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- Author or Editor: Stuart L. Warren' x
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`Redchief Red Delicious'/MM.lll (Malus domestica Borkh.) apple trees were grown for 12 years in six vegetative covers: rye mulch (RM), bare soil (BS) maintained by herbicides, mechanical cultivation (MC), tall fescue (TF), Kentucky bluegrass (KB) and nimblewill (NW). Apple root distribution was determined using the trench profile method. A trench two meters long and one meter deep was dug perpendicular to the tree row, 80 cm from both sides of the tree. One meter square grids, sectioned into 10 cm squares, were placed on the profile walls and root diameter and number were recorded. Trees grown in RM had the highest number of roots, greater than all other covers, followed by BS. MC and NW had fewer roots than BS. However, MC and NW were higher than KB and TF. KB had fewer roots than all covers except TF. TF had the lowest number of roots.
Five ratios of NH4:NO3 (100:0, 75:25, 50:50, 25:75, and 0:100) were evaluated for impacts on growth of Cotoneaster dammeri Schneid. `Skogholm' (cotoneaster) and Rudbeckia fulgida Ait. `Goldsturm' (rudbeckia). Nitrate decreased dry weight and leaf area, while nutrient solutions containing >25% NH4 increased shoot and root growth of cotoneaster and rudbeckia. Additionally, NO3 decreased accumulation of some cationic nutrients and N in roots and shoots of cotoneaster and rudbeckia compared to solutions containing either NH4 alone or mixes of NH4 and NO3. Nitrogen contents (in milligrams) in cotoneaster fertilized with NO3 decreased an average of 54% and 58% in rudbeckia compared to N supplied as NH4 alone. These dramatic reductions in growth and tissue nutrient content reiterate the need for proper N form selection. Root diameter of cotoneaster was higher with a mix of NH4 and NO3 than with NO3 alone; whereas, the N form had no impact on diameter of rudbeckia roots. However, the stele of both cotoneaster and rudbeckia roots was larger and contained more secondary xylem with larger tracheary elements with a mix of NH4 and NO3 compared to nutrient solutions with NO3 alone. Increased number and size of secondary tracheary elements may relate to increased dry weight and leaf area of both cotoneaster and rudbeckia fertilized with mixes of NH4 and NO3 compared to NO3 alone.
An experiment with a factorial treatment combination in a split plot design with five single plant replications was conducted to evaluate the effects of five rates of fertilizer addition and two irrigation volumes on plant growth in a composted turkey-litter-amended pine bark substrate. Main plots were daily applications of 600 or 900 ml/3.8-L container. Subplots were either 0, 1.0, 2.0, 3.0, or 4.0 g N additions (Osmocote High H 24N–1.7P–5.8K) per container topdressed on a substrate composed of pine bark amended with 8% (by volume) composted turkey litter. No additional amendments were made to the compost amended substrates. An additional “industry control” treatment consisted of an 8 pine bark: 1 sand (by volume) substrate amended with 3.0 kg/m3 dolomitic limestone and 0.9 kg/m3 Micromax and topdressed with 3.5 g N (Osmocote High N) per container. After 134 days, Cotoneaster dammeri `Skogholm' and Rudbeckia fulgida `Goldsturm' plants were harvested and shoot and root (cotoneaster only) dry weights were determined. Cotoneaster shoot and root dry weights and rudbeckia shoot dry weight increased linearly as N rate increased from 0 to 4.0 g N. Irrigation volume did not affect cotoneaster shoot or root dry weights. Rudbeckia shoot dry weight was 18% greater with 900 ml than with 600 ml of irrigation. Rudbeckia growth in compost amended substrate was greater than in the industry control when topdressed with ≥1.0 g N. Shoot growth of cotoneaster in the industry control substrate and compost amended substrate with ≥ 3.0 g N applied was similar.
An experiment was conducted to develop a protocol for using compost in nursery crop production. Five rates of inorganic fertilizer (0, 1, 2, 3, and 4 g N) and two irrigation volumes (600 and 900 mL per 3.8-L container) were evaluated for their effects on Rudbeckia fulgida Ait. `Goldsturm' and Cotoneaster dammeri Schneid. `Skogholm' growth in a pine bark substrate amended with composted turkey litter (CTL). Additions of ≥2 g N per container for cotoneaster and ≥1.0 g N for rudbeckia were required to produce growth equivalent to that of plants in a control treatment that simulated typical production by a grower in the southeastern United States. Phosphorus, Ca, and Mg contents of cotoneaster and rudbeckia plants grown in CTL-amended substrates with no fertilizer added (0 g N) were similar to or greater than that of the control. Phosphorus concentrations in the substrate solutions were higher in all CTL-amended substrates than in the control regardless of fertilizer addition. This suggests that P released from CTL had a greater impact than P added with fertilizer. The greatest nutrient value of CTL may be as a P source and a replacement for dolomitic limestone and micronutrients in container-grown plant production.
