bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and temporal distribution of soil inorganic nitrogen concentration in potato hills
Authors: Zebarth B. J. , Milburn P. H.
Published: April 2011

The purpose of this study was to determine the spatial and temporal variation in soil inorganic N concentration in the potato hill, and to discuss the implications of this variation on soil sampling strategies. The experiment was conducted in 1999 and 2000 using four treatments: bare soil with no N fertilizer applied, and a potato crop with no fertilizer N added, with 180 kg N ha-1 applied at planting, or with 120 kg N ha-1 applied at planting plus 60 kg N ha-1 applied at hilling. Elevated (above background) soil NH4+-N concentrations were measured for 40 or more days after planting, therefore in-season sampling should be done for both soil NO3−-N and NH4+-N. There was a period of up to 50 days between planting and rapid crop N uptake during which loss of NO3−-N from the root zone could occur. Split fertilizer application reduced the risk of NO3−-N loss during this time, but resulted in reduced tuber yield in 1999. Strong vertical variation in soil inorganic N concentration was measured in the potato hill as a result of fertilizer banding and soil N mineralization at shallow depths. Soil inorganic N concentrations were elevated in the hill, but not in the furrow, resulting in strong horizontal variation in soil inorganic N concentrations in the potato hill. Despite this variation, a systematic sampling strategy where soil was sampled in the centre of the hill, the centre of the furrow, and mid-way between the hill and furrow, done in combination with elevation control of soil sampling, resulted in an unbiased estimate of soil inorganic N concentration in the potato hill. Key words: Solanum tuberosum, nitrification, nitrate leaching, mineralization, sampling strategies
Nitrous oxide production from granular nitrogen fertilizers applied to a silt loam soil
Authors: Tenuta and E. G. Beauchamp M.
Published: April 2011

One field and two laboratory experiments were conducted to determine the relative magnitude and pattern of N2O production from several granular N fertilizers including urea, ammonium nitrate, calcium nitrate, ammonium sulfate and, in a laboratory experiment, monoammonium and diammonium phosphates. Several parameters, in particular soil water content, were studied for their roles in N2O production with these fertilizers. The field experiment was conducted at the Elora Research Station (20 km north of Guelph) on Conestoga silt loam during July on a site previously cropped to barley. Three methods were employed to assess N2O production following N fertilizer treatments in the field experiment, viz., soil cover, soil core and profile distribution. The data with each method revealed that incorporated urea produced the greatest quantity of N2O especially in the first few days following application. Shortly after urea application and incorporation (10 cm), N2O was detected at a depth of 50 cm indicating gas produced in the tilled layer was transported to lower depths. Data obtained with the intact core method showed that nitrification preceeded denitrification as the source of N2O produced during a wetting event as air-filled porosity decreased from 65% to less than 50%, respectively. The laboratory experiments showed that under aerobic conditions N2O production was generally greater with urea than the other N fertilizers. The greater production of N2O with urea was associated with N2O-accumulation. In the second laboratory experiment, saturating the soil following 14 d of aerobic incubation showed enhanced N2O production with ammonium phosphate fertilizers. Our findings indicate refinement of methods to predict N2O emissions based on N fertilizer source use and moisture can reduce uncertainties in national estimates of N2O emissions from agricultural soils. Key words: Nitrous oxide production, nitrogen fertilizers, soil atmosphere profiles, nitrification, denitrification, air-filled porosity
Crop response to topsoil replacement depth and organic amendment on abandoned natural gas wellsites
Authors: Larney F. J. , Akinremi O. O. , Lemke R. L. , Klaassen V. E. , Janzen H. H.
Published: April 2011

The reclamation success of abandoned wellsites in agricultural areas depends on their capacity to sustain levels of biomass production similar to those which existed prior to soil disturbance. We examined the effect of four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendment treatments [compost, manure, alfalfa (Medicago sativa L.) hay, wheat (Triticum aestivum L.) straw, check) in the reclamation of three wellsites in south-central Alberta. The largest incremental effect of TRD on spring wheat response in the 4 yr (1997-2000) study occurred between the 0 and 50% treatments. Increasing TRD from 100 to 150% had little impact on crop response. Of the 20 treatments (four TRD × five amendments), the reclamation capacity of the 100% TRD-compost treatment ranked highest, being 19% higher than the baseline treatment (100% TRD-check). The lowest-ranking treatment overall , was the 0% TRD-straw treatment, which yielded 64% of the baseline treatment. Crop yield responses to organic amendments were larger when the recipient soil was lower in organic matter. Positive responses to one-time applications of organic amendments in the short-term (4 yr), advocate their use in soil reclamation of abandoned wellsites, despite a lingering question about the longevity of their beneficial effects. Key words: Soil reclamation, topsoil, organic amendments, natural gas wellsite
Relationship of soil phosphorus fractions to phosphorus soil tests and fertilizer response
Authors: McKenzie R. H. , Bremer E.
Published: April 2011

