Alberta Soils Research Articles

Simplified Microtox® bioassay for drilling waste disposal on lease soils in Alberta

Ashworth, J. and Symonds, C. 2013. Simplified Microtox ® bioassay for drilling waste disposal on lease soils in Alberta. Can. J. Soil Sci. 93: 109–111. The Microtox bioassay is specified in regulations governing drilling waste disposal in western Canada. Traditionally, four serial dilutions of waste-derived fluid are tested, to bracket the regulatory Pass threshold concentration. We find that an equally valid Pass/Fail result can be obtained from one test at the threshold concentration. The simplified method has labour and cost-saving advantages.

Soil pH has contrasting effects on gross and net nitrogen mineralizations in adjacent forest and grassland soils in central Alberta, Canada

Soil pH can be affected by land use change and acid deposition and is one of the primary regulators of nutrient cycling in the soil. In this study, two soils from adjacent forest and grassland sites in central Alberta were subjected to different pH treatments to evaluate the short-term effects of pH on soil gross N transformations using the 15N tracing technique and calculated by the numerical model FLUAZ. For the forest soil, gross NH4+ immobilization increased faster than gross N mineralization rates with increasing soil pH, leading to a declining pattern in net N mineralization rates; however, none of those rates changed with pH in the grassland soil. In contrast, the increase in pH significantly stimulated gross and net nitrification rates while soil acidification decreased gross and net nitrification rates for both the forest and grassland soils. The ratio of gross nitrification to gross NH4+ immobilization rates (N/IA) was significantly increased by KOH addition but declined to nearly zero by HCl addition for each soil. The low and high KCl addition treatments partially or completely inhibited gross nitrification rates, respectively, but gross mineralization was less sensitive to salt additions than the nitrification process. We conclude that based on the short-term laboratory incubation experiments both pH and salt (osmotic effect) affected gross N transformations and pH had contrasting effects on gross and net nitrogen mineralization but not on nitrification in the adjacent forest and grassland soils.

Relationship between ammonia oxidizing bacteria and bioavailable nitrogen in harvested forest soils of central Alberta

Forest soils are commonly limited in nitrogen (N), and the removal of aboveground biomass in harvesting operations can exacerbate the problem. Thus, the soil organisms that facilitate the rate-limiting step in the N cycle, the oxidation of ammonium (NH 4 +), are of special interest in harvested environments. The objective of this study was to investigate the changes in ammonia oxidizing bacteria (AOB) communities that occurred in the years following clear cutting, and link those community shifts to availability of inorganic N forms NH 4 + and nitrate (NO 3 −). Genetic fingerprinting targeting the amoA gene coupled with denaturing gel gradient electrophoresis was carried out over two summers on forest floor (LFH) and mineral (Ae) soils of three similar cutblocks harvested during different years. In- situ NH 4 + and NO 3 − availability was measured over the growing seasons of 2009 and 2010, as well as a suite of physical soil characteristics. Results indicated that the AOB community composition differed in younger vs. older cutblocks, but not by soil horizon. The changes seen in the AOB paralleled the change in N bioavailability across sites, soil horizons, and sampling years, thus indicating that N bioavailability may be directly linked to AOB community composition. This link may provide the basis for the use of AOB as indicators of nutrient availability in the future.

Accumulation and redistribution of residual chloride, nitrate, and soil test phosphorus in soil profiles amended with fresh and composted cattle manure containing straw or wood-chip bedding