In two experiments, uniconazole (0.25 to 16 mg·L-1 a.i.) was applied as a root drench to containerized Fraser fir [Abies fraseri (Pursh) Poir.] at various times of the year. Leader length, stem diameter, length of laterals, and number of subterminal buds were reduced the following growing season. Treatment during the 1994 growing season reduced lateral bud formation on the leader in 1995, whereas treatment with 8 or 16 mg·L-1 in Mar. 1995 (prior to budbreak) increased it. Uniconazole caused needle discoloration and abscission at concentrations ≥4 mg·L-1. Leader growth was reduced more than branch elongation, which tended to make plants more decurrent. The utility of uniconazole in production of tabletop Fraser fir Christmas trees was unclear; reduced shoot elongation was often accompanied by fewer lateral buds and needle discoloration and/or abscission. Chemical name used: E-1-(p-Chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazole-1-penten-3-ol) (uniconazole).
Traditional N mineralization studies have been conducted by soil scientists using soils and temperatures found in field production. As temperature, in part, governs the rate of mineralization, and container substrates reach much higher temperatures than do soils, the effect of these elevated temperatures on mineralization must be considered to begin to understand N mineralization in container substrates during production. The N mineralization patterns of three composts [turkey (Meleagris gallopavo) litter, yard waste, and municipal waste] were determined under three temperature regimes (45, 25, and 45/25 °C). More organic N was mineralized from composted turkey litter (CTL) than from municipal or yard composts, regardless of temperature. The percentage of organic N mineralized from CTL was greater at 45/25 and 45 °C than at 25 °C.
Root growth is a critical factor in landscape establishment of container-grown woody ornamental species. Kalmia latifolia (mountain laurel) often does not survive transplanting from containers into the landscape. The objective of this experiment was to compare rate of root growth of mountain laurel to that of Ilex crenata `Compacta' (`Compacta' holly) and Oxydendrum arboreum (sourwood). Six-month-old tissue-cultured liners (substrate intact) of mountain laurel, 1-year-old rooted cutting liners (substrate intact) of `Compacta' holly (liner holly), 6-inch bare root seedling liners of sourwood, and 3-month-old bare-root rooted cuttings of `Compacta' holly were potted in containers in Turface™. Prior to potting, roots of all plants were dyed with a solution of 0.5% (w/v) methylene blue. Plants were greenhouse-grown. Destructive harvests were conducted every 2 to 3 weeks (six total harvests). Length, area, and dry weight of roots produced since the start of the experiment, leaf area, and dry weight of shoots were measured. Sourwood and liner holly had greater rate of increase in root length and root dry weight than mountain laurel and bare root holly. Rate of increase in root area was greatest for sourwood, followed by (in decreasing order) liner holly, mountain laurel, and bare-root holly. Increase in root length and root area per increase in leaf area was highest for liner holly, possibly indicating why this species routinely establishes successfully in the landscape. Increase in root dry weight per increase in shoot dry weight was lowest for mountain laurel. The slow rate of root growth of mountain laurel (compared to sourwood and liner holly) may suggest why this species often does not survive transplanting.
Five ratios of NH4+: NO3-(100:0, 75:25, 50:50, 25:75, and 0:100) were evaluated for impact on growth of Cotoneaster dammeri Schneid. `Skogholm' (cotoneaster), a woody ornamental shrub, and Rudbeckia fulgida Ait. `Goldsturm' (rudbeckia), an herbaceous perennial. Nitrate alone decreased dry weight and leaf area of cotoneaster and rudbeckia compared with mixtures of NH4+ and NO3- and NH4+ alone. Additionally, NO3- alone suppressed accumulation of cationic nutrients and N in cotoneaster, while mixes of NH4+ and NO3- enhanced accumulation of nutrients in roots and shoots of rudbeckia compared with solutions containing either NH4+ or NO3- alone. The steles of roots of cotoneaster and rudbeckia contained more secondary xylem with larger tracheary elements with a mix of 25 NH4+: 75 NO3- than with NO3- alone.