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Agriculture is one of the largest contributors of greenhouse gas (GHG) emissions. To date, much work on reducing GHG emissions has centered on row crops, pastures, forestry, and animal production systems, while little emphasis has been placed on specialty crop industries such as horticulture. In this horticulture container study, Japanese boxwood (Buxus microphylla Siebold & Zucc.) was used to evaluate the interaction of irrigation (overhead vs drip) and fertilizer placement (dibble vs incorporated) on GHG emissions (CO2, N2O, and CH4). Plants were grown in 11.4 L (#3) containers with a 6:1 pine bark:sand substrate with standard amendments. All containers received 6.35 mm (0.25 in) water three times daily. Gas samples were collected in situ using the static closed chamber method according to standard protocols and analyzed using gas chromatography. Total cumulative CO2 loss was not affected by differences in irrigation or fertilizer placement. Total cumulative N2O efflux was least for drip-irrigated plants, regardless of fertilizer placement. For overhead-irrigated plants, N2O efflux was greatest for those with incorporated fertilizer. Efflux of CH4 was generally low throughout the study. Findings suggest that utilizing drip irrigation could decrease N2O emissions, regardless of fertilizer placement. However, when limited to overhead irrigation, dibbled fertilizer placement could decrease N2O emissions. Index words: carbon dioxide, methane, nitrous oxide, trace gas Species used in this study: Japanese boxwood (Buxus microphylla Siebold & Zucc.)

Current weed control practices in nursery container plant production consist primarily of hand weeding and application of preemergence herbicides. Non-chemical weed control methods, such as mulches, could reduce herbicide use, reduce potential environmental concerns from offsite herbicide movement, and decrease the expense of weed control. Before implementation, alternative methods of weed control must be evaluated for effects on the growth of common container-grown species. Mulches made from readily available tree species, including eastern red cedar (Juniperus virginiana), ground whole loblolly pine (Pinus taeda), Chinese privet (Ligustrum sinense), and sweetgum (Liquidambar styraciflua), were evaluated at multiple depths with and without the herbicide dimethenamid-P (Tower®). Wax-leaf ligustrum (Ligustrum japonicum) and snowball viburnum (Viburnum macrocephalum) treated with dimethenamid-P, averaged over mulch treatments, had up to 7% less growth compared to non-herbicide treated plants, but marketability was not affected. Mulch species and depth had no effect on plant growth. Results indicate that these readily available mulch species can be applied at depths up to 10.2 cm (4 in) for weed control in container plant production.

Flumioxazin is commonly used in nursery production for PRE weed control. Container nursery producers are of the opinion that the granular formulation is less effective than the sprayable formulation. Under the hypothesis that the granular formulation may require more water for activation, an experiment was conducted to evaluate the interaction of flumioxazin formulation, rate, and activation moisture for PRE control of spotted spurge in a pine-bark substrate. Experiment consisted of a factorial arrangement of four experimental variables; flumioxazin formulation (granular and spray), and flumioxazin rate (0.28 and 0.42 kg ai ha−1), substrate moisture level at the time of application (dry, medium, and wet), and after-application irrigation level (a single irrigation at 0.6, 1.3, 2.5, and 5.1 cm). Treated pots were seeded with spotted spurge 2 d after the herbicide application, which was 1 d after the first irrigation. Control as indicated by spotted spurge counts and fresh weight was influenced only by flumioxazin rate and formulation. The sprayable formulation provided excellent control regardless of rate. Granular formulation was generally less effective, and additional activation moisture did not improve efficacy. Further studies were conducted with the granular formulation to determine the maximum separation distance between the spotted spurge seed and herbicide prills at which control is possible. Individual prills and spotted spurge seeds were placed on media surface at progressively increasing separation distances. Nonlinear regression of seedling survival data revealed that ≥99% control required a prill–seed separation of ≤5.2 mm. This prill–seed separation requirement is only marginally obtained with the current registered rate, i.e., 0.42 kg ai ha−1 or 168 kg product ha−1. The relationship between control and prill–seed separation distance cannot be manipulated by additional activation moisture. Inadequate contact between the spotted spurge seeds and the flumoioxazin-containing prills is likely the sole cause of inadequate control.