Soil tests for available P may not be accurate because they do not measure the appropriate P fraction in soil. A sequential extraction technique (modified Hedley method) was used to determine if soil test P methods were accurately assessing available pools and if predictions of fertilizer response could be improved by the inclusion of other soil P fractions. A total of 145 soils were analyzed from field P fertilizer experiments conducted across Alberta from 1991 to 1993. Inorganic P (Pi) removed by extraction with an anion-exchange resin (resin P) was highly correlated with the Olsen and Kelowna-type soil test P methods and had a similar relationship with P fertilizer response. No appreciable improvement in the fit of available P with P fertilizer response was achieved by including any of the less available P fractions in the regression of P fertilizer response with available P. Little Pi was extractable in alkaline solutions (bicarbonate and NaOH), particularly in soils from the Brown and Dark Brown soil zones. Alkaline fractions were the most closely related to resin P, but the relationship depended on soil zone. Inorganic P extractable in dilute HCl was most strongly correlated with soil pH, reflecting accumulation in calcareous soils, while Pi extractable in concentrated acids (HCl and H2SO4) was most strongly correlated with clay concentration. A positive but weak relationship as observed between these fractions and resin P. Complete fractionation of soil P confirmed that soil test P methods were assessing exchangeable, plant-available P. Key words: Hedley phosphorus fractionation, resin, Olsen, Kelowna
Effects of eight years of crop rotation and tillage on nitrogen availability and budget of a sandy loam soil
Authors: Soon Y. K. , Clayton G. W.
Published: April 2011

The effects of tillage and crop rotations on soil N availability and economy were evaluated over two rotation cycles to address the paucity of such information. From 1993 through 2000, soil was sampled to 120 cm in the autumn from four crop rotations : (i) continuous wheat (Triticum aestivum L.), (ii) field pea (Pisum sativum L.)-wheat-canola (Brassica rapa L.)-wheat, (iii) red clover (Trifolium pratense L.) green manure-wheat-canola-wheat/red clover, (iv) fallow-wheat-canola-wheat, and analysed for KCl-extractable N. The rotations were managed under a conventional tillage (CT) or a no-till (NT) system, and were fertilized based on soil test results. A N budget was constructed for each cropping system comprising N added in seed and fertilizers, and by symbiotic fixation and N exported in the grain. More nitrate accumulated under CT than NT, resulting in lower N fertilizer application rates for CT plots. Soil mineralizable N was higher under NT than CT, and was not influenced by crop rotations. The trend for residual soil nitrate among crop rotations was: fallow rotation > green manure rotation > continuous wheat > field pea rotation, due mostly to residual nitrate following the first phase of the rotations. There was no interaction of tillage with rotation. The continuous wheat and field pea rotation maintained a balanced N budget. The red clover rotation resulted in net N import in each rotation cycle of approximately 25 kg ha-1 under CT and 37 kg ha-1 under NT; net N export from the fallow rotation was 30 kg ha-1 under NT and 46 kg ha-1 under CT. Key words: Field pea, fallow, red clover, N economy, tillage, wheat
Patterns and simulation of soil water under different grazing management systems in central Alberta
Authors: Mapfumo E. , Chanasyk D. S. , Baron V. S.
Published: April 2011

A study was conducted at the Lacombe Research Centre to quantify and simulate the impacts of forage and grazing systems on soil water content. Four forages used in the study were alfalfa (Medicago sativa L.), a mixture of meadow bromegrass (Bromus riparius L.) and alfalfa, an annual pasture and an old grass pasture that was composed of mainly quackgrass (Elytrigia repens L.), smooth bromegrass (Bromus inermis L.) and Kentucky bluegrass (Poa pratensis L .). Within each 1.2-ha paddock were two grazing treatments: rotational grazed and ungrazed. Soil water measurements to a 65-cm depth were conducted between May and October of 1999 and 2000 using a neutron moisture probe. Total soil water was affected by forage species more than grazing. Actual evapotranspiration rates were 3-4 mm d-1 in both years. Simulation of daily volumetric soil water content (%) for each year was conducted using the Versatile Soil Moisture Budget (VB2000) model on grazed alfalfa, ungrazed alfalfa, grazed annual and ungrazed annual treatments. During calibration year of 1999, the overall modeling efficiency (EF) was 0.58 while, during the evaluation year it was 0.43. Further, simulations for alfalfa were better than those for annual treatments. These EF values are relatively low indicating substantial discrepancies between observed and simulated results, which could have been attributed to a combination of input data errors, model errors and propagation errors in output. Key words: Evapotranspiration, forages, model calibration, model evaluation, versatile soil moisture budget model
Phosphorus status of a Humic Gleysol after 10 year of cultivation under contrasting cropping practices
Authors: John A. MacLeod Zhiming Zheng, , J. Brian Sanderson Jean Lafond, , Campbell Allan J.
Published: April 2011

Cropping practices interactively affect soil P status. Previous studies mostly focused on cropping practices individually and limited assessments within the plow layer. This study assessed the P status of a Labarre silty clay (Humic Gleysol) profile after 10 yr cultivation under contrasting practices. Soils of 0–15, 15–30, 30–60, and 60–90 cm layers were sampled from a split-plot experiment comprising barley (Hordeum vulgare L.) monoculture and a 3-yr barley-red clover-timothy rotation both tilled with either chisel or moldboard plow as main plots, and receiving fertilizer P or liquid dairy manure as subplots. A modified Hedley sequential fractionation was used to characterize soil P status. Labile P pools were more affected than stable ones by cropping practices. The P fractions depended more on nutrient sources than cropping systems in the 0- to 30-cm soil layer, whereas the impacts were predominated by cropping systems in the subsoil. Compared to the manure, fertilizer P resulted in higher contents of Mehlich III extractable P, resin-P, NaHCO3-Pi and NaOH-Pi, and lower contents of NaHCO3-Po, NaOH-Po and H2SO4-P in the 0- to 30-cm layers. The rotation produced larger labile P fractions than the monoculture in the 30- to 60-cm layer. The impacts of the investigated cropping practices on labile P fractions extended deeper in the soil profile than the depth disturbed by primary tillage. Crop sequence, primary tillage and nutrient source had large effects on P status in the soil profile, of this clayey and poorly drained soil. Key words: rotation; primary tillage; liquid dairy manure; P forms, Mehlich III extractable P (M3P)
The use of 15N-enriched feed to label pig excreta for N cycling studies
Authors: Chantigny Martin H. , Angers Denis A. , Pomar Candido , Morvan Thierry
Published: April 2011

Isotopic labelling can help improve our knowledge of the fate of manure N in agroecosystems. Our objective was to investigate the labelling dynamics of excreta N by feeding a pig with a 15N-enriched diet (2.808 atom % 15N) and to establish the implications of using the labelled excreta for N cycling studies. Pig urine and feces were collected and pooled each day for 20 d following the start of 15N-feeding. Each of the 20 excreta samples were analyzed for pH, dry matter content, C and N contents, and 15N distribution between the mineral and organic N pools. Sub-samples of each excreta sample were incubated for 84 d, and the 15N abundance of N mineralized after 7, 21 and 84 d of incubation was determined. The 15N concentration in pig excreta increased sharply during the first 3 d of 15N-feeding and slowly thereafter. The 15N concentration in excreta decreased rapidly when an unlabelled feed was served after 12 d of 15N-feeding. On the first day and after 9 d of 15N-feeding, the mineral and the organic N pools of the collected excreta had similar 15N content. However, from day 2 to 9 of 15N-feeding, the 15N abundance of excreta mineral N was 0.1 to 0.3 atom % lower than in the organic N pool. During incubation of the excreta samples, the 15N content of the mineralized N was 0.1 to 0.4 atom % lower after 84 d than after 21 d of incubation, indicating a heterogeneous distribution of 15N between the rapidly and the slowly mineralizable N pools of pig excreta. Despite some heterogeneity, the measured differences in 15N enrichment among the various excreta N pools were generally less than 15% for the first 9 d of 15N-feeding, and less than 5% afterwards. The labelled excreta were thus considered appropriate for short-term studies on the fate of manure N in the soil-plant system, especially for excreta collected after 9 d of 15N-feeding. Key words: 15N labelling, animal feeding, swine manure, pig slurry
Soil tests for predicting the N requirement of corn
Authors: Beauchamp E. G. , Kay B. D. , Pararajasingham R.
Published: April 2011

Several soil N tests were compared with the one currently used for predicting the N requirement for corn in Ontario. The current test involves a measurement of nitrate (NO3−, 0–30 cm) before N fertilizer sidedressing. The study was done to determine the efficacy of other tests for N fertilizer prediction. The tests chosen varied in the quantity of N “extracted” and included hot KCl-extractable NH4+, anaerobically released NH4+, extractable NH4+ following autoclaving in CaCl2 solution and total N of soil sampled to a depth of 30 cm. The 3-yr study was conducted on a sloped (simple) field site, which provided a wide range in soil organic matter (SOM) contents. A corn crop was grown each year following a barley crop with or without red clover cover crop residues incorporated in the spring and with or without N fertilization. Corn grain yields were obtained at the end of the growing season. Grain yields were lowest at the shoulder and backslope locations and highest at the footslope and toeslope locations. Corn plant shoot biomass and N content and soil mineral (NH4+and NO3−) N (0–30 cm) were measured biweekly to provide an estimate or index of available N. Plant and soil samples were taken at the summit, shoulder, backslope, footslope and toeslope locations providing a wide range of SOM levels, which, in turn, provided a range in available N for comparing the various soil N tests. The increase in estimated available N during the growing season was most rapid in the 120–180 day of year (DOY) period and substantially slower in the 230–260 DOY period. An available N index (AVN) was obtained by averaging the N measured with three plant and soil samples taken in the late August to early September period. Thus, the AVN was determined during a period when the increase in available N was relatively slow. Regressions of corn grain yield (not fertilized with N) on AVN produced R2 values ranging from 0.61 to 0.93. Values of R2 for AVN vs. the soil tests ranged from 0.34 to 0.88 where red clover crop residues were not involved. The AVN values were less correlated with the soil N test values where red clover cover crop residues were incorporated with R2 values ranging from 0.11 to 0.92. It was concluded that the hot KCl test would be a suitable alternative to the currently used soil NO3− test because of relatively simple soil sample preparations and storage, and analytical procedures. Key words: Soil N tests, corn, available N index, soil organic matter, landscape location
Nitrogen mineralization and uptake by ryegrass in a clay loam soil amended with composts or liquid pig manure
Authors: Yang X. M. , Drury C. F. , Reynolds W. D. , Tan C. S.
Published: April 2011

Although composted liquid pig manure is increasingly being applied to agricultural soils, little is known about its impacts on N dynamics (mineralization, denitrification, immobilization, and plant uptake) in the crop root zone compared to liquid pig manure (LPM) or other types of composts. A greenhouse pot experiment was conducted to determine N mineralization and plant uptake in a ryegrass-cropped clay loam soil that had been amended with either LPM, LPM + wheat straw compost (PMS), or yard waste compost (YWC). Over a 20-wk growth period, plant biomass was increased relative to the control by 164% for LPM, 64.3% for YWC, and 39.6% for PMS. However, the recovery of amendment N in the ryegrass was low and variable at 3.3% for PMS (12.7 mg N kg-1), 3.7% for YWC (21.5 mg N kg-1), and 15.3% for LPM (90.9 mg N kg-1). Although gains and losses of mineral N occurred primarily within the first 8 wk, assimilation of amendment N by the ryegrass appeared to continue throughout the entire growth period. High amounts of inorganic N present in the LP M treatment led to the greatest loss of N, as N2O, through denitrification and nitrification (39.1 mg N kg-1). This was 35 times greater than the YWC treatment (1.1 mg N kg-1), over 50 times greater than the N2O loss from the PMS treatment (0.7 mg N kg-1) and over 76 times greater than the N2O loss from the control (0.5 mg N kg-1). There was a net gain in mineral and plant assimilated N from mineralization with the control (6.4 mg N kg-1) and YWC treatments (8.8 mg N kg-1) over 20 wk. However, there was a small decrease in mineral and plant assimilated N with the PMS treatment (4.3 mg N kg-1) and a large decrease with the LPM treatment (90.1 mg N kg-1). From an environmental perspective, the large amount of N2O generated by the LPM treatment compromises the usefulness of LPM as a source of crop-available N. Key words: Compost, pig manure, ryegrass, swine, hog, nitrogen mineralization
Nitrate leaching as affected by liquid swine manure and cover cropping in sandy soil of southwestern Ontario
Authors: Ball-Coelho B. R. , Roy R. C. , Bruin A. J.
Published: April 2011

To assess the risk that liquid swine manure (LSM) application posed to groundwater quality and determine how to manage excess nitrates, LSM pre-plant injected at 75% (LSMlow) and >100% (LSMhigh) of corn (Zea mays L.) N requirements was compared to inorganic fertilizer (Fert), with (RC) or without (NC) a rye (Secale cereale L.) cover crop in 2 dry years (1999, 2001) and 1 wet year (2000) on sandy soil in Ontario. Corn yields in LSM and Fert treatments were comparable each year. When drainage potential was high, solution nitrates below the root zone in Fert (14 mg L-1) > LSM (7 mg L-1) in 1999, but in LSM (39 mg L-1) > Fert (13 mg L-1) in 2000. Occasionally in 2001, solution nitrates in LSMhigh > LSMlow and/or Fert plots, but drainage potential was low. Earlier N application in LSM (pre-plant) than Fert (77% of N sidedressed) plots in relation to rain events may have increased solution nitrates in LSM plots in 2000. Rye cover reduced solution nitrates from 8.8 mg L-1 (NC) to 4.3 mg L-1 (RC, average of all dates), regardless of nutrient source. In-season risk of NO3 leaching can be reduced by split application of N between pre-plant and sidedress, while overseeding cereal rye into standing corn minimizes leaching post-harvest (fall and spring). Key words: Zea mays, Secale cereale, pre-sidedress nitrate test, swine manure, nitrate leaching
Effect of in-season application methods of fertilizer nitrogen on grain yield and nitrogen use efficiency in maize
Authors: Ma B. L. , Li M. , Dwyer L. M. , Stewart G.
Published: April 2011

Little information is available comparing agronomic performance and nitrogen use efficiency (NUE) for N application methods such as foliar spray, soil application, and ear injection in maize (Zea mays L.). The objective of this study was to investigate the effects of various N application methods on total stover dry matter, grain yield, and NUE of maize hybrids using a 15N-labeling approach. A field experiment was conducted on a Dalhousie clay loam in Ottawa and a Guelph loam in Guelph for 2 yr (1999 and 2000). Three N application methods were tested on two maize hybrids, Pioneer 3893 and Pioneer 38P06 Bt. At planting, 60 kg N ha-1 as ammonium nitrate was applied to all treatments. In addition, 6.5 kg N ha-1 and 13.5 kg N ha-1 as 15N-labeled urea were applied to either foliage (Treatment I) or soil (Treatment II) at V6 and V12 stages, respectively. In Treatment III, 20 kg N ha-1 as 15N-labeled urea was injected into space between ear and husks at silking. The results showed that compared with soil N application neither foliar spray nor injection through ear affected grain yield or stover dry matter. The NUE values ranged from 12 to 76% for N fertilizer applied at V6 a nd V12 stages, or at silking for all treatments. There was no interaction of hybrid × N application methods on any variables measured with the only exception that for soil N application, grain NUE in Pioneer 38P06 Bt was significant higher than in Pioneer 3893. The difference in total N and NUE of grain and stover between soil N application and foliar N spray was inconsistent. However, NUE was substantially higher for N injection through the ear than for foliar or soil application without differential responses between the two hybrids. Nitrogen injection through the ear at silking might have altered N redistribution within the plant and improved NUE. Hence, it can potentially enhance grain protein content. Foliar N spray is not advocated for maize production in Ontario. Key words: Maize, Zea mays, nitrogen application methods, nitrogen-15, yield, nitrogen use efficiency
Calibration and modification of impedance probe for near surface soil moisture measurements
Authors: Tsegaye T. D. , Tadesse W. , Coleman T. L. , Jackson T. J. , Tewolde H.
Published: April 2011

A reliable and low cost sensor that can measure soil moisture at or near the soil surface is currently not available. The objectives of this study were: (i) to evaluate the possibility of modifying an impedance probe (IP) to measure soil moisture content at a very shallow depth (2–5 cm); and (ii) to compare the soil moisture values obtained using the IP to the values obtained using the traditional gravimetric method. The research was conducted at the Winfred A. Thomas Agricultural Research Station (WTARS) Hazel Green, Alabama. The standard IP that is capable of measuring soil moisture content at 6-cm soil depth was modified to measure soil moisture at 2-, 3-, and 5-cm depths. Using a site and depth-specific calibration technique it provided results that were comparable to the values that were obtained following the traditional gravimetric water content determination protocol. We found that the instrument was very sensitive to changes in soil moisture content and has great potential as a replacement for the gravimetric technique. It allows repetitive measurements of soil moisture content at a very shallow depth with minimal soil disturbance. Fur thermore, the instrument is particularly valuable for providing ground- truth soil moisture contents to validate remotely sensed data. Key words: Soil moisture, remote sensing, impedance probe, ground-truth, validation
Decomposition of residues and loss of the δ-endotoxin from transgenic (Bt) corn (Zea mays L.) in soil
Authors: Hopkins D. W. , Gregorich E. G.
Published: April 2011

Corn and other crops genetically modified to express the insecticidal δ-endotoxin from Bacillus thuringiensis (Bt) are grown widely across north America. Studies have shown that the δ -endotoxin can be stabilised on soil colloids where its activity is retained, but reports of direct ecological effects of the δ-endotoxin on soil processes are limited. We have determined the concentrations of the δ-endotoxin in organic residues fro m Bt-corn plants at increasing stages of ageing and decay, and the subsequent decomposition in soil of these residues and the δ-endotoxin in them. The δ-endotoxin concentrations declined from 6.8 μg g-1 in the fresh plant material, to 0.82 μg g-1 in the post-harvest residues collected in the fall, and to 0.026 μg g-1 in the residues collected from soil surface the following spring. The concentration of δ -endotoxin in buried residues collected in the spring was not significantly different from zero. When incubated in soil in the laboratory over 84 d, the δ-endotoxin decomposed more rapidly than bulk plant C by factors of 1.85 for the fresh plant materials and 3.21 for the post-harvest residues. Within 14 d of incubation, the δ-endotoxin concentration in the residues collected at the soil surface was below the limit of detection. We contrasted the laboratory decomposition data with data from a field experiment to estimate the period that the δ-endotoxin in corn residues may survive in the field. Based on estimates derived from this comparison, we predict that following an October harvest in eastern Ontario the δ-endotoxin would fall below the detection threshold during November for post-harvest residues. Since stabilisation of the δ-endotoxin on soil colloids depends on it surviving (i.e., not being decomposed) for long enough to be released from the plant residue matrix and come into proximity with colloid surfaces, the rapid decay of the δ-endotoxin suggests that only a small fraction of the δ-endotoxin from post-harvest residues persists long enough to become stabilised in the field. Key words: Bt, corn, crop residue decomposition, maize
Extractable phosphorus in alkaline soils amended with high rates of organic and inorganic phosphorus
Authors: Kashem Md. Abul , Akinremi Olalekan Oluwole , Racz Geza Joseph
Published: April 2011

Information on the extractable P in soils treated with different organic amendments and how it changes with time is important to a sound management of manure addition to agriculture soils. This laboratory study investigated the impact of adding municipal biosolids, hog and cattle manures and monoammonium phosphate (MAP) on extractable P in soils. Phosphorus was added at rates of 0, 110, 220, 440 and 880 mg P kg-1 for the Osborne soil (Gleysolic Humic Vertisol), and 0, 123, 307 and 614 mg P kg-1 for the Lakeland soil (Gleyed Rego Black Chernozem) in the form of biosolids, hog manure, cattle manure and MAP. The soils were incubated at field capacity for 1, 4, 16 and 32 wk after which they were extracted using H2O, NH4Cl, NaHCO3 (Olsen P), and the Kelowna and Mehlich-3 extracts. Regardless of extractant and soil, extractable P was small 1 wk after adding biosolids (17-93 mg kg-1 as Olsen P) and large with MAP (59-672 mg kg-1 as Olsen P) while hog and cattle manures were intermediate between biosolids and MAP (20-461 mg kg-1 as Olsen P). In biosolids-amended soils, extractable P increased slightly with increasing incubation time indicating net P mineralization. With MAP, extractable P declined from 672 mg kg-1 after 1 wk to 157 mg kg-1 after 16 wk of incubation at the highest P application rate in the Osborne soil. In the Lakeland soil, the decrease in extractable P with MAP addition was small (from 398 to 332 mg kg-1) and was similar to the changes with cattle manure P with incubation time. Extractable P with cattle manure in the Osborne soil and with hog manure in the Lakeland soil did not change with incubation time. In both soils, extraction efficiency was in the order of H2O < NH4Cl < NaHCO3 < Kelowna < Mehlich-3. Across P application rates, the efficiency of added P as measured by NaHCO3 increased only with biosol ids from 12% after 1 wk to 21% after 32 wk of incubation, while it decreased in the same period from 55 to 44% with hog manure, from 34 to 32% with cattle manure and from 74 to 17% with MAP in the Osborne soil. Soil samples taken 4 wk following addition o f hog and cattle manures should reflect plant-available P, while soil samples taken within the same period following the application of biosolids are likely to underestimate plant-available P. Key words: Extractable phosphorus, organic amendments, soils, single extraction, incubation
Does the presence of glomalin relate to reduced water infiltration through hydrophobicity?
Authors: Feeney Debbie S. , Paul D. Hallett Tim Daniell, , Karl Ritz Janine Illian, , Young Iain M.
Published: April 2011

