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`Eight deciduous ornamental shrubs-deutzia (Deutzia gracilis Siebold & Zucc.), dogwood (Cornus alba L. `Argenteo-marginata'), forsythia (Forsythia × intermedia Zab. `Lynwood Gold'), ninebark [Physocarpus opulifolius (L.) Maxim.], potentilla (Potentilla fruticosa L. `Red Ace'), privet (Ligustrum vulgare L.), rose (Rosa L. `John Frank. lin'), and weigela [Weigela florida (Bunge) A. DC. `Variegata Nana']—were grown in trickle-irrigated containers with 100% bark (control) or with bark and 33%, 67%, and 100% (by volume) of each of three sources of spent mushroom compost (unweathered, weathered, and unweathered compost leached with water). Despite large variation in species growth response to sources and levels of compost, most grew equally well or better in the compost-amended regimes than in 100% bark and were influenced little, or not at all, by initial or prevailing salt levels in the media. Shoot and root dry weight of dogwood, forsythia, ninebark, rose, and weigela (all sources), and shoot dry weight of deutzia and potentilla (weathered source only), increased linearly or curvilinearly with increasing compost levels. The reverse relationship occurred (all sources) in shoot and root dry weight of privet and root dry weight of weigela and potentilla. Leaf nutrients (N, P, K, Ca, Mg, Fe, Mn, and Zn) tended to increase with increasing compost levels, but not all species showed this response with all nutrients. Regardless of compost source or level, all shrubs were of marketable quality when harvested, except privet, which showed leaf chlorosis in all compost-amended regimes.

Abstract

Three consecutive annual nitrogen applications on trees of ‘Bartlett’ pear (Pyrus communis L.) at 120 kg/ha increased leaf N, shoot growth, number of expanded shoot leaves, crop density, fruit size, and yield compared to no N. N application without butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) increased late bloom and fruit russet associated with pear psylla honeydew. Daminozide at 2 g/liter sprayed twice annually for 3 years, 30 and 50 days after bloom with or without N application, reduced minal growth, number of expanded shoot leaves, late bloom, fruit size, density of psylla nymphs, (Psylla pyricola Foerster) and fruit russet from psylla honey dew. The effects of N and daminozide on tree growth, fruit size, and yield, as well as on psylla density, varied from year to year. Daminozide can reduce shoot growth of pear and subsequently reduce psylla densities and resultant damage but with some reduction in fruit size.

A study was conducted at Auburn University to evaluate freshly chipped pine trees as an alternative substrate in container nursery crops. Two substrates were tested alone and in combination with aged pine bark (PB), peat (P), and composted poultry litter (PL). A 6:1 (v:v) PB: sand control treatment was also included. The two substrates were both composed of small caliper (2 to 10 cm) Pinus taeda processed in a chipper (including needles) (AUC); however, one substrate was additionally processed through a hammermill with a 0.95-cm screen (AUHM). Treatments included were 100% AUC, 3:1 (v/v) AUC:PB, 3:1 (v/v) AUC:P, 3:1 (v/v) AUC:PL, 1:1 (v/v) AUC:PB, 1:1 (v/v) AUC: P, 1:1 (v/v) AUC:PL, and the same treatments for the AUHM substrate. There were a total of 15 treatments with six replications per treatment. Each substrate was amended with 0.45 kg·m^-3 gypsum, 6.35 kg·m^-3 Polyon 17–6–12 (17N–2.6P–10K) and 0.68 kg·m^-3 MicroMax. Trade gallon (2.8-L) containers were filled with respective substrates and planted with Lantana camera `New Gold' on 20 July 2005. AUC and AUHM treatments amended with either PL or P resulted in Lantana with growth indices similar to PB:sand (6:1). In general, plants tended to be larger when amended on a 1:1 basis with either PL or P, but were similar statistically to those amended 3:1. For example, plants grown with AUHM:P 1:1 or AUHM:PL 1:1 were 7.3% and 8.8% larger, respectively, than plants grown in the same medium at 3:1. The lowest growth indices tended to occur with AUC and AUHM alone or amended with pine bark. Lantana root growth followed a similar trend to growth indices in that greatest coverage of the rootball surface occurred with AUC or AUHM treatments amended with PL or P.

Increased trace gas emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) are widely believed to be a primary cause of global warming. Agriculture is a large contributor to these emissions; however, its role in climate change is unique in that it can act as a source of trace gas emissions or it can act as a major sink. Furthermore, agriculture can significantly reduce emissions through changes in production management practices. Much of the research on agriculture’s role in mitigation of greenhouse gas (GHG) emissions has been conducted in row crops and pastures as well as forestry and animal production systems with little focus on contributions from specialty crop industries such as horticulture. Our objective was to determine efflux patterns of CO₂, CH₄, and N₂O associated with three different fertilization methods (dibble, incorporated, and topdressed) commonly used in nursery container production. Weekly measurements indicated that CO₂ fluxes were slightly lower when fertilizer was dibbled compared with the other two methods. Nitrous oxide fluxes were consistently highest when fertilizer was incorporated. Methane flux was generally low with few differences among treatments. Results from this study begin to provide data that can be used to implement mitigation strategies in container plant production, which will help growers adapt to possible emission regulations and benefit from future GHG mitigation or offset programs.

