Hardwood Bark Research Articles

Nitrogen Dynamics and Nutrient Budgets in Four Orchard Groundcover Management Systems

Excessive nitrogen (N) applications can increase surface and water contamination, and leaching losses may occur when N fertilizer rates are too high relative to crop demands and soil N availability. Quantifying nutrient inputs, cycling, and outputs from orchards provides a method to measure surplus of nutrients, particularly N, that may leach or runoff. We conducted a long-term study to develop N budgets based on observed nutrient dynamics under four groundcover management systems (GMSs) with and without N fertilization. Four GMS treatments were randomly assigned to 12 plots and maintained since 1992 in 2-m-wide strips within tree rows: pre-emergence residual herbicide (PreHerb), post-emergence herbicide (PostHerb), mowed-sod (Sod), and hardwood bark mulch (Mulch). We measured system N inputs in fertilizer, mulch biomass, rain, and irrigation water; N outputs in harvested fruit, surface runoff, and subsurface leaching; and internal N cycling from surface vegetation, soil mineralization, leaf fall, and pruned wood. For the year with N fertilizer (2005), the overall N balance was positive (inputs exceeded outputs) in all GMSs but greater in the PostHerb and Mulch treatments. In the year without N fertilizer (2007), the overall N balance was negative for PreHerb and PostHerb and positive for Mulch and Sod treatments. Soil mineralization and recycling groundcover biomass accounted for greater than 60% of internal N fluxes, and harvested fruit represented greater than 70% of N outputs from the system during both years. During the year with N fertilizer, N losses were 1% to 4% and 18% to 22% through surface runoff and subsurface leaching, respectively. During the year without fertilizer, surface runoff N losses were twice the subsurface leaching N losses in all GMSs.

Water Treatment Residual as a Bioretention Amendment for Phosphorus. II: Long-Term Column Studies

Bioretention is an EPA-designated best management practice developed to mitigate negative ecological effects from urban storm-water. However, while these facilities perform well for the removal of a multitude of pollutants, in many cases they are ineffective in treating excessive storm-water nutrients such as phosphorus (P) that may induce surface water eutrophication. This work builds on the results of a previous paper, which describe initial studies on the use of aluminum-based water treatment residual (WTR) as a bioretention soil media (BSM) amendment. A 5% WTR-, 3% triple-shredded hardwood bark mulch-amended loamy sand BSM was investigated in a large-scale (0.9 m) column to determine the media P adsorption performance under varying hydrologic and pollutant concentration conditions. Results indicate that the WTR-amended media adsorbed 88.5% of the applied P mass, relative to a non-WTR-amended control media for which effluent P mass increased by 71.2%. The amended media consistently produced total phosp...

Water Treatment Residual as a Bioretention Amendment for Phosphorus. I: Evaluation Studies

Urban stormwater runoff has been implicated as a major source of excess nutrients to surface waters, contributing to the development of eutrophic conditions. Bioretention, a promising technology for urban stormwater pollution treatment, was investigated to determine whether an aluminum-based water treatment residual (WTR) amended bioretention soil media (BSM) could adsorb sufficient P at low concentrations (120 μg P L-1), extrapolated for a 20-year facility lifetime. Batch and minicolumn studies were employed to determine both an optimal BSM mixture and media performance. Media tests demonstrated P adsorption proportional to WTR addition. Additional amendments such as quartz sand and hardwood bark mulch produced further significant variations in adsorptive behavior. WTR-amended media showed excellent P removal, meeting the developed benchmark for adsorptive behavior. Predominantly, media met minimal P adsorption requirements when it contained at least 4 to 5% WTR by mass (air dried). The use of an oxalat...

