Brushing Treatments Research Articles

Can Spot Motor-Manual Brushing Treatments Be Effective for Controlling Aspen and Increasing Spruce Growth in Regenerating Mixedwood Stands?

Broadcast motor-manual or manual brushing treatments applied to control aspen (Populus tremuloides Michx.) in young spruce (Picea glauca (Moench) Voss) plantations often result in increases in the number of aspen stems and the amount of aspen competition. In this study data collected at three locations is used to examine the potential effectiveness of spot brushing treatments, applied over radii ranging between 1.0 and 2.5 m around individual spruce, to aspen that are two, four or six years old. Results indicate that spot manual or motor-manual treatments result in reductions in the number and size of aspen stump sprouts compared to the untreated control. However, when aspen size and vigour are reduced due to site or other factors, as observed for blocks at one location, post-treatment aspen densities may still be high (e.g., above 5000 stems ha−1). Spot treatments applied when aspen regeneration was two years old were observed to be less effective than treatments applied at ages 4 or 6. At two study locations where control was effective, spot brushing treatments significantly increased spruce diameters after treatment compared to untreated. Broadcast or spot treatment using basal bark application of triclopyr ester (Release®) herbicide at one of the study sites resulted in similar increases in spruce diameter to those observed for motor-manual treatment.

Unidirectional versus bidirectional brushing: Simulating wind influence on Arabidopsis thaliana.

Plants acclimate to various types of mechanical stresses through thigmomorphogenesis and alterations in their mechanical properties. Although resemblance between wind- and touch-induced responses provides the foundation for studies where wind influence was mimicked by mechanical perturbations, factorial experiments revealed that it is not always straightforward to extrapolate results induced by one type of perturbation to the other. To investigate whether wind-induced changes in morphological and biomechanical traits can be reproduced, we subjected Arabidopsis thaliana to two vectorial brushing treatments. Both treatments significantly affected the length, mechanical properties and anatomical tissue composition of the primary inflorescence stem. While some of the morphological changes were found to be in line with those induced by wind, changes in the mechanical properties exhibited opposite trends irrespective of the brushing direction. Overall, a careful design of the brushing treatment gives the possibility to obtain a closer match to wind-induced changes, including a positive tropic response.

Mechanical stimulation in wheat triggers age- and dose-dependent alterations in growth, development and grain characteristics.

Background and AimsWheat crops are exposed to a range of mechanical stimulations in their natural environment, yet we know very little about their response to such conditions. The aim of this study was to better understand the effect of mechanical stimulation on wheat growth and development, stem mechanical properties and grain measures. We focused on the following questions: (1) Does plant age affect the response to mechanical stimulation? (2) Is there a minimum threshold for the perception of mechanical stimuli? (3) Is the effect of manual brushing different to natural wind stimulation?MethodsFor age– and dose–response experiments, wheat plants were grown under controlled glasshouse conditions with brushing treatments applied using a purpose-built rig. The results of the controlled experiments are compared with those from an outside experiment where wheat plants were exposed to natural wind, with or without additional brushing. Detailed phenotypic measurements were conducted and treatment effects on grain characteristics were determined using micro-computed tomography imaging.Key ResultsTwo-week-old wheat plants were particularly sensitive to mechanical stimulation by controlled brushing treatments. Amongst others, plants exhibited a large reduction in height and grain yield, and an increase in tillers, above-ground biomass and stiffness of stem segments. Plants responded significantly to doses as small as one daily brushstroke. Outdoor experiments by and large confirmed results from controlled environment experiments.ConclusionsThe morphological and developmental response to mechanical brushing treatment, in relation to vegetative above-ground biomass and grain yield, is dependent on plant age as well as the dose of the treatments. This study shows that mechanical stimulation of wheat impacts on a multitude of agriculturally relevant traits and provides a much needed advancement of our understanding of wheat thigmomorphogenesis and the potential applications of mechanical conditioning to control relevant traits.

Effectiveness of Thymoquinone and Fluoridated Bioactive Glass/Nano-Oxide Contained Dentifrices on Abrasion and Dentine Tubules Occlusion: An Ex Vivo Study.

