bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of continuous wheat and amendments in ameliorating an artificially eroded Dark Brown Chernozemic soil under dryland conditions
Authors: Dormaar J. F. , Lindwall C. W. , Kozub G. C.
Published: April 2011

Complete loss of topsoil resulting from erosion or other causes generally results in reduced crop yield. To determine, under dryland conditions, the effect of loss of various amounts of soil and of various amendment practices suitable for use under a cereal production program on soil properties and crop yields, a field was artificially eroded during cut and fill of land-levelling in 1957. Continuous cropping to barley for 7 yr was followed by a wheat-fallow rotation for 22 yr. A continuous wheat experiment was conducted from 1987 to 1991 to determine the effects of five fertility amendments on restoring the productivity to soil from which 10–20 cm and 46+ cm of soil had been removed. In 1990, a below-average precipitation year, after 33 yr and 23 crops, yields from the unfertilized 46+ cm eroded field were only 44% of the yields from the uneroded field. However, with the increased precipitation in 1991 this value was 66%. A one-time topsoil amendment was beneficial in the earlier stages of the experiment, but lost its effect as cultivation mixed it into the "subsoil" over time. Plot treatments with annual applications of manure and high rates of fertilizer generally out-yielded the yields of the check plots of the uneroded treatment. Amendment with straw + fertilizer was not very effective. Soil, once lost, is non-renewable without amendments within the working lifetime of the producer.

Key words: Soil erosion, manure, commercial fertilizer, topsoil soil, productivity
Phosphorus in zero tension soil solution as influenced by long-term fertilization of corn (Zea mays L.)
Authors: Zhang T. Q. , MacKenzie A. F.
Published: April 2011

Phosphorus from fertilized agricultural land may contribute to ground or surface water inputs and accelerate eutrophication. With increases in soil P saturation and organic P in long-term fertilized soils, soil P leaching losses may increase. The effect of long-term P fertilization (6 to 11 yr) on inorganic and organic P in soil solutions at zero tension was studied on two soils, a Chicot sandy clay loam (Grey Brown Luvisol) and a Ste. Rosalie clay (Humic Gleysol). Soil solution samples were collected using a cylinder technique and analyzed for total dissolved P (TDP), dissolved inorganic P (DIP), and dissolved organic P (DOP). Levels for DIP ranged from 0.15 to 1.01 mg P L−1 and TDP ranged from 0.33 to 1.19 mg P L−1 in the Chicot soil. In the Ste. Rosalie soil, values of DIP ranged from 0.04 to 0.23 mg P L−1 and TDP ranged from 0.15 to 0.36 mg P L−1. Increasing fertilizer P applications from 44 kg ha−1 to 132 kg ha−1 increased DIP and TDP in soil solutions in both soils. There was no effect of P fertilization rate on DOP values. Soil P movement below 45 cm during the non-growing season was estimated at 633 to 2732 g ha−1 yr−1 in the Chicot soil and from 312 to 974 g ha−1 yr−1 in the Ste. Rosalie soil. Soil solution DIP was found to be linearly related to soil P extractable with 0.5 M NaHCO3, but levels of NaHCO3-extractable P required to produce 0.05 mg P L−1 DIP varied with soil, ranging from 70 to 110 mg P kg−1 soil. The critical level of extractable P has to be considered in association with soil type to predict potential water contamination. Key words: Continuous corn, long-term fertilization, soil solution, dissolved inorganic and organic P, NaHCO3 extractable P
Sensitivity of soil structure to changes in organic carbon content: Predictions using pedotransfer functions
Authors: Kay B. D. , Silva A. P. da , Baldock J. A.
Published: April 2011

Pedotransfer functions (PTFs) were used to assess the sensitivity of the structural characteristics of coarse- and medium-textured calcareous illitic soils at different levels of relative compaction (RC) to changes in the organic carbon (OC) content. The analyses predicted that an increase in the OC content of 0.01 kg kg−1 would:• increase the available water content from 0.02 to 0.04 m3 m−3 with the largest increases occurring in coarser-textured soils and not being strongly influenced by RC;• decrease the air-filled porosity at field capacity from 0.01 to 0.04 m3 m−3 with the largest decreases occurring in the finer-textured soils and not being strongly influenced by RC;• decrease the soil resistance to penetration with the decreases most pronounced at lower water potentials and higher RC; at the permanent wilting point and a RC of 0.95 the decrease would range from 1.2 to 3.8 MPa;• increase the least limiting water range from 0.01 to 0.05 m3 m−3 with the increase varying with clay content.A comparison with predictions based on PTFs derived from data sets from other parts of the world indicated caution should be exercised in applying PTFs to soil and climatic conditions that are different from those from which the PTFs were derived until the impacts of these conditions are better understood. Key words: Bulk density, field capacity, permanent wilting point, available water; aeration, soil resistance, least limiting water range
Denitrification and nitrous oxide emissions from a Black Chernozemic soil during spring thaw in Alberta
Authors: Nyborg M. , Laidlaw J. W. , Solberg E. D. , Malhi S. S.
Published: April 2011

