bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring the saturated hydraulic conductivity of peat substrates in nursery containers
Authors: Allaire S. E. , Caron J. , Gallichand J.
Published: April 2011

Pore size, distribution and continuity are important characteristics for the exchange and storage of air and water in artificial mixes. Saturated hydraulic conductivity (Ks) measurements can be used to obtain such a characterization. However, two difficulties are encountered when using Ks in potting media. First, the validity of Ks may be limited because it may not apply in media composed of coarse material or peat. Second, the structure of peat substrates is very sensitive and in situ measurements of potted peat substrates (i.e. measurements made directly in the pots) should be carried out to avoid any disruptive effect due to handling. Such a measurement, when made in pots, may require the evaluation of the water flux reduction resulting from the container outflow configuration. The objectives of this study were therefore to check the validity of Darcy’s law for peat substrates and to propose an approach for estimating the saturated hydraulic conductivity from flow measurements made in nursery containers. For three different substrates, water flow in artificial mixes followed Darcy’s law for hydraulic gradients ranging from 1.1 to 1.6 cm cm−1. Experimental results showed that the measured fluxes in 5-L nursery container filled at five different substrate heights (9, 11.5, 14, 16.5 and 19 cm) with laterally located drainage holes were significantly different from those measured in pots with the bottom removed (therefore equivalent to measurement currently made in cylinders) at P = 0.0022. Fluxes in containers with bottoms removed were 7–31% higher than in intact pots. Water flux measurements may therefore need to be corrected for this flux reduction in order to accurately estimate hydraulic conductivity from flow experiments run in pots. A correction factor based on the results obtained from a finite difference model was derived and calibrated. Then, this correction factor was used to convert flux measurements made in pots with lateral holes into equivalent flux that would have been obtained had the pot had an open bottom. After correction, no significant flux reductions were found between pots with open bottoms and pots with lateral holes (P = 0.55). A correction factor estimated from Laplace’s equation, once calibrated, can therefore be applied to flux measurements obtained from pots to obtain estimates of Ks of undisturbed potted media. Key words: Hydraulic conductivity, peat substrates, container
Cultivation effects on dispersible clay of soil aggregates
Authors: Fuller L. G. , Goh Tee Boon , Oscarson D. W.
Published: April 2011

The objective of this study was to examine the effect of long-term cultivation on clay dispersibility of four aggregate size fractions (2.0–9.5 mm, 0.85–2.0 mm, 0.25–0.85 mm, and < 0.25 mm) obtained from a Chernozemic soil by comparing two cultivated sites with an adjacent native prairie site. Aggregate size fractions (ASF) were subjected to increasing levels of ultrasonic energy and the amount of clay dispersed at each energy level was determined. Organic carbon, hexose carbon, soluble hexose C, total clay, cation exchange capacity (CEC), and exchangeable cations were measured for each ASF. Clay contained within prairie aggregates was held much more strongly within the aggregate and therefore showed greater stability towards dispersion by ultrasonic vibration. More energy was required to disperse one-half of the ASF clay under prairie than under cultivated soils (228–425, and 95–229 kJ L−1 for prairie and cultivated macroaggregates, respectively; 370–433, and 249–334 kJ L−1 for prairie and cultivated microaggregates, respectively). Clay dispersibility was significantly correlated with organic C, hexose C, soluble hexose C, non-hexose C, CEC, and exchangeable Ca and Mg but was not correlated with total ASF clay. Long-term cultivation of this soil resulted in a decrease in the energy required to disperse an equivalent proportion of clay from aggregates relative to that of the grassland soil. Thus, cultivation of these soils has resulted in aggregates which are more susceptible to clay dispersion and therefore prone to water erosion and surface crusting. Key words: Clay dispersion, aggregation, carbohydrate
Testing effectiveness of four simulation models for estimating nitrates and water in two soils
Authors: Beckie H. J. , Moulin A. P. , Campbell C. A. , Brandt S. A.
Published: April 2011

Information is required on the usefulness and limitations of simulation models for estimating nitrate-nitrogen (NO3-N) and water status of soil in different agroecological zones of western Canada. Therefore, four simulation models (CERES, EPIC, NLEAP and NTRM) were used to predict distribution of NO3-N and water in the soil profile from long-term spring wheat (Triticum aestivum L.) rotations for the 1990 growing season at Melfort and Scott, Saskatchewan. The models estimated NO3-N and water levels in the crop rooting zone (0–1.5 m) of the soil profiles generally well. However, EPIC underestimated NO3-N levels in the top 0.3 m for fallow (F) rotations at Melfort, whereas NLEAP overestimated amounts in the same depth increment of Melfort soil for the majority of rotations. In addition, CERES and NTRM markedly overestimated NO3-N levels in the Melfort soil solum (0–0.6 m) for the unfertilized continuous wheat (W) rotation. Soil water content was overestimated in the top 0.3-m layer of Melfort soil for the two W rotations by CERES and EPIC and for all rotations by NTRM. As well, EPIC markedly overestimated water content in the crop rooting zone for both rotations at Scott. There were differences among models in accurately simulating NO3-N and water status of the soil profile, but these differences were not great. Overall, these models should be effective in estimating soil NO3-N and water content for wheat cropping systems, thereby aiding agronomic decisions and environmental impact assessments. Key words: Crop Estimation through Resource and Environment Synthesis (CERES), Erosion/Productivity Impact Calculator (EPIC), nitrogen, Nitrogen Leaching and Economic Analysis Package (NLEAP), Nitrogen, Tillage, and Residue Management (NTRM), Triticum aestivum L.
The fate of chromium and nickel in subalpine soils derived from serpentinite
Authors: Gasser Ubald G. , Juchler Stephan J. , Sticher Hans , Hobson William A.
Published: April 2011

