University of New Brunswick, HJF Forestry Centre, 1350 Regent St., Fredericton, New Brunswick, Canada E3C 5G6
The purpose of this study was to determine whether change of forest cover had an effect on the development of the organic surface horizons, particularly on those variables that influence nutrient cycling and forest productivity. Jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana [Mill.] B.S.P.) plantations were selected from among the youngest to oldest (2--16 yr) within a 100 km2 area in southeastern New Brunswick. Natural forests were also included as benchmark sites. The forest floor and tree foliage was sampled and trees measured on 0.05-ha plots. The forest floor samples were used to determine organic mass, nutrient contents and pH. In pine plantations, organic matter accumulated rapidly during the period of exponential tree growth, but leveled off at about 45 Mg ha--1. This was within the range of benchmark sites with mixed conifer-hardwood cover. In spruce plantations, the forest floor mass ranged upward to 77 Mg ha--1. Development was strongly influenced by the nature of the previous forest. Spruce forest floors were on average more acid and had lower nutrient concentrations, particularly N and Ca. The observed differences suggest that nutrients are recycled more rapidly in the pine plantations, partly explaining the superior growth of the latter.
Key words: Forest floor, Kalmia angustifolia L., Picea mariana (Mill.) B.S.P., Pinus banksiana Lamb., nutrient cycling, plantation forest
Environment Canada, National Hydrology Research Institute, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada S7N 3H5, e-mail: elliottj@nhrisv.nhrc.sk.ec.gc.ca
Soil moisture profiles at two mature forest sites (Pine and Mixed-Wood) and two plantations (1981 Pine and 1992 Mixedwood) in central Saskatchewan were studied in conjunction with soil properties, precipitation, interception and evapotranspiration. Sampling locations within each stand were chosen to highlight differences in soil moisture due to interception, evapotranspiration and soil physical properties.
Soil moisture storage to 1-m depth was greatest on the 92-Plantation where transpiration and interception of precipitation were less than the other sites. Moisture storage in the 81-Plantation was similar to that in the mixed-wood stand. The Pine stand had the lightest textured soils and stored least water to 1-m depth. Variability in moisture storage was also observed within stands and was associated with canopy structure and density, water extraction patterns and mechanical site preparation. In the furrows at the 92-Plantation, wet soils in combination with low infiltration rates and transpiration may have lead to the generation and channelling of rainfall runoff during a major rainfall event.
Key words: Boreal forest, hydrological pathways, soil moisture, infiltration, interception, evapotranspiration
Forest Resources, Alberta Research Council, Bag 4000, Vegreville, Alberta, Canada T9C 1T4
Soil biota response to changes in the soil physical environment following forest harvesting is relatively unknown in boreal forests. Soil biological activity was measured at four sites with Luvisolic soil following clear-cut forest harvesting. Aerobic respiration rate and cellulose decomposition in flooded soils were measured on soil samples collected from treatment plots subjected to tree removal only and tree removal associated with three levels of skidding activity immediately after clear-cut harvesting and after 1 and 2 yr. More than half of variation in respiration and cellulose decomposition rates was related to soil properties. Soil respiration rate increased significantly after 1 yr but was not affected by skidder traffic. Cellulose decomposition was highest in soil with air-filled porosity <0.10 m3 m--3, and increased significantly with skidder traffic. Air-filled porosity measured in the field at the time of harvest indicated a poorly aerated environment that becomes wetter in subsequent years. The results imply that soil had biota well adapted to poor soil aeration. The development of a fully anaerobic soil environment following forest harvesting only occurred on compacted soil after heavy precipitation, but partial anaerobiosis of these boreal forest soils was common. Although partial anaerobiosis increased decomposition rate, it is considered sufficient to adversely affect the growth of plant roots and change the availability and mobility of nutrients.
Key words: Forest harvesting, soil compaction, biological activity, respiration rate, decomposition rate, Alberta, boreal forests
1Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, 5320, 122nd Street, Edmonton, Alberta, Canada T6H 3S5; and 2Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
The effects of soil compaction and depth of chipped aspen residue on aspen regeneration, plant community development, decomposition, and nutrient cycling were tested on an Orthic Gray Luvisol in the Lower Foothills of Alberta. Twenty-seven 100-m × 15-m plots were established in 1992. Three depths of chipped aspen residue (0, 1--5 cm and >10 cm) and three levels of compaction (no compaction, 6 and 16 skidder passes) were applied following whole-tree harvesting in 1993. Sixteen skidder passes and chip residue depths >10 cm resulted in reduced plant cover and aspen sucker densities for at least 2 yr following treatment. Nutrient concentrations of the chip residue and surface organic horizon (LFH) were similar for the three compaction treatments. The initial total nitrogen (N) concentration of the chipped aspen residue was 3.6 g kg--1. Ammonium (NH4+-N) concentrations in the LFH of the chip residue treatments, particularly at the >10-cm residue depth, were lower compared with the no-residue treatment. However, adequate N apparently was available to the aspen suckers and understory vegetation as the NH4+-N concentration remained higher than in the LFH before harvesting. Compaction and woody residue applications had only short-term (3 yr) effects on soil properties, plant community development and aspen suckering at this site when clear-cut harvesting was done in the fall with low soil moisture content.
