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United States Department of Agriculture

Agricultural Research Service


Location: Application Technology Research Unit

2010 Annual Report

1a.Objectives (from AD-416)
The objective of this project is to enhance food and ornamental production through improved means for delivering agrochemicals such that utilization of the materials is maximized while losses from leaching, drift, or off-target loss are minimized. These methods will provide abundant, safe food and ornamental crops. These discoveries will minimize environmental impact, reduce production costs, and reduce worker exposure. The specific objectives for the next five years include: Objective 1: Develop new or enhanced delivery technologies that provide the most efficacious application of production materials, including nutrients and pest management materials. Sub-objectives: Identify application factors affecting distribution and quality of deposits of pest management materials applied to nursery, floricultural, vegetable, fruit, and field crops, and to integrate findings with Drift Reduction Technology (DRT) research into crop production programs. Develop automated or mechanized chemical delivery technologies for greenhouse production systems based on pest population information and/or plant development and plant stress information. Objective 2: Improve understanding of substrate chemical, physical, and biological properties to improve container crop production while minimizing agrichemical leaching. Sub-objectives: Evaluate the use of regional agricultural/forest byproducts and synthetic materials for use as a substrate in nursery containers. Determine the effects of irrigation parameters and hydraulic properties of soilless substrates on nutrient and pesticide leaching from pot-in-pot production systems.

1b.Approach (from AD-416)
Application systems will be evaluated by examining deposition patterns on artificial targets and plant tissue, atomization characteristics, and off-target spray movement on passive ground and airborne collectors. The effect of air and travel speed and their interaction with droplet size on deposition patterns on artificial targets placed within different field crop canopies will be examined in field trials. Full assessment of the potential benefits of any DRT will be measured in the field under varying canopy conditions. The effect of air speed and its interaction with droplet size on deposition patterns on artificial targets placed within different field crop with horizontal and vertical target surfaces will be examined in field trials. Droplet size distributions and droplet velocities from atomizers will be determined using a particle/droplet laser image analysis system. Granular delivery systems will be evaluated for their ability to apply herbicides to potted surfaces. Pneumatic and mechanical means for aiding in movement through canopies will be incorporated into the delivery systems. The effectiveness of the delivery systems will be evaluated by examining the deposition granule patterns on the target surface as well as measurement of the amount of active ingredient. To improve safety, reduce production costs, and to put spray only where needed, a carrier system will be evaluated to automate spray delivery in greenhouse and sheltered environments. First studies will utilize a wheeled, hand-cart to evaluate technology to target spray delivery. Air-assist and electrostatic technology appropriate to a greenhouse production system will be evaluated. One or more synthetic materials and one or more agricultural materials will be compared with conventional pine bark for production of nursery plants. Polyethylene terephthalate (PET) is a synthetic material currently used for many applications that has potential as a substrate component. Another strategy will be to grow the substrate. Agricultural crops which produce large amounts of biomass will be grown, harvested, and processed into a substrate. PET, switchgrass chips and willow chips will be the first candidates tested for suitability as substrates. To determine the effects of irrigation parameters and hydraulic properties of soilless substrates on nutrient and pesticide leaching from pot-in-pot production systems a commercial pot-in-pot (PIP) system will be used. Pine bark will be amended with peat at three rates and irrigation will be applied either with a timer or automatically activated according to soil moisture readings from a neutron probe irrigation sensor. A complete fertilizer package and an insecticide will be incorporated into the substrate during the mixing process. A preemergence herbicide will be applied to the substrate surface of all containers after they are filled and planted. All production inputs and all climactic inputs will be recorded by data loggers. Leachates will be collected weekly and analyzed for all macro- and micro-nutrients using ICP analysis; insecticide and herbicide concentration in the leachates and plant tissue will be quantified with GC-MS analysis.

3.Progress Report
Significant progress was made on this research project in the last year in the areas of pesticide application efficiency, drift management, substrate analysis, and nursery weed management. Field studies have identified improved methods to apply pesticides in crops of different architecture such as those with the primary structure components being broad leaves or vertical stems. Field research was initiated to estimate the amount of fungicide moving through a potted plant canopy and ending up on the soil surface. Air-assist sprayer parameters including droplet size and air speed were evaluated to determine the most effective means of treating abaxial leaf surfaces on mature poinsettias. Fields studies were conducted to assess the potential benefits of using towers on tree sprayers as a potential Drift Reduction Technology for orchard or shade tree pest management. Lab and field studies have shown that alternative substrates to peat moss have acceptable potential for use in production of containerized ornamental plants. A new method for developing Moisture characteristic curves for soilless substrates at low tensions was successfully demonstrated.

1. Spray delivery to mature poinsettias could reduce insecticide use and improve pest control. Few recommendations are available on how to best match application systems to greenhouse ornamental production systems. ARS researchers in Wooster, Ohio initiated greenhouse studies to understand foliar deposit characteristics provided in a mature poinsettia canopy by handgun and boom delivery systems. All systems tested had difficulty treating the underside of leaves in the poinsettia canopy. Air-assisted, boom delivery produced the most uniform deposits which could result in more predictable insect control. Droplet size decreased with increasing nozzle pressure in the handgun systems but air entrainment aided delivery in the handgun applications as well as the air-assist boom systems. Producers can use these findings to better match the pest management need with the pesticide application options they have available as well as use these findings to reduce overall pesticide use and improve pest control.