Objectives Dentin hypersensitivity (DH) is mainly due to the loss and replenishment of minerals from tooth structure, where the lost minerals can be rehabilitated with a biomimetic approach. The objectives were to determine the relative dentin abrasivity (RDA) of experimental (EXT) dentifrices and to determine the efficacy to occlude dentinal tubules. Materials and Methods Experimental dentifrices contained nano-fluoridated bioactive glass (n-FBG: 1.5 wt.% [EXT-A], 2.5 wt.% [EXT-B], and 3.5 wt.% [EXT-C]), nano-zinc oxide (n-ZnO), and thymoquinone as active agents. Bovine dentin blocks were subjected to brushing treatments as per groups, that is, distilled water; commercial dentifrice (control, CT); EXT toothpastes; and EXT-D without active agents. Samples were tested for three-dimensional (3D) abrasion analysis according to ISO-11609:2010 (International Organization for Standardization [ISO]). The roughness average (Ra), RDA, surface topography, and elemental compositions were investigated. Statistical Analysis One-way analysis of variance (ANOVA) with post-hoc Tukey’s and Tamhane’s test was performed for characterizations using Statistical Package for the Social Sciences (SPSS) version 21. The result was considered significant with p -value ≤ 0.05. Results Comparisons of Ra differed significantly between all groups with p < 0.05 except CT and EXT-A. The RDA values of EXT-A, EXT-B, and EXT-C were calculated as 74.04, 84.26, and 116.24, respectively, which were well within the acceptable limit set by international standards. All n-FBG containing dentifrices demonstrated uniform occlusion of dentinal tubules; however, highly concentrated EXT dentifrices showed more occlusion. Conclusions Acceptable range of RDA and superior occlusion of tubules by novel dentifrices suggest that it may be recommended for treating DH.

Effects of theobromine toothpaste on prevention of enamel discoloration from coffee

This study investigated whether tooth brushing with toothpastes containing theobromine could prevent enamel discoloration due to coffee consumption. Thirty-five bovine incisor teeth were divided into groups that included brushing and no brushing treatments. Two brushing treatments consisting of two types of toothpaste: Theodent®, which contains theobromine, and Pepsodent®, which contains fluoride were crossed two brushing durations: 4 minutes 40 seconds and 20 minutes. Following the treatments, tooth specimens were immersed in coffee for 45 hours and the color change was measured using a Vita EasyShade spectrophotometer. Significant changes occurred in the color levels between the brushing and no brushing groups (ÄE* values; P <0.05), but there was no significant difference between the types of toothpaste used. These results indicate chemicals in both toothpastes can effectively reduce enamel discoloration due to coffee consumption. Future studies should consider the importance of natural substances, like theobromine, for tooth whitening.

Selective removal of paper birch increases growth of juvenile Douglas-fir while minimizing impacts on the plant community

ABSTRACTBroadcast weeding of naturally regenerating paper birch (Betula papyrifera) to improve performance of conifer crop trees is common in forest plantations in British Columbia, Canada, but such treatments are costly, reduce biodiversity and may increase disease. To investigate whether alternative treatments can enhance conifer performance with minimal loss of other ecosystem services, we examined effects of selective removal of paper birch in two interior Douglas-fir (Pseudotsuga menziesii var. glauca) plantations on Douglas-fir growth and survival, and cover and height of residual birch and the understorey plant community. Douglas-fir-centred birch-free patches of varying radius (0–2.5 m) were created by single and repeated manual cutting and Triclopyr® application. The “threshold brushing radius,” defined as the birch removal radius at which Douglas-fir performance was optimized was 2.0 m at the more productive site and 1.5 m at the less productive one. Armillaria root disease, the major Douglas-fir mortality agent, spiked in the 1.0 m radius manual cutting treatment at one location. The greatest reductions in birch and understory plant abundance occurred following the most intensive treatments. Selective brushing treatments are an effective alternative to broadcast removal of paper birch for increasing conifer performance, and have less impact on the plant community.

Effects of excising and washing treatments on the root respiration rates of Japanese cedar (Cryptomeria japonica) seedlings

Tree root respiration is an important component of the carbon balance in forest ecosystems; however, it is not clear whether root preparation treatments (such as excising and washing) affect root respiration measurements. Here, we aimed to compare the respiration rates of roots subjected to different treatments (i.e., washing with water vs. brushing without water, and excising vs. not excising) for 17-month-old seedlings of Cryptomeria japonica. Immediately after sampling an entire root system, the root respiration rate was measured on a mass basis using a closed static chamber system equipped with an infrared gas analyzer. We found that the respiration rates for roots that were excised 10–20 times were significantly higher than those for roots that were not excised. There was no significant difference in the root respiration rates between washing and brushing treatments. Our results indicate that large numbers of excisions (>10 times) could lead to bias in the measured changes in specific root respiration rates, and imply that differences between washing and brushing treatments do not affect the specific root respiration rate. We conclude that potential variation in recorded root respiration rates could be minimized by standardizing the root preparation technique, which should involve rapidly removing all loose soil and limiting the extent of root excision.