Previous field research in Alberta has suggested that denitrification occurs mostly when soil thaws in the spring, with associated soil water saturation. Our objective was to determine if denitrification and N2O emission in fact take place in cold, thawing soil in the field. Denitrification and N2O flux were measured in two springs and the intervening summer. Cylinders were placed in soil in November, 1988, and 57 kg N ha−1 of 15Nlabeled KNO3 was added. Soil 15N mass balance technique showed 23 kg N ha−1 of added-N was lost by 15 May 1989. Gas trappings were made (28 March to 29 April) and nearly all of the N2O emission (3.5 kg N2O-N ha−1) occurred during an 11-d period of thaw. The accumulated N2O flux from 20 June to 31 August was small (0.5 kg N2O-N ha−1, or less); during that time there were no rainfall events intense enough to produce water saturated soil. In 1990, 15N-labeled KNO3 (100 kg N ha−1) was applied on 26 March (outset of the thaw) and mass balance showed 32.7 kg N ha−1of added-N was lost by 7 May. A flux of 16.3 kg N2O-N ha−1 occurred largely in a 10-d period during and immediately after soil thaw. The N2O emitted from soil left a considerable fraction of the lost N unaccounted for. This unaccounted N was most likely lost as gaseous N other than N2O (e.g., N2). We conclude that large amounts of soil nitrate may be denitrified, with smaller amounts emitted as N2O, as the soil thaws and soon thereafter.

Key words: Denitrification, frozen soil, thawing soil, nitrogen, nitrous oxide
Use of hot KCl-NH4-N to estimate fertilizer N requirements
Authors: Campbell C. A. , Jamel Y. W. , Jalil A. , Schoenau J.
Published: April 2011

We need an easy-to-use chemical index for estimating the amount of N that becomes available during the growing season, to improve N use efficiency. This paper discusses how producers may, in future, use crop growth models that incorporate indices of soil N availability, to make more accurate, risk-sensitive estimates of fertilizer N requirements. In a previous study, we developed an equation, using 42 diverse Saskatchewan soils, that related potentially mineralizable N (N0) to NH4N extracted with hot 2 M KCl (X), (i.e., N0 = 37.7 + 7.7X, r2 = 0.78). We also established that the first order rate constant (k) for N mineralization at 35°C is indeed a constant for arable prairie soils (k = 0.067 wk−1). We modified the N submodel of CERES-wheat to include k and N0 (values of N0 were derived from the hot KCl test). With long-term weather data (precipitation and temperature) as input, this model was used to estimate probable N mineralization during a growing season and yield of wheat (grown on fallow or stubble), in response to fertilizer N rates at Swift Current. The model output indicated that the amount of N mineralized in a growing season for wheat on fallow was similar to that for wheat on stubble, as we hypothesized. Further the model indicated that rate of fertilizer N had only minimal effect on N mineralized. We concluded that, despite the importance of knowing the Nmin capability of a soil, it is available water, initial levels of available N and rate of fertilizer N that are the main determinants of yield in this semiarid environment. The theoretical approach we have proposed must be validated under field conditions before it can be adopted for use.

Key words: N mineralization, Hot KCl-NH4-N, potentially mineralizable N, CERES-wheat model
Soils as sources and sinks for atmospheric methane
Authors: Topp Edward , Pattey Elizabeth
Published: April 2011

Methane is considered to be a significant greenhouse gas. Methane is produced in soils as the end product of the anaerobic decomposition of organic matter. In the absence of oxygen, methane is very stable, but under aerobic conditions it is mineralized to carbon dioxide by methanotrophic bacteria. Soil methane emissions, primarily from natural wetlands, landfills and rice paddies, are estimated to represent about half of the annual global methane production. Oxidation of atmospheric methane by well-drained soils accounts for about 10% of the global methane sink. Whether a soil is a net source or sink for methane depends on the relative rates of methanogenic and methanotrophic activity. A number of factors including pH, Eh, temperature and moisture content influence methane transforming bacterial populations and soil fluxes. Several techniques are available for measuring methane fluxes. Flux estimation is complicated by spatial and temporal variability. Soil management can impact methane transformations. For example, landfilling of organic matter can result in significant methane emissions, whereas some cultural practices such as nitrogen fertilization inhibit methane oxidation by agricultural soils.

Key words: Methane, methanogenesis, methane oxidation, soil, flux measurement
Description of a dynamic closed chamber for measuring soil respiration and its comparison with other techniques
Authors: Rochette P. , Ellert B. , Gregorich E. G. , Desjardins R. L. , Pattey E. , Lessard R. , Johnson B. G.
Published: April 2011

Soil respiration is an important component of the net carbon dioxide exchange between agricultural ecosystems and the atmosphere, and reliable estimates of soil respiration are required in carbon balance studies. Most of the field measurements of soil respiration reported in the literature have been made using alkali traps. The use of portable CO2 analysers in dynamic closed chamber systems is recent. The introduction of this new technique requires its evaluation against existing methods in order to compare new information with older data. Nine intercomparisons between dynamic systems and alkali traps were made. Measurements of Fc,s obtained by both chambers showed a good agreement in all but two comparisons in which alkali trap measurements were lower than the dynamic chamber by about 22%. This first report of agreement between both techniques suggests that many measurements made in the past using alkali traps may be comparable to the measurements made more recently using the dynamic chambers. Analysis of the soil temperature and CO2 concentration inside the alkali traps failed to explain why the alkali traps occasionally underestimated the fluxes. Soil respiration measured with a dynamic closed chamber were also compared to eddy-correlation measurements. The results did not reveal any consistent bias between techniques but the scattering was large. This dispersion is likely the result of the difference between the areas measured by the two techniques.

