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Free access

Esmaeil Fallahi, Brenda R. Simons, John K. Fellman, and W.M. Colt

Influence of different quantity and timing of nitrogen application on various physiological aspects of `Redspur Delicious' apple, including nutritional partitioning, bud initiation, fruit set, yield, fruit quality and nitrate movement in the soil were studied over several growing seasons. Urea at the rates of: 40.2 Kg/ha; 160.8 Kg/ha; 281.3 g/ha; 401.9 Kg/ha; 522.4 K /ha were applied. Each rate of urea was applied: all at full bloom; half at full bloom and half at late spring; or all in fall. In 1993, time of application did not influence yield, fruit weight, color or soluble solids at harvest. Trees that received 401.9 and with 522.4 Kg/ha had higher yield than those with other quantities. Trees with 160.8 and 281.3 Kg/ha had higher yield than trees with 40.2 Kg/ha. Fruit weight in all quantities, except that of 522.4 Kg/ha, were similar. Fruit weight of trees with 522.4 K /ha was reduced. Fruit color was reduced as N quantities increased. Trees with 40.2 Kg/ha N had lower soluble solids than all other quantities. A high level of N increased ethylene and respiration in the fruit. Thus, if the poor color of fruit is due to high nitrogen, a long delay in harvest to improve the color could lead to an over ripe fruit. A preliminary test did not indicate harmful levels of nitrates movement in the soil.

Free access

Anita N. Azarenko, Annie Chozinski, Sarah F. McDonald*, Thomas A. Forge, and Timothy Righetti

Information about the use of alternative management practices (AOFMP) in perennial systems to manage soil biota and influence the uptake of nutrients is limited. The objectives of this study are to evaluate AOFMP on soil quality, focussing on soil biology, and on nitrogen uptake efficiency. Research plots are located in Lewis-Brown Farm (LB), Corvallis, OR (`Fuji' apple trees) and Mid-Columbia Ag. Research & Extension Cent. (HR), Hood River, OR (`Red Delicious' apple trees). Main plot treatments were weed control methods: herbicide or cultivation. Sub plot treatments were soil amendments: no amendment, bark mulch (BM), compost, and green vetch/barley mulch (VB). A split-plot completely randomized design with 3 replications was used. Depleted NH3 SO4 was applied to single-tree replicates at bud break in 2001, 2002, and 2003. Compost amended plots contained more fungivorous nematodes than other treatments, although this difference was not significant at LB. At both sites there was a significant interaction between main and sub plot treatments in the number of bacterivores. At LB, the interaction between main and sub plot treatments affected the number of enrichment opportunists and the F-ratio was affected by amendment. At HR, the structural index was also affected by amendment. Compost resulted in the most diverse populations. Soil respiration rates in compost and BM plots were consistently higher than in unamended and VB treated plots. Soil P, pH, and organic matter content were increased by compost amendment and bulk density was decreased. At HR mid-season leaves, fruit, and first year growth from compost treated plots contained the least nitrogen derived from fertilizer, followed by bark mulch. The highest nitrogen derived from fertilizer was in unamended plots.

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Antonio Figueira and Jules Janick

In vitro culture of axillary cotyledonary shoots of Theobroma cacao L. (cacao) under increasing CO2 concentration from ambient to 24,000 ppm (culture tube levels) significantly increased total shoot elongation, number of leaves, leaf area per explant, and shoot dry and fresh weight. Although light was necessary for the CO2 response, the effect of various photon fluxes was not significant for the measured growth parameters. Net photosynthesis estimated on the basis of CO2 depletion in culture tubes increased 3.5 times from 463 to 2639 ppm CO2, and increased 1.5 times from 2639 to 14,849 ppm CO2, but declined from 14,849 to 24,015 ppm CO2. Ethylene concentration in culture vessels increased under enriched CO2 conditions. Depletion of nutrients (fructose, K, Ca, Mg, and P) from the medium was increased under enriched CO2 conditions.