Clarifying the role of fire heat and daily temperature fluctuations as germination cues for Mediterranean Basin obligate seeders

This study aims to determine the role that both direct effects of fire and subsequent daily temperature fluctuations play in the seed bank dynamics of obligate seeders from the Mediterranean Basin. The short yet high soil temperatures experienced due to passage of fire are conflated with the lower, but longer, temperatures experienced by daily fluctuations which occur after removing vegetation. These germination cues are able to break seed dormancy, but it is difficult to assess their specific level of influence because they occur consecutively after summer fires, just before the flush of germination in the wet season (autumn). By applying experimental fires, seed treatments were imposed that combined fire exposure/non-fire exposure with exposure to microhabitats under a gradient of disturbance (i.e. gaps opened by fire, mechanical brushing and intact vegetation). The seeds used were representative of the main families of obligate seeders (Ulex parviflorus, Cistus albidus and Rosmarinus officinalis). Specifically, an assessment was made of (1) the proportion of seeds killed by fire, (2) seedling emergence under field conditions and (3) seeds which remained ungerminated in soil. For the three species studied, the factors that most influenced seedling emergence and seeds remaining ungerminated were microhabitats with higher temperature fluctuations after fire (gaps opened by fire and brushing treatments). The direct effect of fire decreased the seedling emergence of U. parviflorus and reduced the proportion of seeds of R. officinalis remaining ungerminated. The relevance of depleting vegetation (and subsequent daily temperature fluctuation in summer) suggests that studies focusing on lower temperature thresholds for breaking seed dormancy are required. This fact also supports the hypothesis that the seeding capacity in Mediterranean Basin obligate seeders may have evolved as a response to a wide range of disturbances, and not exclusively to fire.

The dentine remineralization activity of a desensitizing bioactive glass‐containing toothpaste: an in vitro study

Dentine hypersensitivity occurs easily on exposed dentine. This study aimed to evaluate the effectiveness of a novel bioactive glass-containing toothpaste on dentine permeability and remineralization. Thirty dentine discs were divided into three groups of 10 specimens each. The groups corresponded to the following brushing treatments: no brush, distilled water, and bioactive glass-containing toothpaste (Novamin). The toothpaste was applied twice a day for 7 days. Dentine permeability was measured after ethylene-diamine-tetraacetic acid (EDTA) etching, initial application, 3-day application, 7-day application and citric acid challenge, respectively. The dentine morphology was investigated using scanning electron microscopy (SEM). Attenuated total reflection Fourier transform infrared (ATR/FTIR) spectroscopy was performed to monitor the mineral variation on demineralized dentine. Qualitative information of elemental variation before and after treatments on completely demineralized dentine was detected by energy dispersive X-ray (EDX) analysis. The bioactive glass-containing toothpaste significantly reduced dentine permeability after the 7-day treatment and showed, under SEM, excellent resistance to acid challenge compared to the other groups. ATR/FTIR and EDX revealed increased mineral content after treatment with Novamin. As the innovative bioactive glass-containing toothpaste occlude dentinal tubules and resist acid challenge, it may be useful for the treatment of dentine hypersensitivity and dentine remineralization.

Effect of mechanical perturbation on the biomechanics, primary growth and secondary tissue development of inflorescence stems of Arabidopsis thaliana