Weathering of serpentinitic parent material, naturally rich in both Cr and Ni, provides soils that generally contain elevated concentrations of both metals. In this study, soil development as well as the fate of Cr and Ni in Dystric Eutrochrepts derived from serpentinitic rock slide material were investigated in the Swiss Alps under subalpine climatic conditions. Exchangeable Ni was ≤ 0.2 mmol kg−1, but exchangeable Cr was always < 0.01 mmol kg−1. Linear correlation between dithionite-extractable Cr and Fe was positive, but negative between pyrophosphate extractable Cr and total soil carbon. Total Ni and Mg generally increased with depth. While most of the Cr was located in refractory primary minerals (pyroxene, garnet and spinels), a minor part was found in secondary Fe oxides; therefore, Cr tended to accumulate in the upper mineral part of the soil profiles and was generally less mobile than Ni. Soil Cr was not readily available for plant uptake. In some soils, exchangeable Ni reached concentrations potentially toxic to plants. Key words: Serpentinite, weathering, chromium, nickel, iron, subalpine zone
Cesium-137-measured erosion rates for soils of five parent-material groups in southwestern Saskatchewan
Authors: Pennock D. J. , Jong E. de , Lemmen D. S.
Published: April 2011

Despite the wide-spread perception that the soils of southwestern Saskatchewan are particularly erosion prone, few observations have been made on soil loss in this area. We used 137Cs redistribution to examine rates of soil loss associated with five parent-material groups in this area. Five sites were sampled in each parent-material group: one uncultivated site and four cultivated sites. Ten samples were taken at each site from landscape positions that have been shown in previous studies to have the highest rates of soil loss. The highest rates (median soil loss of −30 t ha−1 yr−1) were associated with glacial till landscapes; medium (−21 t ha−1 yr−1) but highly variable rates of loss, with coarse sandy glaciofluvial–lacustrine landscapes; and lower and consistent losses of around −12 t ha−1 yr−1, with silty glaciolacustrine and aeolian landscapes and with fine sandy glaciofluvial–lacustrine landscapes. The observed rates of loss can be used to calibrate models of geomorphic instability for this area. Key words: Soil erosion, soil quality, landscape-scale analysis, soil organic matter
Tillage translocation and tillage erosion on shoulder slope landscape positions measured using 137Cs as a tracer
Authors: Lobb D. A. , Kachanoski R. G. , Miller M. H.
Published: April 2011

Tillage erosion, the net downslope translocation of soil by tillage, was measured on eight shoulder slope landscape positions within two fields in the upland regions of south–western Ontario. Translocation of soil by tillage was measured by labelling plots of soil with 137Cs and measuring its displacement in response to tillage. Paired plots were utilized to compare soil translocation by upslope and downslope tillage. A single sequence of conventional tillage operations, consisting of mouldboard plough, tandem disc (double pass) and C-tine cultivator, translocated 90 kg soil m−1 slope width when tillage was conducted upslope, and 142 kg m−1 when conducted downslope. Net downslope translocation resulting from one upslope tillage sequence and one downslope, was 52 kg m−1. Assuming one sequence of tillage operations occurs per year and is conducted upslope and downslope equally often, the rate of net downslope translocation would be 26 kg m−1 yr−1. The source area from which this soil loss occurred was defined by an average slope length of 5.2 m between paired plots and hillslope summit. The estimated rate of soil loss from this area was in excess of 5.4 kg m−2 yr−1 (54 t ha−1 yr−1). Tillage erosion accounted for at least 70% of the total soil loss from natural and tillage erosion as estimated by resident 137Cs. Key words: Tillage translocation, tillage erosion, 137Cs, complex topography, spatial variability
Effects of coarse-fragment content and size on soil erosion under simulated rainfall
Authors: Chow T. L. , Rees H. W.
Published: April 2011

Farmers have long considered coarse fragments a hindrance in potato production. Rock picking or crushing has become a routine operation. Using simulated rainfall events and runoff-erosion plots (1 m × 1 m), the effects of coarse-fragment content (0, 7, 15 and 25% by volume) and size (1.0–1.9, 1.9–5.1 and 5.1–7.6-cm diam) on runoff, infiltration and soil loss were evaluated on an Orthic Dystric Brunisol. Study objectives were to quantify the influence of coarse fragments on soil erosion and to convert these relationships into mathematical equations for use with existing models to predict soil loss. Although there were only marginal increases in infiltration and reductions in runoff attributable to increasing content and size of coarse fragments, the rate of soil loss from the control was higher than that from all other treatments. In general, the rate of soil loss decreased with increasing content and size of coarse fragments. The effects of content and size of coarse fragments on soil-loss reduction, either individually or in combination, were expressed mathematically with correlation coefficients greater than 0.82. The study also revealed that for a given volumetric coarse-fragment content, the percentage surface cover increased with increasing coarse-fragment size. This finding has important practical implications because most reporting of coarse fragments is done on the basis of volume rather than percentage surface cover. Key words: Rock content, rock size, rainfall simulator, infiltration, soil loss
N uptake and recovery by onions from peat-mineral fertilizers
Authors: Abbès C. , Parent L. E. , Karam A. , Isfan D.
Published: April 2011

Nitrogen release from peat-ammonia-mineral fertilizers (PAMF) could be partly controlled by granule size and soil application of nitrification inhibitors. The objective of this study was to evaluate the effects of various combinations of nitrapyrin, a nitrification inhibitor, and granule sizes of PAMF on onion (Allium cepa L. ’Norstar 210B’) yield and N recovery. The study was conducted in a growth chamber, with two soils, two nitrapyrin rates (0 and 8 mg kg−1), three PAMF rates (0, 133 and 266 mg N kg−1) and three granule sizes (2-, 4- and 10-mm diameters). Nitrogen-use efficiency was assessed using the 15N technique. Nitrapyrin considerably depressed onion yield and failed to improve PAMF efficiency because of apparent ammonia toxicity. The 10-mm granules produced higher dry matter yield (3–8%) and root length (1–9%) than 2-mm and 4-mm granules. Maximum N recovery from PAMF 10-mm granules reached 47% in the Tilly soil and 76% in the Chaloupe soil. In contrast to nitrapyrin, granule size may improve N availability to onions from PAMF. Key words: Ammonia, fertilizers, 15N isotope, nitrapyrin, N recovery, onions, peat
SHORT COMMUNICATION: Difficulties in using 137Cs to measure erosion in stubble-mulched soil
Authors: Bremer E. , Janzen H. H. , Jong E. de
Published: April 2011

Soil erosion may be difficult to quantify from redistribution of 137Cs at sites where stubble-mulch techniques were adopted prior to 137Cs deposition, because appreciable 137Cs may have been transported before it was mixed into the soil Ap layer. We present evidence that this occurred in two long-term cropping experiments in southern Alberta. Key words: Cesium-137, tillage, long-term crop rotations, fallow
Measurement of the sensitivity of orchard soils to acidification
Authors: Neilsen Denise , Hoyt Paul B. , Parchomchuk Peter , Neilsen Gerald H. , Hogue Eugene J.
Published: April 2011

The pH buffer curves for 45 surface soils from apple (Malus domestica Borkh.) orchards in southern British Columbia were determined. Buffer curve shape differed according to the initial soil pH and incubation treatment. Soils with initial pHw < 7.4 and incubated with either H2SO4 or CaCO3 had typically sigmoid or modified sigmoid buffer curves. Non-calcareous soils with initial pHw > 7.4, incubated with H2SO4 were far less buffered above pH 6.5–7.0 than soils with initial pH < 7.4. Thus, non-calcareous neutral to alkaline soils may be more susceptible to acidification than buffer curves derived from liming acid soils might predict. A new measure of soil susceptibility to acidification, the acidification resistance index (ARI), was derived from buffer curves. It is defined as the amount of acid (cmol (p+) kg−1) required to reduce soil pH from its initial level to pH 5.0. Best-fitted multiple regression equations between ARI and soil properties routinely measured in soil test laboratories determined that 79% of the variation in ARI could be explained by a combination of extractable cations and initial soil pH. This regression model could be used to provide an inexpensive measure of soil susceptibility to acidification for orchards where acidifying fertilizers are applied through drip irrigation systems. Key words: Soil acidification, pH buffer curves, Malus domestica Borkh, drip irrigation
Root mass distribution under conventional and conservation tillage
Authors: Dwyer L. M. , Ma B. L. , Stewart D. W. , Hayhoe H. N. , Balchin D. , Culley J. L. B. , McGovern M.
Published: April 2011

Tillage effects on the soil environment suggest that it may influence rooting depth and root distribution. In this study, corn (Zea mays L.) rooting depth and root mass distribution were compared under conventional and conservation (chisel, ridge, no-) tillage on sandy loam and clay loam soils at Ottawa, Ontario. Root depth and distribution in 0.10-m vertical increments during vegetative growth were estimated using a combination of excavation of the surface horizon (0–0.10 m) and 0.05-m diameter cores obtained in the row and midway between two rows over a 3-yr period. An exponential model was used to fit root mass distribution data normalized with respect to total root density summed over all increments and maximum rooting depth in the profile. Soil moisture, temperature, mechanical resistance and bulk density varied with tillage treatment, but differences were not associated with root mass distribution. Rooting depth varied with soil texture, year and tillage, with increased rooting depth associated with increased tillage and decreased moisture in surface soil layers. In contrast, a common exponential model was found to fit normalized root mass distribution data under all tillage treatments. Our data suggest that simulation of root mass distribution under all tillage practices is possible if rooting depth and root mass density of the surface soil layer are known. Key words: Corn, model fitting, root distribution, tillage, Zea mays
Influence de la fertilisation azotée, des bâches et des cultivars sur la productivité des fraisiers à production continue au Québec
Authors: Lamarre Michel , Payette Suzanne , Lareau Michel J. , Fortin Charles
Published: April 2011

The effects of two nitrogen sources and a row cover were studied for 2 day-neutral strawberry cultivars covered with different row covers and grown for 3 yr at two sites at Lavaltrie and L’Acadie. The nitrogen sources did not significantly (P ≤ 0.05) affect yield and fruit size at either site. However, the black polyethylene mulch combined with cultivar Tribute increased yield and fruit size at both sites. The use of a row cover in the fall did not prevent early frosts or lengthen the picking season. Despite a smaller fruit size and 5–8 d of earliness, good total yields appear possible from a second year crop of day-neutrals. Key words: Strawberry, nitrogen, NH4, sulphur-coated urea, mulching, yield, fruit size.
Influence of source, method of placement and simulated rainfall on the recovery of 15N-labelled fertilizers under zero tillage
Authors: Malhi S. S. , Nyborg M. , Solberg E. D.
Published: April 2011

The availability of fertilizer N to crop under zero tillage (ZT) versus conventional tillage (CT) is affected by immobilization, ammonia volatilization, denitrification or leaching. This study examined the relative importance of those four factors in influencing the availability of N to the crop and the recovery of applied 15N-labelled N in soil and plants. Field experiments were conducted at two sites in central Alberta to determine the influence of tillage, N source, method of N placement and simulated rainfall on the recovery of 15N-labelled fertilizers in spring barley (Hordeum vulgare L.) plants and soil. A first experiment compared four soil surface broadcast N sources [urea, ammonium sulphate (AS), ammonium nitrate (AN) and potassium nitrate (KNO3)]. The N recovery in barley plants was KNO3> AN > AS > urea. With the exception of KNO3, plant N recovery was greater under CT than under ZT, particularly for urea. Immobilized N in soil was often less with KNO3 than the other N sources. There was apparently virtually no denitrification loss during the one crop season used in these experiments, and the recovery of KNO3 was complete. In a second experiment, methods of placement were evaluated. The recovery of N in plants was lowest for surface broadcast urea under ZT, particularly when no water was added after urea application. Banding urea beside and/or below the seedrow in comparison to broadcasting markedly increased N recovery in plants, especially under ZT. The differences in N recovery between ZT and CT were greater for broadcast application than for band placement. Method of placement had little effect on N immobilization under ZT, but under CT the amount of immobilized N was less with subsurface banding than incorporation. Simulated rainfall immediately after surface broadcast urea application under ZT increased the N recovery in plants. In conclusion, surface broadcast urea under ZT was less efficient than the other N sources and its recovery improved considerably when placed in bands below the soil surface near the seedrow. Key words: Ammonium nitrate, banding, fate of applied N, 15N-labelled fertilizers, N immobilization, N recovery, surface broadcasting, urea
Estimation régionale de l’humidité du sol par télédétection
Authors: Boisvert J. B. , Crevier Y. , Pultz T. J.
Published: April 2011

Several pilot projects have demonstrated that estimation of soil moisture over a large area can be done using remote sensing. Three main methods have been tested with some success: thermal inertia, passive microwave and synthetic aperture radar (SAR). The advantages and limitations of each approach were summarized. Most Canadian research has focused on SAR data. It has shown that several parameters can affect the accuracy of soil moisture estimation using radar such as incidence angle, roughness, polarization and frequency. The data collected during the SIR-C/X-SAR experiment in Altona, Manitoba, were used to evaluate the impact of incidence angle on soil moisture estimation accuracy. Incidence angle was the most significant factor to explain the signal variations over time. The effect of incidence angle (38° to 58°) on the signal was linear in October. Correlation between soil moisture and the signal was higher with surface (0–2.5cm) measurements in the wet period (April) but there was no significant correlation during the dry period (October). A statistical model using soil moisture and incidence angle in April showed that an increase of 1° in incidence angle could decreased the C-HH signal by 0.25 dB and the L-HH signal by 0.30 dB. Such variation would generate a change of 2% (C-HH) and 5% (L-HH) in soil moisture estimation. Key words: Radar, remote sensing, soil moisture, microwave
The problem of establishing ecologically based soil quality criteria: The case of lead
Authors: Cook Nicola , Hendershot William H.
Published: April 2011

Soil quality guidelines are being developed to address the problem of lead in soils. They define an acceptable total soil concentration of lead. Recent studies indicate that only a small portion (found m the soil solution) of the total is immediately available to biota and therefore a direct ecological hazard. This paper focuses on the difficulty of assessing the ecological risk of lead in soils and the factors controlling the fraction of the total that is available to soil organisms. Toxicity data on plants and soil animals used to create guidelines indicate that the lowest observed adverse effects occur at concentrations ranging from 50 to over 40 000 mg Pb kg−1 soil; however, the tests, using clean soil spiked with soluble lead salts, do not adequately reflect the conditions likely to be found in the field. In most cases the lead in contaminated soils can be expected to be transformed into relatively stable, insoluble forms over time; although the final form of the metal will depend on the form in which the lead was originally introduced and the environmental conditions that have persisted. The selective chemical extraction procedures used to define different "pools" of lead in soils, and to define the amounts of bioavailable lead, have not been properly validated. The philosophy behind the derivation of soil quality guidelines is discussed and recommendations are made for the development of scientifically defensible guidelines for lead in soils. Key words: Bioavailability, soil contamination, toxicity, soil quality criteria
Soil nitrate levels as influenced by apple orchard floor management systems
Authors: Walsh B. D. , MacKenzie A. F. , Buszard D. J.
Published: April 2011

Mulches are an alternative to herbicidal control of weeds in orchards. Mulches may affect soil nutrient levels and consequently alter tree growth, fruit yield, and quality. The objective of this study was to determine the effects of cultivation, straw mulch, geotextile mulch, grass cover, a cover crop mixture of lupin and wild carrot, and manure compost mulch on extractable soil nutrients in two newly established dwarf apple orchards in Quebec. In 1992, manure compost and straw mulches resulted in higher soil NO3−-N and K relative to those levels under ground cover. Levels of soil NO3−-N were related to soil water content under any particular mulch. Straw mulch resulted in high July NO3−-N levels and low September levels of soil NO3−-N. Geotextile and cultivation treatments resulted in higher September NO3−-N levels relative to July. Soil under manure compost tended to have higher P levels than soil under other treatments. There was little or no effect of mulch treatments on extractable levels of soil NH4+-N, Ca, or Mg. Key words: Orchard, apple, mulches, geotextiles, straw, nutrients, manure compost, grass sod
SHORT COMMUNICATION: Soil microbial biomass C, N mineralization, and N uptake by corn in dairy cattle slurry- and urea-amended soils
Authors: Paul J. W. , Beauchamp E. G.
Published: April 2011

A spring application of dairy cattle slurry (300 kg total N ha−1) on high- and low-fertility sites resulted in higher microbial biomass C during the growing season than on a control soil or a soil receiving 100 kg N ha−1 as urea. Microbial biomass C was also significantly higher on the high-fertility site and was reflected in greater N mineralization and N uptake by corn. There was no greater net N mineralization in the manured soil than in the control or fertilized soil as would be expected as a result of higher microbial biomass C and significant organic N contribution from the manure. Key words: Animal manure, nitrogen mineralization, corn, grain yields, soil fertility
Rocky Mountain forest soils: Evaluating spatial variability using conventional statistics and geostatistics
Authors: Rahman S. , Munn L. C. , Zhang R. , Vance G. F.
Published: April 2011

Spatial variability of soils is a landscape attribute which soil scientists must identify and understand if they are to construct useful soils maps. This paper describes the spatial variability of soils in a forested watershed in the Medicine Bow Mountains, Wyoming, using both conventional statistics and geostatistics. Principle Components Analysis indicated that flow accumulation and aspect were the two terrain attributes that most economically described terrain variability. Thickness of A and B horizons, organic carbon and solum coarse fragments were variable in the study area (CVs of 40 to 58%). Simple correlation and regression analyses suggested there were no statistically significant relationships between soil properties (texture, pH, coarse fragments, organic carbon content) and terrain attributes (elevation, slope gradient, slope shape, flow accumulation, aspect). Geostatistical analysis indicated thickness and coarse fragment contents of the A and B horizons, and solum thickness were spatially independent variables; however, pH, organic carbon content, and solum coarse fragment content were spatially correlated. Spatial variability was described by both linear (pH and organic carbon content) and spherical (solum coarse fragment) models. Use of geostatistics provided insight into the nature of variability in soil properties across the landscape of the Libby Creek watershed when conventional statistics (analysis of variance and regression analysis) did not. Key words: Rocky Mountains, Medicine Bow Mountains, forest soils, spatial variability, principle component analysis, geostatistics
α-Naphthol sorption as regulated by structure and composition of organic substances in soils and sediments
Authors: Chen Z. , McGill W. B. , Dudas M. J. , Xing B.
Published: April 2011

Humic acids (HAs) from major horizons of a Gleyed Black Chernozem and a set of soil and sediment samples were examined to understand the influence of the structure a composition of organic substances on sorption of organic pollutants. Solid state 13C cross-polarized/magic angle spinning (CP/MAS) NMR results indicated that the aromaticity of HAs increased with soil depth. The aromaticity of organic substances in bulk soils and sediments varied with the degree of geological diagenesis. Sorption experiments showed a linear relationship between the carbon normalized partition coefficient (Koc) of α-naphthol and the aromaticity of HAs and non-extracted organic substances in whole soils and sediments. The Koc values of α-napthol had a log-linear relationship with the atomic mass ratio (N+O)/C of the organic substances in soils and sediments. Correlation analysis for the literature data further revealed that the compositional and structural properties of organic substances were related, suggesting possibilities of predicting Koc with either compositional or structural parameters Measured Koc values demonstrated considerable deviations from those calculated with prediction models using Kow. The prediction models may not be accurate because they do not account for the compositional and structural differences in organic substances of sorbents. Key words: sorption, organic substances, aromaticity, Koc, α-naphthol
Impacts of harvesting and mechanical site preparation on soil chemical properties of mixed-wood boreal forest sites in Alberta
Authors: Schmidt M. G. , Macdonald S. E. , Rothwell R. L.
Published: April 2011

We examined the impacts of harvesting and mechanical site preparation (MSP) on soil chemical properties of mixed-wood boreal forest sites in west central Alberta. Treatments included: 1) disc trencher, hinge, and trench microsites; 2) ripper plow, hinge, and trench microsites; 3) blading thin (organic layer depth < 2 cm), and thick (organic layer depth > 2 cm) microsites; 4) harvested with no site preparation; and 5) unharvested. Twenty months after harvesting, the forest floor of harvested areas with no MSP (vs. unharvested) had higher carbon:nitrogen ratios lower pH, and lower concentrations of total and mineralizable nitrogen, available phosphorus, and exchangeable bases Fifteen months after MSP, treated areas had either reduced or unchanged concentrations of total nitrogen and carbon, available phosphorus, and mineralizable nitrogen in the surface mineral soil, compared with harvested sites with no site preparation. The MSP-treated areas also had increased or unchanged pH, base saturation, and exchangeable base concentrations. Microsites adjacent to the displaced forest floor (hinge for disc and ripper treatments) or with a thicker organic layer (thick for blading) generally had higher concentrations of total nitrogen and carbon, and mineralizable nitrogen in the surface mineral soil as compared to trench and thin microsites. Key words: Forest soils, mechanical site preparation, harvesting, N, P, mixed-wood boreal forest
Persistence of deep loosening of naturally compacted subsoils in Nova Scotia
Authors: Carter M. R. , Holmstrom D. A. , Cochrane L. M. , Brenton P. C. , Thomas W. G. , Roestel J. A. van , Langille D. R.
Published: April 2011

Naturally compacted subsoils, as a result of geogenic and/or pedogenic processes, are a common phenomenon in soils formed on medium textured basal tills in the Maritimes. This study was conducted to determine whether soil loosening following tile drainage could improve the long-term physical condition of naturally compacted subsoils and consequently improve soil permeability and crop productivity. The effects of subsoiling at various soil depths (35 to 70 cm) perpendicular to tile lines on soil structural form, and crop biomass yield and root growth were investigated over a 4-yr period (1989–1993) on sandy loam to loam Luvisolic, Gleysolic, and Brunisolic soils, at three sites in Nova Scotia. For two of the sites, soil bulk density measured using gamma ray attenuation showed a significant decrease immediately after subsoiling, and soil hydraulic conductivity determined using a constant head well Guelph permeameter was increased, relative to the non-subsoiled control. At one of the sites, subsoil loosening increased crop winter survival and productivity. Subsoiling did not appear to significantly improve the long-term permeability or environment for root growth below the 45-cm soil depth. Evidence of subsoil reconsolidation was found at each site within the three year period. Key words: Subsoiling; drainage; Luvisolic, Gleysolic and Brunisolic soil; soil physical properties
Effects of day and night air temperature in early season on growth, productivity and energy use of spring tomato
Authors: Papadopoulos Athanasios P. , Hao Xiuming
Published: April 2011

Effects of air temperature on tomato (Lycopersicon esculentum Mill) growth, yield and heating energy consumption were investigated in spring of 1993 and 1994. Tomato plants were grown under nine day/night air temperature regimes formed by factorial combination of three day (19, 20 and 21°C) and three night (16, 17 and 18°C) heating temperature set points. Early (until 30 April) fruit yield increased but early fruit size decreased with increasing daily average air temperature (MT, 24-h mean). The plants grown under high daily average air temperature early in the season had lower fruit yield late in the season. Plants grown under high night air temperature (NT) and low day air temperature (DT) during the early production period achieved high fruit yield in early season and avoided the negative effects of high MT on early fruit size; these plants also had high yield and large fruit size late in the season. The different day and night heating temperature regimes studied caused no more than 10% in heating energy use variation. Therefore, for greenhouse tomato production under Great Lakes conditions (approx. 42°N), the optimal day/night air temperature (from January to April) is 20.8–21.0/18.5–19.0°C (actual air temperatures). Key words: Lycopersicon esculentum, tomato, yield, quality, fruit size, daily average air temperature (MT), day-night air temperature difference (DIF), day air temperature (DT), night air temperature (NT)
Fresh-cut apples: Challenges and opportunities for multi-disciplinary research
Authors: Toivonen Peter M. A.
Published: April 2011

The fresh-cut apple industry has recently become established in North America. The future looks very bright for this value-added fruit product, however its growth requires improvements in quality and reduction of production costs. The existing industry has grown from concept to reality in response to research activities in anti-browning dips, package technology, sensory analysis, postharvest physiology, postharvest pathology and food microbiology. Several examples of how these critical research inputs have impacted and continue to impact on the industry practice are discussed. The next generation of questions and challenges posed by the industry will require some new inputs. Research in several disciplines will be need accessed to resolve the emerging issues. Traditional breeding effort and/or molecular technologies will be needed to provide non-browning fruit, fruit with better processing characteristics such as small cores to reduce waste and improved flavour and nutrition retention after cutting. With new cultivars, further work will be required to understand the commercial handling of each, including selection of harvest maturity and optimization of storage protocols. Also, pre-harvest factors such as phosphorus nutrition will need to be investigated further in terms of their effects on fruit tissue and membrane stability. Management of fungal pathogens is a key issue that needs to be studied from the field through storage and after cutting and packaging of the sliced fruit. The very nature of fresh-cut fruit has and continues to require a coordinated multi-disciplinary research strategy. Key words: Value-chain, value-added, apples, fresh-cut, integrated research
Petiole sap NO3-N testing as a method for monitoring nitrogen nutrition of potato crops
Authors: Waterer D.
Published: April 2011