2. Drift reduction opportunities identified for tree crops. Orchard spraying can result in significant off-target spray movement if the spray delivery is not matched to the canopy development and the size of the canopy. ARS researchers in Wooster, Ohio conducted several field trials to evaluate the differences off-target spray movement detected between tower sprayers and conventional, axial-fan, air blast sprayers during dormant season and fully mature stages of canopy development. Significantly more material delivered by the conventional orchard sprayer was detected above the canopy than for the tower sprayer. The dormant canopy permitted more material to flow through the target tree and deposit downwind but a mature canopy deflected spray above the canopy where it could be carried away more easily by the wind. These results will help identify the off-target spray risks when fruit growers treat trees at different stages of development and help identify methods to keep more spray material in the target area.

3. Improved weed management for potted nursery plants. Herbicide delivery through a potted nursery plant to the surface of the pot is difficult because the canopy can intercept a significant portion of the spray material. ARS researchers planned and conducted herbicide delivery studies using potted hydrangea plants and various application tools that have been shown to provide improved canopy penetration in field crop applications including large droplet nozzles, air-assisted delivery, and increased spray volume applications. Tests revealed that nearly 50% of the spray material was captured by the plant canopy and was unavailable to provide weed control on the surface of the pot. The multi-port air-assist sprayer produced the highest canopy deposits but the lowest spray deposits on the pot surface. There were no significant differences in the deposits on the pot surface by using coarse spray compared to medium spray nozzles. Spray volume had a slight effect but depended on the overall droplet size. There were no significant differences in droplet size observed. Commercial potted plant producers can use this information to help better target the pot surface with weed control materials and more accurately estimate the amount of herbicide that will be available to provide the desired weed control.

4. Wheat disease management spray delivery parameters identified. Cereal crops such as wheat are a challenge to protect from infection because different pathogens will cause infection in different parts of the plant canopy. The vertical (head and stem) and horizontal (leaf) structures may require different forms of treatment to achieve the necessary spray coverage for effective disease management. Field trials were designed by ARS researchers in Wooster, Ohio, to test the differences in spray deposits found on wheat heads, stems, and leaves following treatment by different droplet size nozzles and air-assisted delivery. Air-assisted delivery was found to be less effective at treating the upper canopy of the wheat. Twin-fan nozzles produced the highest deposits on the vertical plant surfaces (heads and stems). Growers and pest management specialists can use this material to optimize set-up of their wheat plant protection equipment when necessary to protect different parts of the canopy from infection which will result in higher crop yields.

5. Substrate alternatives for high pH loving plants. Decreasing availability of traditional potted plant substrate materials such as pine bark makes it necessary to identify alternative substrate materials. Several different plants were grown in various blends of cedar with pine bark and sand. Plant response varied depending on the plant and the rate of cedar mixed in the substrate. The physical properties data showed that there was significantly less water holding capacity and increased air space in the 80% cedar treatment. Thus, we think the differences in growth were primarily due to physical properties of the substrate rather than an allopathic response to chemicals in the cedar. Additionally, the pH of cedar is 6.57 compared to the pH of pine bark at 4.17. This could be a significant issue for plants requiring a low pH. However, most soils in Kansas (and the Great Plains) have inherently high pH (6-8) so plants grown in this region need to be suited for this climate.

6. Transition of alternative switchgrass substrate from replicated research to adoption by nursery producers. Pine bark is currently used as the primary potting substrate for the nursery industry, but its cost is increasing, its availability is decreasing, and it currently must be imported from southern U.S. states and transported over long distances. We have developed a new potting substrate comprised primarily of switchgrass, a biofuel crop that can be grown and harvested locally. Our goal for this year was to apply our research findings to a commercial-scale operation. We recently were able to obtain a large quantity of switchgrass, then use a cooperating nursery’s equipment and traditional production procedures to pot plants with our new substrate and compare to their traditional pine bark substrate. The processing and transportation of the switchgrass went smoothly, and the potting of the switchgrass substrate at the nursery went well. The switchgrass substrate performed as well as the traditional nursery substrate, demonstrating that it is a viable alternative to traditional pine bark based substrates. Successful adoption of switchgrass substrate will facilitate future adoption by the greater nursery industry. Adoption of this new substrate will decrease the industry’s reliance on pine bark that must be imported from far distances.

Review Publications
Altland, J.E., Krause, C.R. 2009. Use of Switchgrass as a Nursery Container Substrate. HortScience. 44(7)1861-1865.

Altland, J.E., Ream, J. 2010. Control of Butterfly Bush with Postemergence Herbicides. Journal of Environmental Horticulture. 238(1):48-52.

Wehtje, G., Altland, J.E., Gilliam, C.H., Marble, S.C., Van Hoogmoed, A.J., Fain, G.B. 2009. Weed Growth and Efficacy of Pre-Applied Herbicides in Alternative Rooting Substrates Used in Container-Grown Nursery Crops. Weed Technology. 23:455-459.

Wehtje, G., Altland, J.E., Gilliam, C. 2009. Interaction of Glyphosate and Pelargonic acid in Ready-To-Use Weed Control Products. Weed Technology. 23:544-549.

Altland, J.E., Magdalena, Z., Owen, J. 2009. Effect of Peat Moss and Pumice on Douglas Fir Bark based Soilless Substrate Physical and Hydraulic Properties. HortScience. 44(3):874-878.

Bell, N., Altland, J.E. 2010. Growth, Flowering and Cold Hardiness of Rockrose in Western Oregon. HortTechnology. 20(3): 652-659.

Altland, J.E. 2010. Use of Processed Biofuel Crops for Nursery Substrates. Journal of Environmental Horticulture. 28:129-134.

Derksen, R.C., Ranger, C.M., Canas, L.A., Locke, J.C., Zhu, H., Krause, C.R. 2010. Evaluation of Handgun and Broadcast Systems for Spray Deposition in Greenhouse Poinsettia Canopies. Transactions of the ASABE. 53(1): 5-12.

Last Modified: 4/20/2014
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