Mechanical perturbation is known to inhibit elongation of the inflorescence stem of Arabidopsis thaliana. The phenomenon has been reported widely for both herbaceous and woody plants, and has implications for how plants adjust their size and form to survive in mechanically perturbed environments. While this response is an important aspect of the plant's architecture, little is known about how mechanical properties of the inflorescence stem are modified or how its primary and secondary tissues respond to mechanical perturbation. Plants of the Columbia-0 ecotype were exposed to controlled brushing treatments and then submitted to three-point bending tests to determine stem rigidity and stiffness. Contributions of different tissues to the inflorescence stem geometry were analysed. Perturbed plants showed little difference in stem diameter, were 50 % shorter, 75 % less rigid and 70 % less stiff than controls. Changes in mechanical properties were linked to significant changes in tissue geometry - size and position of the pith, lignified interfascicular tissue and cortex - as well as a reduction in density of lignified cells. Stem mechanical properties were modified by changes in primary tissues and thus differ from changes observed in most woody plants tested with indeterminate growth - even though a vascular cambium is present in the inflorescence axis. The study suggests that delayed development of key primary developmental features of the stem in this ecotype of Arabidopsis results in a 'short and flexible' rather than a 'short and rigid' strategy for maintaining upright axes in conditions of severe mechanical perturbation. The mechanism is comparable with more general phenomena in plants where changes in developmental rate can significantly affect the overall growth form of the plant in both ecological and evolutionary contexts.

Climate and site characteristics affect juvenile trembling aspen development in conifer plantations across southern British Columbia

In southern British Columbia, juvenile trembling aspen is managed primarily as a competitor with conifers rather than for its ecological and economic value. As a result, brushing treatments have been applied on a widespread basis and this practice is likely to continue in the near future. Given the potential for climate change to affect our valuation of aspen, we require a better understanding of factors that affect its development, its competitive ability with conifers and its responses to brushing. We used data from 11 aspen management experiments to examine the influence of climate and site factors on aspen height, cover, and density in 17–24 year-old control stands and 9–16 years after manual cutting or girdling. Models explained 64% and 89% of the variation in aspen height in control and manually brushed stands, respectively, but were poor for girdling. Increasing length of the frost-free period was associated with increasing aspen height in control stands, whereas drier summer conditions on cool aspects favoured height growth of aspen suckers following manual cutting. We also examined the influence of climate and site factors on three simple competition indices that describe the height and density of aspen relative to conifer height, and then tested how well these indices predicted conifer growth. The density of aspen taller than conifers accounted for 39% of the variation in lodgepole pine diameter and the ratio of aspen/conifer height accounted for 33% of the variation in Douglas-fir height, suggesting that aspen competition was only moderately important to conifer growth. Our findings imply that aspen may become more productive with warmer summers provided it is not limited by summer moisture availability and that mixed stand management is a viable option in southern interior stands.

Profitability of manual brushing in young lodgepole pine plantations

Manual brushing is an important silvicultural tool commonly used to control competing vegetation in young conifer plantations. Yet little is known about the short-term economic benefits of one versus two brushing treatments. Using forest establishment data from the Fraser Lake and Bednesti areas of the Central Interior of British Columbia, we examined the profitability of one and two applications of brushing treatments under different internal rates of return (IRR) and three brushing radii (0.75, 1.00, and 1.25 m). Our results showed that one year of brushing treatment would be profitable for almost all brushing radii since profitability required only a short reduction in cutting age and lower IRRs. Applying two consecutive years of brushing would clearly require either higher discount rates or a longer waiting period for the brushing to be profitable. We believe that the approach described in this paper will assist forest practitioners when analyzing the value of brushing in terms of return on investment over time. The economic framework will also assist forest practitioners when deciding on brush control options for young conifer plantations.

Modelling vegetation management treatments with the Tree and Stand Simulator

The Tree and Stand Simulator (TASS) has been used for over 20 years in British Columbia to generate yield tables for managed stands. In order to explore the impacts of weed control on site productivity we chose two vegetation management research trials where 10- to 15-year post-treatment data were available (Boston Bar and Mica research sites). Tree survival and height growth results were used to adjust the TASS input parameters to simulate the various brushing treatments. At the Boston Bar site, all vegetation reduction treatments shortened the Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) physical rotation age by up to 10 years and culmination mean annual increment (cMAI) was increased 8% to 11% relative to the untreated control. At the Mica site, the glyphosate and all repeated manual cutting treatments resulted in a shortening of the Engelmann spruce (Picea engelmannii Parry) rotation age by seven years and increased cMAI by approximately 11% to12%. Key words: growth and yield modelling, vegetation management, Pseudotsuga menziesii, Picea engelmannii

