P fertilization were sampled separately. There was no evidence of root proliferation in the fertilized zones, even with the 100 kg P ha−1 rate mixed with 3% of the soil volume. There was a significant response of shoot dry matter, shoot P concentration, shoot P uptake, and root growth to applied P. Shoot P concentration and shoot P content increased as the volume of soil with which fertilizer P was mixed decreased. Mixing 100 kg P ha−1 with 3–6% of the soil volume resulted in the highest shoot P content in the early growth stages. There was no evidence that fertilizing a greater proportion of soil than the conventional band method will result in higher P uptake of maize in early growth in the soil studied. Because the soil in the study had a relatively low P adsorptive capacity, this conclusion is likely valid for a broad range of soils, which have a greater P adsorptive capacity. Key words: Phosphorus placement, maize, root growth, phosphorus absorption
Soil water under conventional and alternative cropping systems in cryoboreal subhumid central Alberta
Authors: Izaurralde R. C. , Chanasyk D. S. , Juma N. G.
Published: April 2011

Soil water limits plant growth in the Canadian Prairie Provinces. Efficient use of soil water is, therefore, paramount in crop production. Two 2-yr field studies were conducted (i) to determine the effects of crop selection and cropping practice on the temporal and spatial distribution of soil water and (ii) to quantify water use and water-use efficiencies (WUE) of alternative crop/cropping systems for a subhumid region of Alberta. The first study was at the Ellerslie Research Station on an Orthic Black Chernozemic and the second at the University of Alberta Breton Plots on an Orthic Gray Luvisol. At each site three annual crops/cropping systems [barley (Hordeum vulgare L.), barley intercropped with field pea (Pisum sativum L.), and faba bean (Vicia faba L.)] and a perennial forage [creeping red fescue (Festuca rubra)] were grown in 1987 and in 1988. At Ellerslie, tillage methods to grow annual crops were conventional and zero tillage. At Breton, the two tillage methods used were: (i) conventional and (ii) deep tillage (to enrich the surface horizon with clay from the subsoil). The experimental design used was a split plot with four replications. Soil water was measured by neutron attenuation. Evapotranspiration was calculated as the change in soil water to 0.80-m depth plus precipitation. Soil water changes were more closely associated with the kind of crop grown than with the method of tillage used. The barley/field pea intercrop exhibited a pattern of water use similar to barley. Greater water-use efficiency measured in the intercrop system was attributed to differences in canopy structure and plant biomass production. Faba bean and red fescue had lower WUE than barley and the intercrop. The water requirement by faba bean was close to that of red fescue and related to leaf area development. Small tillage effects on soil water were observed during 1988. Soil water under zero tillage was greater than under conventional tillage. Faba bean and red fescue are likely to succeed more in agro-ecological regions such as Breton. Further studies are required to improve our understanding of the effects of these cropping systems on water resources when they are used in rotational-production systems. Key words: Barley, field pea, faba bean, creeping red fescue, conventiional tillage, zero tillage, deep tillage, water-use efficiency