bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of soil nitrogen supply in potato fields using a plant bioassay approach
Authors: Zebarth B J , Leclerc Y. , Moreau G. , Sanderson J B , Arsenault W J , Botha E J , Wang-Pruski G.
Published: April 2011

Soil N supply is an important contributor of N to crop production; however, there is a lack of practical methods for routine estimation of soil N supply under field conditions. This study evaluated sampling just prior to topkill of whole potato plants that received no fertilizer N as a field bioassay of soil N supply. Three experiments were performed. In exp. 1, field trials were conducted to test if P and K fertilization, with no N fertilization, influenced plant biomass and N accumulation at topkill. In exp. 2, plant N accumulation at topkill in unfertilized plots was compared with mineral N accumulation in vegetation-free plots. In exp. 3, estimates of soil N supply were obtained from 56 sites from 1999 to 2003 using a survey approach where plant N accumulation at topkill, and soil mineral N content to 30-cm depth at planting and at tuber harvest were measured. Application of P and K fertilizer had no significant effect on plant N accumulation in two trials, and resulted in a small increase in plant N accumulation in a third trial. Zero fertilizer plots, which can be more readily established in commercial potato fields, can therefore be used instead of zero fertilizer N plots to estimate soil N supply. In exp. 2, estimates of soil N supply were generally comparable between plant N accumulation at topkill and maximum soil NO3-N accumulation in vegetation-free plots; therefore, the plant bioassay approach is a valid means of estimation of plant available soil N supply. Plant N accumulation at topkill in exp. 3 averaged 86 kg N ha-1, and ranged from 26 to 162 kg N ha-1. Plant N accumulation was higher for sites with a preceding forage crop compared with a preceding cereal or potato crop. Plant N accumulation was generally higher in years with warmer growing season temperatures. Soil NO3-N content at harvest in exp. 3 was less than 20 kg N ha-1, indicating that residual soil mineral N content was low at the time of plant N accumulation measurement. Soil NO3-N content at planting was generally small relative to plant N accumulation, indicating that soil N supply in this region is controlled primarily by growing season soil N mineralization. Use of a plant bioassay approach provides a practical means to quantify climate, soil and management effects on plant available soil N supply in potato production. Key words: Solanum tuberosum, nitrate, ammonium, N mineralization, plant N accumulation
Soil diversity and properties in mountainous subtropical areas, in Sierra Sur de Oaxaca, Mexico
Authors: García Calderón N. E. , Ibáñez Huerta A. , Alvarez Arteaga G. , Krasilnikov P. V. , Hernández Jiménez A.
Published: April 2011

Agroforestry is a new practice of sustainable soil use in the mountainous Sierra Sur de Oaxaca area of Mexico. Coffee is also a common cash crop grown in the region. The objective of this study was to investigate the pedodiversity in the area. Soil development is very complex, and is influenced by slope parameters and parent materials. Several soil groups are found in the area investigated: Alisols, Umbrisols, and Cambisols. Morphology, chemical properties, and mineralogical composition of the clay fraction of these soils were studied. The soils vary in the extent of weathering, morphology, and chemical properties, which are important to farming in the area. Most of the soils have heterogeneous parent material. The distribution of major soil types of the area is related to mass movement along the slopes, both past and present. The studied soils represent a chronosequence from unleached and unweathered Cambisols to Alisols, characterized by strong clay illuviation and dominance of kaolinite and gibbsite in clay fraction. A mosaic of landslides and gullies of various ages, formed by catastrophic events such as earthquakes and hurricanes, form the pedodiversity of the area studied. Key words: Landslides, chronosequence, pedodiversity, Cambisols, Umbrisols, Alisols
The role of crop rotations in determining soil structure and crop growth conditions
Authors: Ball B. C. , Bingham I. , Rees R. M. , Watson C. A. , Litterick A.
Published: April 2011

Increasing concern about the need to provide high-quality food with minimum environmental impact has led to a new interest in crop rotations as a tool to maintain sustainable crop production. We review the role of rotations in the development and preservation of soil structure. After first introducing the types of rotations in current practice and their impact on yield, we assess how soil and crop management in rotations determines soil structure, and in turn how soil structure influences crop growth and yield. We also briefly consider how soil structure might contribute to other beneficial effects of rotations, namely nutrient cycling and disease suppression. Emphasis is given to the influence of crop choice and, where relevant, interaction with tillage system and avoidance of compaction in the improvement and maintenance of soil structure. Crop rotations profoundly modify the soil environment. The sequence of crops in rotation not only influences the removal of nutrients from a soil, but also the return of crop residues, the development and distribution of biopores and the dynamics of microbial communities. These processes contribute to the development of soil structure. We have identified areas where further research is needed to enable the potential benefits of rotations in the management of soil structure to be fully exploited. These include: improved quantitative linkages between soil structure and crop growth, the consequences to soil structure and nutrient cycling of crop residue incorporation, developing natural disease suppression, amelioration of subsoils by crop roots, the fate of carbon deposited by plant roots in soil and the fate of organic nitrogen in soil. Key words: Organic farming, microbial activity, nutrient cycling, compaction, disease suppression, soil structure
Nitrate leaching in the semiarid prairie : Effect of cropping frequency, crop type, and fertilizer after 37 years
Authors: Campbell C A , Selles F. , Zentner R P , De Jong R. , Lemke R. , Hamel C.
Published: April 2011