Open access

Dale M. Maronek, James W. Hendrix, and Paul L. Cornelius


Seedlings of pitch pine (Pinus rigida mill.) and Virginia pine (P. virginiana mill.) were grown with and without inoculum of the ectomycorrhizal fungus Pisolithus tinctorius [(Pers.) Coker & Couch] in a sphagnum peatmossperlite medium supplemented with various rates of the slow-release fertilizer (18N–2.5P–10K Osmocote or single rates of 14N–6P–11.6K Osmocote and 19N–3P–8.3K Sierrablen plus ON–19.8P–OK superphosphate) or a soluble 20N–8.6P–16.4K fertilizer treatment. Mycorrhizal development was evaluated after 5 months of growth and then after a 3-month cold storage period. Seedlings heavily mycorrhizal with P. tinctorius and of acceptable planting size were produced with 2.3 to 4.5 kg 18N–2.5P–10K Osmocote/m3 medium. Higher fertilizer rates reduced or eliminated mycorrhizal development and reduced plant growth. Seedlings grown with soluble fertilizer were comparable in size to those produced with slow-release fertilizers, but mycorrhizal development was eliminated. The 3 slow-release fertilizer formulations produced seedlings of comparable size and mycorrhizal development. Superphosphate with or without slow-release or soluble fertilizer did not influence seedling growth or mycorrhizal development. Mycorrhizae continued to develop while plants were in cold storage. The ITW One-Way tube produced seedlings equal in size to those produced in the Leach Pine Cell, but mycorrhizal development appeared to be more sensitive to high fertilizer rates with the ITW tube. Mycorrhizal development did not affect seedling size.

Free access

Chieri Kubota* and Mark Kroggel

Increasing numbers of vegetable growers purchase their transplants from specialized transplant producers. Possible deterioration of transplants during transportation limits the market size as well as the potential sources of high quality transplants. To determine best conditions for transportation of seedlings, tomato (Lycopersicon esculentum; `Durinta') seedlings with visible flower buds were placed for 4 days under varied air temperature (6, 12, or the conventional transportation temperature of 18 °C) and light intensity 0 (conventional darkness) or dim light at 12 μmol·m-2·s-1 PAR). Plants were evaluated for visual quality, photosynthetic capacity, growth and ultimately fruit yield. Lower temperatures and illumination significantly maintained visual quality of the seedlings. Lower temperature maintained high photosynthetic capacity of the seedlings during transportation. Growth and development of the seedlings were significantly affected by higher temperature resulting in significantly delayed growth and development. Number of fruits set on the first truss was significantly reduced when seedlings were at 18 °C during transportation. Overall, simulated transport at 6 °C under light showed the best transportability without experiencing negative impact for the 4-day simulated transportation. Seedlings at 6 °C in darkness and at 12 °C under light and in darkness also showed satisfactory transportability. Seedlings at 18 °C exhibited serious quality deterioration of seedlings, delay in early growth and development, loss of flower buds on the first truss and yield reduction, which agrees with the fact that conventional transportation is currently able to be no longer than 3 days in duration.

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Michael Raviv, J. Heinrich Lieth, David W. Burger, and Rony Wallach

Physical characteristics of two media were studied concerning water availability to roots, as reflected in specific transpiration rate, stomatal conductance, and specific growth rate of very young leaflets of `Kardinal' rose (Rosa ×hybrida L.), grafted on Rosa canina L. `Natal Brier'. Plants were grown in UC mix [42% composted fir bark, 33% peat, and 25% sand (by volume)] or in coconut coir. Water release curves of the media were developed and hydraulic conductivities were calculated. Irrigation pulses were actuated according to predetermined media moisture tensions. Transpiration rate of plants was measured gravimetrically using load cells. Specific transpiration rate (STR) was calculated from these data and leaf area. STR and stomatal conductance were also determined using a steady-state porometer. Specific growth rate (RSG) of young leaflets was calculated from the difference between metabolic heat rate and respiration rate, which served as an indicator for growth potential. Low STR values found at tensions between 0 and 1.5 kPa in UC mix suggest this medium has insufficient free air space for proper root activity within this range. Above 2.3 kPa, unsaturated hydraulic conductivity of UC mix was lower than that of coir, possibly lowering STR values of UC mix-grown plants. As a result of these two factors, STR of plants grown in coir was 20% to 30% higher than that of plants grown in UC mix. STR of coir-grown plants started to decline only at tensions around 4.5 kPa. Yield (number of flowers produced) by coir-grown plants was 19% higher than UC mix-grown plants. This study demonstrated the crucial role of reaching sufficient air-filled porosity in the medium shortly after irrigation. It also suggests that hydraulic conductivity is a more representative measure of water availability than tension.

Free access

Abdoulaye Traore, Zizhuo Xing, Amy Bonser, and John Carlson

A successful tissue culture initiation step often begins with effective explant sterilization. To improve douglas fir bud culture initiation, five sterilization treatments (20% bleach, 100% bleach, 3 second flaming, 5 second flaming, and self-extinguishing flaming) were evaluated for their effectiveness on winter and spring bud sterilization. The 20% and 100% bleach treatments resulted in the highest percentage of healthy bud cultures (>90% for winter buds). Spring buds showed a higher level of contamination with 20% bleach sterilization (36%) than did winter buds (1%). Successful sterilization was also achieved by flaming, but bud injury was observed. Increased flaming time caused a decrease in the percentage of healthy actively growing buds. The percentage of healthy bud cultures after 3 second flaming, 5 second flaming and self-extinguishing-flaming (9 to 14 s) were 66%, 59%, and 10% respectively. In addition, sterilization by either approach required subsequent bud dissection to remove the outer scales; otherwise most buds were lost to contamination. When sterilization was followed by bud dissection, contamination rates for winter buds were <2% for all treatments. After successful sterilization and culture initiation, bud expansion was the highest (50% to 98%) in the presence of low concentrations of BA (0 to 0.045 μmol·L–1), while high concentrations of BA (0.448 to 4.527 μmol·L–1) reduced bud expansion (0% to 60%), but promoted bud multiplication.