Miller, J. J., Beasley, B. W., Drury, C. F. and Zebarth, B. J. 2011. Accumulation and redistribution of residual chloride, nitrate, and soil test phosphorus in soil profiles amended with fresh and composted cattle manure containing straw or wood-chip bedding. Can. J. Soil Sci. 91: 969–984. Limited research has compared the effect of fresh versus composted beef (Bos taurus) cattle feedlot manure containing straw or wood chips on accumulation and redistribution of residual chloride (Cl), NO3-N, and soil test P (STP) in soil profiles of the Great Plains region of North America. Barley (Hordeum vulgare L.) was grown (1999–2007) on an irrigated clay loam soil in southern Alberta where organic amendments and fertilizer were annually applied for 9 yr from 1998 to 2006. The field experiment was a factorial arrangement of two manure types (fresh versus composted feedlot manure), two bedding materials (straw versus wood-chips), and three application rates (13, 39, 77 Mg ha−1dry wt). There was also one inorganic (IN) fertilizer treatment and an unamended control. The soil profile (0–1.5 m) was sampled in the fall of 1999 to 2002, 2004, 2006, and 2007 and analyzed for residual soil NO3-N, Cl, and STP. Manure type had a significant (P≤0.05) effect on the accumulation of these chemicals, but there was an interaction with application rate (NO3-N), or with bedding and year (STP). The maximum accumulation of Cl after 9 yr was at the 0.6 to 0.9 m depth, but mean values at this depth were similar for the four organic amendments. The maximum accumulation of NO3-N after 9 yr (2007) was at the 0.3 to 0.6 m depth, and mean values at this depth were significantly greater by four- to sixfold for FM and CM with straw than wood-chips, which suggested greater N immobilization in soils with wood. Redistribution of Cl and NO3-N downward into the soil profile suggested a potential for leaching of these chemicals below the root zone. In contrast, soil test P did not accumulate below the 0.3 m depth, suggesting little potential for leaching. However, accumulation of soil test P at this depth was generally greater for the amendment treatments compared with inorganic fertilizer and was likely related to greater P applied in the amendments.

Soil moisture effects on gross nitrification differ between adjacent grassland and forested soils in central Alberta, Canada

Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates. A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity, WHC) on gross N transformation rates using the 15N tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta, Canada. Gross N mineralization and gross NH 4 + immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg-1 soil d-1 in the grassland and forest soils, respectively, at 100% WHC, but were not different from zero at 65% WHC. In the forest soil, both the ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) and cumulative N2O emission were lower in the 65 than in the 100% WHC treatment, while in the grassland soil, the N/IA ratio was similar between the two soil moisture content treatments but cumulative N2O emission was lower at 65% WHC. The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N2O emissions in both soils.

The origin and significance of pedogenic dolomite from the Upper Permian of the South Urals of Russia

AbstractPedogenic carbonate nodules from six sections spanning the continental Permian–Triassic boundary in the South Urals, Russia, were analysed. Morphological, petrographic, SEM and XRD analyses have demonstrated that many of the latest Permian palaeosols are dolomitic. This dolomite forms the microcrystalline (5–16 μm) groundmass of the nodules. Later diagenetic phases, represented by coarser crystalline textures, were identified as calcite. Isotopic analysis of the microcrystalline dolomite has revealed it to be similar in isotopic composition to authigenic dolomite forming today in saline soils in Alberta, Canada. These data indicate that the dolomite found in these nodules is pedogenic, and formed in equilibrium with the atmosphere. Upper Permian pedogenic dolocretes in the studied sections are most frequent in (a) palaeosols that formed on palaeo-highs and (b) in the latest Permian period (Changhsingian), which may indicate that there was an increase in seasonality and evaporation in the South Urals region at this time. The presence of only calcitic palaeosols in the earliest Triassic may reflect a subsequent dramatic change in the basin conditions, possibly relating to the Permian–Triassic mass extinction, which stopped the conditions that are necessary for dolomite formation.

Evaluation of elemental depletion weathering rate estimation methods on acid-sensitive soils of north-eastern Alberta, Canada

Immobile element-based weathering estimation methods assume that Zr (or Ti) is an immobile element, and that weathering rates of other elements can be estimated according to the enrichment of Zr in weathered horizons relative to an unweathered parent material. This approach was used to estimate base cation weathering rates for 33 soil profiles on acid-sensitive terrain in north-eastern Alberta. Zirconium generally showed enrichment within the rooting zone, but the deepest (subsoil) samples were not always associated with the lowest Zr concentrations. Weathering rates estimated with the Zr depletion and Pedological Mass Balance (PMB) methods were generally low (ranges: 0–51 and 0–58 mmol c m − 2 yr − 1 , respectively); however, low base cation oxide concentrations and heterogeneity within soil profiles complicated weathering rate calculations and net base cation gains were calculated for several (six) sites. Evaluation of the Zr depletion and PMB weathering estimates against those calculated with the process-oriented PROFILE model at a subset (n = 9) of the sites indicated the estimates were poorly related, with PROFILE rates typically being higher. The effects-based emissions management strategy for acid precursors in this region requires spatial coverage of soil properties (including weathering rates) across a large area, but the apparent limitations associated with the immobile element based methods in this region: identifying representative parent soils and deriving weathering rate estimates comparable to more robust methods are arguments against their candidacy for future use.

Nitrous oxide emissions from Chernozemic soils amended with anaerobically digested beef cattle feedlot manure: A laboratory study

Biogas production from beef cattle (Bos taurus) feedlot manure results in co-generation of anaerobically digested manure (ADM), a nutrient rich substrate with a solid fraction (SS) often applied to cropland. Application of SS to cropland may result in lower N2O emissions than raw manure due to biochemical changes occurring during anaerobic digestion. We tested this hypothesis using a laboratory incubation study in which N2O fluxes from two Alberta soils, being a Dark Brown Chernozem clay loam (Typic Haploboroll) and a Black Chernozem silty clay (Typic Haplocryoll) amended with raw beef cattle feedlot manure, SS, pelletized SS (PSS), and urea+monoammonium phosphate (UMP) were measured over 10weeks. Amendments were applied at rates corresponding to 100 and 200kgN/ha, with a 0N control included for comparison. Amended soils were maintained near 70% of field capacity moisture content and incubated for 10weeks at 22°C. Gas samples were collected 0, 3 and 7days after the start of the incubation and weekly thereafter for N2O and CO2 analysis by gas chromatography. The N2O fluxes differed among amendments with the differences dependent on soil, amendment application rate, and time. Across amendment rates, mean cumulative emissions from SS- (2.38mgN/kg) and UMP amended soils (0.59mgN/kg) did not differ, but were both lower than emissions from PSS amended soils (10.7mgN/kg) and those from the higher manure rate (15.6mgN/kg). The high N2O emissions from PSS amended soils were likely due to the concentrated microsites of N in pellets. A difference in cumulative N2O emissions between PSS and SS only occurred in Black Chernozem. Microbial activity as indicated by cumulative CO2 fluxes was highest in SS amended (6.7gCO2-C/kg) and lowest in UMP amended soils (0.14gCO2-C/kg). Post-incubation net mineral N content was highest in manure amended soils (144mgN/kg), marginal in SS amended soils (23mgN/kg), and lowest in PSS amended soils that had net N immobilization (−67mgN/kg) due to low available N content in the pellets. Results suggest that field application of SS may reduce N2O emissions relative to raw manure.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Available nitrogen and phosphorus in soil amended with fresh or composted cattle manure containing straw or wood-chip bedding