Key words: Carbon dioxide, greenhouse gases, CO2 flux, soil carbon
Organic carbon and nitrogen stocks and storage profiles in cool, humid soils of eastern Canada
Authors: Carter M. R. , Angers D. A. , Gregorich E. G. , Bolinder M. A.
Published: April 2011

Current interest in carbon (C) exchange processes between terrestrial ecosystems and the atmosphere have identified a need to assess soil C stocks or inventories for specific soil types and climates. In this study, the mean store of C and nitrogen (N) was determined in the soil profile of several Gleysolic, Podzolic, Luvisolic, and Brunisolic soils under different agricultural management systems, in the cool, humid region of eastern Canada. Based on a total of 69 management treatments from 16 agroecosystem sites, mean soil C and N densities (to a soil depth of 60 cm) ranged from 3.1 to 13.1 kg C m−2 and from 0.36 to 1.05 kg N m−2 The C:N ratio ranged from 8.3 to 17.1. Distribution of C and N down the soil profile showed a relatively regular pattern of C and N decrease with depth. Estimated C stocks or storage for the 1-m soil depth ranged from 8.3 to 13.3 kg C m−2 for the Gleysolic soils, and 5.4 to 10.5 kg C m−2 for the Podzolic soils, with an overall range and mean for all soils of 3 to 16 kg C m−2 and 9.8 kg C m−2 ± 2.8 This indicates that some agricultural soils in eastern Canada possess a relatively high potential for organic matter storage.

Key words: Organic carbon and nitrogen storage, agroecosystem, Gleysol, Podzol, Luvisol, Brunisol, cool-humid climate
Effect of agriculture and of clear-cut forest harvest on landscape-scale soil organic carbon storage in Saskatchewan
Authors: Pennock D. J. , Kessel C. van
Published: April 2011

The development of sound management approaches to reduce soil organic carbon (SOC) losses presupposes that we thoroughly understand the sources of these losses. We used a landscape-scale research design to estimate human-induced SOC losses by comparing SOC storage in undisturbed landscapes with comparable landscapes disturbed by clear-cutting of forests in the Mixedwood/Gray Luvisolic zone of central Saskatchewan and by agricultural activity in the Black soil zone. A 14.0% decrease in soil organic carbon storage in the upper 45 cm of the soil (from 57.1 Mg ha−1 in mature Mixedwood sites to 49.1 Mg ha−1 in clear-cut landscapes) occurred due to clear cutting at the research sites in the Mixedwood forest. The dominant soil type at these sites, Gray Luvisolic soils developed in glacial till, experienced a 11% loss in SOC storage; higher losses (36% loss) occurred from sandy Brunisolic inclusions in the sites. Changes in SOC storage at the research sites in the Black soil zone landscapes varied with texture and parent material: sandy glacio-fluvial landscapes experienced slight gains of SOC (from 54.1 to 60.1 Mg ha−1); silt and clay glacio-lacustrine landscapes experienced a 15.3% decrease in SOC (from 145.2 to 122.9 Mg ha−1); and loamy glacial till landscapes underwent a major decrease in SOC storage (from 116.2 to 75.2 Mg ha−1) Our results indicate that attempts to increase SOC storage in Saskatchewan soils should concentrate on agricultural landscapes, especially those dominated by glacial till.

Key words: Landscape, soil organic carbon, Chernozemic, Mollisol
Soil moisture storage in mature and replanted sub-humid boreal forest stands
Authors: Elliott J. A. , Toth B. M. , Granger R. J. , Pomeroy J. W.
Published: April 2011

Soil moisture profiles at two mature forest sites (Pine and Mixed-Wood) and two plantations (1981 Pine and 1992 Mixedwood) in central Saskatchewan were studied in conjunction with soil properties, precipitation, interception and evapotranspiration. Sampling locations within each stand were chosen to highlight differences in soil moisture due to interception, evapotranspiration and soil physical properties.Soil moisture storage to 1-m depth was greatest on the 92-Plantation where transpiration and interception of precipitation were less than the other sites. Moisture storage in the 81-Plantation was similar to that in the mixed-wood stand. The Pine stand had the lightest textured soils and stored least water to 1-m depth. Variability in moisture storage was also observed within stands and was associated with canopy structure and density, water extraction patterns and mechanical site preparation. In the furrows at the 92-Plantation, wet soils in combination with low infiltration rates and transpiration may have lead to the generation and channelling of rainfall runoff during a major rainfall event. Key words: Boreal forest, hydrological pathways, soil moisture, infiltration, interception, evapotranspiration
Letter to the Editor
Authors: Kowalenko C. G.
Published: April 2011

not available
Evaluation of organic wastes as soil amendments for cultivation of carrot and chard on irrigated sandy soils
Authors: Neilsen G. H. , Hogue E. J. , Neilsen D. , Zebarth B. J.
Published: April 2011

