Low-input management practices for container Ericaceous nursery crops

Low-input management practices for container Ericaceous nursery crops

Summary

We have conducted tests at nursery operations and research station. At all locations, ‘DVD’ plants were larger than those of ‘SS’ in either medium. However, plant biomass was significantly different between treatments especially for ‘DVD’ in peat-based medium. The overall root biomass was highest in plants grown in bark-based and treated with natural mycorrhiza and half rate of fertilizer. Roots of DVW were highly and negatively affected by phytophthora while those of SS were not significantly different from those non-infected with phytophthora. In peat-based medium, there was a significant effect of phytophthora on azalea’s AG dry weight. Plants infected with phyophtora had lower dry weight. This effect was particularly pronounced in ‘DVW’ plants and was not significant with ‘SS’ plants. In this study, there was no significant difference in root mycorrhizal colonization index (RMCI) among cultivars, treatments, phytophthora infection, or in their interactions in bark-based medium. However, RMCI was almost 3 times higher for ‘DVW’ than for ‘SS’ in peat-based medium. At the research station, for fall harvest, we found that plants grown in peat-based medium were significantly higher by 26% than those in bark-based growing medium. It was highest in plants treated with natural mycorrhiza with full fertilizer rate and lowest in plants treated with commercial mycorrhiza with half rate of fertilizer. Tissue N concentration was higher in ‘DVW’ than in ‘SS’. It was not affected by medium but with treatment. Plant species varied in their tissue nutritive concentration. RMCI was higher in ‘DVW’ than in ‘SS’ plants. In comparison to fall harvest, ‘DVW’ and ‘SS’ plants harvested in spring were higher for those grown in bark-based medium. RMCI was low in all root samples between cultivars and treatments but colonization was four times higher in SS than DVW in the bark-based medium.

Objectives/Performance Targets

Accomplishments/Milestones

We successfully planted, harvested, and analyzed plants for nutritional concentration, phytopthora, and root mycorrhizal colonization at all locations we have conducted these experiments. We have accomplished the objectives of this project except the impact of chlorination on root colonization. It was not practical for the grower to set up irrigation system specifically to irrigate the plants especially when his irrigation system in his operation changed totally to chlorination by the time we set up the experiment.

Impacts and Contributions/Outcomes

The results obtained in this study were very valuable for growers. First, we identified plant cultivars that are susceptible to photophthora and those are tolerant. Second, we showed that the substrate medium has effect on root growth but does not have influence on phytophthora infection. Third, we showed that the use of mycorrhiza especially with half rate of fertilizer provided higher plant biomass for ‘DVW’ and was comparable to those inoculated with commercial mycorrhizal source with full fertilizer rate. For ‘SS’ the addition of mycorrhizae from any source with full rate of fertilizer were significantly higher than other treatments. Fourth, in achieving low-input container production for azalea, selecting phytopthora tolerant plant such as ‘SS’ will aid in reducing the losses of plants due to root rot disease. Mycorrhizal inoculum may not be of additional benefit for ‘SS’ for defence against root rot disease. However, the use of mycorrhizae for ‘DVW’ with lower rate of fertilizer, not only reduces the fertilizer rate as commonly used by nursery growers (using full rate) but also provided better growth of these plants in presence of mycorrhizae especially when exposed to phytophthora. The cost of mycorrhizae constitutes a minimal expense to the grower in comparison to cost of fertilizer and its transportation.

We are working on the statistical analyses for the collected data and preparing publications for this project.

We have presented the results at the national ASHS conference in July 2009 and abstract documented part of the results.
Presentations:
Zinati, G. M., J. Dighton, and A. Gould J. 2009. Substrate media, fertilizer rate, and mycorrhizal inoculum source affect azalea plant root mycorrhizal colonization and severity of Phytophthora cinnamomi infection. Presented at the 2009 ASHS Annual Conference, St. Louis, MO July 28, 2009. (presentation was chosen for podcast recording at ASHS conference)

Abstracts:

Zinati, G. M., J. Dighton, and A. Gould J. 2009. Substrate media, fertilizer rate, and mycorrhizal inoculum source affect azalea plant root mycorrhizal colonization and severity of Phytophthora Cinnamomi infection. HortScience 44(4):1064.

Collaborators: