As an alternative to testing nutrient components separately, four common media formulations were used: Murashige and Skoog (MS), Driver and Kuniyuki (DKW), woody plant medium (WPM) and Anderson's revised medium (AND). Each medium was tested separately. Then high salts formulation (MS and DKW) were mixed with low salts formulation (WPM and AND) at a half and half concentration. In total, eight different media were tested spanning high, intermediate and low nutrient salts concentrations. To test the media two different plant species were chosen, a woody species Hydrangea quercifolia (oakleaf hydrangea) and an herbaceous species Tagetes erecta (African marigold). Nodal explants were harvested from H. quercifolia `Dayspring' stock plants grown in raised beds in a greenhouse. After being disinfested, explants were placed on the eight treatment media, along with 1.0 µM benzyladenine (BA) and 1.0 µM indolebutryic acid (IBA). In addition to the plant growth regulators (PGR's), 10 ppm Orthene insecticide and 150 ppm Benlate fungicide were included in the tested media to prevent contamination from a spider mite infestation. Explants placed on WPM were significantly different than explants on other media. WPM explants initiated growth the most, but elongation was sluggish and leaves showed signs of deficiencies after 8 to 10 weeks in vitro. Intermediate salts media DKW/WPM and DKW/AND had fewer explants initiate growth then explants on WPM, but the few that did elongated. These explants had the maximum lengths of any other explant on all other treatments. Tagetes erecta `Marvel Orange' seeds were sown in polyethylene flats in a lab under cool white fluorescent lamps. After about a month apical shoot tips were harvested, surface disinfested, and placed in vitro on the eight treatment media, with the same PGR's and additives as the hydrangea experiment. Tagetes explants responded substantially faster than the Hydrangea explants, with growth initiating on all treatments within a week. Initially there were significant differences between treatments, but after 3 months in vitro there were no differences between treatments. Although no data was taken, there was observed differences between the treatment media. Explants on low salts media of WPM and AND show signs of nutrient deficiencies, with high salt media showed no deficiencies. Overall the best growth of axillary shoots was seen on high salt media of MS and DKW.

Pine tree substrate (PTS) is a relatively new substrate for container crop production. There are no detailed studies that elucidate how storage time impacts PTS chemical, physical, and biological aspects. The objective of this research was to determine how PTS storage time influenced PTS chemical and physical properties, nitrification, and plant growth. Pine tree substrate was manufactured by hammer-milling chips of loblolly pine trees (Pinus taeda L.) through two screen sizes, 4.76 mm (PTS) and 15.9 mm amended with peat (PTSP). PTS and PTSP were amended with lime at five rates. A peat-perlite mix (PL) served as a control treatment. Prepared substrates were placed in storage bags and stored in an open shed in Blacksburg, Virginia. Subsamples were taken at 1, 42, 84, 168, 270, and 365 days. At each subsampling day, twelve 1-L containers were filled with each substrate. Six containers were left fallow and six were planted with marigold (Tagetes erecta L. "Inca Gold") seedlings. Substrate was also collected from select treatments for Most Probable Number assays to estimate density of nitrifying microorganisms, and for chemical and physical property analyses. Pour-through extracts were collected from fallow containers at 0, 2, and 4 weeks, and from marigold containers at harvest for determination of pH, electrical conductivity, ammonium-N and nitrate-N. At harvest, marigold height, width, and dry weight were measured. At least 1 kg·m-3 lime for PTS, and 2 to 4 kg·m-3 lime for PTSP were needed to maintain pH values ≥ 5.5 for 365 days. Bound acidity of unlimed PTS increased but cation exchange capacity for unlimed PTS and PTSP decreased over 365 days. Carbon to nitrogen ratio and bulk density values were unchanged over time in all treatments. There were minor changes in particle size distribution for limed PTS and unlimed and limed PTSP. Marigold growth in PTS and PTSP was ≥ PL in all limed treatments, except at day 1. Nitrite-oxidizing microorganisms were present and nitrification occurred in PTS and PTSP at all subsampling days. Pine tree substrate is relatively stable in storage, but pH decreases, and lime addition may be necessary to offset this decrease. / Ph. D.