Canadian Journal of Soil Science
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Root mass distribution under conventional and conservation tillage 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
Canadian Journal of Soil Science - Tập 76 Số 1 - Trang 23-28 - 1996
Quality and dynamics of soil organic matter in a typical Chernozem of Ukraine under different long-term tillage systems Kravchenko, Y., Rogovska, N., Petrenko, L., Zhang, X., Song, C. and Chen, Y. 2012. Quality and dynamics of soil organic matter in a typical Chernozem of Ukraine under different long-term tillage systems. Can. J. Soil Sci. 92: 429–438. Tillage has been reported to induce changes in soil organic matter (SOM) concentrations and quality. Conversion of plow-tillage to minimum till and no-till (NT) farming enhances the SOM pool. Enrichment of the SOM pool is essential for maintaining fertility of Chernozems, advancing food security, and improving the environment. The main objective of this study was to examine the effect of different tillage systems on the SOM concentration, its quality and dynamics including CO2 assimilation by heterotrophic bacteria and humus characteristics – the carbon (C) concentration in humic substances and the labile soil organic C fraction (SOCL) extracted with 0.1 N NaOH – as well as the molecular masses, spectroscopic parameters and physiological effects of humic acids on germinating pea (Pisum sativum L.) seeds. Our study was conducted on a long-term experimental site on a Haplick Chernozem in the Poltava region of Ukraine over a 10-yr period from 1996 to 2006. Results indicate that conversion from conventional to reduced soil tillage systems increased SOM concentrations in 0- to 10-cm soil layer and led to the accumulation of C in fulvic acids and humins. No significant differences in SOM storage in the 0- to 100-cm layer were observed among tillage systems. However, reduced tillage systems had a higher proportion of SOCL, a lower ratio of C in humic acids/C in fulvic acids and more humic acids with molecular masses from 110 to 2000 kDa. Our study demonstrated that the quality and dynamics of SOM are closely related to soil tillage practices.
Canadian Journal of Soil Science - Tập 92 Số 3 - Trang 429-438 - 2012
Towards accurate measurements of soil organic carbon stock change in agroecosystems In response to Kyoto Protocol commitments, countries can elect agricultural carbon sinks to offset emissions from other sectors, but they need to verify soil organic carbon (SOC) stock change. We summarize issues we see as barriers to obtaining accurate measures of SOC change, including: soil depth, bulk density and equivalent soil mass, representation of landscape components, experimental design, and the equilibrium status of the SOC. If the entire plow depth is not considered, rates of SOC storage under conservation compared with conventional tillage can be overstated. Bulk density must be measured to report SOC stock on an area basis. More critical still is the need to report SOC stock on an equivalent mass basis to normalize the effects of management on bulk density. Most experiments comparing SOC under differing management have been conducted in small, flat research plots. Although results obtained from these long-term experiments have been useful to develop and validate SOC prediction models, they do not adequately consider landscape effects. Traditional agronomic experimental designs can be inefficient for assessing small changes in SOC stock within large spatial variability. Sampling designs are suggested to improve statistical power and sensitivity in detecting changes in SOC stocks over short time periods. Key words: Soil organic carbon change, agroecosystems, experimental design, sampling depth
Canadian Journal of Soil Science - Tập 86 Số 3 - Trang 465-471 - 2006
Grazing impacts on bulk density and soil strength in the foothills fescue grasslands of Alberta, Canada Alberta foothills fescue grasslands are very productive ecosystems but there is concern that the traditional season-long (continuous) grazing regimes may be leading to soil deterioration due to compaction and increased soil strength. The objectives of this study were to quantify grazing effects on soil bulk density and soil strength of sloped areas in the Alberta foothills fescue grasslands at the Agriculture Canada Stavely Range Substation. The effects of two grazing intensities (heavy and very heavy) for two treatments (short duration and continuous) on these two parameters were compared to an ungrazed control. Soil bulk density and soil water to a depth of 7.5 cm were measured with a surface water/density gauge. Soil strength was measured with a hand-pushed cone penetrometer to a depth of 45 cm. Cone index, the maximum penetration resistance in a given depth interval, was used as a measurement parameter for soil strength.Grazing affected both soil bulk density and penetration resistance. Even short-duration treatments affected these soil properties, although their effects were similar for both heavy and very heavy grazing intensities. Distinction between heavy and very heavy continuous grazing treatments was clear for both bulk density and penetration resistance, with the very heavy treatment having the greatest detrimental effect on these two soil parameters for all treatments. Bulk density and soil strength values were always lowest in the spring after snowmelt and highest late in the growing season, reflecting the water status of these ecosystems. Identical treatment rankings were obtained using bulk density and penetration resistance, but cone index was a more sensitive indicator of the effects of grazing than bulk density. Key words: Grazing, fescue grasslands, bulk density, soil strength
Canadian Journal of Soil Science - Tập 75 Số 4 - Trang 551-557 - 1995
Effect of soil acidification on nitrification in soil Zebarth, B. J., Forge, T. A., Goyer, C. and Brin, L. D. 2015. Effect of soil acidification on nitrification in soil. Can. J. Soil Sci. 95: 359–363. This laboratory experiment examined the effect of elemental S-induced variation in soil pH (3.97–5.29) on nitrification enzyme activity and conversion of [Formula: see text] to [Formula: see text]. Nitrification rate generally decreased with decreasing soil pH, but still proceeded rapidly within the pH range (4.5 to 5.2) recommended for blueberry production, contrary to what is generally assumed.
