bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of tillage practice on carbon sequestration is scale-dependent
Authors: Bergstrom D W , Monreal C M , St. Jacques E.
Published: April 2011

While the influence of management practices on soil organic C (OC) concentration and mass has been evaluated for the surface layer of small plots of homogeneous soils, there are few studies at a scale inclusive of the entire solum and heterogeneous soils. The objective of this study was to test for an interaction between tillage practice [no-till (NT) vs. conventional tillage (CT) by chisel-plow] and topography as determinants of OC stocks in the entire solum and layers thereof at a field-scale. Adjacent fields of contrasting tillage practice were stratified by soil series and drainage class for comparison. The effect of tillage practice on OC mass was contingent on slope position and sampling depth, i.e., scale-dependent. There was more OC in the surface layer (0–8 cm) of the A horizon of the NT than the CT field at well-drained upper slope positions, but not at imperfectly drained lower slope positions. At lower slope positions there was more OC in the entire A horizon of the CT than the NT field. Results of small-plot studies with homogeneous soils cannot be extrapolated arbitrarily to larger scales. Rather, assessments at larger scales that encompass heterogeneous soils are required. Key words: Carbon sequestration, soil series, tillage, topography
Fractionation of P in soil as influenced by a single addition of liquid swine manure
Authors: Qian P. , Schoenau J. J.
Published: April 2011

Limited information exists as to the short-term effect of liquid swine manure on P distribution in soil. To address this issue, forms and distribution of inorganic P (Pi) and organic P (Po) at 2 wk and 16 wk after manure addition were investigated through a sequential extraction procedure. An Orthic Black Chernozem was sampled from a field research plot (Dixon, SK) without previous manure and urea additions. Liquid swine manure and urea were applied at rates of 0, 100 and 400 mg N kg−1, corresponding 10 and 40 mg P kg−1 from manure. Manure addition did not increase the most labile P fractions in soil. Instead the initial fate of the P from the manure was mainly to enter moderately labile and stable fractions such as calcium phosphate and organic P forms. This is consistent with observations in the field that a single application of swine effluent does not have a large impact on extractable "available" P in the soil. Further studies are needed to determine how much manure P loading is required for saturation of the "fixed pool" of P in Saskatchewan soils. Key words: Phosphorus fractions, sequential P extraction, incubation, urea, swine manure, anion exchange membrane
Grouping soils of the Montreal Lowlands (Quebec) according to fertility and P sorption and desorption characteristics
Authors: Leclerc M L , Nolin M C , Cluis D. , Simard R R
Published: April 2011

Soil tests P (STP) developed to estimate P fertilizer needs and designed to produce optimal economic crop yields, are often not well suited to assess potential environmental impact of fertilization practices. The objective of this study was to develop interpretative soil groupings of the Montreal Lowlands area (MLA) based on soil physico-chemical properties and on soil P sorption and desorption characteristics. Soil P sorption and desorption characteristics together with STP may help in evaluating potential risks of soil P addition. Sixty-six soil types (phases of soil series based on surface texture) were selected as representative soils of the study area. Twenty-seven soil properties were used, including Mehlich-3 extractable P and Al, ammonium-oxalate extractable P, Fe and Al, P sorption index (Psi) and Bray-2 extractable P(BR2P). Multivariate analysis was applied to generate clusters and interpret soil groupings. Principal components analysis yielded two components related: (1) to soil inherent fertility (texture) and (2) to P sorption capacity and desorption intensity. The Ward's clustering method was then applied to the first two component scores. Five soil fertility groups were obtained. Multiple discriminant analysis proposed a classification model using a small subset of variables. Five variables were selected among the soil survey characteristics for discriminating soil groups: clay content, pH measurement in water, cation exchange capacity, BR2P and ammonium-acetate extractable Mg. Adding Psi in the model improved the classification correctness. The results of this study indicate that physico-chemical properties of the surface layer used together with soil P sorption-desorption characteristics contributed to the development of an interpretative grouping that may also be useful to assess vulnerability to water contamination by P. Key words: Soil behavior, soil fertility groups, multivariate analysis techniques
Nitrous oxide production by manure samples collected from six manure-handling systems
Authors: Tenuta M. , Barry D. A. J. , Fairchild G. , Beauchamp E G
Published: April 2011

Stored manures are often considered to be source of nitrous oxide (N2O). A study was done to identify manure characteristics and handling stages related to N2O production. In two laboratory experiments we investigated the production of N2O from several animal manures collected at different stages of manure handling or locations in stored-manure systems. Denitrifying enzyme activity, denitrification and CO2 production rates and chemical and fibre characteristics of manure samples were also determined. Most samples had low rates of N2O production. Exceptions were open piles of fresh beef manure and the moist surface layer near the base of an open pile of poultry manure. Production of N2O was most highly correlated with nitrite plus nitrate (NO2− + NO3−) content of manure regardless of whether results were expressed on a wet or a dry weight basis. Denitrification was the most probable source of N2O because N2O production with acetylene and denitrifying enzyme activities was higher than N2O production without acetylene. Stored manure is potentially an important source of N2O emissions, particularly when storage conditions are conducive to formation of (NO2− + NO3−). Key words: Nitrous oxide production, denitrification, denitrifying enzyme activity, manure
Estimated changes in soil carbon associated with agricultural practices in Canada
Authors: Smith W N , Desjardins R L , Grant B.
Published: April 2011