The resilience and stability of the physical structure of soil impacts directly on all soil processes, mediating microbial activity and defining the flow pathways between the soil ecosystem, waterways and the atmosphere. The effect of the presence of the glycoprotein glomalin exuded from Arbuscular Mycorrhzal (AM) fungi, on soil hydrophobicity is presented. A possible role for glomalin as improving soil structural stability is important in the context of soil protection. Using total glomalin, together with measurements of soil hydrophobicity, we investigate the spatial correlations between the two measurements in the presence and absence of pea roots. Whilst AM fungi were visible within roots (up to 52% root length colonization), no differences in glomalin concentration between planted and unplanted controls were observed. The presence and amount of glomalin did not correspond to the presence or level of hydrophobicity in soil. We discuss these results in relation to AM fungal-glomalin interactions, soil structure and root exudation. Key words: Glomalin, water infiltration, mycorrhizae, soil structure, hydrophobic
Laboratory and field evaluation of five soil water sensors
Authors: Huang Q. , Akinremi O. O. , Sri Rajan R. , Bullock P.
Published: April 2011

Accurate in situ determination of soil water content is important in many fields of agricultural, environmental, hydrological, and engineering sciences. As numerous soil water content sensors are available on the market today, the knowledge of their performance will aid users in the selection of appropriate sensors. The objectives of this study were to evaluate five soil water sensors in the laboratory and to determine if laboratory calibration is appropriate for the field. In this study, the performances of five sensors, including the Profile Probe™ (PP), ThetaProbe™ , Watermark™, Aqua-Tel™, and Aquaterr™ were compared in the laboratory. The PP and ThetaProbe™ were more accurate than the other soil water sensors, reproducing soil water content using factory recommended parameters. However, when PP was installed on a loamy sand in the field, the same soil that was used for the laboratory evaluation, it overestimated field soil water, especially at depth. Another laboratory experiment showed that soil water content readings from the PP were strongly influenced by soil bulk density. The higher the soil bulk density, the greater was the overestimation of soil water content. Two regression parameters, a0 and a1, which are used to convert the apparent dielectric constant to volumetric water content, were found to increase linearly with the soil bulk density in the range of 1.2 to 1.6 Mg m-3. Finally, the PP was calibrated in the field and a good calibration function was obtained with an r2 of 0.87 and RMSE of 2.7%. The values of a0 and a1 obtained in the field were different from factory recommended parameters (a0 = 2.4 versus 1.6 while a1 = 12.5 versus 8.4) and were independent of soil depth, bulk density, and texture. As such, individual field calibration will be necessary to obtain precise and accurate measurement of soil water content with this instrument. Key words: Soil water content, Profile Probe, calibration, soil water content sensor
Arbuscular mycorrhizae, glomalin, and soil aggregation
Authors: Rillig Matthias C.
Published: April 2011

Arbuscular mycorrhizae are important factors of soil quality through their effects on host plant physiology, soil ecological interactions, and their contributions to maintaining soil structure. The symbiosis is faced with numerous challenges in agroecosystems; in order to inform sustainable management strategies it is hence a high priority to work towards mechanistic understanding of arbuscular mycorrhizae contributions to soil quality. This review focuses on glomalin-related soil protein (GRSP), operationally defined soil C pools that have been linked to arbuscular mycorrhizal fungi (AMF). In discussing this protein pool, we propose a new terminology used to describe fractions of soil proteins and glomalin. GRSP concentrations in soil are positively correlated with aggregate water stability. GRSP has relatively slow turnover in soil, contributing to lasting effects on aggregation. Controls on production of GRSP at the phenomenological and mechanistic level are evaluated. While there are significant gaps in our knowledge about GRSP and glomalin (particularly at the biochemical level), it is concluded that research on GRSP holds great promise for furthering our knowledge of soil structure and quality, for informing suitable management, and as a foundation for novel biotechnological applications in agriculture and beyond. Key words: Glomalin, GRSP, soil structure, land use, restoration, soil protein, sustainability, arbuscular mycorrhizae
Residues of DDT and other selected organochlorine pesticides in soils from Saskatchewan, Canada (1999)
Authors: Don Waite Phillip Bailey, , Quinnett-Abbott Lynne , Ripley Brian D.
Published: April 2011

A study of samples from a broad range of soils across the province of Saskatchewan, Canada, in 1999 has shown evidence that residues of organochlorine pesticides, and in particular DDT [1,1,1-trichloro-2,2- bis(4-chlorophenyl)ethane] and related compounds, are present even after several decades since the last application. In particular, residue levels of total DDT {DDTt = DDT + DDD [1,1-dichloro-2,2- bis(p-chlorophenyl)ethane] + DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene]} in Prince Albert National Park approach some of the highest levels measured to date at non-agricultural locations with concentrations of 119 to 150 ng g-1. Ratios of DDT:DDD:DDE were relatively consistent even from sites separated by several hundred kilometers and seem to be independent of soil properties and sample moisture levels over the region of study. These DDT:DDD:DDE ratios ranged from 9:1:4 for the Prince Albert Park site to 5:1:2 for Agriculture and Agri-Food Canada (AAFC) Research Centres and privately owned agricultural land. Data collected from AAFC Research Centres showed somewhat elevated levels of lindane [γ-1,2,3,4,5,6-hexachlorocyclohexane] (maximum 14 ng g-1), dieldrin [(1R,4S,4aS,5R,6R,7S,8S,8aR)-1,2,3,4,10,10-hexachloro-=6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro- endo-1,4,-exo-5,8-dimethanonaphthalene] (maximum 27 ng g-1) and chlordane [1,2,4,5,6,7,8,8-octachloro-2,3,3a,4,7,7a-hexahydro-4,7-methanoindene] (maximum 10 ng g-1), while samples collected from sites designated as “background” locations demonstrated a minimal effect from long-range atmospheric transport of organochlorines. Key words: Organochlorine residues, soil, Canada, decomposition products, pesticides
The tolerance and Zn2+, Ba2+ and Fe3+ accumulation by Trichoderma atroviride and Mortierella exigua isolated from contaminated soil
Authors: Kacprzak Malgorzata , Malina Grzegorz
Published: April 2011

This paper presents the results of studies on tolerance to and bioaccumulation of selected heavy metals by filamentous fungi, as a result of natural adaptation and improved resistance of fungal cells. The fungal communities were selected from soils highly contaminated with Zn, Ba and Fe in the vicinity of the chemical plant in Tarnowskie Gory (South Poland, the Silesia Region). The isolates of Trichoderma atroviride and Mortierella exigua were most frequently present in soil with high contents of metals; however, they did not occur in non-contaminated soil samples. The metal tolerance of fungi was determined by measuring growth by means of mycelium diameter on solid medium, dry weight of mycelium on Czapek-Dox solid and Sabouraud liquid media amended with increasing concentrations of Zn2+, Ba2+ and Fe3+ up to 1000 mg L-1. Zn2+, Ba2+ and Fe3+ affected the fungal growth, dry weight and metal uptake. The studied fungi were able to grow at high Zn2+ and Ba2+, but not Fe concentrations. The weight of biomass was dependent on the medium used. The highest accumulation by both T. atroviride and M. exigua was found in the case of Ba2+. Maximal concentrations in T. atroviride mycelium were 21.3, 25.0 and 4.5 mg g-1, in the case of Zn2+, Ba2+and Fe, respectively. Maximal concentrations in M. exigua mycelium were equal to 32.9 mg L-1 (Zn2+), 15.3 mg L-1(Ba2+) and 1.2 mg g-1 (Fe3+). Worldwide occurrence of T. atroviride and M. exigua and their easy adaptation to different conditions is promising for their use as bioagents in remediation processes. Key words: Heavy metals, Trichoderma atroviride, Mortierella exigua, tolerance, bioaccumulation
Lead migration in Podzolic soils from Scandinavia and the United States of America
Authors: Steinnes and A. J. Friedland E.
Published: April 2011

In the past two decades, investigators have documented a decrease in total lead concentration and amount in upper soil horizons of forest soils following a reduction in the use of gasoline lead additives. In this study, we compare three data sets of lead isotopic ratios in forest soils from Sweden, Norway and the United States of America in order to formulate hypotheses relating to the factors that dictate lead distribution among horizons in Podzolic soils. A larger fraction of anthropogenic lead is seen at greater depths in the Swedish sites and in the southern sites from Norway then in the USA site. At present, only the time of onset of lead pollution appears to be related to the observed pattern. These observations could not have been made within any individual study but became clear when the three independent studies were examined together. Key words: Lead, soils, long distance transport, migration rates
Organochlorine pesticides in soils of the horticultural belt of Bahía Blanca (Argentina)
Authors: Andrade M. L. , Reyzábal M. L. , Covelo E. F. , Vega F. A.
Published: April 2011

The land around Bahía Blanca, Argentina, has been farmed intensively for six decades. We report the concentrations of a number of organochlorine pesticides (DDT, dieldrin, endrin, heptachlor epoxide and lindane), and of DDT metabolites (DDD + DDE) in three different layers (0–5, 5–10 and 10–20 cm) of the soils in 44 fields of eight farms that have been devoted to horticulture for periods ranging from 15 to 60 yr. In spite of the horticultural use of these substances having been banned for the past 13–35 yr, high concentrations were found – up to nearly 12 mg kg-1 for DDT + DDD + DDE, 17 mg kg-1 for dieldrin, 4 mg kg-1 for endrin, 7 mg kg-1 for heptachlor epoxide and 0.8 mg kg-1 for lindane. The highest concentrations of DDT, dieldrin, endrin and heptachlor epoxide were found on the oldest farms, the highest levels of DDD + DDE on middle-aged farms (35–40 yr), and the hi ghest levels of lindane on 15–40-year-old farms that had rather lower soil pH than the older farms. Concentrations invariably decreased slightly with increasing depth, and for DDT, dieldrin and heptachlor epoxide they exhibited significant positive correlation with soil organic matter content. Principal components analysis confirmed the distinguishability of three groups of analytes: one comprising DDT, dieldrin, endrin and heptachlor epoxide associated with higher soil organic matter and clay contents; and two singletons, DDD + DDE associated with higher pH and lindane. We conclude that these pesticides have very limited mobility in these semiarid alkaline soils. Key words: Organochlorine, semiarid soils, horticulture, depth variation.
An expert system for allocating soils to landforms through the application of soil survey tacit knowledge
Authors: MacMillan R. A. , Pettapiece W. W. , Brierley J. A.
Published: April 2011

