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G.A. Picchioni

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G.A. Picchioni and C.J. Graham

Asimina triloba (L.) Dunal (pawpaw), a deciduous tree indigenous to the eastern U.S., is being considered as a potential new fruit crop. The difficulty in establishing transplanted pawpaw seedlings has been identified as an important research need for successful cultivation of this species. We have addressed the possible benefits of soil-applied CaSO4 in establishing pawpaw seedlings on acidic, low-Ca orchard soil. Two-year-old seedling rootstocks were planted at a spacing of 1.5 m (within rows) × 5.5 m (between rows), and trickle-irrigated (with N, P, and K) for two growing seasons. Before planting, CaSO4 was applied at rates of 0, 11, and 22 t/ha and incorporated to a depth of 15 cm. Seedling trunk cross-sectional area (TCA) growth increased with increasing CaSO4 application. After the first season, increases in TCA averaged 27% and 44% greater with CaSO4 treatments (11 and 22 t/ha, respectively), as compared to the 0 t/ha treatment. This effect was accentuated by the end of the second season. Average qualitative ratings (based on seedling vigor and appearance) were also improved with CaSO4 treatment. These findings indicate that establishment of pawpaw seedling rootstocks may be improved with Ca fertilization in orchards of low-Ca status. Additional data, including seedling dry matter accumulation, will be presented.

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G.A. Picchioni and Héctor M. Quiroga-Garza

Two greenhouse studies were conducted to trace the fate of fertilizer N in hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy `Tifgreen'], and to estimate total plant N recovery and losses. The first experiment was performed during winter, with artificial light supplementing natural light to provide a photoperiod of 13.6 to 13.8 hours. The second experiment was conducted during summer and fall under only natural light conditions, with a progressively decreasing photoperiod of 13.7 to 11.1 hours. Urea (UR), ammonium sulfate (AS), and ammonium nitrate (AN) were labeled at 2 atom% 15N, and applied at N rates of 100 or 200 kg·ha-1 for 84 days (divided into six equal fractions and applied every 14 days). Fertilizer N source did not affect total dry matter (DM) accumulation by the plant components, but the high N rate increased clipping DM production under the longer photoperiod. Under the decreasing photoperiod, overall DM production was reduced, and clipping DM production was unaffected by increased N rate. Average N concentration of clippings varied between N sources, ranging from a high of 38.6 g·kg-1 DM with AS to a low of 34.7 g·kg-1 for UR. In Expt. 1, the greatest total plant N recovery [clippings, verdure (shoot material remaining after mowing), and thatch plus roots] occurred with AS (78.5%) and the lowest with UR (65.9%). In Expt. 2, these values declined to 53.0% and 38.0%, respectively. Urea fertilization resulted in the greatest N losses as a fraction of the N applied (33.6% to 61.5%) and AS fertilization the lowest (20.7% to 46.3%). In view of the greater N losses, UR may be a less suitable soluble N source for bermudagrass fertilization within the conditions of this study. In addition, late-season N fertilization may result in a significant waste of fertilizer N as bermudagrass progresses into autumnal dormancy when temperature, photoperiod, and irradiance decline and cause reduction in growth and N uptake.

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G.A. Picchioni and C.E. Johnson

Ground water salinity is a major concern for crop diversification in Louisiana where mayhaw (Crataegus opaca) is being considered as a new fruit crop. Its saline resistance is unknown; thus, we evaluated it in greenhouse conditions. One-year-old seedlings were irrigated with tap water, 10 mm NaCl (+ 2 mm CaC12), and 25 mm NaCl (+ 5 mm CaC12) for 9 weeks. Leaf and stem dry matter accumulation were reduced by an average of 80% and 60% below controls, respectively, in seedlings irrigated with 25 mm NaCl. The fresh weight: dry weight ratios of stems and roots also were reduced by 25 mm NaCl (15% and 28% below controls, respectively). Notably smaller leaf growth suppression occurred when 25 mm NaCl was supplemented with 5 mm CaC12 compared to 25 mm NaCl in the absence of CaC12. The fact that CaC12 partially reversed the leaf growth inhibition may indicate that Ca fertilization could be of benefit for mayhaw orchards relying on saline ground water.