Petiole sap NO3-N concentrations were tested as a means for monitoring crop nitrogen (N) status and N fertilizer responses in potatoes. An ion specific electrode was used to monitor sap NO3-N concentrations of three varieties of potatoes grown with differing amounts of N fertilizer in 1993–1995. Plots provided with varying amounts of fertilizer N applied prior to planting or as a split application were sampled on six occasions through the growing season. Sap NO3-N levels were positively correlated with petiole dry matter NO3-N levels. Petiole sap NO3-N levels reflected rates and timing of N fertilizer application. Sap NO3-N levels in the three cultivars showed similar changes with time after planting and increasing N fertilizer rates. However, sap NO3-N levels measured under a particular set of conditions were unique for each cultivar. The correlation between yields and sap NO3-N levels varied with the sampling date and cultivar. Recommendations were developed for critical sap NO3-N concentrations at various stages in the development of the three cultivars. Key words: Ion specific electrode, nitrate, petiole, nitrogen, tissue testing, Solanum tuberosum
Suitability of Brassica juncea (Brassicaceae) as a host plant for oviposition for Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae)
Authors: Gerber G. H.
Published: April 2011

The suitability of Brassica juncea (L.) Czern as a host plant for oviposition for Lygus lineolaris (Palisot de Beauvois) was measured by comparing egg laying on five experimental lines or cultivars of this species with that on B. napus L. (cv. AC Excel, a suitable host) in no-choice or choice tests during a 14-d period in the greenhouse and field. Egg laying was measured indirectly by counting newly hatched nymphs emerging from the plants. The numbers of nymphs emerging from B. juncea (cv. Cutlass) and four experimental lines of B. juncea were about two to ten times lower than from B. napus, indicating that L. lineolaris females lay fewer than half as many eggs on the former species than on the latter species and that B. juncea as a species is a poor host plant for oviposition. The inflorescence was the preferred region of the plant for oviposition on B. napus but not on B. juncea. The numbers of nymphs emerging from the inflorescence of B. juncea (cv. Cutlass) were 8.4 times lower than from the inflorescence of B. napus, indicating that the differences in oviposition on these species were due to the presence of an antixenosis-type of plant resistance factor(s) in the inflorescence of B. juncea. Key words: Insecta, Miridae, Lygus lineolaris, oviposition, resistance, Brassica juncea, B. napus
Short-term effects of nitrogen and phosphorus fertilizers on nitrogen mineralization and trophic structure of the soil ecosystem in forest clearcuts in the southern interior of British Columbia
Authors: Forge T A , Simard S W
Published: April 2011

Ammonium sulphate and an ammonium sulphate-ammonium phosphate mixture were applied at 200 kg N ha-1 and 200 kg P ha-1 at three clearcut sites within the Interior Cedar-Hemlock biogeoclimatic zone in southern British Columbia. N mineralised under aerobic and anaerobic conditions, nitrification, biomasses of fungi and bacteria,the abundance of protozoa, and the trophic structure of nematode communities were studied at 4, 12, 16, and 28 mo after fertilisation. Nitrogen mineralised under aerobic conditions was greater in fertilised soil than in non-fertilised soil at 4 and 16 mo after fertiliser applications. Nitrification also increased after fertilisation. Fertilisation did not affect bacterial or fungal biomasses, but did increase the ratio of bacterial biomass/fungal biomass, the abundance of bacterivorous nematodes, and the ratio of bacterivorous nematodes/fungivorous nematodes. Thus, the fertiliser-induced increase in N mineralization appears to have been the result of increased bacterial decomposition and flow of carbon and nitrogen through bacteria-bacterivore channels of the soil food web. Key words: N mineralization, fertilisation, microbial biomass, microfauna, nematode ecology
Impacts of clearcut harvesting and wildfire on soil nutrient status in the Quebec boreal forest
Authors: Simard D G , Fyles J W , Paré D. , Nguyen T.
Published: April 2011