Key words: Ammonium, aspen regeneration,
wood residue, compaction
1Northern Forestry Centre, Natural Resources Canada, 5320 - 122nd Street, Edmonton, Alberta, Canada T6H 3S5; 2Canadian Forest Service, Natural Resources Canada, 1219 Queen Street East, Sault Ste. Marie, Ontario, Canada P6A 5M7; 4Institute of Geography, University of Tartu, Tartu EE2400, Estonia; and 5Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 6C2
A steady state mass balance model (ForSust), developed to simulate potentially sustainable levels of tree biomass growth and related nutrient uptake dynamics, was applied to 17 jack pine sites across Canada. The model simulates potential tree biomass growth based on nutrient inputs from estimated atmospheric deposition (N, Ca, Mg, K) and soil weathering (Ca, Mg, K), and matches the resulting nutrient supply rates with calculated nutrient demand. Nutrient demand calculations are based on nutrient concentrations in wood, bark, branches, and foliage. Specifically, the model simulates sustainable annual increment (SAI)of biomass growth for stem-only and whole-tree (aboveground biomass) harvesting, and for recurring forest fire conditions. Calculated SAI levels were compared with field-estimated mean annual increments for aboveground forest biomass (MAI). For recurring forest fires, it was found that SAI values, as simulated, corresponded with the MAI field estimates in general. For whole-tree harvesting, SAI was lower than MAI for most but not all sites. For stem-only harvesting, SAI corresponded with MAI, but there was a greater scatter between SAI and MAI values than what appeared to be the case for the recurring forest fire scenario.
Key words: Jack pine; whole tree, stem-only harvesting; steady-state mass balance; forest biomass, N, Ca,
1Canadian Forest Service, Great Lakes Forestry Centre, P.O. Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7; 2Geomatics International Inc., 3370 S. Service Rd., Burlington, Ontario, Canada L7N 3M6
In 1975 and 1976, an experimental burning program was conducted in an immature stand of boreal jack pine (Pinus banksiana Lamb.) growing on level, granitic outwash sands in northern Ontario. Nine 0.4-ha plots were burned under a range of fire weather conditions and sampling was conducted to examine the effect of fire on soil chemical changes and revegetation. Results indicated that depth of burn (DOB) affected both soil chemical changes and plant succession on these pine sites. Vaccinium angustifolium Ait., Oryzopsis spp,. Waldsteinia fragarioides (Michx.) Tratt, Salix spp. and Viola adunca Sm. increased in cover at two levels of DOB but the increase was greatest at the lower DOB and decreased to pre-burn levels after 10 yr. Comptonia peregrina (L.) Coult., Epilobium angustifolium L., Polytrichum commune Hedw. and Amelanchier sanguinea (Pursh) DC. were not found in the pre-burn surveys but appeared after burning. Vegetation cover for these species was always higher at the deeper DOB but decreased almost to zero after 10 yr. Other species such as Pleurozium schreberi (Brid.) Mitt., Linnaea borealis L., Corylus cornuta Marsh., Cladina rangiferina (L.) Nyl. and Aralia nudicaulis L. were eliminated from the site and did not recover even after 10 yr. Soil pH increased 0.3 to 1.0 pH units in the organic and mineral soil layers. The rate of increase in pH was always steeper at the higher DOB and pH returned to pre-burn levels in the mineral soil layers after 10 yr. Immediately after burning, exchangeable Ca in the mineral soil layers doubled but 10 yr later, Ca returned to pre-burn levels. Phosphorus and K increased in the mineral soil, leveled off and were still elevated after 10 yr. Total Kjeldahl N was reduced by 50% in the organic soil while N in all mineral soils increased, and was still increasing after 10 yr. Except for immediate post-fire increases in pH, Ca and N, soil chemical changes were small or they rebounded to pre-burn levels 10 yr after burning. Therefore it is unlikely that these changes were the cause of the plant cover changes that persisted to 10 yr.
Key words: Soil nutrients, plant succession, fire, depth of burn, jack pine
Canadian Forest Service, Natural Resources Canada, Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7.
Forest harvesting on peatland sites during the frost-free season often creates water-filled ruts and transfers more humified layers of peat to the surface. Foresters have generally assumed that such disturbance has negative consequences related to proliferation of graminoid vegetation, disruption of surface drainage leading to raised water tables and, possibly, reduced site productivity. An experiment was established during 1996 near Cochrane, Ontario to examine the physical impacts of site disturbance on peatlands. Summer traffic by forest harvesting equipment was imposed at three intensities on a Black Spruce--Speckled Alder site type. The fractional area of surface disturbance increased with the amount of traffic, but disturbance effects on the thickness of the aerated zone, depth to the water table, and microtopography were not significant. However, the consistency of the effects produced by the most intense disturbance treatment suggests that it reduced average elevations and aerobic layer thicknesses, and increased water levels, by 2 to 6 cm. The hydrological effect of site disturbance in this study was small compared with the typical effect of forest canopy removal on water levels.
Key words: Forest harvesting, peat, peatlands, site disturbance
Ontario Ministry of Natural Resources, Centre for Northern Forest Ecosystem Research, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, Canada P7B 5E1
1Present address (M.J.): Forest Ecosystems Branch, Saskatchewan Environment and Resource Management, Box 3003, Prince Albert, Saskatchewan, Canada S6V 1G6. E-mail: johnston@derm.gov.sk.ca.
