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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

2013 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:

This is the final report for this project. 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 Redcedar 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 5 (2012) we harvested the species that had been grown in the summer of 2011 and planted that fall [lacebark elm (Ulmus parvifolia ‘Emer11’), rose (Rosa ‘Radtkopink’) holly (Ilex glabra ‘Compacta’), blanket flower (Gaillardia x grandiflora ‘Goblin’) dwarf maiden grass (Miscanthus sinensis ‘Little Kitten’) sedum (Sedum telphium ‘Autumn Joy’) daylily (Hemerocallis sp. ‘Charles Johnston’) and hosta (Hosta ‘Sum and Substance’). Plants were potted in May 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. Five replications (with 2 subsamples) of these treatments were planted into a field at the John C. Pair Horticulture Center in Haysville, KS in October 2011. They were harvested in September 2012.

We also conducted 3 greenhouse experiments to evaluate whether changing irrigation frequency (but not volume) could overcome poor physical properties (high air space, low container capacity) associated with alternative, wood-based substrates. Species evaluated in this test has included Sedum telphium ‘Autumn Fire’, Rudbeckia fulgida ‘Goldstrum’ and Hibiscus moscheutos ‘Luna White’.

An eastern redcedar substrate trial is being conducted at Loma Vista Nursery in Ottawa, KS. Work about the most available and least costly agronomic crop waste residues in Kansas (potential for use in substrates) is almost complete. We have identified corn, sorghum and winter wheat as these crops and created maps of their relative abundance per county.

Every species except hosta and holly concluded the study with no significant differences (or very few) in growth index, shoot dry weight, root dry weight or foliar chlorophyll content. Plants that were smaller in 80% eastern redcedar at the end of the production cycle had caught up to other treatments after a year in the landscape. Most plants produced in the pine bark: eastern redcedar mix were marketable at the end of the production cycle. This could mean that plants grown in a redcedar substrate mix are slightly smaller than those grown in pine bark, but more can be shipped at a lower weight (bulk density) and performance at retail and in the landscape will not be adversely affected.

Holly and hosta plants were the only two species to show differences at the end of the study. Both species were subject to some stress as a deer had bedded down on the plants in the study the night before landscape installation. As a result of this damage, blanket flower plants did not have high enough survival to render enough data for analysis. Sedum and dwarf maiden grass also had high variability in plant growth. Hosta plants were grown in a separate location under shade, but there was high slug damage as well as some hail damage. In the case of both hosta and holly, plants favored the pine bark substrate treatment and the mix, trailed by eastern redcedar.

In the greenhouse study results for all 3 species indicated that increasing irrigation frequency did not overcome low water holding capacity. The trend of the smallest plants being those grown in a primarily eastern redcedar substrate was continued, with the smallest plants being those that were irrigated 6x per day. In the last study (Hibiscus), leachate and leaf samples were collected to determine if substrate nutrition was different in the 3 treatments. There were some differences with K and P, but it didn’t completely explain why plants grown in eastern redcedar had smaller shoots. We think that further evaluation of nutrient interaction in eastern redcedar substrate might reveal ways of improving plant growth in these substrates.

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: 11/28/2014
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