Microencapsulated Herbicide-Treated Bark Mulches for Nursery Container Weed Control

Nursery container preemergence herbicides must be applied multiple times, usually every 6 to 8 wk, in order to maintain acceptable weed control. Nursery growers have identified extended duration of container preemergence activity as a research priority for reduction of herbicide usage and costs. The objective of this study was to determine if the combination of slow-release (microencapsulated [ME]) formulations of alachlor and acetochlor with wood-based organic mulches could provide extended efficacy and reduced phytotoxicity vs. over-the-top (OTT) sprays or mulch alone. Efficacy and phytotoxicity studies were conducted over 3 yr with various plants. Both acetochlor formulation OTT sprays reduced spirea shoot dry weights at 45 and 110 days after treatment (DAT) compared with the controls, and emulsifiable concentrate (EC) acetochlor OTT spray also reduced shoot dry weights of rose. No herbicide-treated bark mulch (TBM) combination reduced rose or spirea shoot dry weights. EC acetochlor + hardwood (in 2003) was the only treatment to provide 100% weed control at 45 and 110 DAT. The addition of EC or ME acetochlor to mulch reduced phytotoxicity and extended efficacy in 2002 and 2003; alachlor EC or ME TBM did not. Regardless of bark type, 3-yr average EC and ME TBM were 80% more effective than untreated bark mulch (UBM) and 83% and 98% more effective at 45 and 110 DAT, respectively than their comparable OTT sprays. Of the eight treatments that received ratings above commercially acceptable, averaged over dates and years, the three providing the least phytotoxicity and greatest extent, consistency, and duration of efficacy were all TBM combinations: EC acetochlor + Douglas fir or hardwood bark, EC acetochlor + pine, and ME acetochlor + pine. TBM-reduced phytotoxicity compared with OTT sprays.

Harzianic Acid, an Antifungal and Plant Growth Promoting Metabolite from Trichoderma harzianum

A Trichoderma harzianum strain, isolated from composted hardwood bark in Western Australia, was found to produce a metabolite with antifungal and plant growth promoting activity. The structure and absolute configuration of the fungal compound, harzianic acid (1), were determined by X-ray diffraction studies. Harzianic acid showed antibiotic activity against Pythium irregulare, Sclerotinia sclerotiorum, and Rhizoctonia solani. A plant growth promotion effect was observed at low concentrations of 1.

Timed Release of Flurprimidol from a Granular Formulation in Mulches and Sand

Flurprimidol is a plant growth regulator that can be applied as a granular formulation. Understanding flurprimidol release from a granular formulation and movement in various mediums will impact how it is used. Dissipation of flurprimidol from a granular formulation and movement through organic media and sand were evaluated in a greenhouse and laboratory experiment. Experimental variables included media type, depth, and irrigation event. Dissipation isotherms were determined by applying nonlinear regression. Mobility was evaluated using columns filled with media, which was surface-spiked with the granular formulation and then irrigated once daily for 22 consecutive days. Leachate was collected and analyzed by high-performance liquid chromatography–mass spectroscopy. Half-life (DT50), defined as time to 50% reduction, varied among sand, media, and media depth. Flurprimidol dissipation was rapid through sand with DT50 of 6 days. DT50 increased with increasing media depth from 5 to 10 cm for pine bark plus sand, 18 and 35 days, and hardwood bark plus sand, 77 and 173 days, respectively. Maximum flurprimidol leaching was a cumulative 71% of applied amounts over 22 irrigation events through the sand. Hardwood and pine bark media allowed less than 25% of flurprimidol to escape through the column. Data for all media indicated that flurprimidol was mobile through the substrates but exhibited hysteresis with pine bark and hard wood bark media. An initial pulse of flurprimidol will release slowly from this formulation over time. These results indicate that flurprimidol will dissipate from a granular formulation over time and that it will have movement through sand soil and pine bark and hardwood bark media to reach the roots of growing plants.