The Boreal Mixedwood Ecosystem Study near Thunder Bay, Ontario is a multi-disciplinary investigation of the impacts of harvesting and fire on the structure and function of a boreal mixedwood ecosystem. The fire component comprises a set of treatments in which fire severity was manipulated by adjusting fuel loadings through a variety of harvesting techniques, and also included fire in standing timber. Intensive fuel sampling before and after the fire enabled detailed determinations of fuel consumption, heat output and forest floor reduction. Nutrient concentrations in ash, soil, and plant tissue following the fire were compared with fire severity in order to quantify potential nutrient inputs and their relationship to the amount of biomass consumed during the fire. Forest floor and woody fuel consumption varied significantly among treatments, with the most important factor being whether or not the stand had been harvested previous to the fire. The pH was highest and P concentrations among the lowest in the ash of unharvested blocks. Nutrient concentrations of the remaining forest floor and upper mineral soil were weakly related to the treatments. Forest floor P concentrations were highest on whole-tree harvested and lowest on uncut blocks. Whole-tree harvested blocks also had the highest pH values in forest floor and mineral soil. Concentrations of N, P, and Mg in the foliage of Populus tremuloides Michx. and Rubus idaeus L.were higher on unharvested burned than cut and burned plots, and were negatively correlated with the depth of forest floor reduction. These results indicate that fire severity plays a role in determining the extent of nutrient enrichment following fire, and may be important in influencing long-term site productivity.
Key words: Fire severity, forest fire, nutrient cycles, soil chemistry, fire ecology
1Rocky Mountain Research Station, 1221 S. Main, Moscow, ID, USA 83843; 2School of Forestry and Wood Products, Michigan Technological University, Houghton, MI, USA 49931; 3Pacific Northwest Research Station, Grants Pass, OR, USA 97526
Intensive timber harvesting and site preparation are becoming more common as demand for timber-based products increases. On some harvested sites in the western United Staes of America and Canada, stump removal is used to ameliorate root disease problems. Soil compaction and nutrient loss could become a problem on some sites after harvesting, site preparation, or stump removal. In a non-replicated, randomized block experiment, two levels of soil compaction (none and severe) and a stump extraction treatment were examined on an ash-cap soil in northern Idaho. These treatments were planted with Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) and western white pine (Pinus monticola Dougl. ex D. Don) seedlings. Soil compaction increased post-harvest bulk density 15--20% to a depth of 30 cm. Stump removal decreased surface soil bulk density, but it increased at the 30- to 45-cm depth to levels equal to the soil compaction treatment. One year after outplanting, seedling top weights were similar among treatments, but root volume was significantly reduced in the soil compaction treatment. Soil compaction and stump removal treatments also reduced the numbers and morphological types of ectomycorrhizae and non-ectomycorrhizal short roots on Douglas-fir. Western white pine seedlings had reduced numbers of non-ectomycorrhizal short roots in the same treatments. Three years after outplanting, stump removal resulted in smaller root collar diameters and less total N content for both seedling species. Severe site disturbance, with associated soil compaction and mixing, may decrease productivity of ash-cap sites by reducing pore space and root and ectomycorrhizal activity. Managers must weigh short-term benefits of intensive site disturbance with possible long-term loss of soil productivity.
Key words: Bulk density, compaction, ectomycorrhizae, stumping, site preparation, Douglas-fir, western white pine
1Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5, email btitus@pfc.forestry.ca; 2Natural Resources Canada, Canadian Forest Service, (Newfoundland), Atlantic Forestry Centre, P.O. Box 6028, St. John's, Newfoundland, Canada A1C 5X8, email broberts@nefc.forestry.ca
The effects of conventional stem-only and whole-tree harvesting on nutrient losses in biomass and in leachate fluxes over a 3-yr period after cutting three white birch stands in central Newfoundland were determined. Losses of nutrients in biomass were proportionately greater with more intensive harvesting as tree components with higher nutrient concentrations (branches, foilage) were removed. Stem-only harvesting removed 126, 9, 51, 126 and 23 kg ha--1 of N, P, K, Ca and Mg in biomass, respectively. Whole-tree harvesting led to a 19% increase in biomass removal as compared to stem-only harvesting but nutrient removals with whole-treee harvesting increased by 127% for N, 138% for P, 151% for K, 72% for Ca and 90% for Mg. Nutrient losses in deep percolation of soil solution during the first 3 yr after harvesting were generally greater following stem-only than whole-tree harvesting. This may be the result of increase leaching from slash, increased mineralization beneath slash, and retardation by slash of the successional vegetation that could act as a nutrient sink. In the first 3 yr following harvesting, leaching losses after whole-tree harvesting were 4, 0.2, 8, 23 and 7 kg ha--1 of N, P, K, Ca and Mg, respectively, as compared with 9, 0.1, 7, 28 and 9 kg ha--1 of N, P, K, Ca and Mg after stem-only harvesting. Nutrient losses in leachate were generally small compared to losses in biomass removal.
Key words: Intensive harvesting, slash, nutrient budget, sustainable site productivity, Betula papyrifera (Marsh.)
Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario, Canada M5S 3B3, e-mail: vic.timmer@utoronto.ca .