A high NO3 concentration in drinking water can be a health hazard. Further, leached N represents an economic loss to the producer. Although NO3 leaching to ground water would be minimal on the semiarid prairies, leaching can occur especially where frequent summer fallowing is practiced. We used a crop rotation study, initiated in 1967 on a medium-textured Orthic Brown Chernozem, at Swift Current, Saskatchewan, to determine the influences of fallow frequency, crop types, and fertilizer on nitrate leaching after 37 yr. Nitrate distribution was measured to 4.5 m depth by 0.3-m increments, in 10 cropping systems in fall 2003. We deduced that some NO3 leached beyond the rooting depth (1.2 m) of spring wheat (Triticum aetivium L.), especially under a fallow-wheat rotation receiving N and P fertilizer. The amounts of NO3 leached tended to be greater and to be located deeper in the soil profile as fallow frequency increased (e.g., fallow-wheat > fallow-wheat-wheat > continuous wheat, all receiving N and P fertilizer based on soil test). However, in this semiarid environment, NO3 leaching was not great, being highest under fallow-wheat (N + P) (180 kg N ha-1 leached in 37 yr). In fallow-containing systems inadequate fertilizer N or P resulted in reduced crop growth and N uptake leading to a tendency for greater leaching of the NO3 (about 145 kg N ha-1 in 37 yr) mineralized during the fallow period than when such a system received N and P based on soil tests (about 66 kg N ha-1 leached in 37 yr). In continuously cropped treatments there was little evidence of leaching. Replacing wheat grown on fallow with the shallow-rooted flax (Linum usitatissimum L.) in a fallowwheat-wheat (N + P) rotation resulted in greater NO3 leaching in the flax system (156 vs. 66 kg N ha-1 ) due to less N uptake by flax. In contrast, when the wheat grown on fallow was replaced with fall rye (Secale cereale L.) there was no leaching, perhaps because the fallow period was much shorter (12 mo compared with 20 mo for spring wheat) and also because the fall-seeded crop used soil NO3 in the fall and early spring reducing opportunities for leaching. Key words: Wheat, flax, fall rye, lentil, cropping frequency
Wheat root dynamics as affected by landscape position
Authors: Block R M.A. , Van Rees K C.J.
Published: April 2011

The effects of landscape position on root production and mortality were assessed in a 90-cm-deep soil profile at a shoulder and footslope landscape position seeded to spring wheat (Triticum aestivum L.). Root length was measured over eight sampling dates using a minirhizotron system, and soil water content and temperature were recorded at various depths at each landscape position. The shoulder position was drier than the footslope position in the upper 30 cm due to a greater frequency and duration of soil temperatures > 20°C, and at depth (> 75 cm). Mean root length was greatest at the footslope position and was concentrated in the upper 20 cm of the profile, while the shoulder position had the greatest root length at the 40- to 60-cm depth. Mean daily root production peaked at 5.0 to 6.0 m m-2 d-1 at the 43rd day after planting (DAP) for both landscape positions, which corresponded to the time of booting. Daily rates for root mortality ranged from 0.5 to 2.5 m m-2 d-1. Soil water content and daily root production at the 10-cm depth were positively correlated at both landscape positions. Information on landscape position differences in root productivity and mortality could help to improve placement of inorganic fertilizers, and estimation of below-ground carbon sequestration. Key words: Wheat, roots, minirhizotron, landscape position
Impact of pasture establishment on CO2 emissions from a Vertisol: Consequences for soil C sequestration (Martinique, West Indies)
Authors: Chevallier T. , Blanchart E. , Albrecht A. , Feller C. , Bernoux M.
Published: April 2011

Establishing pasture on cultivated tropical Vertisols can increase soil organic carbon (SOC), but it is not known whether this increase results solely from enhanced inputs or also from suppressed mineralization. We measured CO2 emissions from a Vertisol under market gardening, and under “young” and “old” Digitaria decumbens pastures. Emissions of CO2-C increased in pastures, compared to market gardening, but relative SOC mineralization (CO2-C/SOC) decreased, implying the protection of SOC against mineralization with pasture establishment. Key words: Tropical pasture, carbon fluxes, soil organic carbon, physical protection, C storage
Using automated soil water content measurements to estimate soil water budgets
Authors: McCoy A. J. , Parkin G. , Wagner-Riddle C. , Warland J. , Lauzon J. , von Bertoldi P. , Fallow D. , Jayasundara S.
Published: April 2011

The distribution of precipitation into the components of a soil water budget has a profound impact on crop growth, groundwater recharge, soil erosion, and groundwater and surface water contamination levels. The main objectives of this study were to develop a new method of measuring soil water balances and to demonstrate the use of the method in examining differences between partitioning of water in conventional tillage (CT) and no-tillage (NT) management systems. Hourly precipitation, evapotranspiration, and changes in soil water storage data were collected automatically over a 3-yr period at a field site near Elora, Ontario. Runoff and interception were calculated as the difference between measured increases in soil water storage and total rainfall during each significant rain event when the soil was not frozen. Drainage was then calculated, as it was the only component of the soil water balance not measured. The amount of soil water stored in the NT system was greater than the CT system during the latter part of the study as the NT system aged. The amount of drainage calculated for a 3 -yr period was greater for CT than the NT treatment, a result that is contrary to many previous studies. The measured amount of runoff plus interception was greater in the NT versus CT treatment. Since NT is generally accepted as a means of reducing runoff, this result could be due to the enhanced amount of interception by the crop residue left on the surface of the NT treatment. Key words: Soil water balance, water content reflectometer, drainage, runoff, tillage, time series
Combining subsurface drainage and windbreaks to control dryland salinity
Authors: Steppuhn H.
Published: April 2011