Apple Root Growth, Turnover, and Distribution Under Different Orchard Groundcover Management Systems

Minirhizotrons were used to study root emergence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks (M.9/MM.111) under four groundcover management systems (GMSs)—pre-emergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod grass (Grass), and hardwood bark mulch (Mulch)—that had been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Roots were observed by camera at 2- to 3-weekly intervals during the growing seasons of 2002 and 2003 and from whole tree excavations in Apr. 2000. Tree growth and yield observations from 1992 to 2003 showed that Mulch and Post-H treatments produced more tree growth and higher yields than other treatments during most years; the Grass treatment usually had the smallest trees and lowest yields. More root emergence was observed in a light crop year (2002) than in a heavy crop year (2003). Pre-H treatment trees had more total roots and new roots than all other treatments, and trees in Grass plots had fewer total roots than others. Trees in Mulch plots had more shallow roots, and trees in Grass plots had more deep roots than others. Root diameter was positively correlated with overwintering root survival. The Pre-H treatment trees had greater root mortality than other trees during an unusually hot and dry growing season (2002) and this was attributed to higher shallow soil temperatures in this treatment. The GMS treatments affected root number and root depth distribution patterns. Despite microsprinkler irrigation, hot, dry weather conditions coincided with decreased root growth, increased root mortality, and reduced root median lifespan. GMS treatments affected root growth, turnover, and distribution at this orchard, and these differences were linked with long-term trends in tree growth and fruit production in this study.

The impact of surface applied mulches on selected physical properties of reclaimed mountaintop removal sites

Much of the land reclaimed since enactment of the 1977 Surface Mining Control and Reclamation Act is over-compacted. Excessive compaction in replaced growth media is detrimental to establishment of trees. If trees are to be grown on reclaimed sites, excessive compaction must be alleviated. Dry bulk density and penetration resistance can be used to indicate the level of compaction in replaced growth media. The University of Kentucky has developed reclamation test cells at a surface mine to determine the impact of organic soil supplements on selected soil physical properties of reclaimed sites. The organic soil supplements being evaluated include hardwood bark and straw and manure. Data were collected at the test cells for dry bulk density, maximum penetration depth and penetration resistance. The data show no statistical evidence that applying organic supplements has a major effect on selected soil physical properties in replaced growth media.

ORIGINAL RESEARCH: Removal of heavy metals from polluted waters using lignocellulosic agricultural waste products

Many agricultural wastes, including barks, manures, and composts, contain high levels of lignocellulosic materials. We hypothesized that the lignin fraction, which contains numerous reactive groups, would be highly effective in binding and removing heavy metal ions from contaminated water, and, further, that the absorptive capabilities of the materials would be strongly affected by the pH of the solution. A series of materials were tested, and, at pH levels above about 5.5, they were highly effective in removing heavy metal ions, generally as large or larger than nickel, but ineffective in removal of lighter ions such as sodium or magnesium. Various barks were generally the most effective and were capable of removing more than 90% of iron, copper, or lead from solutions in simple shake flask experiments. Materials that retain cellular structures and that have high lignin contents were highly effective; barks possess these properties. At alkaline pH levels, many heavy metal ions precipitate, but three separate lines of evidence indicate that, in the work reported here, ions were removed from aqueous solutions by absorption to barks rather than by precipitation. At acidic pH levels, they also were partially effective in removal of the oxyanion chromate. However, a more efficient method of removal of chromate involved reduction to chromite in acidic solutions, adjusting pH levels in transit to columns packed with bark, and removal of chromite with hardwood bark. The bark was capable of binding the chromite to a level more than 3% by weight, and the resulting bark-chromite mixture passed toxicity characteristic leaching procedure (TCLP) tests. This system is expected to be deployed to remediate a site with chromate-polluted groundwater.

Organic mulch biowall for PAH contaminated groundwater remediation

Organic mulch was used as an alternative supporting material in permeable, biological, barrier walls to prevent migration of PAHs. Three types of organic mulch, cypress bark (C), hardwood bark (H) and pine bark nuggets (P) were selected as potential media to capture pollutants or to support PAH-degrading microorganisms. Among the media, the hardwood mulch was selected for biowall testing. To simulate the fate and transport of PAHs in the subsurface biowall under aerobic conditions, two lab scale mulch-biofilm column reactors were operated. Naphthalene was chosen as the model PAH in these studies and was supplied at a loading rate of 50.9 g m −2 day −1. During the initial operation period of up to 372 pore volumes, the PAH removal efficiency remained stable at over 99%, due to sorption and biodegradation. After that, the mulch-biowall system showed variable removal efficiencies, in the range of 77–99.99%.

English

In 1996, a multidisciplinary group of researchers at the University of Kentucky initiated a study on the Starfire surface mine in eastern Kentucky to evaluate the effects of soil compaction and two organic amendments on the survivability and growth of high value tree species. Three types of prepared rooting medium were examined: compacted spoil, lightly compacted spoil, and uncompacted spoil. The compacted spoil was prepared using normally accepted spoil handling techniques that resulted in a smooth graded surface. The lightly compacted spoil was loose-dumped and struck-off with one or two passes of a bulldozer. The uncompacted spoil was loose-dumped and not further disturbed. In addition, organic amendments (mulches) were evaluated within the three reclamation techniques. The organic amendments used were processed hardwood bark mulch and a combination of straw and horse manure mulch. The following six species of trees were planted: white oak (Quercus alba), white ash (Fraxinus americana), eastern white pine (Pinus strobus), northern red oak (Quercus rubra), black walnut (Juglans nigra), and yellow poplar (Liriodendron tulipifera). Five of the six species, the exception being white ash, showed increased survivability as compaction was minimized. Additionally, the loose-graded techniques led to enhanced growth in height for the seedlings. The addition of organic amendments also showed additional benefit but results varied by species and by treatment. Results definitively show that strike-off and loose-dump techniques improve seedling height and survival. The data also suggest that even a small amount of traffic (i.e., one or two passes per the strike-off method) may result in enough compaction to significantly reduce survival and growth in some species, such as yellow poplar and white pine. In the backfilling and grading process, spoil material should be placed and compacted according to standard engineering practices so that the required stability and approximate original contour is achieved. However, the top 1.2 to 1.8 meters (4 to 6 feet) of material should not be graded or only lightly graded so that it is as uncompacted as possible.

APPLE ROOT GROWTH, TURNOVER, AND DISTRIBUTION UNDER DIFFERENT ORCHARD GROUNDCOVER MANAGEMENT SYSTEMS

Minirhizotrons were employed to study new root occurrence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks under four groundcover management systems (GMS): preemergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod (Grass) and hardwood bark mulch (Mulch) that have been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Root observations were taken at 2–3 week intervals during growing seasons of 2002 and 2003. Tree growth and yield data were collected annually since 1992. The Mulch and Post-H treatments had bigger trees and higher yields than other treatments; whereas the Grass treatment had the smallest trees and lowest yields. Higher number of new roots was observed in a light crop year (2002) than a heavy crop year (2003). Mulch trees had more shallow roots and Grass trees had fewer total roots than other treatments. Root diameter was positively correlated with overwintering root survival. The Pre-H GMS had higher root mortality during a hot and dry growing season (2002). GMS treatments affected root number and root depth distribution patterns. Hot and dry weather conditions and crop load reduced new root emergence, increased root mortality and reduced root median lifespan. GMS treatments together with environmental factors affected root growth, turnover and distribution.

Estimation of U.S. Bark Generation and Implications for Horticultural Industries

Abstract The historical, current, and projected supply of bark was evaluated. Since the 1980s more than 95 percent of the U.S. bark supply has been utilized in some way. Industrial fuel consumes the largest share of the market for bark, absorbing about 83 percent of softwood bark and 66 to 71 percent of hardwood bark. Current market share of bark for horticulture use (categorized in the miscellaneous group), is about 15 percent of softwood bark supply and about 30 percent of hardwood bark supply. In recent years, domestic timber harvest has been relatively stable or has slightly decreased. During the same time period, there has been an increasing demand for bark as an energy resource. Based on historical data, linear models were fitted between U.S. timber harvest and bark generation at the regional level. With those fitted models, projected bark generation was estimated based on the timber harvest data of the fifth Renewable Resources Planning Act (RPA) timber assessment. It is estimated that only a minor increase in the long term bark output will occur. For softwood bark which has the greatest demand, projected supply will be below the level of 2001 until about 2020. With expected horticulture industry growth, increased value of bark as a readily available energy source for wood processing mills, and a shift in pulp generation from domestic paper mills to international sources, the total amount and share of bark to the horticulture market will likely decrease.