A field trial was designed to test the potential of various wastes as soil amendments in horticultural production. Swiss chard (Beta vulgaris L.) and carrot (Daucas carota L.) were grown during 1993–1995 under irrigation in a coarse-textured, British Columbia soil to which annual applications of 45 t ha−1 of various organic amendments plus NPK-fertilizers had been applied. The amendments included biosolids from Vancouver, Kelowna and Penticton, biowastes from Aldergrove and Abbotsford, and peat. Yield of both chard and carrot was increased for some organic treatments plus fertilizer relative to plots receiving commercially recommended rates of NPK-fertilizer only (control plots). Leaf N, P, Zn and Cu concentrations of both crops were usually elevated, but not to toxic values, in plots receiving wastes containing high concentrations of the respective nutrients. By the end of the third growing season, extractable P, Zn and Cu increased in the surface 15 cm of soil, relative to control plots, with P and Cu increases evident to 30 cm depth. Extractable K and pH varied, with applied waste with some treatments having higher and other treatments lower values than in control plots. The cumulative evidence suggested that many locally produced biosolids and biowastes have the potential to improve soil quality and the growth of high value horticultural crops. Key words: Leaf N, leaf and extractable soil P, K, Mn, Zn and Cu, soil pH and EC, yield
Modeling potentially sustainable biomass productivity in jack pine forest stands
Authors: Bhatti J. S. , Foster N. W. , Oja T. , Moayeri M. H. , Arp P. A.
Published: April 2011

A steady-state mass balance model (ForSust), developed to simulate potentially sustainable levels of tree biomass growth and related nutrient uptake dynamics, was applied to 17 jack pine sites across Canada. The model simulates potential tree biomass growth based on nutrient inputs from estimated atmospheric deposition (N, Ca, Mg, K) and soil weathering (Ca, Mg, K), and matches the resulting nutrient supply rates with calculated nutrient demand. Nutrient demand calculations are based on nutrient concentrations in wood, bark, branches, and foliage. Specifically, the model simulates sustainable annual increment (SAI) of biomass growth for stem-only and whole-tree (aboveground biomass) harvesting, and for recurring forest fire conditions. Calculated SAI levels were compared with field-estimated mean annual increments for aboveground forest biomass (MAI). For recurring forest fires, it was found that SAI values, as simulated, corresponded with the MAI field estimates in general. For whole-tree harvesting, SAI was lower than MAI for most but not all sites. For stem-only harvesting, SAI corresponded with MAI, but there was a greater scatter between SAI and MAI values than what appeared to be the case for the recurring forest fire scenario. Key words: Jack pine; whole-tree, stem-only harvesting; steady-state mass balance; forest biomass; N, Ca, Mg, K growth limitations; atmospheric deposition
Effects of soil temperature and moisture on soil respiration in barley and fallow plots
Authors: Akinremi O. O. , McGinn S. M. , McLean H. D. J.
Published: April 2011

Agricultural systems are sources and sinks for carbon and to quantify the net effect of these systems on atmospheric CO2 concentration, the amounts of carbon fixed in primary production and that respired by the soil must be known. The objectives of our study were (1) to quantify the amount of soil respiration from fallow and barley plots during the growing season; and (2) to determine the relationship between these fluxes and soil temperature and moisture. This study was conducted on field plots measuring 200 by 200 m with one plot planted to barley (Hordeum vulgare L.) while the other plot was in fallow. Two automated chambers were permanently installed in the fallow plot and three in the barley plot at the start of the growing season. When CO2 fluxes were integrated over a 24-h period, the daily soil respiration under fallow ranged from a low of 1.6 g CO2 m−2 d−1 on a dry day to a high of 8.3 g CO2 m−2 d−1 on a wet day. The corresponding values for barley were 3.3 and 18.5 g CO2 m−2 d−1 in 1994. Similar values were obtained in 1996 and, on average, daily soil respiration under barley was twice of that under fallow. The integrated daily CO2 flux under fallow was strongly related to daily soil moisture and mean soil temperature with moisture alone accounting for 76 to 80% of the variation in CO2 flux. While good relationships were obtained between soil moisture and CO2 flux under fallow, the relationship under barley was not as good. The CO2 fluxes, measured eight times per day, displayed a diurnal pattern similar to that of soil temperature; however, there was no consistent quantitative relationship between these 3-hourly fluxes and temperature. A poor relationship was obtained when the fluxes during several days were related to soil temperature as soil moisture confounded flux-temperature relationship. Under the semi-arid conditions of southern Alberta, moisture is the main parameter controlling soil respiration during the growing season. Key words: Soil respiration, soil moisture, soil temperature, CO2 flux, chamber measurements, diurnal CO2 flux
Influence of soil organic matter on sulfate retention in two Podzols in Quebec, Canada
Authors: Courchesne F. , Laberge J.-F. , Dufresne A.
Published: April 2011

The role of soil organic matter (OM) on SO4 retention was investigated by comparing OM content, SO4 retention, and the distribution of Fe, Al and Si compounds in OM-poor (Grands-Jardins, PGJ) and OM-rich (Hermine, HER) Podzols from Québec, Canada. At both sites, four pedons were sampled by horizon; soil pH in H2O, organic C, phosphate-extractable SO4 and, sodium pyrophosphate, acid ammonium oxalate and dithionite-citrate-bicarbonate (DCB) extractable Fe, Al and Si were measured for each mineral horizon. The mineralogy of the clay (<2 µm) and fine silt (2–20 µm) fractions of selected horizons was determined by X-ray diffraction (XRD) and infrared spectroscopy (IR). Weighted mean organic C and pyrophosphate extractable Fe and Al contents were significantly higher in the HER than in the PGJ sola, while the PGJ soils were richer in amorphous inorganic Al. No trends were observed for inorganic Fe compounds. Chemical dissolution and IR allowed the identification of short-range ordered aluminosilicates, probably allophane, in the OM-poor and slightly acidic to neutral PGJ soils. These materials were absent from the OM-rich and acidic HER soils. Phosphate extractions showed that the weighted mean native SO4 content was five times higher in the PGJ than in the HER soil. Finally, native SO4 was strongly related to inorganic Fe, Al and Si (associated with allophane) at PGJ but only to inorganic Fe at HER. These results indicate that OM indirectly affects SO4 sorption through the influence organic substances exerts on the nature and distribution of pedogenic Fe, Al and Si compounds, such as allophane, in Podzolic profiles. Key words: Organic matter, sulfate, imogolite, allophane, silica, Podzol
Freeze-drying processes and wind erodibility of a clay loam soil in southern Alberta
Authors: Bullock Murray S. , Larney Francis J. , McGinn Sean M. , Izaurralde R. César
Published: April 2011