Canadian Journal of Soil Science - Tập 95 Số 4 - Trang 359-363 - 2015
SOIL COMPACTION EFFECT ON PHOTOSYNTHESIS, ROOT ROT SEVERITY, AND GROWTH OF WHITE BEANS The effect of soil compaction on photosynthesis, plant growth and root rot severity of white bean was investigated in a controlled environment using healthy and root rot diseased soil. There was a highly significant reduction in root biomass, shoot growth and total leaf area of plants grown in compacted soil. Soil compaction also significantly reduced photosynthetic rate and increased root rot severity. The reduction in growth for plants subjected to soil compaction is attributable partly due to a decrease in photosynthetic rate and to an increase in root rot severity. Key words: Phaseolus vulgaris L., Fusarium root rot, bean (white)
Canadian Journal of Soil Science - Tập 68 Số 2 - Trang 455-459 - 1988
Comparison of static and dynamic closed chambers for measurement of soil respiration under field conditions The objective of this study was to compare the dynamic closed and static chamber techniques for the measurement of soil respiration under field conditions. The static chamber method consistently produced lower soil respiration values than did the dynamic closed system and the difference was larger at higher CO2 fluxes. A negative exponential model describes the relation between CO2 fluxes measured by both techniques. A good fit was obtained for measurements on a sandy loam soil (R2 = 0.61) and an organic soil (R2 = 0.74) but parameter estimates were different for each soil. Key words: Carbon dioxide, enclosure, gas flux measurement
Canadian Journal of Soil Science - Tập 72 Số 4 - Trang 605-609 - 1992
Effect of nitrogen fertilizer application on seed yield, N uptake, and seed quality of <i>Camelina sativa</i>
Canadian Journal of Soil Science - Tập 94 Số 1 - Trang 35-47 - 2014
Nitrogen release during decomposition of crop residues under conventional and zero tillage The litter-bag method was used in field experiments to determine nitrogen (N) loss patterns from decomposing red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues under conventional and zero tillage. Nitrogen contained in crop residues ranged from 10 kg ha-1 in wheat under both tillage systems to 115 kg ha-1 in clover GM under zero tillage. The patterns of N loss (i.e., release), particularly from GM residues, over 52-wk periods varied with tillage, i.e., residues lost N more rapidly under conventional tillage than under zero tillage in the first 5 to 10 wk after residue placement. Net N immobilization was sometimes observed, particularly under zero tillage. Where net N release occurred, it ranged from 22% of wheat N under conventional tillage to 71% for clover N under conventional tillage; it was positively correlated with residue N concentration and microbial activity, and negatively correlated with C:N and lignin:N ratios in one study period. The amounts of N released were 2 kg ha-1 from wheat, 10 to 25 kg ha-1 from canola, 4 to 18 kg ha-1 from pea, and 46 to 69 kg ha-1 from GM residues. Therefore, when grain is harvested, the remaining crop residues do not release much N to the soil in the first year of decomposition, but the N stored in soil is presumably released in subsequent years. Key words: Crop residues, crop rotation, N mineralization, organic soil amendments
Canadian Journal of Soil Science - Tập 86 Số 1 - Trang 11-19 - 2006
NITROGEN ISOTOPE FRACTIONATION DURING AMMONIUM EXCHANGE REACTIONS WITH SOIL CLAY Nitrogen isotopic fractionation during ammonium adsorption by clay colloids was shown to occur in two time-dependent stages. A rapid 15 N enrichment of the NH4 + in solution was followed by a gradual depletion until, after an 8- to 10-h equilibrium period, the δa 15 N of the NH4 + in solution was approximately 1; this value was significantly lower than the initial value of 2.3 for the NH4 Cl used in these experiments. The isotopic equilibrium constant (ke ) for the ammonium adsorption reaction was greater than unity, and higher for the Ca2+ - than K+ -saturated clay colloids.
Canadian Journal of Soil Science - Tập 58 Số 1 - Trang 53-60 - 1978
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