Limited research exists on the effect of fresh versus composted beef cattle manure containing straw or wood chips on available N and P in the Great Plains region of North America. Barley was grown (1999-2007) on an irrigated clay loam soil in southern Alberta where organic amendments and fertilizer were applied annually for 9 yr from 1998 to 2006. The treatments were three rates (13, 39, 77 Mg dry wt. ha-1) of fresh manure (FM, stockpiled for up to 2 m) or composted manure (CM) containing either straw (ST) or wood chip (WD) bedding, one inorganic (IN) fertilizer treatment, and a unamended control. The soil was sampled in the fall of 1999 to 2002, 2004, 2006, and 2007 and was analyzed for soil inorganic N (SIN), NO3-N, NH4-N, and soil test P (STP). Soil mineralizable N was also determined on surface soil samples collected from 1999, 2002, 2004, and 2007. Manure type had a significant effect on SIN, NO3-N, STP, and soil mineralizable N, but the effects varied with year or bedding and rate (SIN), rate or year (NO3-N), rate and year (soil mineralizable N), or bedding and year (STP). Analysis of covariance for total N or P applied versus SIN or STP after nine applications (2007) indicated greater N release for FM and CM bedded with straw than with wood, whereas P release was similar for FM and CM with straw or wood. Soil NO3-N for the organic amendments exceeded the maximum agronomic limit of 21 mg NO3-N kg-1 for Alberta after 6, 4, and 3 yr of application at the three increasing application rates. The STP for the organic amendments exceeded the maximum agronomic limit of 60 mg kg-1 for Alberta after 4, 2, and 2 yr of application at the three increasing rates. Overall, manure type and bedding material influenced the potential for nutrient losses to the environment through accumulation of soil inorganic N and soil test P; however, their effects on nutrient accumulation varied with year and application rate. Key words: Soil available nitrogen, soil available phosphorus, fresh manure, composted manure, mineralizable N

Barley Yield and Nutrient Uptake for Soil Amended with Fresh and Composted Cattle Manure

Limited research exists on the long‐term effect of fresh (FM) versus composted manure (CM) from beef cattle on barley (Hordeum vulgare L.) yield and nutrient uptake. Barley was grown (1999–2007) as silage on an irrigated clay loam soil in southern Alberta where organic amendments and fertilizer were annually applied for 9 yr in the fall of 1998 to 2006. The treatments were three rates (13, 39, 77 Mg ha−1 dry wt.) of FM or CM containing either straw or wood‐chip bedding, one inorganic fertilizer treatment, and a nonfertilized control. Nine years of annual application of FM and CM resulted in similar aboveground dry matter yield, and total N and total P uptake compared with inorganic fertilizer. However, apparent nitrogen recovery (ANR) and phosphorus recovery (APR) were significantly lower for FM and CM (5–9%) than inorganic (22–47%). Barley dry matter yield, ANR, and APR were similar for FM and CM. Manure type influenced N and P uptake, but the effects varied with bedding type and year. The N and P uptake were greater for CM with straw than the other three treatments except FM with straw. The DM yield was similar for straw and wood bedding, but ANR was greater for straw (10%) than wood (7%). Bedding influenced N uptake, P uptake, and APR, but the effects varied with manure type, rate, and year. Based on the results of this study, producers converting from FM to CM, or from straw to wood‐chip bedding, should suffer no loss in barley silage production.

Soil microbial response to wood ash or lime applied to annual crops and perennial grass in an acid soil of northwestern Alberta