This paper reports on a new graphical analysis technique that facilitates screening alternative strategies for crop management in programs of integrated vegetation management in young forest plantations. The responsiveness of black spruce seedlings to three vegetation management measures (herbicide application, fertilization and seedling nutrient loading) on two contrasting site types (Hardwood [ST 10] and Feathermoss [ST 4]) located in northern Ontario, were compared and evaluated using vector competition analysis. The approach is based on vector diagnosis and regression analysis that compare growth and nutritional interactions between crop and non-crop plants competing for the same growth resources. Response parameters are examined in a bivariate model depicting vectors of changing biomass production or nutrient uptake relative to competition-free treatments. Although herbicide application reduced non-crop vegetation on both sites, it accelerated tree growth and nutrient uptake only in the herb-rich Hardwood site, but had no effect on seedlings in the Feathermoss site. Fertilization stimulated vegetation growth in the competitive Hardwood site causing seedling suppression, but stimulated both tree and non-crop vegetation growth in the Feathermoss site because of weaker competition. Preplant nutrient loading improved seedling growth and nutrition reducing competition of neighboring weeds. Vector competition analysis facilitated interpretation of plant interactive relationships and identification of limiting factors. Advantages over traditional competition indices are that both growth and nutrition parameters, as well as crop and non-crop responses are quantitatively and systematically evaluated, and that simultaneous comparisons simplified screening of the most effective treatments and sites for possible vegetation control.
Key words: Competition indices, treatment screening, nutrient loading, fertilization, herbicide
1Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5; and 2Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, 5320 122nd Street, Edmonton, Alberta, Canada T6H 3S5
Alternate silviculture systems, such as small patch clearcuts, may become important in the development of sustainable forest management strategies in aspen forests. A study was initiated in a 64-yr-old trembling aspen (Populus tremuloides Michx.) stand in Meadow Lake Provincial Park, Saskatchewan to determine changes in nutrient dynamics and secondary succession following patch clear-cutting. One hectare replicated patch cuts were logged in the winter of 1993--1994. There was no site preparation following harvest. Annual vegetation, regeneration and soil and plant nutrient data were collected annually, 1 yr prior to, and 3 yr following harvest. Aspen regeneration was 48 375 stems ha 2 yr after treatment. Stand (alpha) diversity of the understory was not affected by harvesting, although annual species turnover (beta diversity) increased slightly after harvest. There was an increase in aspen foliar nitrogen (N) for 2 yr following harvest. Soil nutrient concentrations did not differ between patch cut and unharvested plots except total potassium (18% lower in the LFH of the harvested treatments 3 yr after harvesting). Small patch cuts with the litter horizon kept intact may be appropriate for aspen-dominated stands in the boreal mixed wood to minimize ecological disturbance while maintaining aesthetics within a park setting.
Key words: Ammonium, aspen regeneration, diversity, nitrate, plant community structure, soil productivity
USDA Forest Service, North Central Forest Experiment Station, 1831 Highway 169, East, Grand Rapids, Minnesota 55744, USA. e-mail: dstone/nc_gr@fs.fed.us.
Forest management activities that decrease soil porosity and remove organic matter have been associated with declines in site productivity. In the northern Lake States region, research is in progress in the aspen (Populus tremuloides Michx. and P. grandidentata Michx.) forest type to determine effects of soil compaction and organic matter removal on soil properties and growth of aspen suckers, associated woody species, herbaceous vegetation, and on stand development. Four treatments: (1) total tree harvest (TTH); (2) TTH plus soil compaction (CPT); (3) TTH plus forest floor removal (FFR); and (4) TTH plus CPT + FFR were applied after winter-harvest of a 70-yr-old aspen stand growing on a loamy sand with a site index (age 50) 20.7 m. The CPT treatment significantly increased bulk density and soil strength of the surface 30 cm of soil and neither have recovered during the 5 yr since treatment. The CPT plots had 19.6 thousand (k) suckers ha--1, less than half that of the TTH and FFR treatments; mean diameter (19.4 mm) and height (271 cm) were greatest on the TTH plots. The disturbance treatments (CPT, FFR, and CPT + FFR) each reduced biomass of foliage, stems, and total suckers compared with the TTH treatment. Total aboveground biomass (herbs + shrubs + suckers) was less than half that of TTH plots. There were 5.0 k saplings (suckers >2.5 cm DBH) ha--1 on the TTH plots, but fewer than 1.0 k ha--1 in the other treatments. The disturbance treatments decreased 5-yr growth of potential crop trees, delayed early stand development, and temporarily reduced stockability and site productivity of an aspen ecosystem.
Key words: Soil compaction, organic matter removal, site productivity, stand development
1Canadian Forest Service, Great Lakes Forestry Centre, Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7; 2Department of Soil Science, University of British Columbia, 139--2357 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4; 3British Columbia Ministry of Forests, Research Branch, 515 Columbia Street, Kamloops, British Columbia, Canada V2C 2T7; 4425 Lower Bench Road, RR #1, S1C8 Penticton, British Columbia, Canada V2A 2B2
Post-harvest levels of soil disturbance and vegetation regrowth strongly influence microclimate conditions, and this has important implications for seedling establishment. We examined the effects of blading (scalping), soil loosening (ripping) and vegetation control (herbicide), as well as no soil disturbance, on growing season microclimates and 3--yr seedling response on two grass-dominated clearcuts at different elevations in the Southern Interior of British Columbia. Warmer soil temperatures were obtained by removing surface organic horizons. Ripping produced somewhat higher soil temperatures than scalping at the drier, lower-elevation site, but slightly reduced soil temperatures at the wetter, higher-elevation site. Near-surface air temperatures were more extreme (higher daily maximums and lower daily minimums) over the control than over exposed mineral soil. Root zone soil moisture deficits largely reflected transpiration by competing vegetation; vegetation removal was effective in improving soil moisture availability at the lower elevation site, but unnecessary from this perspective at the higher elevation site. The expose mineral surfaces self-mulched and conserved soil moisture after an initial period of high evaporation. Ripping and scalping resulted in somewhat lower near-surface available soil water storage capacities. Seedling establishment on both clearcuts was better following treatments which removed vegetation and surface organic horizons and thus enhanced microclimatic conditions, despite reducing nutrient supply. Such treatments may, however, compromise subsequent stand development through negative impacts on site nutrition. Temporal changes in the relative importance of different physical (microclimate) and chemical (soil nutrition) properties to soil processes and plant growth need to be considered when evaluating site productivity.
Key words: Microclimate, soil temperature, air temperature, soil moisture, clearcut, seedling establishment
1Unité de recherche et développement forestiers de l'Abitibi-Témiscamingue, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada, J9X 5E4; 2Centre de recherche en biologie forestière, Faculté de foresterie et de géomatique, Université Laval, Ste-Foy, Québec, Canada, G1K 7P4
Soil compaction induced by forest harvesting operations can reduce site productivity. Intensity, extent and persistence of soil compaction were assessed on fine to medium and coarse textured soils. Severe compaction took place in the wheel track section of the skid trails. On fine to medium textured soils, half of the effects on the 0-10 and 10-20 cm mineral soil bulk densities (+11 and +8 %) and half of the changes in the 10 cm depth soil strength (+69 %) occurred in the course of the first two skidding cycles (cycle of half impact). On coarse soils, half of the effect on the 0-10 cm bulk density (+11%) occurred during the first three passes. Cycles of half impact for soil strength were 9, 14, 7 and 6 for the 2.5, 5, 10, and 20 cm depths and corresponded to increases of 235, 402, 157 and 103% respectively. Compaction was more limited between track sections of trails. Six to twelve years following clearcutting on fine to medium textured soils, 0-10 cm soil bulk density was less in the skid trails than on the undisturbed sections of cutovers. Careful logging on moist, fine to medium textured soils is the safest way to limit the extent of soil compaction. On coarse textured soils, spreading the traffic remains a valid option.
Key words: Soil compaction, bulk density, soil strength, forest harvesting, careful logging
Canadian Forest Service P. O. Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7
Vertical distribution of fine root biomass and nutrient content was examined within a black spruce (Picea mariana) stand growing on a boreal peat soil in northeastern Ontario. The influence of site physical and chemical properties on fine root biomass production was assessed. More then 80% of the fine roots were present in moss plus the top 10 cm of peat where nutrient and aeration are most favourable. The fine root biomass was significantly higher with alder (5.9 kg/m3) (Alnus rugosa) as understory vegetation compared to non-alder locations (2.9 kg/m3). Total nutrient content in fine roots was 54, 3.2, 5.4, 63 and 5.7 kg/ha on the alder site and 20, 1.4, 2.3, 28 and 4.2 kg/ha of N, P, K, Ca, and Mg on the non-alder site, respectively. Nutrient concentrations in fine roots were strongly dependent upon the availability of nutrients in the peat. Fine root biomass had a strong positive relationship with peat available P and exchangeable K contents suggesting that P and K may be limiting nutrients for black spruce in this peat soil.
Key Words: Nitrogen, phosphorus, potassium, boreal peatlands, aeration, water table.
1Centre de recherches sur les sols et les grandes cultures, Agriculture et Agroalimentaire Canada, 2560 boulevard Hochelaga, Sainte-Foy Québec, Canada G1V 2J3; 2Centre d'agriculture biologique (CAB), 401 rue Poiré, La Pocatière, Québec, Canada G0R 1Z0; and 3Ferme de recherches sur le mouton, Agriculture et Agroalimentaire Canada, 1642 rue de la Ferme, La Pocatière, Québec, Canada G0R 1Z0
The addition of compost may mitigate soil degradation and contribute to the soil nutrient supply in spring cereal monoculture. A field study was carried out in eastern Québec (Canada) to assess the impact of composts from four sources and ammonium nitrate (AN) applied at different rates in spring on soil moisture and inorganic N in spring wheat production (Triticum aestivum L. cv. Messier). The experiment was conducted in 1994 and 1995 on two different soils: a Kamouraska clay (Orthic Humic Gleysol) and a Saint-André sandy loam (Fragic Humo-Ferric Podzol). Composts were applied at rates of 0, 90, 180 and 360 kg total N ha-1. Ammonium nitrate was applied at 0, 45, 90 and 180 kg N ha-1. Treatments in which AN was added to composts were also included. Thirty days after N application, profile soil inorganic N increased linearly with rates of commercial composts and AN but not with farm composts whereas at harvest, residual soil N was not affected by composts but was increased by AN. The relative contribution of the compost organic fraction was negligible in the first year of application. Soil inorganic N at 30 d after fertilizer applications was significantly related to plant N uptake at harvest (r2=0.74), suggesting useful index of compost N availability. Large amounts of compost raised soil moisture content of the sandy loam by 3 to 5%, particularly under dry climatic conditions. Commercial composts have a small N fertilizer value whereas composted dairy manure should be preferably considered as a soil amendment.