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G.A. Picchioni, C.J. Graham and A.L. Ulery

Asimina triloba (L.) Dunal is an underused tree species with demonstrated potential as a new fruit crop and landscape ornamental plant. Best management practices for A. triloba are not adequately defined, particularly for field establishment in high-Na conditions characteristic of numerous southern U.S. production areas. We evaluated the growth and net macroelement uptake of field-grown A. triloba seedlings on soil amended with a single addition of gypsum at 0, 7.5, or 15.0 t·ha-1 and later receiving a regular supply of Na-affected but nonsaline irrigation water [sodium adsorption ratio (SAR) of 15.5 and electrical conductivity (EC) at 0.4 dS·m-1]. Over two growing seasons, the soil saturation extract Ca concentration increased while the soil saturation extract SAR decreased with increasing gypsum rate. Amending the soil with gypsum increased total lateral branch extension per tree by 60% to 73% and trunk cross-sectional area (TCSA) per tree by 68% to 87% above a non-gypsum-amended control treatment. Total dry matter accumulation and the net uptake of N, P, and K per tree were over 100% greater following gypsum application as compared to controls. The growth and mineral uptake-enhancing effects of gypsum were likely related to functions of Ca at the root level and on soil physical properties that should be considered in establishing young A. triloba trees with irrigation water containing high sodicity but relatively low total salinity.

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G.A. Picchioni, Wayne A. Mackay and Mario Valenzuela-Vázquez

Correlative control of long-distance transport processes consists of an attraction or mobilizing power of a sink organ coupled to internal degradative reactions in a target source organ and the reallocation of its resources. This phenomenon is widely recognized in the agronomic whole plant literature but poorly recognized in the floriculture literature. We calculated supply and demand balances for water, total dry matter (TDM), and minerals during a 6-day postharvest evaluation of the spatially diverse, detached, indeterminate inflorescence of Lupinus havardii Wats. ‘Texas Sapphire’ held in deionized water. The apex approximately doubled its original (harvest day) amounts of total N, P, K, Mg, and S and increased its TDM and water content by 55% and 85%, respectively, all at the expense of lower-most mature flowers. Net export from the lower mature flower fraction and, when applicable, upper mature flowers, accounted for the following apical gains: 46% of TDM, 102% of water, 100% of N, 94% of P, 99% of K, and 54% of Mg and S. Directed reallocation of resources from the senescing lower mature flowers (the main “target”) to the apical sink (the “mobilizing center”) bore a marked resemblance to the coupling of remote sink demand with vegetative decline reported in monocarpic plants (i.e., vegetative-to-reproductive exchanges), but with two distinguishing characteristics: 1) the TDM and mineral exchanges were strongly restricted to flowering units, and 2) the contributions of water, N, P, and K exports to apical sink demand were at or near 100%. This article is the first that we are aware to provide an internal supply and demand balance sheet reflecting, quantitatively, the postharvest reallocation of internal resources from mature reproductive tissues to generative reproductive tissues of a cut inflorescence.

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G.A. Picchioni, S.A. Weinbaum and P.H. Brown

Leaf retention, uptake kinetics, total uptake (per unit leaf area), export kinetics, and the total export of foliage-applied, labeled B (]0B-enriched boric acid) were determined for apple (Malus domestics Borkh.), pear (Pyrus communis L.), prune (Prunus domestics L.), and sweet cherry (P. avium L.). Foliar uptake of labeled B by shoot leaves was 88% to 96% complete within 24 hours of application. More than 50% of the B retained on shoot leaf surfaces following application was absorbed and exported within 6 hours of application. Genotypic differences in shoot leaf surface characteristics among the species tested greatly influenced the amount of solution retained per unit leaf area. Leaf retention capacity was the primary determinant of the quantity of B absorbed by and exported from shoot leaves following foliar application. On average, apple shoot leaves retained, absorbed, and exported at least twice as much labeled B per unit leaf area as prune and pear shoot leaves and three to four times as much as sweet cherry shoot leaves. The sink demand of nearby, mature apples did not affect the export of labeled B when applied to adjacent spur leaves, but the fruit imported 16% of their total B from the applied solution during a 10-day period. Despite extensive documentation for the immobility of B accumulated by leaves naturally (e.g., from the soil), the B accumulated by leaves following foliage application was highly mobile in all four species tested.