Egg-Laying Preference of Female Fungus Gnat Bradysia sp. nr. coprophila (Diptera: Sciaridae) on Three Different Soilless Substrates

Fungus gnats, Bradysia spp., are major insect pests in greenhouses. Adult female fungus gnats prefer to lay eggs in growing medium that is microbially active or that contains high amounts of peat moss or hardwood bark. However, egg-laying preference has not been demonstrated quantitatively. This study was designed to determine whether fungus gnat Bradysia sp. nr. coprophila females prefer any of the three soilless growing media provided. The three soilless growing media tested were Metro-Mix 560 with Scott's Coir, Sunshine LC1 Mix, and Universal SB 300 Mix. Initially, the egg-laying potential of the fungus gnat species used in this study was assessed by dissecting mated females after 24, 48, and 72 h. For the egg-laying preference experiment, adults that emerged from pupae were aspirated into a plastic vial, sexed, and then allowed to mate for 24 h. Individual mated females were released into an experimental chamber (15 by 15 by 5-cm plastic container) consisting of four 6-cm petri dishes, three of which contained soilless growing media and one with filter paper (control). In total, there were 50 experimental chambers, with each chamber representing a replication. Females remained in the experimental chambers for 48 h after which the growing media were processed using a flotation/extraction method. The number of eggs laid by female fungus gnats ranged from 21 to 217 with most eggs recovered after 48 h (141.0 +/- 9.3). There were no significant differences among the three soilless growing media in terms of number of eggs laid, although all three growing media were significantly different from the filter paper with higher numbers of eggs laid in the soilless growing media than the filter paper. Despite no significant difference among the growing media in the number of eggs laid, fungus gnat females tended to lay eggs more often, based on the number of petri dishes in which at least one egg was laid, in Metro-Mix 560 (86%) than Sunshine LC1 (66%), Universal SB 300 (52%), or filter paper (18%). Based on the results of this study, female fungus gnats may not prefer a specific growing medium for oviposition. However, fungus gnat females may rely on other factors not tested in this study such as moisture content and volatiles emitted from growing media in their decision where to lay eggs.

Using 13C nuclear magnetic resonance spectroscopy for the study of northern hardwood tissues

Nuclear magnetic resonance (NMR) spectroscopy is a useful tool for examining the structural chemistry of natural organic matter. The use of cross-polarization and magic-angle spinning to study 13C functionality (CPMAS 13C NMR) is convenient, but not always quantitative. We used various 13C NMR techniques to examine the structural chemistry of bark and wood of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britt.). Spin counting experiments showed that 87%–97% of the 13C in the samples was observable by CPMAS 13C NMR. A comparison of CPMAS and Bloch decay experiments revealed few differences in spectral properties. Together, these results suggest that CPMAS 13C NMR is quantitative for these tissues. We observed little variation in the structural chemistry of wood, either among samples of the same species or among species. Within-species variations in bark chemistry were greater than in wood, probably because of variations in environmental conditions. However, we observed no significant differences in bark chemistry among the species. Bark and wood chemistry differed significantly, with the bark spectra displaying greater contributions from lignin, suberin, waxes, and resins. Hardwood spectra differ from softwood spectra in the aromatic C regions because of the contribution of syringyl units to hardwood lignin. Hardwood bark appears to contain less tannins than softwood bark. Together, the quantitative and qualitative features of CPMAS 13C NMR spectra are useful for studying the ecology of living and detrital wood and bark.

