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- Author or Editor: Charles Graham x
Research is needed to better understand the influence of cell volume and fertility on watermelon transplant size and field performance in order to determine the most economic production practices. `Jubilee' watermelon transplants were grown using a 4 x 4 factorial experimental design consisting of 4 cell volumes (30.7, 65.5, 147.5, and 349.6 cm3) and 4 fertility rates (0, 1/4, 1/2, and full-strength Hoagland's solution). Transplant shoot dry weight significantly increased as cell volume and fertility increased. Increasing cell volume linearly increased watermelon number/ha and tons/ha for early and total harvest in 1995. The average weight per watermelon significantly increased for early-harvested fruit but not for total harvest as cell volume increased in 1995. Soluble solids concentration linearly increased with increasing cell volume for early and total harvests in 1995. Cell volume had no significant influence on the harvest parameters measured in 1997. In 1995, increasing fertility linearly increased watermelon number/ha and tons/ha for early harvests. Increasing fertility increased the soluble solids concentration linearly for early-harvested watermelons in 1997 but not in 1995. Fertility rate had no significant influence on any of the other harvest parameters measured in 1995 and 1997. The growing conditions and disease pressure in 1997 reduced melons/ha, yield, and soluble solids content when compared to 1995 values. The half-strength Hoagland's solution produced the greatest number of watermelons/ha, tons/ha, and the highest soluble solids concentration in 1995 and 1997. Pretransplant nutritional conditioning had no significant effect on total `Jubilee' watermelon production in Louisiana for 1995 and 1997.
Pollarded `Wichita' pecan [Carya illinoensis (Wang) K. Koch] trees received 2 g uniconazol (UCZ) per tree using four application methods (trunk band, canopy soil injection, crown soil injection, and crown drench). All application methods increased trunk diameter but reduced shoot length, number of lateral shoots per terminal, nodes per terminal, internode length, and leaflets per compound leaf. Only the crown drench reduced leaf area. Area and dry weight per leaflet, and leaflet chlorophyll concentration were not affected by UCZ application. Effectiveness in growth reduction, as assessed by shoot elongation, was crown soil drench > crown soil injection > canopy soil injection > trunk band > control. All application methods increased viviparity. However, total yield per tree, nut size, and percentage of kernel were not affected. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazol).
`Nemaguard' peach [Prunus persica (L.) Batsch] seedlings were grown hydroponically in a modified Hoagland's solution containing NO3N:NH4-N ratios of 100:0, 75:25, 50:50, 25:75 and 0:100. The solutions contained 0 or 50 ppm aluminum supplied as Al(NO3)3·9H2O or AlNH4(SO4)2·12H2O. Analysis of pooled nitrogen source data revealed Al significantly reduced plant leaf area, height, total growth, and root:shoot ratio. Ammonium concentrations > 25% of supplied nitrogen significantly reduced leaf number, leaf area, height, lateral breaks, lateral growth, total growth, and leaf, stem, and root dry weights. Only height and dry weights (stem and root) for plants receiving 100% nitrate were significantly greater than plants receiving 25% of supplied nitrogen as NH4-N. Generally, phosphorus uptake significantly decreased in the presence of Al regardless of nitrogen source, but the greatest reductions occurred at high NH4-N concentrations.
A greenhouse experiment was conducted to assess the effects of increasing aluminum concentrations on carbohydrate levels of peach. Nemaguard and Lovell peach seedlings were grown in sand culture and irrigated daily with one-fifth strength Hoaglands solution containing A1 rates of 0, 25, 50, and 100 ppm. Beginning at week 6, plants were harvested at two-week intervals over an 8-week treatment period, and tissues (root, stem, and leaf) were analyzed for soluble sugars and starch. Lovell had significantly greater concentrations of root sucrose, glucose, fructose, and sorbitol; stem glucose and fructose; and leaf sucrose, glucose, and fructose. Nemaguard contained significantly greater concentrations of root, stem, and leaf starch and total carbohydrates compared to Lovell. Increasing aluminum concentration resulted in a significant linear increase of starch in the root and stem tissue, but a quadratic response in the leaf tissue of both cultivars. Increasing rates of A1 produced a decreasing curvilinear response in the concentration of glucose and fructose in roots, stems, and leaves. Analysis across harvest dates revealed that glucose and fructose declined curvilinearly in all tissues as the treatment duration increased. Starch concentrations increased curvilinearly in the roots and stems but decreased curvilinearly in the leaves when analyzed across harvest dates.
Current recommendations for sufficiency of nutrients in soil-less media for container grown nursery crops have been based on weak acid extraction and pour through sampling of media. Since the concentration of nutrients found in pour through samples are similar to those available in the media solution, sufficiency levels as determined by hydroponics studies have also been considered to be applicable to plants grown in a solid medium such as pine bark. Many variables, however, may affect nutrient availability in a solid medium which are not the same as those in a well-stirred hydroponics system. Objectives of this experiment were to compare growth and nutrient uptake patterns of Euonymous kiautschovica `Manhattan' and Prunus persica `Jefferson' grown in a pine bark/sand medium or a hydroponics system. Quantitative growth characteristics, depletion rates of nutrients in solution, concentration of ions in pour through samples, and tissue levels of N, P, K, Ca, and Mg will be reported.