Free access

Said Ennahli and Sorkel Kadir

Variability due to soil types, topography, and climate within a vineyard influences grapevine physiological parameters and fruit quality. Technical feasibility of using precision Geographic Information System (GIS) as a viticulture tool to improve vineyard management and increase wine quality will be investigated. The study was conducted in an experimental vineyard where rows consist of plots with 24 cultivars and selections randomly planted and managed similarly. Monitored vineyard parameters collected by Global Positioning System (GPS) location include soil characteristics, soil moisture, vine growth, crop load, and fruit characteristics. Geospatial maps are used to differentiate yield between the cultivars and selections as high, medium, or low. Production was determined from each variety/selection within the vineyard. Yield parameters were number of clusters, cluster weight, and weight of 50 berries; fruit composition (such as pH), titratable acidity, soluble solids concentration, and anthocyanins were measured. Maps for each factor will be derived via GIS tools and spatial analysis will be conducted to assess which spatial variability factor has more effect on grapevine physiology, yield, and fruit quality. This type of analysis can be used by grape growers to achieve specific wine characteristics in a large or small vineyard by controlling all sources of variability, leading to the ability to perform precision viticulture in the future, with low cost.

Free access

Raymond P. Chée, Daniel I. Leskovar, and Daniel J. Cantliffe

Embryogenic callus growth of sweetpotato [Ipomoea batatas (L.) Lam.] was selectively enhanced by subculture on basal callus proliferation medium modified to contain 15 mm NH4NO3. Embryogenic callus production was doubled on basal callus proliferation medium modified to contain 60 mm K+, while nonembryogenic callus production was reduced 40%. Additions of up to 40 mm NaCl to basal callus proliferation medium did not affect callus proliferation. The development of embryos from calli subculture to embryo production basal medium was unaffected by the KCl or NaCl treatments of the callus proliferation phase. However, embryo production was increased by subculturing callus from callus proliferation medium containing 20 mm NH4 + to embryo production medium containing 10 mm NH4 + Our results demonstrate that changes in mineral nutrition, in addition to growth regulator differences between callus proliferation and embryo production media, are important factors in sweetpotato somatic embryogenesis.

Free access

Rebecca G. Bichsel, Terri W. Starman, and Yin-Tung Wang

Experiments were conducted to determine how nitrogen (N), phosphorus (P), and potassium (K) rate and fertilizer termination time affect the growth and flowering of a Dendrobium nobile Lindl. hybrid, Dendrobium cv Red Emperor ‘Prince’. Nitrogen, P, and K were tested in separate experiments as a factorial combination of five rates and three termination dates (1 Sept., 1 Oct., and 1 Nov. 2005). Nitrogen and K rates were 0, 50, 100, 200, and 400 mg·L−1. Phosphorus rates were 0, 25, 50, 100, and 200 mg·L−1. Levels of the nutrients not being tested were held constant. For all nutrients, ending fertilization on 1 Sept. resulted in greater or similar pseudobulb thickness compared with ending fertilization on 1 Oct. or 1 Nov. Pseudobulbs grew taller as the N rate increased, peaking at 100 and 200 mg·L−1. There were interactions between the N rate and fertilizer termination time on all reproductive characteristics. For all fertilizer termination times, flower number increased once N was applied. When ended on 1 Nov., 200 and 400 mg·L−1 N caused a delay to reach anthesis. All P rates resulted in taller plants with equally more nodes when compared with 0 mg·L−1. As the K rate increased from 0 to 100 mg·L−1, plant height increased, with no further increase at higher rates. The number of leaves remaining increased as N and K rates increased up to 200 mg·L−1. Total flower number and flowering node number increased as the K rate increased to 100 mg·L−1 (terminated on 1 Sept.) or 50 mg·L−1 (terminated on 1 Oct. or 1 Nov.). In the fourth experiment, only N was ended at four termination times, whereas all other nutrients continued to be supplied until flowering. Control plants received all fertilizer elements until flowering. The duration of N application did not affect vegetative or flowering characteristics. No aerial shoots were observed as a result of prolonged application of N at all rates. In summary, 100 mg·L−1 N, 25 mg·L−1 P, and 100 mg·L−1 K are recommended for optimal vegetative growth and reproductive development of Dendrobium cv Red Emperor ‘Prince’.