EFFECT OF SANITATION TREATMENTS WITH HEATED, CHLORINATED WATER ON THE MICROBIOLOGY OF FRESH-CUT THAI MANGOES

Studies were conducted to investigate the effects of fruit sanitation treatments on the microbiology of fresh-cut Thai mango (Mangifera indica L. 'Chok Anun'). Washing in warm (50°C) or cold (12°C) chlorinated water (100 mg L -1 ) for 5 min significantly (P≤0.05) reduced total microbial populations on the skin and stem end of mangoes. Yeast and mold populations were particularly sensitive to the effects of heat. Brushing did not significantly (P<0.05) improve the removal of microorganisms from the fruit surface at either temperature. Microbial populations on fresh-cut mango slices prepared from unwashed fruit were significantly (P<0.05) higher than those prepared from washed fruit. Chlorinated water washes at both temperatures were equally effective in moderating the transfer of microorganisms from the fruit surface to the flesh. After 7 days in storage at 5°C, microbial populations on slices prepared from unwashed fruit were significantly higher (P≤0.05) than those measured on slices prepared from washed mangoes. Brushing had no effect on the microbiology of the stored mango slices. Washing and brushing treatments did not alter chemical indices (pH, total acidity, soluble solids) or headspace gas composition (CO 2 , O 2 ) in stored mango slices.

Chemical, grazing, and manual cutting treatments in mixed herb–shrub communities have no effect on interior spruce survival or growth in southern interior British Columbia

Interior spruce ( Picea engelmannii Parry × glauca [Moench] Voss) plantations are commonly weeded of herbs, ferns, and shrubs using foliar glyphosate, livestock grazing, or manual brushing treatments, but it is unknown whether they result in improved conifer survival or growth. We found that despite reducing vegetation for 1–5 years, these treatments applied to mixed herb–shrub communities in southern interior British Columbia had no effect on 5-year survival or growth of interior spruce. Biogeoclimatic zone was the factor that most influenced spruce performance, with greater survival and height growth in the Interior Cedar Hemlock (ICH) zone than in the colder, higher elevation Engelmann Spruce–Subalpine Fir (ESSF) zone. Glyphosate caused larger reductions in vegetation cover and height than did grazing or manual cutting. Glyphosate also reduced plant species richness after 5 years, but none of the treatment methods affected species or structural diversity of the plant community. Structural richness was slightly greater in the ICH than ESSF zone. Our results indicate that the vegetation management treatments operationally applied to herb–shrub communities in southern interior British Columbia have been ineffective at releasing interior spruce.

Field Growth and Yield of Tomato Transplants Grown in the Float System Using Low Phosphorus Fertilizer and Height Restricting Cultural Practices

The float system is an efficient method of seedling production. This system requires use of cultural practices to prevent excessive stem elongation of tomato (Lycopersicon esculentum Mill.) seedlings. It is not known how these practices affect field growth and subsequent fruit yield and quality. Experiments were conducted in 2001 and 2002 to determine if restricting P supply, delaying fertilizer application, brushing, clipping, and ethephon application affect field performance of transplants. Transplants subjected to these cultural treatments in the float system were compared to transplants conventionally grown in the greenhouse. In 2001, there was little difference in field performance among transplants produced under the range of cultural conditions. Although differences in total fruit numbers or yields were nonsignificant in 2002, conventionally grown transplants produced higher early yields. Seedlings grown with low P fertilizer and receiving delayed fertilization or delayed fertilization plus brushing performed best of all float treatments in 2002. Ethephon application severely reduced early yield while increasing late-season yield. Production of tomato seedlings with low P in float systems is feasible, at least on a small scale for transplanting locally, when delayed fertilization or delayed fertilization plus brushing treatments are used to control seedling height.

Control of rhizopus rot of peaches with postharvest treatments of tebuconazole, fludioxonil, and Pseudomonas syringae

Rhizopus rot caused by Rhizopus stolonifer is a potentially serious postharvest disease of Canadian-grown peaches. Several new fungicides are effective against brown rot (Monilinia fructicola) of peaches, but little is known of their postharvest efficacies against R. stolonifer. Harvested peaches were arranged in trays, individually punctured once and co-treated with a suspension of both R. stolonifer sporangiospores and cells of an isolate of Pseudomonas syringae or one of 13 fungicides at 0.5–1.0 times the dilute concentration used to control brown rot in orchard programs. In subsequent experiments, the peaches were inoculated with R. stolonifer, incubated for 6 h, chilled, and a day later the inoculated sites were brushed with a suspension of fludioxonil, tebuconazole, or P. syringae. In the co-treatment studies, azoxystrobin, fenhexamid, fenbuconazole, myclobutanil, benomyl, and sulfur reduced rhizopus rot by 0–22%. Cyprodinil and propiconazole gave 20–60% reduction, while fludioxonil, tebuconazole, and two P. syringae isolates gave 75–100% reduction, comparable with that of dicloran and iprodione. Post-inoculation brushing treatments with P. syringae at 10 000 µg ESC 10/mL gave less than 20% control, while fludioxonil and tebuconazole gave 90% control (EC90) at 472 and 718 µg/mL, respectively.