The Century model was used to estimate the influence of changing agricultural practices on C levels in seven major soil groups in Canada for the years from 2000 to 2010. Conversion of arable land to permanent cover, and inclusion of forages in crop rotations would result in the greatest sequestration of C, averaging 0.62 and 0.44 Mg C ha–1 yr–1, respectively. The increase in soil C when conventional-tillage is converted to no-tillage management was estimated to average about 0.13 Mg C ha–1 yr–1. Reduction of summerfallow (wheat-fallow to wheat-wheat-fallow) in the arid and semi-arid chernozems of Western Canada would reduce C losses by about 0.03 Mg C ha–1 yr–1. If fertilizer use efficiency was increased by 50%, 0.04 Mg C ha–1 yr–1 would be sequestered, whereas a decrease of 50% in fertilizer use efficiency would result in a loss of 0.05 Mg C ha–1 yr–1. Timing of N application (fall vs. spring) had little effect on C change. This study indicates that there are several feasible techniques that could be adopted by agricultural producers in Canada that would significantly increase CO2 uptake from the atmosphere. Although our estimates are based on changes in individual management options, we recognize that producers are likely to adopt several options at the same time. Any interactions resulting from such a move have not been assessed in this analysis, in particular the impact on N2O emissions. Key words: Soil carbon, CO2, C sequestration, Century model, soil, tillage, agricultural practices, nitrous oxide emissions, crop rotations
Effects of green manures on soil organic matter and wheat yields and N nutrition
Authors: N’Dayegamiye A. , Tran Thi Sen
Published: April 2011

A field study was conducted for 5 yr (1993-1997) to evaluate the effects of green manure residues applied to the soil in 1993 and 1995, on wheat (Triticum aestivum L.) yields and N nutrition as subsequent crop in 1994, 1996 and 1997. The effect of green manure application was also evaluated on soil microbial activity (CO2), on C and N contents of whole soil and on labile (LF) and heavy fractions (HF) of organic matter (OM). The experiment was initiated on a Le Bras silt loam (Humic Gleysol). The green manures, as a main factor, were clover (Trifolium pratense L.), buckwheat (Fagapyrum esculentum L.), millet (Echinicloa crus galli L.), mustard (Brassica hirta Moench), and colza (Brassica campestris L.), and there was a control without green manure. The sub-factors consisted of four N fertilizer rates for wheat in the subsequent years at 0, 30, 60 and 90 kg N ha–1. Broadcast application of 15N- labelled NH4NO3 was made in 90 kg N ha–1 fertilizer treatments. Two green manure applications did not influence the C and N contents of densimetric fractions of OM (LF and HF), but significantly increased those of whole soil, and microbial respiration (CO2). Green manures significantly increased wheat yields and N uptake in 1994 and 1996. Levels of N derived from fertilizer (Ndff) were lower in all green manure treatments as compared to the control, which indicates that the proportion of N derived from soil and green manures (% Ndfs) was higher in these treatments. The contribution of N from green manure varied in the following order: buckwheat < clover < mustard < millet < colza. With the exception of the clover treatment (< 100%), the N recoveries from the other green manure N (NRGM) ranged from 23 to 34% and from 19 to 36% for 1994 and 1996, respectively. Green manure application provided 15 to 24 kg N ha–1 in 1994 and from 16 to 36 kg N ha–1 in 1996 and this contribution accounted for 25 to 31% of the total wheat N uptake. Significant green manure effects on wheat yield and N nutrition were primarily due to the improvement of soil properties and to high N recoveries from the green manure. In the cold temperate climate of Québec, green manure incorporation into soil in late summer or early fall of the preceding year allowed N synchronization with wheat N needs in subsequent cropping seasons. Nitrogen fertilizer rates could be reduced after the incorporation of green manures having high yields and N contents in the previous season. Key words: Green manure, wheat yields and N uptake, N recoveries, microbial respiration, labile and heavy fractions of OM, C and N contents
The contribution of shrinkage cracks to bypass flow during simulated and natural rainfall experiments in northeastern Mexico
Authors: Návar José , Mendez Jorge , Bryan Rorke B. , Kuhn Niklaus J.
Published: April 2011

Understanding the spatial and temporal dynamics of desiccation cracks and related hydro-geomorphologic processes is a key component for the sustainable management of water resources in Vertisols. The contribution of shrinkage cracks to infiltration of runoff and sediments was studied during natural and simulated rainfall experiments in Vertisols of the semi-arid plains of northeastern Mexico during the summer of 1998. Surface runoff amounted to 10.7% of the total applied rainfall, but it increased from 2.3 t o 18.3% during the first and last applied rainfall. Soil cracks partially filled with transported sediments in surface runoff, but never sealed by swelling or by sedimentation during the sprinkling of 180 mm of rainfall applied in three installments during 1 wk. However, cracks observed in 1999 closed during natural rainfalls with a total depth of 450 mm, distributed in 10 storms during 3 mo. The development of soil cracks and their contribution to promote short-circuit flow are highly variable processes in time and space. Key Words: Dynamics of shrinkage cracks, irregular wetting fronts
Effect of de-inking paper sludge compost application on soil chemical and biological properties
Authors: Baziramakenga Régis , Lalande Régis R. , Lalande Roger
Published: April 2011