Freeze-drying has been implicated as a factor causing soil aggregate breakdown on the Canadian Prairies and northern Great Plains. Aggregates of a Dark Brown Chernozemic clay loam soil sampled in October 1993 and January and April 1994 were subjected to repeated cycles of wetting (to 0.1, 0.2 and 0.3 kg kg−1 water contents) freezing, and freeze-drying under laboratory conditions. The October 1993 samples showed less disruption when initially exposed to freeze-drying cycles compared to samples taken in January and April 1994. Using regression analysis, we predicted that 31 freeze-dry cycles were required for the 0.1 kg kg−1 water content aggregates to reach 60% erodible fraction (EF, % aggregates <0.86 mm), 9 cycles for the 0.2 kg kg−1 aggregates and 2 for 0.3 kg kg−1 aggregates. In a field study, conducted over the 1994–1995 winter on a similar clay loam soil, we estimated the number of freeze-drying cycles using large vapour pressure (VPL) and small vapour pressure (VPS) gradients between the soil surface (which had a mean winter water content of ~0.1 kg kg−1) and the atmosphere. With solar energy adjustments, we predicted that the number of freeze-dry cycles required for the soil to reach 60% EF was 60 for VPL and 37 for VPS conditions. The latter number was similar to the 31 cycles predicted in the laboratory study of aggregates at 0.1 water content. Our results demonstrate that freeze-drying is an important overwinter process in the breakdown of soil aggregates and hence wind erosion risk in the Canadian prairie region. Key words: Freeze-drying, wind erosion, erodible fraction
Distribution of natural radionuclides and 137Cs in soils of southwestern Ontario
Authors: VandenBygaart A. J. , Protz R. , McCabe D. C.
Published: April 2011

In Canada and the United States approximately 82% of the annual total dose of radiation to any person comes from terrestrial and cosmogenic sources. The soil is also the main source of radon exposure to humans. Therefore it is important to know the background levels of natural and anthropogenic radioactivity in soils. In this study the radionuclides 40K, 226Ra, 232Th and 137Cs were measured in the soils of southwestern Ontario in order to determine the background levels and to understand the soil profile distribution. Clay content is the most important variable affecting the background levels of 40K, 226Ra, and 232Th in the soil. The profile distribution of these radionuclides is further influenced by pedogenic processes, particularly carbonate leaching from the solum and clay illuviation from the Ae to the Bt horizons. The lateral and vertical distribution of bomb-fallout 137Cs is influenced by soil management such as tillage, biopedoturbation by soil animals such as earthworms and groundhogs, soil erosion and soil organic matter cycling. Multiple regression analysis showed that clay content, sand content, percent CaCO3, pH and organic carbon content had variable influences on each of the radionuclide contents in the soil. Key words: Radionuclides, 40K, 226Ra, 232Th, 137Cs, pedogenesis
Changes in physical properties of peat substrates during plant growth
Authors: Allaire-Leung S. E. , Caron J. , Parent L. E.
Published: April 2011

Aeration is a critical factor of substrate performance for container grown plants. In a 14-mo nursery study, although air-filled porosity dropped below optimum values, the gas relative diffusivity was unaffected, as a result of an increase in pore effectiveness. This indicates that, contrary to the general belief, aeration properties of potting substrates may not deteriorate with time. Key words: Potting soils, container substrates, air-filled porosity, gas diffusivity
The effect of soil electrical conductivity on moisture determination using time-domain reflectometry in sandy soil
Authors: Sun Z. J. , Young G. D. , McFarlane R. A. , Chambers B.M.
Published: April 2011

A series of laboratory experiments was conducted, in order to systematically explore the effect of soil electrical conductivity on soil moisture determination using time domain reflectometry (TDR). A Moisture Point MP-917 soil moisture instrument (E.S.I. Environmental Sensors Inc., Victoria, BC, Canada) was used to measure propagation time (time delay) of a step function along a probe imbedded in fine sand with different moisture and salinity. The volumetric soil water content was independently determined using a balance. With the help of the diode-switching technique, MP-917 could detect the reflection from the end of the probe as the electrical conductivity of saturated soil extract (ECe) increased to 15.29 dS m−1. However, the relationship between volumetric soil water content and propagation time expressed as T/Tair (the ratio of propagation time in soil to that in air over the same distance) deviated from a linear relationship as the conductivity exceeded 3.72 dS m−1. At the same water content, the time delay in a saline soil was longer than that in a non-saline soil. This leads to an over-estimation of volumetric soil water content when the linear calibration was applied. A logarithmic relationship between volumetric soil water content and T/Tair has been developed and this relation includes soil electrical conductivity as a parameter. With this new calibration, it is possible to precisely determine the volumetric water content of highly saline soil using TDR. Key words: Time domain reflectometry, time delay, bulk electrical conductivity (σ), volumetric soil water content (θ), relative permittivity or dielectric constant (εr), propagation velocity Vp
Soil enzyme activities following paper sludge addition in a winter cabbage-sweet corn rotation
Authors: Gagnon B. , Lalande R. , Simard R. R. , Roy M.
Published: April 2011