Key words: Dairy manure compost, shrimp wastes, peat moss, wheat
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, British Columbia, Canada V0H 1Z0
A field trial was designed to test the potential of various wastes as soil amendments in horticultural production. Swiss chard (Beta vulgaris L.) and carrot (Daucas carota L.) were grown from 1993-95 under irrigation in a coarse-textured, British Columbia soil to which annual applications of 45 t ha-1 of various organic amendments plus NPK-fertilizers had been applied. The amendments included biosolids from Vancouver, Kelowna and Penticton, biowastes from Aldergrove and Abbotsford, and peat. Yield of both chard and carrot was increased for some organic treatments plus fertilizer relative to plots receiving commercially recommended rates of NPK-fertilizer only (control plots). Leaf N, P, Zn and Cu concentrations of both crops were usually elevated, but not to toxic values, in plots receiving wastes containing high concentrations of the respective nutrients. By the end of the third growing season, extractable P, Zn, and Cu increased in the surface 15 cm of soil, relative to control plots, with P and Cu increases evident to 30 cm depth. Extractable K and pH varied with applied waste with some treatments having higher and other treatments lower values than in control plots. The cumulative evidence suggested that many locally-produced biosolids and biowastes have the potential to improve soil quality and the growth of high value horticultural crops.
Key words: Leaf N, leaf and extractable soil P, K, Mn, Zn and Cu, soil pH and EC, yield
Research Centre, Agriculture and Agri-Food Canada, P.O. Box 3000, Lethbridge, Alberta, Canada T1J 4B1
There are several reasons why measuring ammonia emissions are important in agriculture. The emission of ammonia from stored and land-applied manure to the atmosphere can be a significant loss of nitrogen for crop production. It is necessary to quantify this loss to evaluate manure handling practices which maintain the nutritive value of the manure. Minimizing the emissions of ammonia from manure also reduces agriculture's impact on the environment. A high atmospheric concentration of ammonia can result in acidification of land and water surfaces, cause plant damage and reduce plant biodiversity in natural systems. Ammonia emissions from manure coincide with odours which are a nuisance in areas of intensive livestock operations. Reducing ammonia emissions by altering manure management will also reduce odour problems. The purpose of this paper is to review agricultural sources of ammonia and describe techniques used in determining the loss of ammonia from manure-amended soils. Micrometeorological techniques are used to estimate field scale emissions whereas, for small plots where treatment effects are used, chambers and mass balance techniques are more suitable methods. A simple method is described, which, when combined with a denuder sampler mounted on a wind vane, permits flexibility in experimental design, and requires fewer ammonia samples than the traditional mass balance approach. A chamber method making use of diffusion samplers is also described which can measure the ammonia concentration in the air at the soil surface.
Key words: Ammonia, volatilization, nitrogen loss, agriculture, manure, slurry, micrometeorology, dispersion, chamber, wind tunnel
1Department of Soil Science, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A8. (mermut@sask.usask.ca); 2National Research Council, Plant Biotechnolgy Institute
The application of a sugarcane distillery waste known as vinasse to agricultural land has become a common practice in Brazil. The vinasse samples used in this study were collected from several sugarcane distilleries in Northeastern Brazil. These samples were fractionated into dissolved organic carbon (DOC) and particulate organic carbon (POC) fractions. Unfractionated and fractionated vinasse were studied using 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy as well as diffuse reflectance Fourier-transform infrared (DR-FTIR) spectroscopy. Aproximately 79 to 92 % of the total unfractionated vinasse dry matter was in the form of DOC fraction. 0-alkyl C (42-53 % of the total C) and carboxyl C (12-25 % of the total C) comprised a significant portion of the 13C NMR spectra of the DOC fraction. The presence of carbohydrates and COOH/COO- was suggested by the DR-FTIR as well. Both 13C NMR and DR-FTIR spectra of this fraction were generally similar to the spectra of the fulvic acid (FA) fraction of soil and sewage sludge. The spectra of DOC differed from the FA fraction in that it showed smaller amounts of aromatic C and had an absence of amide group (bands at 1650 cm-1 and 1540 cm-1 ). In the POC fraction, 0-alkyl (17-52 % of the total C) and alkyl C (15-41 % of the total C) were the major contributors. The peaks at 62 ppm, 72 ppm, 84 ppm and 105 ppm in the 0-alkyl region indicate the presence of cellulose and/or hemicellulose. The alkyl group was comprised mainly of long-chain structures. The total N content in this fraction is ~3-7 times as much as in the DOC fraction. The presence of amino acids in the POC fraction was suggested by both 13C NMR and DR-FTIR spectra.