The reclamation of salinized soil involves lowering ground water levels, draining the vadose zone, and leaching the salts from the root zone. Plastic drain tubing placed 1.5 to 1.8 m below the land surface can lower water tables and drain phreatic water, but irrigation is usually required to leach the offending salts. The leaching process in non-irrigated drylands depends on natural precipitation. Rows of tall wheatgrass, Thinopyrum ponticum (Podp.) Lui & Wang, (1.2 m mean height) spaced on 15.2-m centres across saline fields can retain blowing snow, augment water for leaching salts, and moderate evapotranspiration, especially when grown in conjunction with subsurface drainage. The mean salinity of saturated soil paste extracts from sets of soil samples taken every fall from such a site in southwestern Saskatchewan averaged 14.1 dS m-1 during 1985–1990 before the drainage was installed, 13.0 dS m-1 for 1991–1992 after drainage but before the grass windbreaks became established, and 9.6 dS m-1 for 1993–1998 with both drainage and windbreaks in place. Key words: Saline soil, engineered drainage, snow management, grass barriers
Collecting large soil monoliths
Authors: Allaire Suzanne A , Bochove Eric van
Published: April 2011

Large soil monoliths (> 50 kg) are required to study and monitor soil energy and water budget, gas and liquid fluxes, and contaminant transport. This paper reviews the types of studies requiring large soil monoliths, design and material for the casing, and collection methods for vertically forced cylindrical and for block (orthorhombic) monoliths. Methods of extraction are described along with recommendations. Advantages and disadvantages of each method are discussed. Vertically pushed cylindrical monoliths are easier to sample, but compared with orthorhombic monoliths that are not pushed into the soil, the pushing process has the disadvantage of modifying certain soil physical properties. Key words: Large soil samples, intact soil cores, acrylic boxes, soil sampling
Diversity and function of fungi in peatlands: A carbon cycling perspective
Authors: Thormann Markus N.
Published: April 2011

Peatlands are a dominant landform in the northern hemisphere, accumulating carbon in the form of peat due to an imbalance between decomposition and plant production rates. Decomposer (saprobes) and mycorrhizal fungi significantly influence carbon dynamics by degrading organic matter via the synthesis of extracellular enzymes. As organic matter decomposes, litter quality variables figure most prominently in the succession of fungi. Hence, litters composed primarily of complex polymers decompose very slowly. Surprisingly, recalcitrant polymer degraders (mostly basidiomycetes) are rarely isolated from peat, which may explain the accumulation of complex polymers in peat profiles. While enzymatic profiles of mycorrhizal fungi and other root endophytes may be more limited compared with saprobes, many of these fungi can degrade polymers of varying complexity as well and hence may also be significant decomposers of organic matter. To date, anamorphic ascomycetes and zygomycetes are the most frequently isolated fungi from peatlands (63 and 10% of all taxa, respectively), and chytridiomycetes, teleomorphic ascomycetes, and basidiomycetes appear to be less common (11% of all taxa). The remaining 16% of taxa remain unidentified or are sterile taxa. How disturbances affect peatland microbial communities and their roles is virtually unknown. This aspect of peatland microbial ecology requires immediate attention. The objective of this paper is to review the current state of knowledge of the diversity of fungi and their roles in carbon cycling dynamics in peatlands. Key words: Peatlands, fungi, carbon dynamics, diversity, functions, saprobes, mycorrhizas
Inferred history of a boreal pond from sediment and vegetation characteristics
Authors: Nicholson B. J. , Bayley S. E. , Whitehouse H. E.
Published: April 2011

Shallow ponds associated with peatlands in boreal Alberta contain large quantities of stored carbon in their peaty sediments, and exhibit spatial changes in response to dry or wet conditions. Peatland ponds around Utikuma Lake experienced a partial to nearly complete drawdown in 2002, in response to drought. A fourfold investigation was begun to assess the natural drought and flood cycles, assess the current C stocks along the shore, determine what species were colonizing the newly exposed shorelines, and to place the magnitude of the current drought into historical perspective. Ten vegetation communities were found to have colonized the exposed sediments. Paleostratigraphy shows that the surface communities differ markedly from paleocommunities. Stratigraphy of the wetland sediments demonstrates that only two changes occurred, one a successional switch from a sedge-dominated marsh to a forested bog, the other a much more recent disturbance that caused water levels near the pond to rise. No evidence of constantly changing paleocommunities was found, suggesting that previous droughts have not left a visible paleorecord. The more recent disturbance has likely redistributed peat into the pond basins and subsequently it has broken down to detritial peat, altering its physical structure, and perhaps its rate of decomposition. Continued exposure of the peat is likely to enhance decomposition. In this study both flooding and drought may have impacted the wetland in ways likely to result in higher rates of decomposition and enhanced CO2 emissions under global warming. Key words: Peat stratigraphy, Holocene climate, thermokarst melting, detrital peat, carbon stocks
Towards standards for measuring greenhouse gas fluxes from agricultural fields using instrumented towers
Authors: Pattey E. , Edwards G. , Strachan I B , Desjardins R L , Kaharabata S. , Wagner Riddle C.
Published: April 2011

This is a discussion of the available technology for measuring turbulent fluxes using instrumented towers. This review focuses on the flux measurements of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) for agricultural systems and the development of standards and protocols for measuring them. Agroecosystems present unique challenges because they undergo large leaf area index (LAI) and canopy architecture changes in a relatively short period of time (i.e., months) coupled with the fact that many of the greenhouse gas sources are diffuse. This review examines all aspects of the theory and application of the micrometeorological techniques, with focus on the flux gradient, eddy accumulation and eddy covariance techniques. Instrument placement, sens or response and noise characteristics are also explored. Innovative applications of micrometeorological methods are discussed for closed- and open-path trace gas sensors and commonly used meteorological instrumentation. The use of fast response single-pass optical tunable diode laser (i.e., CH4, N2O) and infrared gas analyzers (i.e., CO2, H2O) is described. Consideration is also taken of the trace gas sensors’flow system design, mixing ratio measurement, and data acquisition and reduction requirements for micrometeorological flux measurement. Procedures are outlined for the meteorological instrumentation necessary for eddy covariance-based energy budget measurement including ultrasonic anemometry. Key words: Tower-based greenhouse gas flux measurements, nitrous oxide, methane, carbon dioxide, tunable diode laser
Pulp and paper mill by-products as soil amendments and plant nutrient sources
Authors: Camberato J J , Gagnon B. , Angers D A , Chantigny M H , Pan W L
Published: April 2011

Pulp and paper mill sludges are produced from primary and secondary treatment of wastes derived from virgin wood fiber sources, recycled paper products, and non-wood fibers. Sludges and sludge composts may be utilized in agriculture to increase soil organic matter, improve soil physical properties, provide nutrients, and increase soil pH. Positive effects of primary, deinking, and low-nutrient combined sludges on soil quality are primarily due to increased soil organic matter, aggregation, water holding capacity, infiltration rate, and cation exchange capacity. Nitrogen and P immobilization are often induced by primary and deinking sludges, but can be overcome by delayed planting, adding N and P, planting of legumes, or composting. Improved crop production obtained with secondary treatment sludges is most often attributable to enhanced nutrient availability, particularly N, but improved soil physical properties are implicated in some studies. Pulp and paper mill sludges and sludge composts are useful soil amendments and plant nutrient sources. Key words: Paper mill sludge, soil physical properties, N and P immobilization, nutrient efficiency, land application
Evaluation of LEACHMN for simulating seasonal changes in plant available nitrogen across a variable landscape
Authors: Dadfar H. , Kay B D , Pararajasingham R. , Dharmakeerthi R S , Beauchamp E G
Published: April 2011

A model that accurately simulates the seasonal variation in nitrogen (N) dynamics may represent an important additional tool in N management. The objectives of this study were to evaluate whether seasonal changes in the amount of N that becomes available to a maize crop in a variable landscape can be simulated with LEACHMN and, in particular, to assess the potential value of LEACHMN in estimating N available at the time of the presidedress soil nitrate test (PSNT). Soil mineral N (SMN) and shoot N were measured biweekly over seven growing seasons in corn (Zea Mays L.) grown under conventional tillage in a variable landscape in Southern Ontario, Canada. The model was calibrated using data from 2002 and 2003 from each of five positions in the landscape and then evaluated using data from the 1997–2001 growing seasons. Although the model under-estimated SMN and over-estimated shoot N, the model was more successful in simulating the sum, defined as plant available N (PAN). Simulations of PAN were best at the summit and shoulder positions. The agreement between measured and simulated PAN were poorest early in the season. Although the accuracy of PAN simulations late in the growing season indicates this model has potential value in N management decisions, the errors in simulating SMN early in the season suggest adjustments are required before it can be used, along with other tools, as a substitute for the PSNT in cool humid environments. Key words: Soil mineral N, Plant available N, variable landscapes, LEACHMN
Controlled-release urea for winter wheat in southern Alberta
Authors: McKenzie R H , Bremer E. , Middleton A B , Pfiffner P G , Dowbenko R E
Published: April 2011

The recent development of low-cost controlled-release urea (CRU) may provide additional options for N fertilization of winter wheat (Triticum aestivum L.). Two field experiments were conducted over 3 yr at three locations in southern Alberta to evaluate different options of applying CRU to winter wheat. In the first experiment, three N fertilizers (20-day CRU, 40-day CRU and urea) were seed-placed and side-banded at the time of seeding at 0, 30, 60, 90 and 120 kg N ha-1. Stand densities were substantially reduced by seedrow application of urea at rates greater than 30 kg N ha-1, but were unaffected by seedrow application of CRU, even at the highest rate of N application. When N fertilizer was sidebanded, stand densities were unaffected by fertilizer type or N rate. Yield gains due to N application were reduced by application of high rates of seed-placed urea, but similar for other treatments. Grain protein concentration and N uptake were also similar for CRU and seed-placed urea. In the second experiment, three N fertilizers (CRU, urea and ammonium nitrate) were broadcast at 30 kg N ha-1 in early spring on plots that had received 0, 30 or 60 kg N ha-1 of CRU at the time of seeding. Inadequate release of spring broadcast CRU was indicated by reduced grain protein concentrations relative to conventional N fertilizers. Under the conditions experienced in our study, CRU substantially increased the maximum safe rate of seed-placed urea, provided minimal benefits to N response relative to side-banded urea, and was less effective than conventional N fertilizers when broadcast in early spring. Key words: N fertilizer use efficiency, slow release, winter survival
Development of a Canadian Agricultural Nitrogen Budget (CANB v2.0) model and the evaluation of various policy scenarios
Authors: Yang J Y , De Jong R. , Drury C F , Huffman E C , Kirkwood V. , Yang X M
Published: April 2011

A Canadian Agricultural Nitrogen Budget model was developed to calculate the agro-environmental indicators: Residual soil nitrogen (RSN) and Indicator of Risk of Water Contamination by Nitrogen (IROWC-N) for 3500 polygons of the 1:1 m Soil Landscapes of Canada scale. Residual Soil Nitrogen was calculated for the census years 1981, 1986, 1991, 1996 and 2001. These results were then used in conjunction with climate data to calculate over-winter N loss and its concentration in the drainage water. The main inputs were the acreages, yields and N recommendation rates for major crops, and the types and numbers of livestock. Various coefficients and assumptions were incorporated into the calculations. Validation of the model was carried out using provincial nitrogen sales data, and results showed good agreement between the calculated fertilizer N and the amount of fertilizer N sold in each province in 1996 and 2001. The two indicators were linked to outputs of the economic-based Canadian Regional Agricultural Model in order to assess the impacts of policy scenarios on nitrogen balance. At the national scale, the scenario of improved N fertilization practices reduced the RSN by 13%. RSN was also sensitive to the N2O:N2 ratio resulting from N losses through denitrification. Key words: Landscape nitrogen model, Agri-Environmental Indicator, Soil Landscapes of Canada, Census of Agriculture
Indicator of risk of water contamination by phosphorus: Temporal trends for the Province of Quebec from 1981 to 2001
Authors: Bochove Eric van , Thériault Georges van , Dechmi Farida , Leclerc Marie-Line , Goussard Nadia
Published: April 2011

An indicator of risk of water contamination by phosphorus (IROWC-P) was developed to estimate the risk of phosphorus (P) contamination in water by agriculture, and to evaluate how this risk changes over time based on the census data obtained every 5 yr. For the province of Quebec, IROWC-P is calculated with census data from 1981, 1986, 1991, 1996 and 2001. In 2001, 85% of the Soil Landscapes of Canada (SLC) agricultural polygons of Quebec were in the low and moderate risk classes and the remaining 15% in the high risk class. Although agricultural production statistics show marked changes from 1981 to 2001 in livestock herd composition, area under cultivation, agricultural land use and use of inorganic phosphorus fertilizer and animal manure, no trend was observed in the estimated risk over the same period. Increased risk of P transport from agricultural fields to water is expected when agricultural soils are rich in P or have excess P relative to crop needs and have a high potential for soil erosion and surface runoff. Key words: Risk indicator, water contamination, phosphorus, soil landscapes of Canada, agriculture
Sediment yield and seasonal soil erodibility for semiarid cropland in western Canada
Authors: McConkey B.G. , Nicholaichuk W. , Steppuhn H. , Reimer C. D.
Published: April 2011

Despite its importance to the degradation of the land resource, few estimates of soil loss or soil erodibility for water erosion from cropland have been made for the semiarid Brown soil zone of western Canada. To estimate these, we calibrated the event-based Modified Universal Soil Loss Equation with measured sediment yield for three 5-ha fields near Swift Current, Saskatchewan. The calibration used predetermined C, LS, P, and warm-season K factors with all erositivities and the K factors for other seasons optimized. Using this calibrated equation with 31 yr of measured runoff data, mean annual sediment yield for a conventional-tillage spring wheat-fallow cropping system on an undulating landscape (0 to 5% slopes) was estimated to be 0.8 Mg ha−1 yr−1. Estimated erosion from fallow land from 16 March to 15 April constituted 86% of the mean annual sediment yield. Erosion occurring during rainfall-runoff were relatively unimportant, accounting for about 4% of the estimated total sediment yield. An exceptionally severe rainstorm was predicted to have caused erosion of many Mg ha−1but the frequency of such events on a given field is too low to greatly affect mean annual erosion. Apparent field-scale soil erodibility was least in the winter (November to 15 March) when the soil would typically be frozen to the surface and was greatest in April when the soil would typically be partially frozen. Apparent erodibility in the summer and in late March was intermediate between those values.

Key words: Erosion, runoff, snow, Universal Soil Loss Equation
Age, turnover and molecular diversity of soil organic matter in aggregates of a Gleysol
Authors: Monreal C. M. , Schulten H.-R. , Kodama H.
Published: April 2011