More than 90% of acid soils in western Canada are in Alberta, yet the use of agricultural lime is limited because it is expensive. Wood ash, a by-product of pulp and lumber mills, can be used for liming acid soils. We investigated the effects of amending an acid Luvisol with wood ash or lime on soil microbiological properties at Beaverlodge, Alberta. Both soil amendments were applied at a calcium carbonate rate of 6.72 t ha-1, which was 8.40 t ha-1 for wood ash and 7.47 t ha-1 for lime, in 2002. Soil microbial biomass C (MBC) and the functional diversity and community structures of soil bacteria (indicated by substrate utilization patterns) were measured from 2002 to 2005 under barley (Hordeum vulgare L.), canola (Brassica napus L.), field pea (Pisum sativum L.), and timothy grass (Phleum pratense L.). In the rhizosphere, wood ash increased soil MBC between 2.4-fold in 2002 and 1.3-fold in 2005, and lime increased MBC from 3.2-fold in 2002 to 1.3-fold in 2005. In bulk soil, the increases in MBC ranged from 3.0-fold in 2003 to 1.8-fold in 2005 for wood ash, and from 4.9-fold in 2002 to 2.0-fold in 2005 for lime. Crop effects on MBC were not consistent. Because annual crops were grown in rotation, it is possible that the results obtained in one crop were confounded by effects of the preceding crop. In 2003 and 2004, both amendments increased Shannon index (H’) of bacterial functional diversity in the rhizosphere, and similar results were observed in 2005 in bulk soil. Shifts in the functional structure of bacterial communities due to soil amendment were observed in bulk soil, and shifts due to crop effects were observed in the rhizosphere. In 2003, the average soil pH(CaCl2) increased from 4.91 in control treatments of different crops to 6.60 in lime-amended plots and 6.70 in wood ash-amended plots. In 2004, both wood ash and lime significantly increased soil C mineralization (up to 10 d incubation), but basal respiration (11-24 d incubation) was not affected. The large effect (up to about fivefold) of soil amendments on MBC implies that soil acidity is a major limiting factor for biological processes and the productivity of some Luvisolic soils in Alberta. Wood ash could be used to alleviate these limitations. Key words: C mineralization, microbial diversity, microbial biomass, soil amendment, soil acidity

The green manure value of seven clover species grown as annual crops on low and high fertility temperate soils

Annual and perennial clover species may differ in green manure value. Seven clover (Trifolium) species were grown as annual crops on low fertility (Breton) and high fertility (Edmonton) soils in Alberta. Four annual clovers [balansa (T. michelianum Savi), berseem (T. alexandrinum L.), crimson (T. incarnatum L.), and Persian (T. resupinatum L.)], three perennial clovers [alsike (T. hybridum L.), red (T. pratense L.), and white Dutch (T. repens L.)] and a non-legume reference crop [fall rye (Secale cereale L.)] were ploughed-down as green manure in autumn, and followed by barley (Hordeum vulgare L.). Annual clovers had greater biomass yields than perennial clovers, and berseem clover had the highest yield. At Breton, mean biomass N content was greater for perennial clovers (2.9 g N kg-1) than annual clovers (1.9 g N kg-1). Clover biomass at Breton yielded an average of 77 kg N ha-1, with N derived from the atmosphere averaging 88% by N difference method and 75% by 15N natural abundance method. At Edmonton, the green manures had few effects on soil nitrate and subsequent barley yields. At Breton, all clover green manures except balansa increased barley yields, and grain yields were greater following perennial clovers than annual clovers in one year. Annual clovers will provide forage biomass and add N in areas where rainfall is adequate, and they may be preferable under zero tillage. However there is no advantage of annual clovers, relative to perennial clovers, in terms of N supply.Key words: Green manure, clover, Trifolium species, nitrogen fixation

Effects of compaction on aeration and morphology of boreal forest soils in Alberta, Canada

Poor soil aeration is a factor limiting the productivity of boreal forests in western Canada. Soil compaction reduces air-filled porosity, which is hypothesized to further restrict soil aeration. Soil morphology at nine clearcut sites in west-central Alberta that had been significantly compacted by ground-based harvesting equipment and soil in an adjacent non-trafficked control were related to air-filled porosity and redox regimes. A warm-season air-filled porosity of about 0.1 m3 m-3 separated soils having adequate or restricted aeration, and was confirmed by redox < 200 mV. The values applied to both the undisturbed and compacted soil. Ratios of Feo:Fed and acid-soluble Fe:Mn in concretions were only associated with hydromorphism of undisturbed soil. Compaction reduced soil aeration for 3–4 yr after harvesting, and changed morphology of moderately well-drained soil to imperfectly drained soil at two of four sites; faster removal of water because of slope or vegetation probably prevented changes at the other two sites. Morphology of better and poorer drained soils was not altered by compaction because they either remain adequately aerated or aeration was naturally restricted. Sites with moderately well-drained soils are most at risk of detrimental soil compaction and in need of protective measures to maintain their productivity in these forests. Key words: Soil morphology, drainage class, air-filled porosity, soil aeration, redox potential, boreal forest soils, compaction

