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Michael J. Lamb, George H. Clough, and Delbert D. Hemphill

The effects of supplemental Ca and varying NO3:N H4 ratios on transplant growth and NH4-N utilization were studied using watermelon (Citrullus vulgaris L. `Crimson Sweet') seeded in plastic multicell trays. The growing media consisted of a commercial peat mix amended with CaCO3 (10% w/v). Fertigation with five NO3:N H4 ratios and five levels of supplemental Ca (4, 8, 12, 16 mmol.) was applied daily in factorial combinations. The highest NO3:N H4 ratio produced greatest shoot dry weight, shoot N, and shoot NO3-N and K concentrations. Increasing NH4 and Ca decreased media pH and increased EC. After 21 days, supplemental Ca decreased shoot N and dry weight, but after 28 days had no effect. Additional Ca increased shoot Ca but decreased Mg and K. Supplemental Ca and N ratio interacted to affect leaf area. Pretransplant N ratio and supplemental Ca effects on seedling field performance, flowering, and yield were evaluated.

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F.M. del Amor, V. Martinez, and A. Cerdá

The shortage of good quality water in semiarid zones necessitates the use of saline water for irrigation. In order to simulate the usage of brackish irrigation water in greenhouse melon (Cucumis melo L. cv. Galia) culture in perlite, plants were supplied with nutrient solutions containing 0 (control), 20, 40, and 60 mm NaCl applied at four different times. Treatments were applied during early vegetative growth [14 days after transplanting (DAT)], beginning of flowering (37 DAT), beginning of fruit set (56 DAT), and beginning of fruit ripening (71 DAT). All vegetative and fruit yield parameters were significantly reduced when salinization was started 14 DAT. This inhibitory effect of salinity was progressively lessened when salinity was imposed at later dates. This suggests that the response of melons to salinity depends on the duration of exposure to saline water. Salinity treatments increased fruit reducing sugars, acidity, and total soluble solids. Fruit yield reduction at each salinization time was correlated with salinity levels, but there was some evidence of a nutrient imbalance, since leaf concentrations of N-NO3, and especially K, were low at higher salinities. These results indicate that brackish waters can be used for growing melon with minimum yield losses if concentration and duration of exposure are carefully monitored.

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Juan Carlos Díaz-Pérez, Jesús Bautista, Gunawati Gunawan, Anthony Bateman, and Cliff Martin Riner

Vidalia onions (Allium cepa L.) are sweet, short-day, low pungency, yellow Granex-type bulbs that are popular in the United States because of their mild flavor. There are limited studies on sweet onion plant growth in response to organic fertilization rate. The objective of this report was to evaluate the effects of organic fertilizer rates on sweet onion plant growth, and leaf and bulb mineral nutrients. Experiments were carried out at the Horticulture Farm, Tifton Campus, University of Georgia, in the Winters of 2012–13 and 2013–14. There were five treatments [organic fertilizer 3–2–3 equivalent to 0, 60, 120, 180, and 240 kg·ha−1 nitrogen (N)]. During the season and at the mature plant stage, root, stem, and bulb biomass increased whereas the root-to-shoot ratio decreased with increasing fertilization rate up to 120 kg·ha−1 N. Foliar concentrations of N and Ca decreased whereas Cu concentration increased with increasing organic fertilization rate. Bulb Mg and Mn increased whereas P and Cu decreased with increasing organic fertilization rate. The accumulation of mineral nutrients by onion whole plants increased quadratically (N, P, K, and S) or linearly (Ca and Mg) with increasing fertilization rate. The N use efficiency decreased with increasing organic fertilization rate; the agronomic efficiency of N (AEN) decreased quadratically and the marginal yield decreased linearly with increasing fertilization rate. Chlorophyll indices (CI) were highest with 240 kg·ha−1 N and lowest with 0 kg·ha−1 N. In conclusion, onion plant growth increased with increasing organic fertilizer rate probably because of augmented soil N levels. Observation of nutrient deficiencies late in the season, even at high organic fertilization rates, indicates that preplant application of organic fertilizer was sufficient to cover plant nutritional needs only partially and that applications of N fertilizer later in the season may be necessary. High application rates of organic fertilizer (above those required by the crop) may have resulted in significant N leaching because it is unlikely that the crop used most of the N that was mineralized. Bulb concentrations of P, K, Ca, Mg, S, B, Fe, Cu, and Mn were higher compared with values reported in the literature for onions produced with inorganic fertilizers.

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Dominique-André Demers, André Gosselin, and H. Chris Wien

Sweet pepper (Capsicum annuum L.) plants were grown under natural or supplemental lighting that extended thephotoperiods to 16, 20, or 24 hours. Increasing the photoperiod to 16 and 20 hours increased pepper plant yields, but continuous light (24 hours) decreased yields compared to the 20-hour photoperiod. In a second experiment, plants were exposed to a photoperiod of 14 or 24 hoursand either pruned to one fruit every four nodes or not pruned. During the first weeks of treatments, plants grown under continuous light had higher shoot mass (fresh and dry) and yields. After 7 to 8 weeks of treatments, plants under continuous light grew more slowly than plants exposed to a 14-hour photoperiod. At the end of the experiment, shoot mass and yields of plants grown under a 14-hour photoperiod were equal to or higher than plants under continuous light. So, it seems possible to provide continuous lighting for a few weeksto improve growth and yields. Limiting the number of fruit per plant increased shoot mass and decreased yields, but had no effect on the general response of pepper plants to photoperiod treatment. Leaf mineral composition was not affected by photoperiod treatment, indicating that reduced growth and yields under continuous light were not due to unbalanced mineral nutrition. Leaf starch and sugar contents were increased under continuous light. However, fruit pruning treatments did not modify the pattern of starch and sugar accumulation under the different photoperiod treatments. Reduced growth and yields measured under a 24-hour photoperiod are probably explained by starch and sugar accumulation in leaves as a result of leaf limitations rather than a sink limitation.