We used an integrated approach to describe soil organic matter (SOM) dynamics through known inorganic and organic components in aggregates of adjacent forested and cultivated Gleysolic soil. Mineral and SOM components were examined in water stable macroaggregates (>250 µm), microaggregates 1 (50–250 µm) and microaggregates 2 (<50 µm) fractions. SOM was characterized by pyrolysis-field ionization mass spectrometry (Py-FIMS), and soil minerals by X-ray diffraction analysis. The mean residence time of organic-C (OC) was determined using radiocarbon dating. OC turnover was determined using the natural abundance of native 13C and that derived from corn residue. We found that OC in macroaggregates was young (<100 yr), turned over in 14 yr, and consisted of OM typical of that found in tissues of plants and soil organisms. Chemical classes of compounds in macroaggregates consisted mainly of carbohydrates, lignin monomers and phenols, lignin dimers, lipids (alkanes, alkenes, n-alkyl esters), fatty acids, sterols, suberin and aliphatic and aromatic N compounds. The fast turnover time of OC in larger size aggregates supports the hypothesis that the initial decline in SOM after breaking native land is associated with losses of SOM stored in macroaggregates. OC in microaggregates 1 was young (<100 yr) and turned over in 61 yr. OC in microaggregates 2 was old, turned over in 275 yr, and consisted of highly humified macromolecules. Pyrolyzable SOM products representing plant and microbial components like lignin dimers, sterols, suberin and fatty acids were absent from microaggregates 2 containing old OC. The turnover time of OC correlated directly with the amount of smectite and Al extracted with ammonium oxalate, inversely with non-expandable phyllosilicates, and weakly with the total clay content of aggregates. Thermolabile and thermostable molecular components in aggregates indicated degree of association between SOM and clay minerals. Carbohydrates, peptides and alkylaromatics appeared to be less affected by abiotic stabilization reactions.

Key words: Soil organic matter, turnover, mean residence time, inorganic soil components, mass spectrometry, macroaggregates and microaggregates
Effet à long terme d'apports d'engrais minéraux et de fumier sur les teneurs en C et en N des fractions densimétriques et des agrégats du loam limoneux Le Bras
Authors: N'Dayegamiye A. , Goulet M. , Laverdière M. R.
Published: April 2011

Long-term mineral fertilizer applications could reduce organic matter (OM) levels in soil if coupled with crop rotations with low organic residues inputs. The main objective of this study was to evaluate the C and N contents in whole soil, in densimetric OM fractions and in different aggregate size fractions of a Le Bras silt loam (Humic Gleysol). The treatments were arranged in a split-plot design, with dairy cattle manure applied at 0 and 20 Mgha−1 as the main factor. The subplots consisted of six fertilizer treatments (NK, PK, NP, NPK, NPKMg and the unfertilized check). The four year rotation included silage corn, (Zea mays L.) silage corn, wheat (Triticum Aestivum L.) and barley (Hordeum vulgaris L.). Contrary to mineral fertilizer, long-term manure applications significantly increased the C content in whole soil and also in the light and heavy fractions of OM (Fl and Fd). Mineral fertilizer significantly increased the C and N contents only in Fl. Moreover, manure application also increased the weight of the 5–8 mm aggregate size fraction and the C and N content in the 5–8 mm, 2–5 mm, 1–2 mm and 0,25–1 mm aggregate size fractions, compared to mineral fertilizer alone. In manured plots, soil C biomass, microbial respiration (CO2) and N mineralization (NO3) levels increased by 30% compared with mineral fertilizer treatments. Results of this study demonstrate the important effect of manure applications on C and N enrichment in soil and also on soil macroaggregation and biological activity. To maintain optimal C and N levels in soil and to favour soil macroaggregation, long-term mineral fertilizer application should be combined with crops in rotations which ensure high organic residues returns to soils.

Key words: Macroaggregation, microbial biomass, N mineralization, long-term, light fraction, heavy fraction
Cadmium and lead concentrations of commercially grown vegetables and of soils in the Lower Fraser Valley of British Columbia
Authors: Pieri L. A. De , Buckley W. T. , Kowalenko C. G.
Published: April 2011

The cadmium (Cd) and lead (Pb) concentrations in various tissues of economically important crops (potato, cabbage, cauliflower, carrot, turnip, corn and lettuce) grown in three regions within the Lower Fraser Valley were examined in a survey study. The objective of the study was to determine the current concentrations of Cd and Pb in Fraser Valley vegetables and vegetable-producing soils as background data for pollution evaluation and reference purposes. Concentrations of both metals in the vegetable tissues and the soils (based on total metal analysis) were similar to those reported for uncontaminated soils of the world. Cadmium in edible parts of vegetables had site means that varied from 0.03 to 1.74 µg g–1 DM, while mean soil Cd in these sites varied from 0.17 to 1.02 µg g−1. Mean Pb in edible parts of vegetables at these sites varied from 0.03 to 0.16 µg g−1 DM, while soils varied from 4.9 to 26.4 µg Pb g–1. Potatoes grown on Spetifore soil series exhibited a high concentration of Cd in the tubers (site mean of 1.74 µg g−1 DM), and coincided with high extractable soil sulphur and sodium contents, which showed the influence of a marine environment on that soil. A comparison between a cultivated and uncultivated adjacent site showed that the soil at the former had almost double the Cd concentration of the latter. The Pb concentration at the two sites did not differ. The increased Cd in the cultivated site coincided with a greater amount of extractable phosphorus and potassium, which may indicate a history of excessive fertilizer application. No clear relationship was observed between total soil and plant tissue concentration for Cd or Pb. Cadmium was more variable in the plant tissues than Pb, particularly in the leaves.

