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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

2010 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

Program Effort: In Year 2 (2009) we conducted a 3-gallon container-grown plant study for 113 days to look at the effect of growing woody plants in chipped Eastern Redcedar (Juniperus virginiana). Treatments were blends of cedar (0, 5, 10, 20, 80%) with pine bark and 20% sand. There were also 2 levels of fertilizer (low and high). Plants grown included Baldcypress (Taxodium distichum), Chinese Pistache (Pistachia chinensis), Green Giant Arborviate (Thuja ‘Green Giant’) and Silver Maple (Acer saccharinum) from seed in 1-gal. containers.

Results and Impacts: In general, trends for fertilizer were the same for all plants with the high level of fertilizer resulting in larger plants. In the future we will conduct studies at one rate of fertilizer. Green Giant plants failed to have a response in any treatment. Other plants seemed to grow well until the highest rate of cedar was reached (80%). 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. 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.


Last Modified: 11/22/2014
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