Key words: 13C NMR, FTIR, vinasse, DOC, POC
1Agriculture and Agri-Food Canada, Semiarid Prairie Agricultural Research Centre, Box 1030, Swift Current, SK, S9H 3X2, and 2Agriculture and Agri-Food Canada, Research Farm, Box 760, Indian Head, SK, S0G 2K0
Society is interested in increasing C storage in soil to reduce CO2 concentration in the atmosphere, because the latter may contribute to global warming. Further, there is considerable interest in the use of straw for industrial purposes. Using soil samples taken from the 0-7.5 and 7.5-15 cm depths in May 1987 and September 1996, we determined organic C and total N in five crop rotations (9 treatments) using automated Carlo Erba combustion analyzer. The experiment was managed using conventional mechanical tillage from 1957 to 1989; it was changed to no-tillage management in 1990. Our objective was to determine: (a) if change to no-tillage management had changed soil C and N storage, and (b) if method of calculating organic C and N change would influence interpretation of the results. All three methods of calculation confirmed the efficacy of employing best management practices (e.g., fertilization based on soil tests, reducing summerfallow, including legumes in rotations) for increasing or maintaining soil organic matter, and showed that the latter was directly associated with the amount of crop residues returned to the soil. Where bulk density was significantly different between sampling times, the often used mass per fixed depth (MFD) (i.e., volume basis) calculation can lead to erroneous conclusions. When the recently recommended mass per equal depth (MED) method of calculation was used, it showed that 6 yr of no-tillage did not increase soil organic C or total N. However, in unfertilized systems, where crop yields are gradually decreasing since the change, there is an accompanying decrease in organic matter, while fertilized, or high fertility systems that include legume hay crops, in which wheat yields have been maintained have tended to maintain the organic matter level over time. When the MFD calculation was used, there was no change in C over time when straw was harvested in the F-W-W system; however, the MED calculation and concentrations tend to show a decrease in soil C and N. This suggests that in time, industrial use of straw may have negative consequences for soil conservation. We concluded that concentrations may be as effective as MED for assessing changes in organic matter, provided "amounts" are not required.
Key words: Straw removal, fertilizers, legumes, cropping frequency, C mass calculation
Department of Land, Air, and Water Resources, University of California, Davis, CA 95616 (U.S.A.).
Knowledge of the transfers of selenium (Se) in the soil-plant-atmosphere environmental compartments is fundamental in assessing Se cycling through the environment. The purpose of this study was to determine the effects of straw amendments and barley (Hordeum vulgare L.) on Se cycling in soils from Kesterson Reservoir, Merced County, CA, and to evaluate the feasibility of these agricultural practices as bioremediation strategies. Four treatments were evaluated: soil only, soil + straw, soil + plant, and soil + straw + plant. Straw amendments greatly reduced Se from soil solution (92-97% of initial soluble Se). Selenate [Se(VI)] was the predominant species in soil solution. Phosphate-extractable Se did not account for the decline in soluble Se. Selenium volatilized by microbes represented only 4-5% of the soluble Se removed. Highest Se removal from soil solution and highest Se volatilization rates occurred when both microbial activity and growth were maximal. Selenate microbial reduction to more insoluble Se forms may be responsible for this removal. Plants did not account for as much Se removal from soil solution as did straw amendments. Total shoot Se corresponded to 1-9% of soluble Se removal. At the end of the experiment, Se in plants represented 0.1-0.7% of total Se in the system, and the Se volatilized accounted for 0.2 to 0.5% of total Se inventory. The results obtained in this study suggest the use of straw amendments as a remediation technique for managing Se contamination at Kesterson Reservoir.
Key words: Barley, selenium, soil solution, straw, volatilization
1Research Station, Agriculture and Agri-Food Canada, P.O. Box 1240, Melfort, Saskatchewan, Canada S0E 1A0; 2Research Station, Agriculture and Agri-Food Canada, Agassiz, British Columbia, Canada, V2B 8A9; 3B.C. Ministry of Forestry, Kamloops, British Columbia, Canada, V2B 8A9; 4Research Centre, Agriculture and Agri-Food Canada, Swift Current, Saskatchewan, Canada S9H 3X2; and 5Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, Saskatchewan, Canada S7N 0X2
Uptake of N, P and S nutrients in the herbage of different pasture species were determined at eight sites within pastures located on Luvisolic soils in northeastern Saskatchewan, Canada. Also, the nutrient status of the soil was related to herbage yield response to N, P, and S fertilizers. Soil tests would be used to establish the initial response to fertilizer and thereafter, nutrients removed from the soil could be replaced by fertilizer. Experiments in the study included one site with bromegrass (Bromus inermis Leyss.) and alfalfa (Medicago media Pers.), six sites on a pasture mixture ( Bromus inermis Leyss., Festuca rubra L., Poa pratensis L. and Medicago media Pers.) and one site with Russian wildrye (Psathyrostachys juncea (Fisch.) Nevski) at both Pathlow and Pleasantdale pastures. Nitrogen and P fertilizers were applied at 0, 45 and 90 kg N ha-1 in combination with P at 0 and 20 kg ha-1. Sulphur treatments included 90N-20P-20S (sulphate source, kg S ha-1) on pasture mixture sites and two treatments 90N-20P-23S and 90N-20P-45S (elemental source, kg S ha-1) on bromegrass and alfalfa. Maximum uptake of nutrients were 103.6 kg N, 11.5 kg P and 5.2 kg S ha-1 with the application of 90N-20P-45S (kg ha-1) on the bromegrass-alfalfa pasture. The controls resulted in the lowest uptake of 20.2 kg N, 1.9 kg P (pasture mixture) and 1.5 kg S ha-1 (bromegrass and alfalfa). Yield response to N and P fertilizers (percentage yield over control) was related to soil tests for N, P and S (R2=0.42). Herbage yield increase (log10 mean of years) from S fertilizer over the control was negatively related to the soil test for S on six sites (r2=0.77). Uptake of N, P and S in herbage gave an adequate estimate of nutrient removal and the amount of fertilizer to apply to maintain soil nutrient levels.