A 2-yr field study evaluated the effect of applying compost of de-inking paper residues and poultry manure (DSPC) on the chemical and biological properties of Tilly silt loam (Gleyed Humo-Ferric Podzol) in Sainte-Croix de Lotbinière, Qué bec, Canada. The experiment began in 1996 with snap bean ( Phaseolus vulgaris L. ‘Centralia’) and continued in 1997 on the same plots with potato ( Solanum tuberosum L. ‘Gold Rush’). In 1996, treatments included three rates of mineral fertilizer (MF) (60, 120 and 180 kg P2O5-K2O ha-1), three rates of DSPC (14, 28 and 42 Mg ha-1 on a dry matter basis) alone or in combination with MF, and an untreated control. In the spring of 1997, main plots were divided into four subplots and P fertilizer was applied at 0, 44, 88 and 132 kg ha-1. The DSPC increased soil pH and water content. Soil inorganic N increased just after DSPC application, but this effect lasted only 1 yr. Soil Mehlich-3 extractable P showed a significant increase due to DSPC application and the increase was much larger when DSPC was applied in combination with P fertilizer. Soil phosphatase and urease activities were also increased by DSPC. Application of DSPC increased soil Mehlich-3 extractable K and Mg contents. Except for Mn and Zn, soil Mehlich-3 extractable heavy metal contents were not influenced by DSPC. This experiment indicates that compost derived from a mixture of de-inking papermill sludges and poultry manure is a potential source of nutrients for crops and can effectively improve chemical and biological properties of low fertility or degraded soils. Key Words: De-inking sludge, paper biosolids, poultry manure, phosphorus, potassium, enzyme activity
Adsorption of nucleic acid constituent uracil on copper(II)-loaded, solid peat and soil-derived humic acids
Authors: Ghabbour E A , Davies G. , Dunfee R L , Smith N A , Vozzell M E
Published: April 2011

Humic acids (HA) in compost, peats and soils sorb organic compounds selectively. This paper investigates the micro- and macroscopic properties of solid HAs isolated from a German peat (GHA) and a New Hampshire soil (NHA) using tightly bound copper(II) and nucleic acid constituent uracil adsorption as analytical probes. Isotherm measurements at 5.0–35.0°C show that tightly bound Cu(II) decreases the amount of uracil adsorbed by GHA at mM or lower uracil concentrations whereas previous work revealed the opposite effect for bound Hg(II). Site capacity comparisons are consistent with lower coordination numbers for HA-bound Hg(II) than for HA-bound Cu(II). Low coordination numbers leave Hg(II) sites open for uracil binding. Enthalpy and entropy changes for uracil adsorption on GHA, NHA, their Cu(II) and Hg(II)-loaded forms and on compost-derived HA are linearly correlated, indicating that HAs are free energy buffers. Water and bound metals evidently play major roles in HA-solute interactions and in HA aggregation/disaggregation. Key words: Humic acids, metal binding, nucleic acid constituents, uracil, adsorption, isotherms, thermodynamics
Effects of organic matter on the rate of potassium adsorption by soils
Authors: Wang F L , Huang P M
Published: April 2011

Soil organic constituents may strongly affect the kinetics of soil chemical processes, including K exchange reactions. We investigated the influence of organic matter on the rate of K adsorption by selected soils (Ferric Ultisol, Orthic Ultisol and Vertisol) using a H2O2 treatment and a K ion-selective electrode technique. In the reaction period of 0–30 s, in which the adsorption was too fast for one to determine rate coefficients of K adsorption, the amount of K adsorbed by the untreated soils was 158–363 mg kg–1, compared with 0.5–47 mg kg–1 for the treated soils. In the reaction period of 30–120 s, K adsorption data based on the first-order kinetics show that rate coefficients of K adsorption by the untreated soils were 47 × 10–5 s–1 (Ferric Ultisol), 59 × 10–5 s–1 (Orthic Ultisol) and 61 × 10–5 s–1 (Vertisol); by contrast, after H2O2 treatment, the rate coefficients were 23 × 10–5 s–1 (Ferric Ultisol), 17 × 10–5 s–1 (Orthic Ultisol) and 42 × 10–5 s–1 (Vertisol). Similar treatment effects were observed for the reaction period of 120–600 s, though the difference in the rate coefficients between the treatments was not as great as that for the reaction period of 30–120 s. These results indicate that organic matter considerably promotes the initial fast rate of K adsorption and has more easily accessible adsorption sites for K compared with mineral constituents of the soils. Key words: Organic matter, kinetics, potassium adsorption, adsorption site, accessibility
Importance of charred organic matter in Black Chernozem soils of Saskatchewan
Authors: Ponomarenko E V , Anderson D W
Published: April 2011