Key words: Cadmium, lead, survey
Overseeding rye into corn reduces NO3 leaching and increases yields
Authors: Ball-Coelho B. R. , Roy R. C.
Published: April 2011

Non-irrigated corn (Zea mays L.) produced on coarse-textured soils during droughty years can result in excess NO3 available for leaching. To evaluate the effect of overseeding cereal rye (Secale cereale L.) into corn on yields, NO3 leaching and a pre-sidedress nitrate test (PSNT), we broadcast rye seed (Aug. 1993, 1994 and 1995) into conventional tillage (CT) and no-tillage (NT) corn receiving six fertilizer N rates. There was no corn yield penalty with the cover crop. Corn grain yields and the extent to which NO3 leaching was reduced by the rye cover depended on rainfall. With the rye (compared with no rye) subsoil solution NO3 concentrations were: unchanged (fall 1994) following above normal rainfall and corn yields; reduced by 8 mg NO3N L−1 (fall 1995) following intermediate rainfall and yields; and reduced by 28 mg NO3-N L−1 (fall 1993) and 11 mg NO3-N L−1 (spring 1994) following the driest growing season (average of CT and NT). Improved N availability with the rye was detected by a PSNT under CT, but not under NT. Therefore sidedress N rates can be adjusted for release of rye residue-N under CT, and potential NO3 contamination of groundwater can be reduced by overseeding winter rye into both CT and NT corn systems.

Key words:Zea mays, Secale cereale, pre-sidedress nitrate test, tillage, nitrogen fertilization
Snow management and deep tillage for increasing crop yields on a rolling landscape
Authors: McConkey B. G. , Ulrich D. J. , Dyck F. B.
Published: April 2011

Snow management (tall vs. conventional height stubble) and one-time deep tillage were investigated for increasing water conservation and annual crop production on a rolling soil landscape developed on glacial till in the semiarid Brown soil zone of the Canadian prairies. Tillage depths were 0, 13, 25, and 45 cm. Gleysolic soils had more soil water at time of seeding and greater 3-yr mean durum wheat (Triticum turgidum L.) grain yields than the Chernozemic soils. On the Chernozemic soils, tall (25 cm) stubble increased over-winter soil water at seeding by 15 mm compared with conventional short (14 cm) stubble. Mean 3-yr durum grain yields were 165 kg ha−1 higher with tall than short stubble although yield increases were only significant (P < 0.05) in one year. Extended rotations with tall cereal stubble are particularly attractive for cropland with a rolling topography when a significant part of the landscape is occupied by Gleysolic soils. Water conservation and grain yields for fall chiselling to 13 cm were not different than those for no fall tillage. Fall chiselling to 25 cm or subsoiling to 45 cm increased grain yields by 300 kg ha−1 in the year following tillage compared with no fall tillage. This yield increase was not related to soil water and may be due to physical disruption of an apparent tillage pan that existed between 10 and 20 cm depths.

Key words: Wheat, water conservation, snow, subsoiling, rolling landscape
Petroleum residues as water-repellent substances in weathered nonwettable oil-contaminated soils
Authors: Roy Julie L. , McGill William B. , Rawluk Marvin D.
Published: April 2011

Some soils develop severe water repellency several years or decades following oil contamination. We previously reported on the characteristics of three such soils. Here we report on the characteristics of putative water-repellent substances in them. We examined the effectiveness of various polar, nonpolar and amphiphilic solvents for removal of water-repellent substances in three nonwettable soils. Only the amphiphilic solvent mixture isopropanol/14.8 M ammonia (7:3, vol/vol) (IPA/NH4OH) completely eliminated soil water repellency in all three soils. We thus define putative water-repellent substances as those substances whose removal from soil by IPA/NH4OH removes water repellency. High-resolution CPMAS 13C-NMR spectroscopy and thermal desorption followed by conventional gas chromatography/mass spectroscopy with electron impact ionization (GC/EI/MS) and GC/MS with chemical ionization (GC/CI/MS) were used to characterize extracted putative water-repellent substances. We conclude that: (i) the identified representatives of these substances consist mostly of homologous series of long-chain and polycyclic aliphatic organic compounds; namely, n-fatty acids, n-alkanes, and cycloalkanes, and that (ii) they are of petroleum origin rather than plant or microbial origin. Key words: Soil hydrophobicity, petroleum hydrocarbons, soil water repellency, amphiphilic solvents, crude oil, nonwettable soil
Carbon dioxide efflux from the floor of a boreal aspen forest. I. Relationship to environmental variables and estimates of C respired
Authors: Russell C. A. , Voroney R. P.
Published: April 2011

Soil CO2 efflux (Soil Fc) in a boreal aspen (Populustremuloides) forest was related to environmental variables to estimate the mass of carbon (C) annually respired. Measurements of soil Fc were made between April and September with a dynamic closed chamber via an infra-red gas analyzer.Over the course of the study day-time soil Fc ranged from 0.027 to 0.411 mg CO2 m−1s−1. Summertime estimates of soil Fc were higher than expected, and this was attributed to underestimation by static chamber methods. Strong relationships were found between seasonal patterns of (1) soil Fc and soil temperature (Ts) at various depths (R2 = 0.77 to 0.87, Q10 = 3.9 to 5.1), (2) soil Fc and humus [CO2] and volumetric moisture (θv; R2 = 0.76 to 0.88) and (3) humus [CO2] and humus Ts and θv (R2 = 0.74). On their own, θv, litter and soil organic matter content explained little (<5%) of the variation in soil Fc. Ts was the single most effective variable used to predict soil Fc.Annual masses of soil Fc C were estimated from the relationship between soil Fc and 0.1 m Ts in 1994. Long-term (49-yr) estimates were generated from monthly mean air temperatures (Ta) using the relationship between Ts (0.10 m) and Ta (2 m) at the site throughout 1994–1995. In both years, Ta explained about 70% of the variability in Ts. Estimates of annual soil Fc C were 905 (1994), 870 (1995) and 809 (long-term) g m−2. Growing season soil Fc approximated 75% of the annual C mass respired. These annual C fluxes far exceed current estimates for boreal and most temperate forest ecosystems. 1994 soil Fc C also exceeded the site estimate of aboveground net primary productivity (361 g C m−2yr−1). This extreme shortfall, along with the inability of soil organic matter or litter mass to explain soil Fc, suggests that about 60% of annual soil Fc C is attributable to the presence of roots. If soil Fc in vegetated environments is primarily due to the presence of roots then the significance of soil Fc to global C cycling can only be understood with concurrent estimates of net ecosystem C exchange. Key words: Soil CO2 flux, soil respiration, soil temperature, soil moisture, root respiration, boreal forest
Transport of soluble organic and inorganic carbon in sandy soils under nitrogen fertilization
Authors: Wang F. L. , Alva A. K.
Published: April 2011

Leaching of water soluble soil carbon plays an important role in downward transport of soil nutrients and pollutants and may be influenced by soil and management factors. We examined the leaching of water soluble carbon from two sandy soils under nitrogen fertilization by adapting an intermittent leaching-incubation technique using packed soil columns (94 × 10 cm). After 30 d, cumulative amounts of water-soluble organic carbon (SOC) leached from the Candler and Wabasso sand for various treatments in mg C column−1 were: 77 and 302 (NH4NO3), 64 and 265 (control), and 45 and 239 (isobutylidene diurea, IBDU), respectively. The IBDU and NH4NO3 treatments increased the leaching of water-soluble inorganic carbon (SIC), which ranged from 2 to 38 mg C column−1 over 30 d. At the end of eight cycles of leaching/incubation, the total carbon content increased at depth (control and NH4NO3 treatment) in the Candler sand, but decreased in the Wabasso sand. In the first leaching event, the average rate of SOC leaching from the Wabasso sand was 26 mg C column−1 d−1 which dropped rapidly to about 5 mg C column−1 d−1 towards the end of the experiment. The rate of SOC leaching from the Candler sand was much lower (<8 mg C column−1 d−1) than the rate of SOC leaching from the Wabasso sand. Compared with the unamended treatments, application of NH4NO3 increased and IBDU decreased the leaching of SOC in both soils. These effects of N application were considerable during the initial two to three leaching events only. Our results suggest that the initial rainfalls that follow a dry period may be critical for transporting SOC from the upper layer of these sandy soils. Key words: C leaching, sandy soil, intermittent leaching condition, isobutylidene
An assessment of potato sap flow as affected by soil water status, solar radiation and vapour pressure deficit
Authors: Gordon R. , Brown D. M. , Madani A. , Dixon M. A.
Published: April 2011

Water-use of three field-grown potato cultivars (Atlantic, Monona and Norchip) was examined using a commercially available sap flow monitoring system over three consecutive growing seasons. The objectives of the investigation were to utilize the sap flow system to assess the water use of three field-grown potato cultivars. This included an assessment of the relationship between environmental conditions, water status and measured sap flow including the plant-to-plant variation in sap flow and an evaluation of relative transpiration in relation to the soil water status.Each cultivar maintained daily sap flow close to the atmospheric potential transpiration until approximately 70% of the available water was depleted. Under conditions where the soil was drier (>70% depleted), Monona potato plants exhibited a more rapid decline in transpiration than Norchip and Atlantic.Hourly sap flow rates were closely related to solar irradiance, especially under well-watered conditions, with no apparent light saturation point. Vapour pressure deficit effects on sap flow were less pronounced, although maximum vapour pressure deficits encountered were only 2 kPa. Key words: Water use, sap flow, transpiration, potato
An automated chamber system for measuring soil respiration
Authors: McGinn S. M. , Akinremi O. O. , McLean H. D. J. , Ellert B.
Published: April 2011

To quantify the net effect of agricultural systems on CO2 emissions to the atmosphere, the amount of carbon fixed (primary production) and emitted (soil respiration) under different agronomic management must be estimated. A dynamic chamber system was constructed to automatically measure CO2 concentration in chambers and provide diurnal flux estimates of soil respiration. In fallow, the mean respiration was measured over 4 d using four chambers and ranged from 6.5 to 8.6 g m−2 d−1. During this time, the coefficient of variation between chambers ranged from 9 to 18%. The mean daily soil respiration in fallow was also measured over a second period (13 d) using both chambers and a Bowen ratio technique. The mean value from the chambers was 6.4 g m−2 d−1, which was not significantly (P > 0.05) different from that Bowen ratio value of 7.1 g m−2 d−1. The chambers were also utilized to measure the impact of tillage on soil respiration for 11 d following tillage. During this period, the tilled plot lost 92 kg ha−1 of carbon compared with 52 kg ha−1 from the untilled plot. Approximately half of the total tillage-induced carbon loss from soil occurred in the first 48 h. Key words: Soil respiration, carbon dioxide, soil chamber, tillage, Bowen ratio