Effect of toothbrushing on the toxicity of casting alloys

Statement of Problem. The biological properties of casting alloys have been assessed largely under passive conditions. The effect of common intraoral stresses such as brushing, toothpastes, and low pH on alloy toxicity are not known. Purpose. This study assessed the toxicity of 5 types of casting alloys commonly used in prosthodontics after toothbrushing, brushing in an acidic environment, or brushing with toothpaste. These toxicities were compared with those observed without any brushing. Material and Methods. Au-Pt, Au-Pd, Pd-Cu-Ga, Ni-Cr-Be, and Ni-Cr (no Be) alloys were brushed for 48 hours in a toothbrushing machine at 90 strokes/minute and 200g force. Alloys were brushed with either saline at pH 7, saline at pH 4 (acidified with sodium lactate), or saline with 1:7 (wt/wt) toothpaste. After the brushing regimen, the cytotoxicity of the alloys was assessed in a standard in vitro test. Cytotoxicities of the alloys after different brushing treatments were compared with unbrushed (control) specimens. Analysis of variance (ANOVA) and Tukey multiple comparison intervals (α=.05) were used to identify significant differences among brushing conditions. Results. Brushing at pH 7 significantly increased the toxicity of the Pd-Cu-Ga alloy (15% to 20% over unbrushed specimens). Brushing at pH 4 increased the toxicity of the Au-Pt and Au-Pd alloys by 30% and the Pd-Cu-Ga alloy by >40%. The Ni-based alloys were not affected by acid. After being brushed with toothpaste, both Ni-based alloys were significantly more toxic, but Ni-Cr-Be was the worst, increasing more than 60% in toxicity over the controls. The toxicity of the Au-Pd alloy also increased significantly (15%). Conclusion. Brushing dental casting alloys may increase their cytotoxicity in vitro, but the increase depends heavily on the alloy type and brushing condition. (J Prosthet Dent 2002;87:94-8.)

Effects of Surface Preparation on Pitting Resistance, Residual Stress, and Stress Corrosion Cracking in Austenitic Stainless Steels

Surface finishing treatments such as shot blasting and wire brushing can be beneficial in improving the integrity of machined surfaces of austenitic stainless steels. These operations optimize in-service properties such as resistance to pitting corrosion and stress corrosion cracking (SCC). In this study, ground steel surfaces were subjected to a series of sand blasting and wire brushing treatments. The surfaces were then characterized by their hardness, surface residual stress state, and resistance to stress corrosion and pitting corrosion. Some samples were selected for depth profiling of residual stress. It is found that surface hardening and the generation of near-surface compressive residual stress are the benefits that can be introduced by sand blasting and brushing operations.

Nitrogen competition using 15N between early successional plants and planted white spruce seedlings

The ability of noncrop plants to compete with white spruce (Picea glauca (Moench) Voss) seedlings for applied fertilizer N is not well understood. Therefore, the objective of this study was to examine the efficacy of fertilizer N uptake using 15N by planted white spruce seedlings and understory vegetation. Double 15N-labeled NH4NO3 was broadcast in 1-m2plots for control, disc-trenched, and disc-trenched + manual brushing treatments. The fate of applied 15N in white spruce and noncrop plants was determined at the end of the first two growing seasons. The major competitors for fertilizer 15N were Populus tremuloides Michx. and grasses during the first growing season, and Populus tremuloides, Epilobium angustifolium L., and Achillea millefolium L. during the second growing season. Disc-trenching plus manual brushing significantly increased the fertilizer use efficiency of white spruce seedlings by limiting competition; however, &lt;1% of the applied fertilizer 15N was utilized by the spruce seedlings after two growing seasons. The ability of competing vegetation to absorb broadcast fertilizer N suggests that alternative fertilizer types and placements be investigated to increase N uptake by white spruce seedlings planted in the boreal mixedwood forest.