A combination of both conventional and novel techniques, such as micromorphology, scanning electron microscopy, and high energy ultraviolet photo-oxidation, have been applied to estimate the proportion of charred organic C in Black Chernozem soils in Saskatchewan. Char was represented by products of incomplete combustion of both arboreal and herbaceous vegetation. Char was found in all particle size fractions of A horizons of Black soils. Char was represented by a variety of forms, from fresh and angular, to rounded and clay-coated particles in the silt fraction. It is likely that the surface area and ability to adsorb clay vary with the size and nature of char particles. Sand-sized char includes particles with various surface properties and adsorptive ability. Generally, younger and lighter char with hydrophobic properties appears to be in the clay-sized fractions, whereas the silt contains heavier char particles coated with clay or containing clay in pores. Ultrasound, used to disperse soils, may fracture larger particles to finer sizes. The proportion of organic C in soils and fractions that is resistant to UV-oxidation was as high as 60%, which, based on published guidelines, indicates a very substantial char component in Black soils. CPMAS 13C NMR spectra indicate a strong aromatic peak at 130 ppm, also consistent with the presence of char. Results indicate that char particles as fine as silt size are present in significant amounts in Black soils, suggesting that char is an important component, and indicating the need for a new concept of humus formation and storage in Black soils. Key words: Char, carbon flows, carbon pool, UV-oxidation, fire, soil organic matter
Assessing organic phosphorus status of Cerrado oxisols (Brazil) using 31P-NMR spectroscopy and phosphomonoesterase activity measurement
Authors: Chapuis-Lardy Lydie , Brossard Michel , Quiquampoix Hervé
Published: April 2011

Plant production in the Brazilian savannas, also known as the Cerrados, is limited mainly by low P availability in soils. Little is known about the P status in the Cerrados region, despite its increasing significance for the country’s agriculture. 31P-NMR spectroscopy of alkali extracts and phosphomonoesterase (PME) activity measurements were used to study forms of P and their stability in oxisols of natural and pasture systems. Total P content (Pt) in topsoils ranged from 301 to 456 mg kg-1 and organic P content (Po) from 84 to 194 mg kg-1 with the highest values under natural vegetation. The estimation of forms of soil P with different lability (provided by NaHCO3 and NaOH extractions) showed little difference between natural vegetation and pastures, but the proportions of Po extracted suggest the importance of organically bound P as a source of plant-available P. All NMR spectra showed signals of organic P (monoesters and diesters) and inorganic P forms (orthophosphate and pyrophosphate), with little influence of land use. Organic P appears to be mainly in the form of stable phosphomonoesters. The most marked effect of land use was a decrease in PME activity under recent pastures, indicating an increase of PME stability in topsoils after the maize-grass ley plantation. The importance of the pH of the PME activity measurement is also discussed. Key Words: Organic P, labile P, 31P-NMR, phosphosmonoesterase, Cerrado, Oxisols
Models for potassium release kinetics of four Humic Gleysols high in clay by electro-ultrafiltration
Authors: Ziadi N. , Simard R. R. , Tran T. S.
Published: April 2011

The rate of K release from the soil solid phase to its solution, especially from its rapidly and slowly exchangeable forms, can affect plant K uptake. The electro-ultrafiltration (EUF) technique was used to kinetically characterize the K release from four soils (Humic Gleysols) from Abitibi-Temiscaming, Quebec, Canada. Potassium was desorbed from soils that received over 166 kg K ha-1 yr-1 from 1994 to 1996. The desorption was carried out for 58 min (4, 4, and every 5 min thereafter for a total of 12 desorptions) at 400 V and 80°C. The amount of K desorbed was between 199 and 342 mg kg-1. Cumulative K desorption was described by the following six equations: power function, simplified Elovich, extended Elovich, parabolic diffusion, zero-order, and first-order. An incremental first-order equation was also tested. The studied soils have large K supplying capacities as suggested by forage K-uptake and total soil K desorption by EUF. In general, all tested equations adequately described the K release by EUF from the four soils. The incremental first-order equation, used for the first time, described well the soil K release data. The k rate constant from this model was significantly related to forage K uptake (R2 = 0.58). Results from this study indicate that the investigated soils have large K reserves and that the incremental first-order equation and most of the cumulative ones are suitable for describing the kinetics of the large K release from these fine-textured Gleysols. Key Words: Potassium, desorption, cumulative model, incremental model
Geostatistical analysis of heavy metals in a one-hectare plot under natural vegetation in a serpentine area
Authors: Paz-Gonzalez A. , Taboada Castro M T , Vieira S R
Published: April 2011

The objective of this study was to examine the spatial variability of selected heavy metals in a soil developed over serpentine. Both total and EDTA-extractable Fe, Mn, Cr, Ni, Cu, Zn and Co were determined in 53 samples, collected from the topsoil of a 1-ha forested plot. Naturally occurring soil Cr and Ni concentrations were much higher than critical limits for safety. Experimental semivariograms were computed and modelled by a nugget component plus a structure with autocorrelation ranges varying between 25 and 90 m. EDTA-extractable heavy metal contents exhibit a different spatial variation pattern from that of total contents, although Ni and Cu semivariograms present some similarities. The joint spatial variation for pairs of variables with significant correlation was also investigated. The nugget variances in the cross-semivariograms were not very different from those of individual semivariograms, suggesting heterogeneity within the shortest sampling interval. Semivariograms provided a clear description of the spatial structure of heavy metals and some insight into possible processes affecting their distribution. Kriging maps allowed the identification of small regions with distinct metal concentrations and confirmed the suitability of geostatistics for investigating processes controlling heavy metal variation. Isotopic cokriging performed better than kriging, but the gain for mapping purposes was limited. Key words: Serpentine, heavy metals, geostatistics, scaling, spatial variability
Magnetic susceptibility of Gleysolic and Chernozemic soils in Saskatchewan
Authors: de Jong E.
Published: April 2011