Peaches are often grown on sandy, low pH soils which may predispose plants to aluminum (Al) toxicity. Previous research has shown that peach (Prunus persica, L. Batsch) is not tolerant to Al and toxicity may be associated with occurence of peach tree short life syndrome. Current recommendations to control PTSL include soil calcium (Ca) applications to reduce soil acidity and Al availability. However, these applications often result in inconsistent responses. Objectives of this study were to determine if Ca would ameliorate the effects of Al toxicity and whether different Ca compounds would provide different responses.
Rootstock were grown in sand culture supplied with Hoagland's solution containing 16.7 mM aluminum Trees received weekly foliar sprays containing 12.5 uM calcium and 0.1% Chevron X-77 as a spreading agent. Calcium compounds tested included calcium chloride, formate, lactate, nitrate, phosphate, and sulfate. Stem dry weights were significantly increased by Ca lactate and sulfate, leaf dry weight by Ca lactate, and Ca formate significantly increased leaf retention. Nutrient concentrations and interactions in leaves, stems, and roots will be discussed.
A field experiment was conducted to assess the effects of several foliar nutrient sprays on the vegetative growth of 'Jefferson' peach budded on 'Nemaguard' and 'Lovell' rootstocks planted on a site with a history of Peach Tree Short Life. The trees received foliar applications of 2 mN solutions of ammonium citrate, calcium citrate, calcium lactate, calcium phosphate, or a water control at 3 week intervals from April to August. Vegetative growth measurements were taken after one growing season. Trunk cross-sectional area (TCSA) was significantly increased by ammonium citrate (TCSA=20.35 cm2), calcium citrate (TCSA=20.03 cm2), and calcium lactate (TCSA=19.91 cm2) when compared to controls (TCSA=16.75 cm2). Trees on 'Nemaguard' responded more to treatments than those on 'Lovell'. All nutrient sprays increased TCSA, lateral growth, terminal growth, and total tree growth on 'Nemaguard' rootstock. Terminal growth increased 12-36%, and total tree growth increased 18-51 % compared to control trees, but only ammonium citrate applications were significantly greater. Lateral growth and TCSA of treated trees increased 65-168% and 17-28%, respectively.
'Redhaven' and 'Springcrest' peach cultivars were budded to 12 rootstock selections and planted on a non-fumigated peach tree short life site. After 2 growing seasons, 2 shoots/tree (20 trees/stion) were collected in late November 1990 and again in early March 1991. Samples were immediately frozen in liquid nitrogen and later freeze dried and prepared for analysis. Total soluble sugars and starch were extracted from the shoot and quantified. No significant differences among rootstocks or cultivars were found for total soluble sugars and starch. No significant correlations were found between stion carbohydrates in fall and spring and the incidence of bacterial canker in April 1991. Total soluble sugars and starch averaged 110 and 120 mg/g dry tissue for fall and spring sample times, respectively. Cultivars on the hybrid plum rootstock 'Edible Sloe' had the highest soluble carbohydrates in both fall and spring.
Late spring freezes often result in significant flower bud kill in deciduous fruit trees. Some products have been marketed as frost protectant compounds which purportedly protect flower stigmas and ovaries from freezing injury and death. Two of these compounds, Frost Free and Frostgard, were tested at two locations in South Carolina over three years. Varieties `Junegold', `Loring', `Redhaven', and `Jefferson' were treated with Frost Free (FF) in years 1988-1990 and with Frostgard (FG) in 1990. Significant differences in fruit yield and vegetative growth occurred during this period, but no consistent trends were evident. In 1989, FF-treated `Redhaven' and `Jefferson' trees averaged 10.5 and 21.8 kg more fruit/tree than the controls. However, no lethal cold temperatures occurred during the bloom period. In 1990, FG-treated `Redhaven' trees averaged 8.0 kg more fruit/tree than the control trees. The fruit from FF-treated trees were lower in Brix, had less red color, and vegetative shoot growth was slightly greater than that of the FG and check trees. These data suggest that Frost Free may have plant growth regulator properties.
Increasing cell volume or pretransplant nutrient conditioning (PNC) reduced the time to flowering for staminate and pistillate flowers in watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. Larger cell volumes increased the number of early harvested watermelons and average watermelon weight in two of three studies. Similarly, larger cell volume increased the early and total yield per area of watermelons harvested in 1995 and 1998, but not in 1997. Effect of transplant cell volume on soluble solids varied seasonally. PNC increased the number of melons and the yield per area harvested early in 1995 and soluble solids in early harvested fruit in 1997, but had no significant effect on total `Jubilee' watermelon size or total production in Louisiana for 1995, 1997, or 1998. PNC offers the transplant grower little advantage, while increasing transplant cell size provides a grower with a better opportunity to produce increased early and total yields.