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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF ALTERNATIVE SUBSTRATES FOR CONTAINER NURSERY CROPS

Location: Application Technology Research Unit

2012 Annual Report


1a.Objectives (from AD-416):
The objective of this research will be to screen and identify potential alternative substrates for use in nursery containers. Substrate materials regional to the midwest area (Kansas) will be collected and evaluated for suitability as substrate alternatives.


1b.Approach (from AD-416):
Once materials are procured for testing, they will be evaluated three ways. First, plant bioassays will be used to observe the overall suitability of the materials for use as a substrate. Containers (6 in.) will be filled with the substrates and grown in a greenhouse with fast growing crops. Plants will be grown in a climate controlled greenhouse or nursery setting. Measured parameters will include plant growth, substrate nutrient capacity using the saturated media extraction procedure, plant nutrition using ICP analysis of foliage, and plant water use. Those that perform similar to traditional pine bark substrates will be evaluated further. Several iterations of the plant bioassay will be conducted to allow researchers to alter the substrates (particle size, for example) and optimize their potential for suitability. Once a suitable alternative substrate is identified, it will be studied more closely to understand how the material functions in a container environment. Further testing will include evaluation of the materials physical and chemical properties. Products will be measured for their porosity using NSCU porometers, particle size distribution, particle density, and moisture characteristic curves. This will provide a better understanding of the substrates hydrologic properties. Chemical analyses will include the substrates’ ability to buffer pH, provide macronutrients and micronutrients, and cation and anion exchange capacity.


3.Progress Report:

There is no local source for pine bark in Kansas thus pine bark for container-grown plant production must be shipped, typically from Texas or Arkansas to growers in the Great Plains region. This added expense might be prohibitory to many growers or at least may place growers at a competitive disadvantage when selling wholesale. Overcoming the shortage of substrate material could greatly increase the acreage of container production of nursery crops in the Great Plains and therefore increase overall gross sales of the Nursery and Greenhouse industry. Eastern red cedar has become a nuisance plant to many landowners across the region. Once held back by grazing and wild fires from fully entering the grasslands of the Great Plains, community development and farming have reduced these natural control measures. Additionally, the use of the species in windbreaks, for erosion control, and wildlife cover since the 1960’s has increased the seed population. Although regular burning can easily control young plants, established trees are difficult to control. In many cases the only option is to hire a contractor to cut the trees, grind them, and haul away the chips. The resulting mountains of chips are then sold as landscape mulch. This, however, is a very expensive endeavor for the landowner and is often not done. As a result, eastern red cedar continues its march across open lands within Kansas. Any means by which the landowner could recoup some of their expense would be a welcome addition. In Year 4 (2011) we expanded our list of crops for evaluation to include more trees (Ulmus parvifolia ‘Emer11’), shrubs (Rosa ‘Radtkopink’ and Ilex glabra ‘Compacta’), and perennials (Gaillardia x grandiflora ‘Goblin’, Miscanthus sinensis ‘Little Kitten’, Sedum telphium ‘Autumn Joy’, Hemerocallis sp. ‘Charles Johnston’, and Hosta ‘Sum and Substance’). Plants were potted on May 19, 2011 into 3 substrate treatments a) 80% pine bark: 20% sand, b) 80% 3/8-in eastern redcedar: 20% sand, or c) 40% pine bark: 40% 3/8-in eastern redcedar: 20% sand. There were 12 replications so that some plants could be harvested at the end of the production cycle and the remaining plants could be planted into a landscape establishment study. That study will be harvested this fall. We also conducted a greenhouse experiment to evaluate whether changing irrigation frequency (but not volume) could overcome physical properties (high air space, low container capacity) associated with alternative, wood-based substrates. Species evaluated in this test have included Sedum telphium ‘Autumn Fire’, Rudbeckia fulgida ‘Goldstrum’ and Hibiscus moscheutos ‘Luna White’. Eastern red cedar substrate material was processed and delivered to Loma Vista Nursery (Ottawa, KS) for trial use. Their potting schedule did not allow for installation of the project this spring, but it is anticipated in August 2012. For all species tested, plants grew similarly to the pine bark control when amended with half eastern red cedar. Several of the perennials also grew equally as well in the primarily eastern red cedar substrate. This is encouraging for growers interested in using eastern red cedar as a local substrate component and is the beginning of developing guidelines for alternative substrate use. Plants growing in the landscape establishment study are performing quite well for the most part. The perennials did not come out of winter well. Quite a few died and we are unsure why since several factors were at play including a) a deer bedded down in the Gaillardia the night before we installed the project, b) there was a delay in irrigation installation in the spring, and c) potential herbicide damage. The damage does seem to be random and some of the plants have recovered, though not to the greatest growth possible. The greenhouse study (still underway) has shown similar results in terms of substrates: the largest plants are those grown in pine bark, but the pine bark/eastern red cedar substrate is still marketable. It doesn’t appear that increasing irrigation frequency is overcoming the problem of less growth in primarily eastern red cedar substrates. This leads us to believe that the problem may be rooted in fertilizer leaching or eastern red cedar allelopathy. We are still gathering data and will have a lot to look at with data probes recording soil temperatures, air temperatures and humidity. The project helps to address Sub-objective 2A of the parent project: “Evaluate the use of regional agricultural/forest byproducts and synthetic materials for use as a substrate in nursery containers.”


Last Modified: 10/22/2014
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