In Saskatchewan, Gleysolic and Chernozemic soils often are found close to each other in hummocky terrain. Magnetic susceptibility (χ) is known to be reduced in poorly drained soils compared to well-drained soils, and this study investigated the use of χ as an accessory criterion for identifying Gleysols. Archived soil samples from an area near Saskatoon were analyzed for χ and sand content, and where necessary for organic and inorganic C and oxalate (Feo) and dithionite (Fed) extractable iron. The lowest χ values were found in Humic Luvic Gleysols and the highest in Dark Brown Chernozems; Rego and Orthic Gleysols and Rego Humic Gleysols had χ values that overlapped those of the Dark Brown Chernozems. Within the upper 50 cm of the profile, all Gleysols except the Rego Humic Gleysol had at least one horizon with %chi; less than 150 × 10-9m3kg-1. The χ of the A and B horizons was negatively correlated to their Feo/Fed ratios, and not correlated to their sand content. The χ of the deep tills was positively correlated to sand content, and not correlated to Feo/Fed ratio. It appears that χ may be as useful as the Feo/Fed ratio for assisting in classifying Gleysols. Key words: Magnetic susceptibility, Gleysols, Chernozems, Feo, Fed, CaCo3
Cattle manure and lime amendments to improve crop production of acidic soils in Northern Alberta
Authors: Whalen Joann K , Chang Chi , Clayton George W
Published: April 2011

Crop production on acid soils can be improved greatly by adjusting the pH to near neutrality. Although soil acidity is commonly corrected by liming, there is evidence that animal manure amendments can increase the pH of acid soils. Fresh cattle manure and agricultural lime were compared for their effects on soil acidity and the production of canola (Brassica napus L.) and wheat (Triticum aestivum L.) in a greenhouse study. Canola and wheat yield, the nutrient content of grain and straw, and selected soil properties were determined on a Gray Luvisol (pH 4.8) from the Peace Region of Alberta. Soil pH increased with lime and manure applications, and canola and wheat yields were higher in limed and manure-amended soils than unfertilized, unlimed soils. Macronutrient uptake by canola and wheat was generally improved by liming and manure applications, and micronutrient uptake was related to the effects of lime and manure on soil pH. An economic analysis compared the costs of using cattle manure and lime to increase soil pH to 6.0. The costs of applying lime and fresh cattle manure to increase soil pH were compared, based on the fees for purchasing and applying lime or loading, hauling and applying manure. The nutrient value of manure was calculated based on the quantities of plant-available N, P and K in fresh manure. At distances less than 40 km, it is economical to substitute fresh cattle manure for agricultural lime to increase soil pH of acidic soils. However, good manure management practices should be followed to minimize the risk of nutrient transport and environmental pollution from agricultural land amended with cattle manure. Key words: Agricultural economics, canola production, cattle manure, lime, soil pH, wheat prodution
Evaluating the use of digital terrain modelling for quantifying the spatial variability of 2,4-D sorption by soil within agricultural landscapes
Authors: Farenhorst A. , Florinsky I. V. , Monreal C. M. , Muc D.
Published: April 2011

The most sensitive input parameter in many herbicide fate and transport models is the sorption-partitioning coefficient (Kd), a measure of herbicide sorption by soil. Spatial analyses of Kd are traditionally performed using geostatistics, but this approach requires intensive soil sampling and herbicide analysis. This study examined the use of digital terrain modelling as an alternative tool for quantifying the distribution of herbicide sorption within agricultural fields. Soil samples from a conventional-till (CT) and zero-till (ZT) field were analysed for soil organic carbon (SOC), soil pH, clay content, and the 2,4-D ([(2,4-dichlorophenoxy)acetic acid]) soil-water partitioning coefficient. Digital terrain models were used to calculate topographical variables (elevation, slope gradient, slope aspect, horizontal curvature, vertical curvature, mean curvature, specific catchment area, topographic index and stream power index) for each sampling point. Results indicated that topographic variables were adequate predictors of all soil properties in ZT (R2 ranging from 0.64 to 0.76), and of SOC in CT (R2= 0.65, P < 0.001). For CT, 2,4-D sorption by soil was very well predicted with soil properties alone (R2= 0.82, P < 0.001) and with soil properties in combination with topographic variables (R2= 0.85, P < 0.001), but was less predicted by topographic variables alone (R2= 0.50, P < 0.001). For ZT, the level of prediction of 2,4-D sorption by soil was weak with soil properties alone (R2= 0.53, P < 0.001) or when topographical variables alone (R2= 0.56, P < 0.001) were used, but a substantial increase in the level of prediction was achieved when both soil properties and topographic variables were used (R2= 0.73, P < 0.001). We conclude that digital terrain modelling, in combination with soil properties data, is an appropriate approach for predicting the spatial distribution of 2,4-D sorption within undulating-to-hummocky glacial till landscapes in western Canada. Key words: herbicide sorption, topography, zero-tillage, conventional-tillage, digital terrain modelling.
Field-scale N fertilizer recommendations: The spatial covariance problem
Authors: Si Bing Cheng , Gary Kachanoski R.
Published: April 2011