Selection and establishment of Alberta agricultural soil quality benchmark sites

Forty-three benchmark sites were established to monitor soils across the agricultural regions of Alberta. Soil chemical and physical properties were examined in an initial pedological investigation in 1997. This paper describes site selection and presents results from the initial pedological investigation. Ninety-five percent of the chosen sites were representative of their provincial ecodistrict, with only two profiles being darker and higher in organic carbon than expected. The majority of selected sites were gently undulating loam soils on morainal parent materials in the dryland regions of Alberta. Soil texture, cation exchange capacity, calcium carbonate content, and soil pH reflected regional differences in quaternary geology and agricultural practices across Alberta. Southern Alberta was characterized by high pH, sandier-textured soil profiles, whereas the Peace Lowlands, being derived from marine shale deposits, exhibited finer soil textures and higher cation exchanges capacities. Owing to climatic and vegetative differences, organic carbon levels were significantly greater in northern Alberta compared with the south, but were found to differ based on soil horizon and slope position. Upper slopes typically had lower organic carbon levels, particularly in the A horizon. Similar results were observed for total soil N, although other soil nutrients differed in relation to soil properties, slope and ecoregion. Data collected will provide: (a) the basis for a detailed Alberta soil quality assessment, (b) data for future modeling efforts, and (c) data necessary to identify temporal changes in soil properties, yield and management relationships. Key words: Agronomic practices, catena, ecodistrict, pedological investigation, soil landscape, soil quality

Degradation of [carboxyl- 14C] 2,4-D and [ring-U- 14C] 2,4-D in 114 agricultural soils as affected by soil organic carbon content

This study compared the degradation of [carboxyl- 14C] 2,4-dichlorophenoxyacetic acid (2,4-D) (C2,4-D) and [ring-U- 14C] 2,4-D (R2,4-D) in 114 agricultural soils (0–15 cm) as affected by 2,4-D sorption and soil properties (organic carbon content, pH, clay content, carbonate content, cation exchange capacity, total microbial activity). The sample area was confined to Alberta, Canada, located 49–60° north longitude and 110–120° west latitude and soils were grouped by soil organic carbon content (SOC) (0–0.99%, 1–1.99%, 2–2.99%, 3–3.99% and >4% SOC). Degradation rates of C2,4-D and R2,4-D followed first-order kinetics in all soils. Although total microbial activity increased with increasing SOC, degradation rates and total degradation of C2,4-D and R2,4-D decreased with increasing SOC because of increased sorption of 2,4-D by soil and reduced bioavailability of 2,4-D and its metabolites. Rates of R2,4-D degradation were more limited by sorption than rates of C2,4-D degradation, possibly because of greater sorption and formation of bound residues of 2,4-D metabolites relative to the 2,4-D parent molecule. Based on the sorption and degradation parameters quantified, there were two distinct groups of soils, those with less than 1% SOC and those with greater than 1% SOC. Specifically, soils with less than 1% SOC had, on average, 2.4 times smaller soil organic carbon sorption coefficients and 1.4 times smaller 2,4-D half-lives than soils with more than 1% SOC. In regional scale model simulations of pesticide leaching to groundwater, covering many soils, input parameters for each pesticide include a single soil organic carbon sorption coefficient and single half-life value. Our results imply, however, that the approach to these regional scale assessments could be improved by adjusting the values of these two input parameters according to SOC. Specifically, this study indicates that for 2,4-D and Alberta soils containing less than 1% SOC, the 2,4-D pesticide parameters obtained from generic databases should be divided by 2.5 (soil organic carbon sorption coefficient) and 1.5 (half-life value).