Combined primary and secondary papermill sludge (PS) is a good source of C and other nutrients for soils devoted to intensive horticultural production. A field study was conducted to evaluate the effect of PS, spring-applied alone or in combination with ammonium nitrate (AN), on the enzymatic activity of a Bedford clay (Humic Gleysol) in the province of Québec, Canada. The experiment was started in 1996 with winter cabbage (Brassica oleracea var. capitata L.) and continued in 1997 and 1998 on the same plots with sweet corn (Zea mays L.). The PS was applied at 0 (control), 8, 16, 32 and 65 Mg ha−1 in 1996 and at 44% of these rates in 1997. No sludge was applied in 1998. Additional treatments consisted of AN applied yearly at 100% of the plant N requirements and a PS and AN combination. Soil arylsulfatase and acid and alkaline phosphatase activities were measured at three different times in each growing season. The PS rate linearly increased the soil acid phosphatase activity in all 3 yr. In contrast, the alkaline phosphatase and arylsulfatase activities were enhanced in 1997 by the 8–16 Mg PS ha−1 treatments, whereas larger amounts of PS showed activity comparable to the control. The second PS application promoted phosphatase activities mostly in fall, but did not sustain arylsulfatase activity. The AN gave lower phosphatase activities than PS, and depressed arylsulfatase. Addition of AN to PS increased only acid phosphatase activity as compared with PS alone or the control. This study indicated that addition of PS improved enzyme activity of this horticultural soil but rates in excess to 32 Mg ha−1 may be detrimental. Key words: Papermill sludge, soil enzyme, cabbage, corn
Oxygen measurements in the root zone facilitated by TDR
Authors: Topp G.C. , Dow B. , Edwards M. , Gregorich E. G. , Curnoe W. E. , Cook F. J.
Published: April 2011

Deleterious soil structural conditions, as from compaction, can reduce plant growth and yields by reducing aeration and oxygen in the rooting environment. Using a double-membrane oxygen cathode in each of four corn plots, we measured soil oxygen concentrations in duplicate at depths of 5, 10, 20 and 30 cm during the growing season. In addition, temperature, water content and bulk density determinations allowed the monitoring of O2 concentration trends under no-till and conventional-till corn management. Carbon dioxide flux from the soil surface was measured weekly. Temporal patterns of O2 levels fluctuated in response to rainfall at all depths but much less so at 30-cm depth. At 30 cm the O2 concentration remained inadequate for optimum plant growth (<0.01 kg m−3) for over 2 mo after planting under no-till with poorly timed trafficking. Under conventional till and appropriately timed trafficking adequate aeration occurred more than a month earlier than under no-till. The CO2 output was generally lower by 10 to 30% in no-till than that in conventional till, indicating measurably lower levels of biological activity. The relative magnitudes of mid-season O2 concentrations and CO2 flux densities showed the same pattern as the crop yields for all tillage treatments. More analyses of seasonal O2 consumption patterns are required to determine if lack of O2 is a causal factor for the reduced crop yield. Key words: TDR, aeration, oxygen measurement, carbon dioxide, tillage, root zone
Salinity and sodicity of irrigated Solonetzic and Chernozemic soils in east-central Alberta
Authors: Bennett D. Rodney , Hecker Frank J. , Entz Toby , Greenlee Graeme M.
Published: April 2011

A 4-yr study was conducted on irrigated Solonetzic and Chernozemic soils in the Berry Creek Basin of east-central Alberta to assess changes in soil salinity and sodicity during irrigated alfalfa production and to evaluate the suitability of Solonetzic soils for irrigation. Two of the study sites consisted mainly of soils classified as Solodized Solonetz, with at least 70% in the Solonetzic order. Two chernozemic sites were almost exclusively Chernozemic soils. A significant increase in soil salinity occurred in the A horizon at one solonetzic site and at both chernozemic sites and in the B horizon of one chernozemic site. Mean electrical conductivity (ECe) in these horizons for all irrigation treatments was less than or equal to 1 dS m−1. Soil sodicity also increased significantly in the A horizon at one solonetzic site, and in the A and B horizons of both chernozemic sites. The mean sodium adsorption ratio (SAR) of the A horizon at this solonetzic site was 2.9, 4.8, 4.4 and 5.0 for the control, low, medium and high irrigation treatments, respectively. The SAR in the A horizon at the chernozemic sites was less than 2.6 for all the irrigation treatments. Increases in soil salinity and sodicity were attributed to the chemistry and amount of irrigation water used at each site. Salinization and sodification in addition to the changes associated with the quality and quantity of irrigation water were not evident at any of the sites. The two-cut yield of alfalfa from the solonetzic sites in the third year of growth was about 25% less than from the chernozemic sites and was below the acceptable yield range for irrigated alfalfa in southern Alberta. Our results confirm existing land classification standards in Alberta that exclude solonetzic landscapes from irrigation development where more than about 30% of the soils have an SAR value greater than 12 in any soil horizon within 1 m of the surface. Key words: Solonetzic soils, irrigation suitability, soil salinity, soil sodicity, irrigated alfalfa
Yield response of forage grasses to N fertilizer as related to spring soil nitrate sorbed on anionic exchange membranes
Authors: Ziadi N. , Simard R. R. , Allard G. , Parent G.
Published: April 2011

Soil N availability is an important factor in forage grass production. Maximising N fertilizer efficiency is essential to improve profitability and to reduce the environmental risk associated with residual excess soil N. The objectives of this study were (i): to determine the effects of N fertilizer on yield, N uptake and NO3–N concentration of forage grasses produced in Western Quebec; and (ii) to compare spring soil NO3−measured by anionic exchange membranes (NO3AEMs) and by water extraction (NO3w) as a criterion to predict fertilizer N requirements of forage grasses. The yield response of grasses, especially timothy (Phleum pratense L.), to different rates of NH4NO3 (0 to 240 kg N ha−1) on heavy clay soils (Humic Gleysols) was studied from 1994 to 1996 at four sites in the Abitibi-Temiscamingue area, Quebec (Canada). Nitrogen significantly (P < 0.001) increased forage yield, N uptake, and NO3–N concentration. The economically optimum N fertilizer rate (Nop) for forage yield varied from 25 to 240 kg N ha−1 depending on sites and years, and averaged 125 kg N ha−1. The Nop can be predicted more adequately by NO3AEMs (R2 = 0.45) than by NO3w (R2 = 0.09). Based only on the relationship between the relative yield and spring soil nitrate, NO3AEMs could be used as a criterion for fertilizer N recommendation of forage grasses in this cool continental climate. Key words: N fertilizer, nitrate, grass, economically optimum N fertilizer rate
Active carbon pools and enzyme activities in soils amended with de-inking paper sludge
Authors: Chantigny Martin H. , Angers Denis A. , Beauchamp Chantal J.
Published: April 2011

Application of paper mill wastes generally improves soil organic matter content, biological activity and physical properties. However, the impact of large application rates (>50 Mg ha−1) on soil microflora and their activity has not been assessed. A field study was undertaken on a well-drained clay loam and a poorly drained silty clay loam amended with de-inking paper sludge (DPS) at rates of 0 (control), 50 or 100 Mg ha−1. K2SO4-extractable C (Cext), soil water content (SWC), microbial biomass C (MBC) and different enzyme activity rates were periodically measured in soil during 1075 d following DPS incorporation. Compared with control soils, Cext content increased by 100 to 200%, and soil water content increased by 35% following incorporation of DPS at 100 Mg ha−1. Those differences decreased in time as DPS decomposed. Soil MBC increased proportionally with the rate of DPS amendment and was about twice the amount in soils amended with 100 Mg ha−1 compared with the control. Microbial quotient (ratio of MBC to total soil organic C) was greater in DPS-amended than in control soils until day 370, reflecting the input of labile C from DPS. Compared with the control, fluorescein diacetate hydrolysis and alkaline phosphatase activity rates increased by 40 to 100% when adding 50 Mg DPS ha−1. However, the rates were similar for 50 and 100 Mg DPS ha−1. We concluded that DPS promoted microbial growth and activity in the soil by improving C and water availability. However, levelling off of enzyme activity at a DPS loading rate above 50 Mg ha−1 could reflect changes in soil microbial community, or some kinetic interference or nutrient deficiency induced by excessive C input. Key words: Microbial biomass, active carbon, soil enzyme, paper sludge
Effects of parent material and climate on the magnetic susceptibility of Saskatchewan soils
Authors: Jong E. de , Kozak L. M. , Rostad H. P. W.
Published: April 2011

Magnetic susceptibility (χ) of soils is easily measured; however, the link between magnetic horizonation and pedogenic factors needs to be clarified. This study compares the χ of the A and C horizons of 89 generally well-drained profiles from the agricultural area of Saskatchewan to quantify the effects of parent material and climate. Total Fe and Mn were only weakly related to χ, but χ increased as the soil texture became coarser. This trend was more noticeable in parent material than topsoil samples, and stronger for till than for fluvial, lacustrine and aeolian parent materials. The A horizon samples showed enhanced low frequency and frequency dependant χ. This increase in topsoil χ was greatest in the more humid areas. Key words: Magnetic susceptibility, parent material, climate, texture, magnetic enhancement, soil zone
Field test of a novel, low‐cost, scanner‐based sediment profile imaging camera
Authors: Patterson Adrian , Kennedy Robert , O'Reilly Ronan , Keegan Brendan F.
Published: April 2011

Sediment profile imagery (SPI) is a well‐established technique for mapping benthic habitat quality in soft marine sediments, but several limitations exist in the apparatus employed, particularly the degree of penetration achieved by the sampling device into more compacted subtidal sands and capped sediments. To address this problem and others, such as the high cost of purchasing and maintaining commercially available instruments and illuminating the area to be photographed, a novel scanning sediment profile camera was designed and constructed. This prototypic system was deployed alongside the existing technology in a survey along an established gradient of organic enrichment and in an area of dredge spoil disposal in Galway Bay on the west coast of Ireland. The results of the survey revealed that the novel system, termed SPIScan, achieved a greater degree of penetration than the digital SPI while losing none of the image quality. Although it addresses most of the limitations of existing SPI technology, the new system has one drawback: it is not suitable for deployments in deeper water because of an air‐filled space in the imaging module. This disadvantage is offset by the incorporation of an air reservoir attached to the prism. The volume of the reservoir is the dependent factor limiting the operating depth of the system. It is important to note, however, that the SPIScan is a prototype, and the problem of depth limitation can be solved completely with further development of the instrument.
A dual‐labeling method for the simultaneous measurement of dissolved inorganic carbon and phosphate uptake by marine planktonic species
Authors: Duhamel Solange , Zeman Florence , Moutin Thierry
Published: April 2011