Theory is needed to estimate field-scale crop response and calibration relationships (soil test versus recommended fertilize r rate) from local scale measurements, in fields with spatially variable soil properties. The objective of this study is to present a theoretical stochastic framework for examining the influence of the spatial variability of soil properties, and covariance between soil properties, on field-scale crop response to fertilizer. An analytical solution of the general stochastic scaling equation is given for the specific case of wheat grain yield response to applied N fertilizer with variable soil-N test and available water in Saskatchewan, Canada. The analytical solution indicates spatial variance of soil properties within fields influences field average yield response to applied fertilizer. The field-scale maximum economic rate of fertilizer N (MERN), depends not only on the average soil properties, but also on (1) the amount of variability of soil properties in the field, and (2) the correlation between the spatial patterns of soil properties (e.g., soil test and available water). For the specific soil examined, positive spatial correlation between soil-N test and available water significantly increases MERN, for the same average soil test and available water. Negative correlation decreases MERN. Key Words: Fertilizer recommendation, soil test, spatial variability, crop response, soil water
Eight years of crop rotation and tillage effects on crop production and N fertilizer use
Authors: Soon Y. K. , Clayton G. W.
Published: April 2011

Although tillage systems and crop rotations can affect crop production and uptake of nutrients, their long-term effects, particularly their interactions, are not well-documented. Therefore, we measured the N, P, and K contents and yields of crops through two rotation cycles, especially wheat (Triticum aestivum L.), of four crop rotations managed under conventional tillage (CT) and no-tillage (NT) systems. The study was conducted 1993 through 2000 on a sandy loam soil in northwestern Alberta, Canada. The four-course crop rotations were: (i) field pea (Pisum sativum L.)-wheat-canola (Brassica rapa L.)-wheat; (ii) red clover (Trifolium pratense L.) green manure-wheat-canola-wheat; (iii) fallow-wheat-canola-wheat, and (iv) continuous wheat (CW). The crops were fertilized using regional recommendations based on soil test results. Previous crop effect on wheat yield was in the order: field pea = red clover green manure > fallow > canola > wheat (CW); it had little influence on N, P or K content in wheat grain or straw. There was no interaction of tillage with crop rotation on wheat production or nutrient content. Tillage treatments affected neither production of other rotation crops nor their nutrient concentrations. During the second rotation cycle, N fertilizer requirement decreased, and wheat yield was 22% higher, under NT as compared to CT. This study showed that (i) field pea is an attractive replacement for red clover green manure; and (ii) recommendations for N from soil test results should factor in the type of tillage system used. Key words: Canola, field pea, red clover, nitrogen, tillage, wheat
Impact of potato-cereal rotations and slurry applications on nitrate leaching and nitrogen balance in sandy soils
Authors: Gasser M O , Laverdière M R , Lagacé R. , Caron J.
Published: April 2011

Groundwater quality is at risk when high levels of N fertilizers are used on sandy soils. A monitoring program was initiated in the summer of 1995, to quantify nitrate leaching in sandy soils used for potato production near Quebec city, Canada. Three drainable lysimeters were installed in each of five fields, for a total of 15 lysimeters. During a 5-yr monitoring period, crop N uptake, mineral and organic N fertilizers use, nitrate concentrations and fluxes from drainage water at 1-m soil depth were assessed under potato, cereal and hay crops. In one field, a clover and timothy sod that received low mineral N fertilizer inputs generated the lowest annual nitrate leaching losses ranging from 7 to 20 kg NO3-N ha-1. High nitrate leaching losses (116 ± 40 kg N ha-1) were measured under potato crops receiving high mineral N fertilizer inputs. Cereals, including barley and wheat receiving moderate mineral N fertilizer inputs and in some instance N from pig slurry, dairy cow manure or paper mill sludge, also generated high nitrate leaching losses (88 ± 45 kg N ha-1). Only sod and oat crops generated annual flux averaged nitrate concentrations lower than 10 mg NO3-N L-1, the accepted standard for drinking water, while higher concentrations, ranging from 13 to 52 mg NO3-N L-1, were recorded under barley, wheat and potato crops receiving moderate to high amounts of mineral N fertilizer. Nitrate flux concentrations were moderate during the cropping season (May-August), highest in fall (September-December) and lowest in the winter-early spring period (January-April). After 5 yr of survey, use of pig slurry and paper mill sludge in potato-cereal crop rotations (51 to 192 kg N ha-1 annually) with mineral N fertilizers (103 to 119 kg N ha-1 annually) resulted in nitrate leaching losses (87 to 132 kg N ha-1 annually), at least 20 kg N ha-1 more than N exported by crop at harvest. More than 60% of N applied as pig slurry seemed to be unaccounted for in the partial N balance that included crop N uptake and nitrate leaching, suggesting that important losses probably occurred through ammonia volatilization, denitrification, or N immobilization in soil organic matter and crop residues. Key words: Barley, lysimeter, nitrate leaching, nitrogen balance, pig slurry, potato
Limitations of methods for preserving ammonium in agricultural runoff samples
Authors: Kowalenko C G , van Vliet L J.P. , Derksen G. , Yu S.
Published: April 2011