Phosphorus Losses in Simulated Rainfall Runoff from Manured Soils of Alberta

Manure applied to agricultural land at rates that exceed annual crop nutrient requirements can be a source of phosphorus in runoff. Manure incorporation is often recommended to reduce phosphorus losses in runoff. A small plot rainfall simulation study was conducted at three sites in Alberta to evaluate the effects of manure rate and incorporation on phosphorus losses. Treatments consisted of three solid beef cattle manure application rates (50, 100, and 200 kg ha(-1) total phosphorus), an unmanured control, and two incorporation methods (nonincorporated and incorporated with one pass of a double disk). Simulated rain was applied to soils with freshly applied and residual (1 yr after application) manure at 70 mm h(-1) to produce 30 min of runoff. Soil test phosphorus (STP), total phosphorus (TP), and dissolved reactive phosphorus (DRP) concentrations in runoff increased with manure rate for fresh and residual manure. Initial abstraction and runoff volumes did not change with manure rate. Initial abstraction, runoff volumes, and phosphorus concentrations did not change with manure incorporation at Lacombe and Wilson, but initial abstraction volumes increased and runoff volumes and phosphorus concentrations decreased with incorporation of fresh manure at Beaverlodge. Phosphorus losses in runoff were directly related to phosphorus additions. Extraction coefficients (slopes of the regression lines) for the linear relationships between residual manure STP and phosphorus in runoff were 0.007 to 0.015 for runoff TP and 0.006 to 0.013 for runoff DRP. While incorporation of manure with a double disk had no significant effect on phosphorus losses in runoff from manure-amended soils 1 yr after application, incorporation of manure is still recommended to control nitrogen losses, improve crop nutrient uptake, and potentially reduce odor concerns.

Discovery of a North American genetic variant of the entomopathogenic fungus Metarhizium anisopliae var. anisopliae pathogenic to grasshoppers

A genetic variant of the entomopathogenic fungus Metarhiziumanisopliae var. anisopliae, isolated from a soil in Alberta, Canada, from a location with a history of severe grasshopper infestations, was evaluated for pathogenicity in bioassays of living grasshoppers. Mortality in treated individuals drawn from a laboratory colony was 99% (LT50 = 6.7 days, LT90 = 9.6 days) at 12 days post-inoculation compared to 100% (LT50 = 4.1 days, LT90 = 5.8 days) mortality at 8 days in insects exposed to a commercial isolate of M. anisopliae var. acridum (IMI 330189). Experimental infection of field-collected grasshoppers under laboratory conditions with the native isolate of M. anisopliae var. anisopliae resulted in 100% (LT50 = 4.4 days, LT90 = 5.4 days) mortality attained within 7 days compared to 100% (LT50 = 4.7 days, LT90 = 6.3 days) mortality in 9 days in insects treated with M. anisopliae var. acridum. Amplification of fungal genomic DNA from the indigenous isolate with primers for the specific detection of M. anisopliae var. anisopliae produced a product almost 300 bp larger than expected based on previously known isolates. This is the first demonstration of a highly virulent, indigenous non-chemical control agent of grasshoppers in North America.

The influence of 12 years of tillage and crop rotation on total and labile organic carbon in a sandy loam soil