Wildfire has historically been the major cause of stand initiation in the boreal forest, shaping species diversity, successional and ecosystem processes. Clearcut harvesting may differ from fire in its effects on soil and vegetation processes and thus may cause long-term changes in stand productivity or biodiversity. This study compared the soil properties of mesic black spruce (Picea mariana) stands burned 2, 14, 21 yr prior to sampling, with stands clearcut within ±3 yr of each wildfire and recently undisturbed control stands. The forest floor (FH) and mineral soil (0-10 cm) were sampled volumetrically, air dried and analysed for pH, organic carbon content, available P, Ca, Mg, and K, mineralizable N and nitrification. Forest floors were also digested and analysed for total N, P, K, Ca and Mg. Significant differences between disturbed and control stands were observed in all study areas, with disturbance effects generally decreasing with time since disturbance. Burned stands generally had forest floors with thinner humus layers, lower mass of organic carbon, higher pH, and higher concentrations of total and available nutrients than in either clearcut or control stands. Significant losses in the total mass of N and K in the forest floor were observed in the youngest burned stands as well as a pulse of extractable P that was at least four times higher than cut or control stands in any other treatment or study area. The forest floor of cut stands had greater mass of organic matter and total nutrients, and higher levels of potentially mineralizable N than either fire or control stands. No significant nutrient loss was observed following clearcut harvesting in any study area. Overall, this study suggested that clearcut harvesting can result in changes to the status of soil nutrients that are different from those produced by wildfire. Further study is necessary to determine whether these differences have significant effects on the long-term productivity or biodiversity of the boreal forest. Key words: Fire, clearcutting, boreal forest, nutrients, Quebec
Practical applications of ion exchange resins in agricultural and environmental soil research
Authors: Qian P. , Schoenau J. J.
Published: April 2011

The use of synthetic ion-exchange resins to examine ion bioavailability in soil and sediment systems has attracted much attention over the years. The first report in this regard was made 7-8 yr after resins were developed in the 1930s. So far, nearly 400 journal articles have been published related to use of resins in soil and environmental studies. The experience gained has led to more widespread applications in research as well as practical use in soil fertility assessment and fertilizer recommendations. Two commercial products developed in North America have directly resulted from years of research efforts. Recent developments in resin technology and availability warrant an updated review of the literature to aid in better understanding and utilizion of this technique.

In this paper we provide an overview of historic and current developments in the use of ion exchange techniques in soil research. We also provide specific examples of successful use of batch and diffusion-sensitive ion exchange techniques in research and commercial use to assess ion availability. Finally, we address certain frequently asked questions about how the ion exchange resin technique is applied and how results are interpreted, including their advantages and limitations. Key Words: Ion exchange resin, agriculture, environment, soil research
A modeling approach to quantifying soil macroaggregate dynamics
Authors: Plante A F , Feng Y. , McGill W B
Published: April 2011

While several researchers have suggested that soil aggregate turnover is a significant control on organic matter dynamics, the quantification of soil aggregate dynamics has yet to be achieved. Quantification of soil aggregate turnover is essential to testing any hypothesis concerning the relationship between aggregate turnover and organic matter dynamics. The goal of the current work was to propose a modeling approach to the quantification of soil macroaggregate dynamics. The approach taken was to define model compartments representing water-stable soil aggregate size fractions and describing the flows between compartments using first-order kinetics. Soil aggregate data from a 2-yr field study on two contrasting soils were used to calibrate the model and yielded soil aggregate mean residence times ranging from 4 to 95 d, where aggregate dynamics were generally two to three times more rapid in a Gray Luvisol compared to a Black Chernozem. The model was subsequently used to predict the distribution of applied tracer spheres in water-stable aggregate size fractions from an initially free state. The models closely predicted the Dy "mean weight diameters" (Dy-MWD) after two growing seasons. While the models have several limitations, they offer the first attempt to quantitatively describe soil macroaggregate dynamics, which is essential to predicting the response in organic matter dynamics to changes in aggregate dynamics. Key words: Soil aggregation, macroaggregate turnover, tracer, model
Crop and soil nitrogen status of tilled and no-tillage systems in semiarid regions of Saskatchewan
Authors: McConkey B G , Curtin D. , Campbell C A , Brandt S A , Selles F.
Published: April 2011

We examined 1990-1996 crop and soil N data for no-tillage (NT), minimum tillage (MT) and conventional tillage (CT) systems from four long-term tillage studies in semiarid regions of Saskatchewan for evidence that the N status was affected by tillage system. On a silt loam and clay soil in the Brown soil zone, spring what (Triticum aestivum L.) grain yield and protein concentration were lower for NT compared with tilled (CT or MT) systems for a fallow-wheat (F-WM) rotation. Grain protein concentration for continuous wheat (Cont W) was also lower for NT than for MT. For a sandy loam soil in the Brown soil zone, durum (Triticum durum L.) grain protein concentration was similar for MT and NT for both Cont W and F-W, but NT had higher grain yield than MT (P < 0.05 for F-W only). For a loam soil in the Dark Brown soil zone, wheat grain yield for NT was increased by about 7% for fallow-oilseed-wheat (F-O-W) and wheat-oilseed-wheat (W-O-W) rotations. The higher grain yields for NT reduced grain protein concentration by dilution effect as indicated by similar grain N yield. However, at this site, about 23 kg ha-1 more fertilizer N was required for NT than for CT. Elimination of tillage increased total organic N in the upper 7.5 cm of soil and N in surface residues. Our results suggest that a contributing factor to decreased availability of soil N in medium- and fine-textured soils under NT was a slower rate of net N mineralization from organic matter. Soil nitrates to 2.4 m depth did not indicate that nitrate leaching was affected by tillage system. Current fertilizer N recommendations developed for tilled systems may be inadequate for optimum production of wheat with acceptable grain protein under NT is semiarid regions of Saskatchewan. Key words: Tillage intensity, N availability, soil N fractions, N mineralization, crop residue decomposition, grain protein