The measurement of primary production is the foundation for aquatic biogeochemistry research. The biogeochemical cycles of phosphate (P) and other biolimiting elements are tightly linked to marine primary production. We have optimized an existing method of carbon (C) and P dual isotope labeling to study the simultaneous C and P uptake by plankton species in marine environments. The two main objectives of this study were (1) to test the preservation properties of the labeled samples and the calculation methods used in separating the signals of the different radionuclides, and (2) to adapt the method to marine environments. The procedure was successfully implemented in contrasting locations within the southeast Pacific (between 146.36°W and 72.49°W). The uptake rates determined using this method ranged from 14 to 900 nM h−1 for dissolved inorganic C and from 0.03 to 4.5 nM h−1 for dissolved inorganic P in surface water. The detection limit found in ultraoligotrophic surface water was 3.33 nM h−1 and 0.01 nM h−1 for C and P, respectively. C and P assimilation fluxes in low‐ and high‐productivity open‐ocean systems may be studied using this sensitive method. We outline a protocol for marine environments that is appropriate for use under oceanographic cruise conditions. Results from the application of this method will lead to a better understanding of the interplay between carbon and phosphate biogeochemical cycles in the upper ocean.
Staging egg development of marine copepods with DAPI and PicoGreen®
Authors: Zirbel Marnie Jo , Miller Charles B. , Batchelder Harold P.
Published: April 2011

Calanoid copepod eggs have a robust, chitinous outer chorion, which makes field‐collected, formaldehydefixed eggs difficult to penetrate with stains or molecular probes. Egg development studies in copepods have involved physical, chemical, and enzymatic treatments to remove the chorion. We present an efficient, one‐step method for staining copepod eggs with the fluorescent nucleic acid stains DAPI and PicoGreen®. Nuclei in treated eggs are clearly visible for examination and counting with compound and confocal microscopy, so that eggs can be rapidly classified with respect to developmental stage. The method is effective for eggs of Calanus, Metridia, and Centropages. Both stains were effective after 24‐h exposure for eggs that were fixed from several days to 8 years. Early stages are distinguished by complete counts of nuclei. A blastula phase and gastrulation are distinctive. Calanus pacificus and Calanus marshallae embryos spend more than half the development period in the later ‘gray ball’ and limb bud stages. Stage classification by this method is useful for studies of cope‐pod egg mortality in the field.
A statistical procedure for unsupervised classification of nutrient limitation bioassay experiments with natural phytoplankton communities
Authors: Andersen Tom , Saloranta Tuomo M. , Tamminen Timo
Published: April 2011

We describe a novel method for statistical analysis of bioassay experiments with natural plankton communities. The procedure allows unsupervised classification of the type of nutrient limitation in factorial experiments with two limiting nutrients, based on objective selection between several generic limitation patterns with direct biological interpretation, using the Akaike Information Criterion (AIC), which balances the concerns of model fit and model robustness. As such, it avoids the interpretation of nuisance parameters related to time effects in classical factorial design analysis of experiments with repeated measurements over time. The proposed limitation patterns discriminate between exclusive and primary limitation, depending on whether the initially nonlimiting nutrient has an effect or not. They also discriminate between two types of colimitation, depending on whether both nutrients only have an effect in combination, or also separately. The latter response is interpreted as the result of different phytoplankton community components being simultaneously limited by different nutrients. The capabilities of the classification procedure is demonstrated on a comprehensive set of 163 bioassay experiments with N and P additions to natural phytoplankton communities from the coast of Finland (NE Baltic Sea).
Use of species‐specific primers and PCR to measure the distributions of planktonic ciliates in coastal waters
Authors: Costas Barbara A. , McManus George , Doherty Mary , Katz Laura A.
Published: April 2011

We developed a method to extract environmental DNA and amplify target portions of the internal transcribed spacer region (ITS) of the ribosomal gene (ITS1‐5.8S‐ITS2) from individual species of oligotrich and choreotrich ciliate microzooplankton. To date, we have lab‐ and field‐tested primers specific to the tintinnid Favella ehrenbergii, the oligotrich Laboea strobila, and the choreotrich Strombidinopsis sp. For all three species, the primers were both species‐specific (not producing PCR product from non‐target DNA) and comprehensive (able to amplify from different populations of the target species). The method is both time‐efficient and sensitive, compared with microscopy. In seawater samples amended with both target and non‐target DNA, we were able to detect the targets at < 1 cell L−1. Some difficulties we encountered resulted from PCR‐inhibitory compounds that co‐extracted with the environmental DNA, and the rarity of the target DNA within natural plankton assemblages. Comparisons with microscopic counts were qualitatively similar to PCR (presence/absence of the species in different amounts of extract). We are evaluating ways to make the method fully quantitative by investigating the degree to which copy number for this gene may vary among individuals.