Residual chipping material, also called clean chip residual (CCR), has potential use as a growth substrate in the nursery and greenhouse horticultural industries. A survey was conducted in the southeastern United States among companies conducting harvesting operations on pine (Pinus sp.) plantations for the production of pulpwood in the forest industry. Fourteen operators in four states (Alabama, Mississippi, Georgia, Florida) were visited to evaluate the on-site status of residual material. Sample analysis of CCR revealed that it was composed of ≈37.7% wood (range, 14.2% to 50.5%), 36.6% bark (range, 16.1% to 68.5%), 8.8% needles (range, 0.1% to 19.2%), and 16.9% indistinguishable (fine) particles (range, 7.5% to 31%). pH ranged from 4.3 to 5.5 for all locations and electrical conductivity (EC) averaged 0.24 mmho/cm. Most nutrients were in acceptable ranges for plant growth with the exception of three sites above recommended levels for iron and four sites for manganese. Survey participants estimated that ≈27.5% of the harvest site biomass was composed of CCR. Some harvesters were able to sell CCR as fuelwood to pulp mills, while others did not recover the residual material and left it on the forest floor (44.3% total site biomass). Operations in this survey included typical pine plantation chipping and grinding operations (harvesters), woodyards (lumber, fuelwood, etc.), and operations processing mixed material (salvage from trees damaged in hurricanes or mixed tree species cleared from a site that was not under management as a plantation). Residual material varied depending on the plantation age, species composition, site quality, and natural actions such as fire. Average tree age was 11.5 years (range, 8 to 15 years), while average tree stand height was 37.0 ft (range, 25 to 50 ft) and average diameter at breast height (DBH) was 5.9 inches (range, 4 to 7 inches). Residual material on site was either sold immediately (28.6%), left on site for 1 to 3 months (28.6%), left on site for up to 2 years (7.1%), or not collected/sold (35.7%). Several loggers were interested in making CCR available to horticultural industries. Adequate resources are available to horticultural industries, rendering the use of CCR in ornamental plant production a viable option.

A study was conducted at Auburn University in Auburn, AL, and the U.S. Department of Agriculture–Agricultural Research Service, Southern Horticultural Laboratory in Poplarville, MS, to evaluate clean chip residual (CCR) as an alternative substrate component for annual bedding plant production. Clean chip residual used in this study was processed through a horizontal grinder with 4-inch screens at the site and was then processed again through a swinging hammer mill to pass a 3/4- or 1/2-inch screen. Two CCR particle sizes were used alone or blended with 10% (9:1) or 20% (4:1) peatmoss (PM) (by volume) and were compared with control treatments, pine bark (PB), and PB blends (10% and 20% PM). Three annual species, ‘Blue Hawaii’ ageratum (Ageratum houstonianum), ‘Vista Purple’ salvia (Salvia ×superba), and ‘Coral’ or ‘White’ impatiens (Impatiens walleriana), were transplanted from 36-cell (12.0-inch³) flats into 1-gal containers, placed on elevated benches in a greenhouse, and hand watered as needed. Ageratum plants grown at Auburn had leaf chlorophyll content similar or greater than that of plants grown in PB. There were no differences in salvia; however, impatiens plants grown in PB substrates at Auburn had less leaf chlorophyll content than those grown in CCR. There were no differences in ageratum, salvia, or impatiens leaf chlorophyll content at Poplarville. There were no differences in growth indices (GI) or shoot dry weight (SDW) of ageratum, while the largest salvia was in PB:PM and the largest impatiens were in PB-based substrates at Auburn. The GI of ageratum at Poplarville was similar among treatments, but plants grown in 4:1 1/2-inch CCR:PM were the largest. Salvia was largest in 4:1 CCR:PM and PB:PM, and although there were no differences in GI for impatiens at Poplarville, the greatest SDW occurred with PB:PM. Foliar nutrient content analysis indicated elevated levels of manganese and zinc in treatments containing CCR at Auburn and PB at Poplarville. At the study termination, two of three annual species tested at both locations had very similar growth when compared with standard PB substrates. This study demonstrates that CCR is a viable alternative substrate in greenhouse production of ageratum, salvia, and impatiens in large containers.

Small- and large-scale farmers must often decide when to begin application of fungicides, either before the onset of disease as a preventative treatment or after disease becomes evident in the field. Growers also must decide about products that claim to enhance fungicide efficacy when added to the spray mixture. A study was conducted during the summer of 2002 to investigate control of foliar diseases of vine crops (Cucurbita spp.) with low-input (LI) or high-input (HI) management approaches and six fungicide/spray combinations at four locations in southeastern United States. Fungicide applications began for LI when leaf disease first became evident and for HI about 20 days after seeding. Both approaches continued applications at 7- to 10-day intervals until harvest. Spray treatments consisted of a water-only control or one of six combinations of azoxystrobin/chlorothalonil alone or in combination with potassium bicarbonate, foliar phosphite (0N–12.2P–21.6K), or foliar nitrogen (25N–0P–0K). Azoxystrobin was applied in rotation with chlorothalonil for all treatments except the control. Seeds of ‘Lil’ Goblin’ pumpkin (Cucurbita pepo) were planted July to August and fruit harvested October to November, depending on location. Plants were rated twice for powdery mildew (Sphaerotheca fuliginea and Erysiphe cichoracearum) and downy mildew (Pseudoperonospora cubensis). HI did not significantly increase yield compared with LI. All fungicide treatments significantly increased yield and reduced foliar diseases compared with the water-only control. The simplest of treatments, the azoxystrobin/chlorothalonil rotation without any other chemicals, can be recommended for general use where strobilurin resistance has not been documented.