Information on which management practices can enhance soil organic matter (SOM) content and quality can be useful for developing sustainable crop production systems. We tested the influence of 12 years of no-till (NT) versus conventional tillage (CT), and four crop sequences on the organic C pools of a Grey Luvisolic sandy loam soil in northwestern Alberta, Canada. The crop sequences were: continuous wheat ( Triticum aestivum L.), field pea ( Pisum sativum L.)–wheat–canola ( Brassica rapa L.)–wheat, red clover ( Trifolium pratense L.) green manure–wheat–canola–wheat/red clover and fallow–wheat–canola–wheat. Soil samples from 1992, when the study was initiated, and 1996, 2000 and 2004 were analyzed for total organic C (TOC), the light fraction (LF) and its C content, and water-soluble and mineralizable C. Total organic C in the top 15 cm of soil was higher in the red clover rotation than either the pea or fallow rotation by 1996. The tillage effect became significant only in 2004 with NT having a higher TOC than CT. The LF dry matter (DM) increased from 6.9 g kg −1 soil in 1992 to a range of 10–13 g kg −1 in 2000 and 2004. It was higher under NT than CT in 2 of 3 years and in the red clover rotation than the pea or fallow rotation in 1 of 3 years. The LF C content exhibited a similar trend as LF DM. The water-soluble and mineralizable C pools were not affected by tillage but decreased with time. Among crop rotations, the red clover rotation tended to result in higher levels of hot water-soluble and mineralizable C. It is concluded that tillage had a greater influence than crop rotation on the LF DM and LF C (as indicators of C storage), whereas the converse effect applied to mineralizable C and, to a lesser degree, hot water-soluble C (as indicators of SOM quality).

Degree of Phosphorus Saturation Thresholds in Manure‐Amended Soils of Alberta

The risk of P losses from agricultural land to surface and ground water generally increases as the degree of soil P saturation increases. A single-point soil P sorption index (PSI) was validated with adsorption isotherm data for determination of the P sorption status of Alberta soils. Soil P thresholds (change points) were then examined for two agricultural soils after eight annual applications of different rates of cattle manure and for three agricultural soils after one application of different rates of cattle manure. Linear relationships were found between soil-test P (STP) levels up to 1000 mg kg(-1) and desorbed P in the five Alberta soils. Weak linear relationships were also found between STP and runoff dissolved reactive phosphorus (DRP) in three of these soils. Change points for the degree of P saturation (DPS) were detected in four of the five soils at 3 to 44% for water-extractable P (WEP) and at 11 to 51% for CaCl(2)-extractable P (CaCl(2)-P). Change points were not found for DPS or runoff DRP. Overall DPS thresholds for the five soils combined were 27% for WEP and 44% for CaCl(2)-P at a critical desorbable-P value of 1 mg L(-1). The corresponding STP levels (44 mg kg(-1) for WEP and 71 mg kg(-1) for CaCl(2)-P) are similar to agronomic thresholds for crops grown on Alberta soils. Soluble P losses in overland flow and leaching may be greater in soils with DPS values that exceed these thresholds than in soils with lower DPS values.

Determining Phosphorus Release Rates to Runoff from Selected Alberta Soils Using Laboratory Rainfall Simulation

Phosphorus losses from agricultural land can cause accelerated eutrophication of surface water bodies. This study evaluated the use of soil test phosphorus (STP) levels to predict dissolved inorganic phosphorus (DIP) concentrations in runoff water from agricultural soils using laboratory rainfall simulation. The objectives of this study were to determine (i) to what extent STP concentrations can be used as a basis to predict P losses from Alberta soils and (ii) how extended rainfall simulation run times affected DIP losses. Soil samples collected from a total of 38 field sites, widely scattered throughout the southern half of Alberta, were subjected to rainfall simulation in the laboratory. The STP concentrations were determined using Miller-Axley, Norwest, Kelowna, Modified Kelowna Mehlich-III, and distilled water extraction methods. Each rainfall simulation event lasted for at least 90 min. Runoff samples were collected in time series for the duration of each simulation, during two distinct runoff intervals: (i) for the first 30 min of continuous runoff (T30) and (ii) for 40 min during runoff equilibrium (Teq). For all the STP extractants and both runoff intervals, the relationship with DIP-flow-weighted mean concentration (FWMC) was linear and highly significant with r2 values ranging from 0.74 to 0.96. However, the slopes of the resulting regression lines were, on average, 1.85 times greater for the T30 runoff interval over those computed for the Teq interval. Thus experimental methodology greatly influenced regression parameters, suggesting that more work was needed to verify these relationships under natural conditions. In addition, with many of the r2 values greater than 0.90 there would be little, if any, benefit derived by including soil properties in regression analysis.