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G.A. Picchioni, S. Miyamoto and J.B. Storey

The degree of salt resistance of Pistacia spp. grown in the western United States is not adequately known. This study evaluated seedling growth and ion uptake characteristics of two Pistacia spp. and one hybrid in outdoor lysimeters for two seasons. After 12 weeks, seedling stem elongation of P. atlantica Desf., P. terebinthus L. (three selections), and P. integerrima Stewart × atlantica (referred to as Gold II) was reduced by an average of 33% at soil solution salinity of 12.6 dS·m-1 (or 8.0 dS·m-1 in the saturation extract). Gold II was the most vigorous genotype and produced the greatest biomass in control and high-salt solutions. Decreases in root and stem growth (average of all seedlings combined) occurred at soil solution salinity of 13.8 dS·m-1 (or 8.7 dS·m-1 in the saturation extract). Increasing salinity resulted in a higher root to stem ratio, which was most pronounced in P. terebinthus. Comparatively small but significant differences in leaf Na and Cl concentrations between species and selections occurred. All species limited Na transport to leaf tissue up to 125 meq Na/liter in soil solution, storing the greatest amount in roots. Chloride concentrations on a dry-weight basis were substantially higher in leaves than in roots. Increasing salinity did not affect leaf K and Mg concentrations, whereas Ca was significantly reduced. Leaf Na and Cl concentrations of P. atlantica and P. terebinthus had significant correlation with Na and Cl concentrations in soil solutions (r = +0.83 to +0.94).

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Brenda L. Jessen, Geno A. Picchioni and John G. Mexal

A field study was conducted in 1997 and 1998 in Ojinaga, Chihuahua, Mexico, to compare biomass production potential and ion uptake capacity of seven tree species and clones, Eucalyptus camaldulensis (4016, 4019, and 505), hybrid Populus (029, 197, and 367), and seedlings of Robinia pseudoacacia irrigated with saline municipal wastewater. Total dry biomass production was greatest with poplar clone 367 (657 g) and eucalypt clone 4019 (643 g). Both clones also provided the most aboveground biomass (463 and 528 g, respectively), essentially because of their greater stem biomass (274 and 234 g, respectively). Poplar clone 367 had the highest lateral branch biomass (84 g), followed by eucalypt clone 4019 (75 g). The clones with the greatest leaf biomass were eucalypt clone 4019 (179 g), followed by eucalypt clone 505 (148 g) and poplar clone 367 (145 g). In all tree selections, Cl concentration was highest in the leaves with poplar clone 197 having the highest concentration (>2%), but the lowest subsequent winter survival at just 55%. The tree with the second lowest survival rate, poplar clone 029 (76%), also had the second highest Cl concentration in its leaves, almost 1.5% Cl. Eucalypt clones 4019 and 4016 accumulated the most total Cl in its tissues (327 and 236 g per tree, respectively) followed by poplar clone 029 (216 g per tree). Eucalypt clone 4019 accumulated the most Na in its tissues (109 g per tree) followed by poplar clone 367 (74 g per tree). In conclusion, poplar clone 367 and eucalypt clone 4019 seem to be sufficiently salt-tolerant for these saline conditions, having high survival, growth, and biomass capacity and perform well under high biomass-generating, short rotation conditions. Eucalypt clone 4019 is also an effective accumulator of Cl and Na ions and may be the most suitable tree for the remediation of salt-affected land in these experimental conditions.