Soil survey is a paradigm-based science that relies heavily on the application of conceptual soil-landscape models, which in turn are based upon tacit pedological knowledge. This tacit knowledge is generally acquired by systematic field observation and recording the relationships between the occurrence of soils and associated landform positions. Soil survey databases identify the types of soils within a delineated area but they do not generally describe the relationship of specific soils with specific landscape positions. A case in point is the recently completed 1:100 000 scale soil landscape database prepared for the agricultural region of Alberta, Canada. In order to utilize this database with various interpretative algorithms a procedure for allocating soils to specific landform positions needed to be developed. The development of this procedure initially involved capturing the local tacit pedological knowledge in a series of tables and programs. The procedure was then applied to the Alberta soil survey database to automatically assign soils to landform positions and then to assign specific slope characteristics to the individual soils. The resulting soil-landform product was more useable than the original data for input to land based process models. Key words: Soil survey, tacit knowledge, soil-landscape modeling, heuristic rule base, predictive mapping
Soil microbial populations, activity, and community structure in continuous corn or forage systems under organic or inorganic fertilization in eastern Canada
Authors: Lalande R. , Gagnon B. , Chapman R. A. , Barnett G. M.
Published: April 2011

Succession of soil microbial communities proceeds interdependently with crop development under the control of edaphic, agricultural, and climatic conditions. Soil microbial community composition and activity were characterized in two managed cropping systems (continuous corn or mixed forage) receiving liquid hog manure (LHM) or inorganic fertilization (IF) since 1989. Microbial community composition was determined from patterns of phospholipid fatty acids (PLFA). Soil microbial biomass C, enzymatic activity, and total phospholipids were greater under forage than under continuous corn. Principal component analysis (PCA) revealed a high degree of variation in PLFA composition and microbial community structure due to treatments and time of sampling. The first two PCA axes explained 80 to 90% of the variability on all sampling dates. Two main groups were created along the first component, the first comprising all forage treatments and a second with LHM-treated continuous corn. The IF and control-treated continuous corn were differentiated from all others on the second component. All groups were characterized by specific microbial communities. The most significant shift in specific groups of fatty acids was caused by LHM addition to continuous corn, especially due to the relative abundance of the fungal fatty acid 18:29,12. Our findings indicated that the addition of organic materials, rich in available C and N, induced development of diverse microbial populations, which can be successfully monitored by phospholipid fatty acid prof iles. Key words: Microbial community, phospholipid fatty acid profiles, hog manure, corn, forage
Optimizing sampling allocation for detecting management effects on soil CO2 emissions
Authors: Wang H. , Clarke F. , Curtin D. , Lemke R.
Published: April 2011

Measurement of soil CO2 flux is an important tool for detecting management induced changes in soil C. The objective of this study was to analyze sources of variability of a recently published CO2 flux dataset to identify a sampling protocol with optimal allocation of replication, sub-sample and treatment numbers for detecting treatment differences. The dataset comprised daily CO2 flux measurements from a long-term study with treatments of conventional tillage (CT) and no-till (NT) under continuous wheat (CONT) and fallow-wheat rotation (F-W) in a randomized complete block design (RCBD) with four blocks. PROC MIXED in SAS was used to estimate variances. The standard error of the difference (SED) between two treatment means was used as the precision indicator. Although increasing the number of replications effectively reduced SED, sub-sampling also often improved detection of treatment differences because sub-sample variance (σ2δ) was higher than experimental unit variance (σ2ε) on most sampling days. When treatments with small CT vs. NT difference were excluded, degrees of freedom for treatment effects were reduced and both variances were generally increased or unchanged, resulting in increased requirement for sub-sampling. Based on the selected dataset, we produced graphs showing the number of days on which a CT vs. NT difference of 0.3 µmol CO2 m-2 s-1 could be detected at P < 0.10 as a function of replication, sub-sample and treatment numbers. This approach may be used as a guide to optimize sample allocation in similar studies, though site- and experiment-specific factors (e.g., spatial and temporal variability of CO2 flux, size of treatment difference to be detected, the required confidence level) should also be considered. Key words: Carbon dioxide emissions, tillage, variance, wheat
Mechanical disturbance impacts on soil properties and lodgepole pine growth in British Columbia’s central interior
Authors: Blouin V. M. , Schmidt M. G. , Bulmer C. E. , Krzic M.
Published: April 2011

Forest landings are areas located adjacent to haul roads where harvested trees that were skidded from the cutblock are processed and loaded onto trucks. Soils on landings are often excessively compacted by heavy timber harvesting machinery and may take many years to recover from such disturbance. This study examined soil properties and tree growth on unrehabilitated landings (with and without natural regeneration) and adjacent naturally regenerated clearcuts in the central interior of British Columbia (BC), 23 yr after landing construction. Landings (both with and without natural regeneration) had less favorable conditions for tree growth than did clearcuts, including significantly greater surface soil bulk density and mechanical resistance (on some dates) and lower total porosity and concentrations of C and N. Landings without natural regeneration had the least favorable soil conditions, which may account for the lack of natural regeneration. Lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) growing on portions of the landings did not differ in height from those growing in adjacent clearcuts. Site index, as estimated using the growth intercept method, did not differ between naturally regenerated landings (21.7 m) and clearcuts (22.0 m), suggesting that the soils may be equally capable of supporting productive forests. Key words: Forest soil disturbance, soil mechanical resistance, soil productivity, soil water content, natural regeneration