(62) Field Evaluation of Various Herbicide and Mulch Combinations for Ornamental Weed Control

Two experiments were conducted at the The Ohio State University Waterman Farm, Columbus, on efficacy and phytotoxicity with evalautions at 30, 60, 90, and 120 DAT using dry weights and visual ratings 0–10 with >7 being commercially acceptable for efficacy, and 1–10 with <3 being commercially acceptable for phytotoxicity. The herbicide-treated mulches and herbicide–mulch application methods were compared to sprays of the five chemicals applied directly to the surfaces of the plots [oryzalin (oryzalin), (AS) Surflan (aqueous solution) 2 lb/acre (a.i.), flumioxazin (SureGuard WDG), 0.34 lb/acre (a.i.), acetochlor 76% (Harness 2.5 lb/acre (a.i.), dichlobenil (Casoron CS) 4 lb/acre (a.i.) and a combination of oryzalin and flumioxazin], two untreated mulches (pine and hardwood) and a weedy. Mulches were applied untreated, over the top of soil surfaces sprayed with the different herbicides. Mulches were also applied untreated to untreated soil surfaces and then sprayed with the different herbicides. Pretreated bark mulches were also evaluated and prepared by placing the mulches on a sheet of plastic, as a single layer thick and sprayed and allowed to dry for 48 hours. Twenty of 38 treatments gave efficacy rating of >7, pooled over all evaluation dates. One was a direct spray, Surflan + SureGuard (7.6). Three were pretreated mulches, Surflan + SureGuard (8.2), Harness (7.8) and Surflan (7.4) treated pine. None of the pretreated hardwood barks provided ratings of >7. Nine were treatments with the herbicides applied under the bark. Seven of the nine provided ratings of >8 and only one involved hardwood bark, Surflan + SureGuard under pine (9.1), Casoron under pine (8.9), Surflan under pine (8.7), Harness under pine (8.3), Harness under pine (8.0) and SureGuard under hardwood (8.0).

Orchard floor management practices that maintain vegetative or biomass groundcover stimulate soil microbial activity and alter soil microbial community composition

Groundcover management systems (GMS) are important in managing fruit-tree orchards because of their effects on soil conditions, nutrient availability, tree growth and yields. We employed a polyphasic approach, incorporating measures of soil microbial abundance, activity and community composition, to study the long-term effects of different GMS on biotic and abiotic factors in an orchard soil. Four GMS treatments – Pre-emergence residual herbicides (Pre-H), post-emergence herbicide (Post-H), mowed-sod (Grass), and hardwood bark mulch (Mulch) – were established in 2-m-wide strips within tree rows in an apple orchard in 1992, and have been maintained and monitored annually until the present. We have measured soil water and nutrient availability, tree growth, and yields annually from 1993 to 2003. Soil nematode numbers and trophic groups were evaluated in July and Oct. 2001, and Sept. 2003. Numbers of culturable bacteria and fungi, soil respiratory activity, eubacterial and fungal community composition were determined in May and Sept. 2003. The Pre-H treatment soil had the fewest culturable bacteria, while the Grass treatment had the largest population of culturable fungi. Soil nematode population size and diversity were also affected by GMS treatments; the Pre-H treatment had the lowest ratio of (bacteriovores + fungivores) to plant parasitic nematodes. Soil respiration rates were higher in the Mulch than in other treatments during a 40-day incubation period. Hierarchical cluster dendrograms of denaturing gradient gel electrophoresis (DGGE) fingerprints for eubacterial community 16S rRNA genes indicated that Post-H and Grass treatments clustered together and separately from the Pre-H and Mulch treatments, which were also grouped together. The influence of GMSs on the fungal community, as assessed by PCR-DGGE of the internal transcribed spacer (ITS) region, was not as pronounced as that observed for bacteria. Soil fungal community composition under the Mulch differed from that under other treatments. The effects of GMS on soil microbial community abundance, activity, and composition were associated with observed differences in soil organic matter inputs and turnover, nutrient availability, and apple tree growth and yields under the different GMS treatments.

The removal of heavy metals in urban runoff by sorption on mulch

A series of adsorption experiments was conducted in order to assess the ability of three mulches to remove several of the heavy metal ions typically encountered in urban runoff. Three types of mulch, cypress bark (C), hardwood bark (H), and pine bark nugget (P), were selected as potential sorbents to capture heavy metals in urban runoff. The hardwood bark (H) mulch had the best physicochemical properties for adsorption of heavy metal ions. In addition, because of its fast removal rate and acceptably high capacity for all the heavy metal ions, it was concluded that the H mulch is the best of the three adsorbents for treatment of urban runoff containing trace amounts of heavy metals. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The sorption of these metals on H mulch conformed to the linear form of the Langmuir adsorption equation. At pH 5 and 6, the Langmuir constants ( S m) for each metal were found to be 0.324 and 0.359 mmol/g (Cu); 0.306 and 0.350 mmol/g (Pb); and 0.185 and 0.187 mmol/g (Zn) at 25 °C.

Evaluation of Dichlobenil and Flumioxazin Preemergent Formulations for Ornamental Weed Control

The objective of this study was to evaluate the extent and duration of efficacy and phytotoxicity of two new formulations of dichlobenil (Casoron 50WP and Casoron CS), applied alone or onto two bark mulches, pine nuggets or shredded hardwood. The herbicide treated bark was compared to a control (weedy check), direct sprays of the herbicides and mulch alone. Three granular preemergent herbicides, dichlobenil (Casoron 4G) and two formulation of flumioxazin (Broadstar 0.17G, VC1351, and VC1453) were also evaluated for a total of 12 treatments. The trial started on May 23, 2003. Visual ratings and dry weights were evaluated for efficacy at 4, 8 and 16 weeks after treatment (WAT) and phytotoxicity 2, 4, 8, and 16 WAT. Ratings of efficacy were based on a 1-10 scale where, 0 represents no control, 10 represents complete control. Visual rating scores of 1 (no injury) to 10 (complete kill) were used for phytotoxicity on Salvia May Night. The two most efficacious treatments are Casoron CS as a directed spray (7.9) and treated on pine nuggets (9.0). The hardwood bark with Casoron CS also was providing an efficacy rating of 7.75 in the analyses of combined dates 4 and 8 WAT. The weed control provided by the untreated hardwood bark and pine nuggets was not significantly different from the control. Four treatments—Casoron CS and 4G, Casoron CS on pine, and CS on hardwood—provided ratings of 3 and above for phytotoxicity, in the analyses of combined dates 2, 4, 8, and 16 WAT. Although the Casoron CS was the second most efficacious treatment it had a phytotoxicity rating of 9.25 over combined dates. The CS on pine, however, had a significantly reduced phytotoxicity rating (3.5) and superior efficacy.

Groundcover Management Systems Influence Soil Microbial Community Composition in an Apple Orchard

An apple (Malus domestica cv. Empire on M9/MM111 rootstock) orchard groundcover management systems (GMSs) study has been underway since 1992 in Ithaca, N.Y. Four GMS treatments are applied each year in 2-m wide tree-row strips: Pre-emergence herbicides (Pre-H: diuron + norflurazon + glyphosate); Post-emergence herbicide (Post-H: glyphosate); mowed-sod (Grass); and composted hardwood bark mulch (Mulch) treatment. The soil (silty clay loam) physical and chemical conditions have been monitored continuously. In May and Sept. 2003, we sampled topsoil beneath trees in each GMS and used PCR-DGGE combined with sequencing to characterize soil microbial community composition. Mulch had more culturable soil bacteria than the Pre-H treatment. Soil in Grass plots had the most culturable soil fungi. Soil microbial respiration rates were higher in Mulch than Grass and herbicide GMSs. Surface vegetation in the Grass and Post-H plots strongly influenced soil bacterial community composition. In Principal Component Analyses, Post-H and Grass treatments comprised one variance cluster, and Pre-H and Mulch treatments another. The soil fungal community was less diverse (fewer DGGE bands) than the bacterial community, and was less affected by GMS. Treatments with more surface vegetation (Post-H and Grass) also had more free-living and phytonematodes than Pre-H and Mulch. A total of 47 clones from 12 DGGE bands yielded 31 unique DNA sequences. Of these, 15 were novel sequences with no matches in the GenBank (NCBI) database. Another 10 (27 clones) could be matched with known fungal species at 96-100% identity. The primer pair used, ITS1F/ITS2, amplified a considerable number of Basidiomycetes and Ascomycetes, but there was no amplification for Zygomycetes and Oomycetes.