Key words: Pasture, N, P. S, herbage, soil tests, yield
Agriculture and Agri-Food Canada, Research Centre, Charlottetown, Prince Edward Island, Canada CIA 7M8
Non-inversion tillage can have significant benefits over inversion tillage in loosening soils under permanent pasture. A suite of attributes was used to characterize the degree of compaction at the 0 to 20 cm depth of a Charlottetown fine sandy loam under a 10 year pasture in Prince Edward Island. Non-inversion tillage, using a paraplow, a slant-legged cultivator loosened the soil at the 10 to 20 cm depth. Penetrometer resistance profiles showed that the loosened soil condition persisted for 3 to 4 years. Non-inversion soil loosening caused a negative yield response, which was possibly related to root injury.
Key words: Podzol, penetration resistance, Kentucky bluegrass, white clover
Agriculture and Agri-Food Canada, Box 29, Beaverlodge, Alberta, Canada T0H 0C0
Sorption is one of the key processes controlling the fate of agrochemicals in soil systems. The sorption of agrochemicals on a soil matrix can be affected by changes in chemical and physical properties caused by different tillage practices. Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), dicamba (3,6-dichloro-2-methoxybenzoic acid), and MCPA ((4-chloro-2-methylphenoxy)acetic acid), weakly acidic herbicides, are commonly used to control broadleaf weeds in crop production. The sorption of the three herbicides by surface soils (0-5 cm) from different tillage systems was studied by batch equilibrium. Of the herbicides used, MCPA was sorbed on soil in the greatest quantity, dicamba was the least sorbed, and the sorption was dependent on the pKa values of herbicides. In a sandy loam soil, more herbicide was sorbed under no-tillage (NT) than conventional tillage (CT). However, in a clay soil the difference in herbicide sorption between the two tillage systems was not consistent. The results can be explained in terms of changes in soil pH and organic matter content. The presence of clopyralid and MCPA lowered the sorption of dicamba, and MCPA was more effective than clopyralid in competing for sorption sites with dicamba.
Key words: Herbicide sorption, clopyralid, dicamba, MCPA, tillage
1Earth System Science Division, Department of Science and Technology, Technology Bhavan, New Delhi 110 016 India; 2Agrometeorology, Land Resource Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1; and 3Field Crop Pest Management, Ridgetown College of Agricultural Technology, Ridgetown, Ontario, Canada N0P 2C0
The onset and cessation of surface wetness on maize ears were simulated with six models, using hourly meteorological data, because of the linkage between wetness duration and possible forecasting of fungal infections that produce mycotoxins. Two threshold models (using relative humidity and dew point temperature), one regression model (using humidity and wind speed), and three physical models based on the energy balance approach, were compared. Also, spatial and temporal variability in wetness duration was measured and simulated at three sites located at distances up to 29 km from a central weather station. The estimated wetness values were compared with observations from cylindrical wetness sensors placed near ear level in maize canopies. The results relate to potential mycotoxin warning systems and indicate that threshold models can provide reasonable estimates of ear wetness duration in this region, that a comprehensive physical model can give superior estimates, and that wetness estimates made from a central weather station data can be extended to nearby crop fields with a moderate degree of confidence.
Key Words: Epidemiology, mycotoxins, surface wetness models
1Atmospheric and Hydrologic Sciences Division, Prairie and Northern Region, Environment Canada, 123 Main Street, Suite 150, Winnipeg, Manitoba, Canada R3C 4W2 and 2Department of Soil Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
How do warm summers (June-July-August) influence the actual evapostranspiration totals from cropped land sown to spring wheat on the eastern Canadian prairies? The eastern prairies is a semi-arid region where over 60% of the land is cultivated. Over a third of the cropped land is usually sown to spring wheat. A comparison of mean summer temperatures and modelled evapotranspiration, for years 1988 to 1996, demonstrated that, with the current environmental conditions and farming practices, warm summers have lower actual evapotranspiration totals from spring wheat than cool summers. The average daily actual evapotranspiration rate is generally higher in years with higher mean summer temperatures, however, the crop growth-period is shorter. The net effect is lower total actual evapostranspiration from spring wheat. This suggests that climate warming on the eastern Canadian prairies, if the current trend continues and all other factors remain equal, will reduce, on average, the total actual evapotranspiration from spring wheat. A reduction in the growth-period evapotranspiration from lands sown to spring wheat will likely decrease the total actual evapotranspiration for the entire warm season as growth-period evapotranspiration currently makes up about three quarters of the seasonal total. However, the magnitude and timing of the reduction is far from certain. The consequence for agriculture may be a reduction in the average spring wheat yield because yield is positively correlated with the actual evapotranspiration total from the crop.
Key words: Modelling, crop growth-period, yield, climate warming