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Humberto Núñez-Moreno, James L. Walworth, Andrew P. Pond, and Michael W. Kilby

relationship was noted in 2008, but the difference was not significant. Concentrations of other nutrients in leaflet tissues were unaffected by treatment. Table 6. Effect of soil zinc (Zn) fertilization on leaf mineral composition of adult pecan ‘Wichita’ pecan

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Chiara Cirillo, Youssef Rouphael, Rosanna Caputo, Giampaolo Raimondi, and Stefania De Pascale

’, B. ‘Lindleyana’ ( =B. ‘Aurantiaca’ )] trained to two canopy shapes (globe and pyramid). For this, plant growth, ornamental quality, WUE, mineral composition, stomatal resistance, and water relations were measured during the growing cycle. These

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Rob M. Stevens, Gordon Harvey, and Gerry Davies

The effect of foliar salt uptake on potted grapevine growth and ionic composition was investigated in a split plot trial. The main plot was a 2 × 2 factorial consisting of separately irrigating the roots and foliage with nonsaline or saline (25 mm NaCl) solutions. The subplot was a 4 × 2 factorial consisting of four grape (Vitis vinifera) cultivars on their own roots or `Ramsey' (Vitis champini) rootstock. Saline foliar irrigation over 27 weeks reduced total vine growth by 14% while saline root irrigation had no effect. Leaf Na and Cl concentrations were elevated by saline foliar and saline root irrigation. The increases in concentrations with saline foliar irrigation were four times those with saline root irrigation. Leaf K concentration was reduced by saline foliar irrigation and increased by saline root irrigation. With saline irrigation of roots and foliage the Cl and Na levels were highest in the leaves of `Shiraz', but with saline irrigation of only the roots `Sultana' had the higher levels of leaf Cl and `Shiraz' the highest leaf Na. Saline foliar irrigation had no effect on the concentrations of Na, Cl, and K in the roots. In `Sultana', saline foliar irrigation did not affect the leaf concentrations of N, NO3-N, P, Mg, Zn, and Cu. It increased the leaf concentration of Fe, and decreased that of Mn. Rootstock modified the effect of salinity on Fe concentrations. The B concentration was decreased by saline irrigation of either the foliage or the roots, but not by saline irrigation of both. In roots, saline foliar irrigation increased B in own-rooted vines, but not in those on `Ramsey' rootstock.

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Elena de Castro, Bill Biasi, Elizabeth Mitcham, Stuart Tustin, David Tanner, and Jennifer Jobling

). Several factors predispose apple fruit to postharvest storage disorders. Variations in mineral composition are widely recognized to affect fruit quality after harvest ( Bramlage et al., 1980 ; Sharples, 1980 ). Mineral composition greatly influences

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A. Bar-Tal, B. Aloni, L. Karni, J. Oserovitz, A. Hazan, M. Itach, S. Gantz, A. Avidan, I. Posalski, N. Tratkovski, and R. Rosenberg

Blossom-end rot (BER) is one of the major physiological disorders of green-house bell pepper (Capsicum annuum L.). The objective of the present work was to study the effects of the solution N concentration and N-NO3: N-NH4 ratio on fruit yield and the incidence of BER and other fruit-quality traits of greenhouse-grown bell pepper in a Mediterranean climate. Three experiments were conducted: Expt. 1 included five total N concentrations (0.25 to 14 mmol·L-1, with a constant N-NO3: N-NH4 ratio of 4); Expt. 2 included five treatments of different NO3: NH4 molar ratios (0.25 to 4, with a constant N concentration of 7 mmol·L-1); and Expt. 3 included three treatments of different NO3: NH4 molar ratios (1.0, 3.0 and 9.0, with a constant N concentration of 7 mmol·L-1). Plants were grown in an aero-hydroponics system in Expts. 1 and 2 and in tuff medium in Expt. 3, in greenhouses in Israel. The optimal values of N concentration for total fruit yield and for high fruit quality (marketable) were 9.3 and 8.3 mmol·L-1, respectively. The total and high-quality fruit yields both increased with increasing N-NO3: N-NH4 ratio in the range studied. The total and high-quality fruit yields both decreased sharply as the NH4 concentration in the solution increased above 2 mmol·L-1. The increase in the NH4 concentration in the solution is the main cause of the suppression of Ca concentration in the leaves and fruits and the increased incidence of BER. The occurrence of flat fruits also increased with increasing NH4 concentration in the solution.

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Cindy B.S. Tong, David S. Bedford, James J. Luby, Faye M. Propsom, Randolph M. Beaudry, James P. Mattheis, Christopher B. Watkins, and Sarah A. Weis

The effects of growing and storage locations and storage temperature on soft scald incidence of `Honeycrisp' apples were examined. In 1999 and 2000, fruits were produced at five different locations, harvested at two different times, and stored at two or five different storage locations. In 1999, fruits were stored at 0 or 2 °C. Soft scald was only observed in fruits from one growing location and primarily at 0 °C. More soft scald was observed from the second harvest than from the first. Scalded fruits were preclimacteric as determined by ethylene production rate, whereas fruits from the other locations were postclimacteric. In 2000, fruits from four of the growing locations developed soft scald, and soft scald incidence was not related to ethylene production rate. Scalded fruits had higher concentrations of phosphorus, boron, and magnesium, and lower concentrations of manganese than unaffected fruit. Development of soft scald was not related to fruit ethylene production rates, was dependent on growing location, increased with later harvest, and may be related to fruit elemental content.