Nine species of container-grown plants were treated over-the-top with Roundup Pro® (41% glyshosate) at four rates: 0.28, 0.56, 1.12, and 2.24 kg ai·ha−1 (0.25, 0.5, 1.0 and 2.0 lb ai·A−1) either in June 2007, September 2007, or February 2008. A fourth group was treated on all three dates (June + September + February) (JSF). The experiment was repeated on eight species in 2008–2009. Growth indices (GI) were taken before the spring growth flush in March and after the first growth flush in June. In Exp. 1, dwarf mondo grass (Ophiopogon japonicus ‘Nana’), mondo grass (O. japonicus), liriope (Liriope muscari ‘Cleopatra’), variegated liriope (L. muscari ‘Variegata’), and ‘Blue Pacific’ juniper (Juniperus rigida subsp. conferta ‘Blue Pacific’) were not affected by glyphosate rates up to 1.12 kg ai·ha−1 (1.0 lb ai·A−1) applied singly or JSF, except for temporary injury on ‘Blue Pacific’ from February applications. The remainder of the species had reduced growth as Roundup Pro® rates increased. ‘Blue Rug’ juniper (J. horizontalis ‘Wiltonii’) was tolerant in February but injured at ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in June and September (JS). Asiatic jasmine (Trachelospermum asiaticum) was tolerant of single applications at rates ≤ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in JS, but showed stunting of new foliage from all February applications. Dwarf yaupon (Ilex vomitoria ‘Stoke's Dwarf’) showed injury at 74 days after treatment (DAT) after June applications, no injury at rates ≤ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in September, and stunting and delay of new foliage from all February applications and rates ≥ 0.56 kg ai·ha−1 (0.5 lb ai·A−1) in June. ‘Pink Gumpo’ azalea (Rhododendron eriocarpum ‘Gumpo Pink’) was injured by rates ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) applied in June, February, and JSF, however no injury occurred with any September treatment. In Exp. 2, dwarf mondo and mondo tolerated all single application rates up to 1.12 kg ai·ha−1 (1.0 lb ai·A−1). Asiatic jasmine was injured by all February treatments and growth was reduced and stunted by ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in February and JSF. Dwarf yaupon GI were reduced by rates ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in February, 2.24 kg ai·ha−1 (2.0 lb ai·A−1) in June, and by all treatments in JSF. February treatments ≥ 0.28 kg ai·ha−1 (0.25 lb ai·A−1) delayed shoot growth of dwarf yaupon for at least 6 weeks. ‘Hardy Daisy’ gardenia (Gardenia jasminoides ‘Hardy Daisy’) showed slight injury from February rates ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1), but growth was reduced at 2.24 kg ai·ha−1 (2.0 lb ai·A−1) for June and JSF. Sky pencil holly (Ilex crenata ‘Sky Pencil’) showed stunting from all February applications, but was tolerant up to 2.24 kg ai·ha−1 (2.0 lb ai·A−1) in June and September; GI were similar for all treatments. Purpleleaf wintercreeper euonymus (Euonymus fortunei ‘Coloratus’) was injured by rates ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) applied in June and JS, all February treatments, and stunted by two or three applications of 2.24 kg ai·ha−1 (2.0 lb ai·A−1), but all other treatments had similar GI. Wintergreen boxwood (Buxus sempervirens ‘Wintergreen’) was injured at 2.24 kg ai·ha−1 (2.0 lb ai·A−1) in June, ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in JS, and all February applications. Growth was reduced by rates of 2.24 kg ai·ha−1 (2.0 lb ai·A−1) in February and ≥ 1.12 kg ai·ha−1 (1.0 lb ai·A−1) in JSF.

Peat and perlite have served as industry standards in greenhouse substrates for over 50 years. The continued availability of peat, paralleled with its inert characteristics, as well as its ability to stay generally pathogen-free have all contributed to its success in the horticulture industry. Expanded perlite has long been used as an amendment in container mediums to provide air space to container substrates without adding to bulk density or affecting substrate pH and EC. However, due to increased restrictions on the harvesting of peat, as well as fluctuations in fuel prices necessary for shipping, the future availability of peat is a largely unknown factor in greenhouse production. Additionally, growers consider perlite to be a general nuisance due to the lung and eye irritation problems. Because of these problems, researchers have focused on identifying and evaluating possible alternatives to standard substrates. These studies evaluated three possible substrate alternatives for use in greenhouse production, including fresh sweetgum (SG), hickory (H), and eastern redcedar (RC), in addition to WholeTree (WT) substrate. Three greenhouse annual crops (petunia, impatiens, and vinca) were planted in varying ratios of these species mixed with peat. Plants grown with SG and H as amendments did not perform as well as a traditional peat:perlite mix with respect to flower number, growth indices, and plant dry weight. However, plants grown in RC tended to be equivalent to those grown in a traditional mix. Data showed that greenhouse producers could amend their standard greenhouse substrate with up to 50% eastern redcedar with little to no differences in plant growth.