Ammonium concentrations in simulated and actual field runoff samples were not stable within 1 d under refrigeration due to microbial activity as shown by evolution of CO2. Changes in frozen samples after freezing and thawing appeared to be due to non-biological processes and this type of preservation should be avoided. A few drops of toluene added to 10 mL of simulated runoff sample stabilized ammonium concentrations at room temperature for 4 d and reduced CO2 evolution during that time substantially. Chemical preservation by adding sufficient HCl, LiCl and CuSO4 to have molarities of these chemicals up to 0.1 M strength was not acceptable because of limited reduction in microbial activity and chemical changes to the sample. Preservation effects of prestorage filtration were not consistent and this would not be a suitable procedure if total N measurements are to be included because a portion of the sample would be removed. It is apparent that microbial activity in runoff or similar types of water samples that contain organic C must be controlled immediately after collection if measurements of specific N ion species are to be made. Although refrigeration slows microbial activity, it may not be an adequate method of preservation for more than 1 d of storage. Even 1 d of refrigeration will be difficult to do under field conditions. Addition of a small amount of toluene to the runoff sample was the most promising preservation method examined. Key words: Runoff samples, sample preservation, ammonium
Challenges related to soil biodiversity research in agroecosystems - Issues within the context of scale of observation
Authors: Fox C. A. , MacDonald K. B.
Published: April 2011

Soil biodiversity, the study of the variety of life in the soil, has received increasing attention as an outcome of recent national and international initiatives, such as the Convention on Biological Diversity, and various programs related to sustainable development of agroecosystems. The broad objectives of this paper are to set the stage for a “state of the art” review of soil biodiversity research in Canadian agricultural systems, to highlight the relevance of soil biodiversity studies at various scales of observation, to acknowledge the importance of soil biodiversity to the soil system with respect to soil functions, and processes and to suggest research challenges and opportunities.

Study scale is of critical importance as it determines both the kind of soil biodiversity information and the feasible level of detail (spatially and temporally). At all scales from global to national to regional to landscape to ecosystems ranging to even fine scales of habitat niches at soil particle level, soil biota respond to the physical, chemical and biological constraints of their environment as mediated by environmental and anthropogenic influences. For example, at the landscape level, there exists a mosaic of ecosystems that can be characterized as a continuum ranging from unmanaged (natural), uncontrolled systems regulated primarily by environmental influences to managed, controlled systems regulated primarily by anthropogenic influences. In agroecosystems, soil biota contribute to the decomposition of crop residues and nutrient cycling, soil aggregation and water infiltration, suppression of soil-borne diseases and pests, and detoxification of chemicals. The intensity and duration of environmental and anthropogenic influences on these soil biota will affect their spatial and temporal distribution within this continuum of ecosystems occurring in the landscape and thereby also affect the extent of their capability for contributing towards soil functions and processes. Within this spatial and temporal context, research challenges are discussed. Key words: Soil biodiversity, scale of observation, agroecosystems, soil quality
Acari and Collembola biodiversity in Canadian agricultural soils
Authors: Behan-Pelletier V. M.
Published: April 2011

In Canadian agricultural soils, mites (Acari) are the most diverse and abundant arthropods. In comparison with other arachnids, mites are notable for their small size, diverse feeding habits, often complex life histories, and the range of habitats in which they live. Collembola are also abundant and diverse in soil and litter, they are in the same size range as the Acari, and for that reason the two groups are often combined in soil ecological studies as “microarthropods ”. This paper provides a descriptive overview of the state of our knowledge on the taxonomy of these arthropods. It reviews the literature on biology and ecology of microarthropods in Canadian agroecosystems, especially on implications of various agricultural practices for their diversity and population structure. It discusses the research challenges in taxonomy and ecology to address effective use of this biodiversity in Canadian agroecosystems. Key words: Acari, Collembola, microarthropods, taxonomy, ecology
Soil salinization and sodication from alternate irrigations with saline-sodic water and simulated rain
Authors: Buckland Gary D. , Rodney Bennett D. , Mikalson Dennis E , Jong Eeltje de , Chang Chi
Published: April 2011

We conducted a greenhouse study on large, semi-disturbed soil cores excavated from the vicinity of Verdigris Lake in southern Alberta to assess the suitability of different saline-sodic waters for irrigation. Soil salinization and sodication, surface soil physical properties, and yield of five soft white spring wheat crops (Triticum aestivum L. var. AC Reed) were examined under alternate applications of simulated rain with saline-sodic irrigation waters ranging from "safe" to "potentially hazardous" for irrigation. Increased salinity and sodicity of irrigation waters alternated with simulated rain resulted in increased salinity and sodicity in the upper 0.60 to 0.90 m of the soil. Salt accumulation in the root zone decreased as the leaching fraction increased. Aggregate stability and infiltration properties of the soil were generally adversely affected by the more saline and sodic irrigation waters. Infiltration properties were significantly greater with irrigation water (IW) than with distilled water (DW). The soil infiltration rate at 2 h, with DW as the infiltrating water, was the most sensitive soil physical property for assessment of irrigation water suitability. The infiltration test after five crop cycles gave a better indication of the effects of excess sodicity of irrigation water on soil structural stability than the aggregate stability test. The cumulative effects of long-term supplemental irrigation with saline-sodic waters on soil chemical and physical properties need to be considered when assessing irrigation water suitability. Irrigation waters with electrical conductivity (EC) less than or equal to 1 dS m-1 and a sodium adsorption ratio (SAR) less than or equal to 5 did not result in deterioration of soil physical properties and were considered "safe" for supplemental irrigation of the Masinasin soil. Alternate applications of irrigation and distilled water should be used to evaluate soil infiltration rates and the structural stability of soils to which saline-sodic waters are to be applied. Key words: Saline-sodic irrigation water, soil salinity, soil sodicity, aggregate stability, infiltration, water quali
Improvement of soil properties and fruit yield of native lowbush blueberry by papermill sludge addition
Authors: Gagnon B. , Simard R. R. , Lalande R. , Lafond J.
Published: April 2011

Combined primary and secondary papermill sludge (PS) is a good potential source of C and other nutrients to restore low organic matter sandy soils supporting native lowbush blueberry (Vaccinium angustifolium Ait.). A 3-yr field study was conducted to compare the effect of PS with mineral fertilizers (MF) on the blueberry yield and soil chemical properties and enzyme activities of a l’Afrique sand (Humo-Ferric Podzol) in the Saguenay-Lac Saint-Jean area (Quebec, Canada). The PS was applied in the spring of the sprout year at 0, 8.5, 17 and 34 Mg ha-1 and MF was applied at 0, 13, 26 and 52 kg N ha-1. The highest fresh fruit yields were obtained at 8.5 and 17 Mg PS ha-1. The 34 Mg PS ha-1 treatment produced berry yield comparable to the control. This PS rate reduced pH, but increased inorganic N, Mehlich-3 extractable P and Mn in the 0- to 15-cm soil layer. The NO3−-N content of the 15- to 30-cm and 30- to 60-cm soil layers was also increased by PS, suggesting leaching. The MF significantly affected soil inorganic N content only at 3 wk after its application in the first year. The PS rate linearly increased the soil acid phosphatase activity in the first year. The arylsulfatase activity was also higher in PS than in MF treatment, but was severely depressed by 34 Mg PS ha-1 in the last 2 yr. This study indicated that PS, when used at low rates, improves lowbush blueberry yield and the soil enzyme activity on this low fertility sand. Key words: Papermill sludge, lowbush blueberry, soil composition, soil enzyme
Soil P fractions as affected by on-farm composts in a controlled incubation study
Authors: Gagnon and R. R. Simard B.
Published: April 2011

Information on the different forms and availability of P following compost addition to soil may help to better manage manure in respect to plant growth and the environment. An experiment was conducted to investigate through a sequential extraction procedure the availability of P of fresh dairy manure and several on-farm compost-soil mixtures after a 13 wk incubation in glass jars at 35°C. Materials were mixed at a rate of 200 mg N kg-1 with an Arago sandy loam (Humo-Ferric Podzol), supplying from 64 to 301 mg P kg-1. Fresh dairy manure gave the highest net increase of resin-P and labile P fractions in terms of percentage of total P added, whereas poultry litter compost was the most efficient in increasing NaHCO3-inorganic P (-Pi). Among compost materials, poultry litter, vegetable residue and sheep manure increased labile P fraction the most. The contribution of the young dairy manure compost to this fraction was largely negative, and lower than those of fresh manure or partially and well-decomposed manure composts. A large part of added P was found in the moderately labile P fraction. The organic P (Po) fractions in the soil were less affected by manure or compost addition. This study indicated that the material P availability was reduced by composting, and was more affected by the origin of residue than by manure management. Key words: Composting, farm manure, soil P fractionation
The influence of understory vine maple on forest floor and mineral soil properties in coastal temperate forests
Authors: Tashe N. C. , Schmidt M. G.
Published: April 2011

In coastal forests of the Pacific Northwest, vine maple (Acer circinatum Pursh) is a common understory tree species. We studied the influence of vine maple, growing in the understory of a stand of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and western hemlock [Tsuga heterophylla (RAF.) Sarg.], on forest floor and mineral soil properties. Fifteen (in a 75-yr-old stand) and 12 (in a 130-yr-old stand) plots containing vine maple were compared to paired plots without the influence of vine maple. Mull humus was dominant under vine maples, while mor humus was mainly found under conifers at the 130 yr-old stand. Common to both stands in the upper mineral soil were greater mineralizable N and total exchangeable bases under vine maple. At the 75-yr-old stand, the forest floor had a higher pH and greater total exchangeable base concentration, while the mineral soil had a lower C:N ratio, greater NO3-availability and lower available P concentration and content under vine maple compared to conifers. The 130-yr-old stand had less available P content and greater concentrations of mineralizable N and exchangeable Mg in the forest floor under vine maple. Results suggest that the presence of vine maple may enhance the availability of N and exchangeable bases, but may adversely affect P availability. Key words: Vine maple, soil-plant interactions, forest floor, Acer circinatum