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United States Department of Agriculture

Agricultural Research Service

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Location: Application Technology Research

2010 Annual Report

1a. Objectives (from AD-416)
The objective of this funded research will be to determine agrichemical leaching levels from container nurseries in regions of the U.S. with no soil surface freezing. Oregon is a major production region of the U.S. where crops are primarily temperate plants that undergo winter dormancy, but where winter temperatures are mild (USDA Zone 7b) and generally above freezing. It has been previously assumed that leaching of agrichemicals (pesticides and fertilizers) is negligible during winter months. This research will initially document agrichemical loads in leachate during winter months, then develop remediation techniques to reduce those loads if necessary.

1b. Approach (from AD-416)
The experiment will be a 2 (CRFs) x 2 (taxa) factorial in a randomized complete block design with four replications and ten plants per replication. Broadleaf evergreen and deciduous shrub liners will be potted in summer (July-August). Both taxa will have either Osmocote (resin -coated) or Polyon (plastic-coated) CRFs. All plants will be potted in a industry representative substrate and receive additional micro-irrigation when there is not adequate rainfall. The experiment will be initiated with established plants in September and be completed in March. Plant, CRF, and substrate nitrogen and phosphorus content will be determined at both the beginning and end of the study to determine CRF release and plant uptake through the winter in mild climates. In addition, effluent nitrogen and phosphorus concentration will be monitored weekly. This data will be used to determine environmental impact of CRF’s. Substrate temperature, air temperature, and rainfall will be recorded hourly throughout the course of the experiment. All variables in the study will be tested for differences using ANOVA Fishers Least Significance Difference means separation where appropriate.

3. Progress Report
Program Effort: Numerous workshops and presentations to increase stakeholders’ fundamental understanding of the hydrology and chemistry associated with soilless substrates have been conducted. In addition, research on individual substrate components and their effect on Douglas Fir bark based soilless substrates, to determine nutrient contribution, effect on pH, water availability, and their overall effect on crop growth and water use efficiency have been completed or underway. Research is ongoing to determine the effect of substrate amendments dolomite and lime on substrate pH over time. Furthermore, we are currently investigating the effect of fertilizer application technique on crop response and environmental impact. In an effort to find multi-faceted solution to the bark shortage, we have begun to screen numerous, readily available products that show promise as an alternative soilless substrate and occur within a 200 mile radius of the Oregon nursery epic center (northern Willamette valley). These may include but are not be limited to: Douglas fir logging slash, whole-tree hybrid poplar, whole-tree ponderosa pine, culled shade trees, culled or disposed Christmas trees, rye grass seed straw, and bamboo. This research project was monitored by frequent communications via email and phone, personal visits at the American Society of Horticultural Science annual meeting, and written reports every 6 months.

4. Accomplishments

Last Modified: 06/23/2017
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