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Jinghua Fan, George Hochmuth, Jason Kruse, and Jerry Sartain

( Table 5 ). The source of N in the turfgrass with the control treatment irrigated by tap water was the N remaining in the sod and natural N input (e.g., atmospheric deposition). Plant N uptake in plants with the other treatments resulted from N in the RW

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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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Tina Wilson, Robert Geneve, and Brent Rowell

Membrane damage associated with rapid influx of water during imbibition can play a role in the poor emergence and seedling vigor associated with sweet corn germination. Film-coating as a seed treatment has been used to improve germination and vigor in sweet corn and this improvement may not be associated with changes in imbibition rate. Two seed lots of shrunken-2 variety sweet corn, low-vigor `Even Sweeter' and high-vigor `Sugar Bowl', were treated with a hydrophilic polymer film-coating and evaluated for differences in emergence and water uptake. Both cultivars were grown at 19, 21, and 26 °C with no effect on emergence due to film-coating. Imbibition curves were established for untreated and hydrophilic film-coated seeds. Film-coated seeds showed an 18% increase in fresh weight compared to untreated seeds for both cultivars during a 6-h period. Bulk conductivity tests resulted in no significant mean difference between untreated and hydrophilic-treated seeds after 24 h. These seed lots have been treated with a hydrophobic polymer and are currently being evaluated for cold temperature emergence and imbibition rates. Water entry during imbibition will also be compared for untreated sugary (su) and shrunken-2 (sh2) seeds using the fluorescent compound trisodium salt, 8-hydroxypyrene-1, 3,6-trisulfonic acid (HPTS).

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Ustun Sahin, Melek Ekinci, Fatih Mehmet Kiziloglu, Ertan Yildirim, Metin Turan, Recep Kotan, and Selda Ors

uptake and promote plant development. Promotion of root growth results in a larger root surface, and can, therefore, has positive effects on water acquisition and nutrient uptake ( Dimkpa et al., 2009 ). In our study, nitrogen fixation ability of PGPR

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William R. Argo and John A. Biernbaum

Hybrid impatiens (Impatiens wallerana Hook. F.) were planted into media containing two dolomitic liming materials {hydrated [Ca(OH)2 and Mg(OH)2] or carbonate (CaCO3 and MgCO3) lime} and subirrigated for 17 weeks with four irrigation water sources (IWS) and three water-soluble fertilizers (WSF). The WSF contained 200N–20P–200K mg·L-1 but varied in NH4 +-N content (50%, 25%, or 3%, respectively). Depending on the IWS and lime type used in the media, root-medium pH ranged from 4.5 to 6.0, 4.8 to 7.1, and 6.0 to 8.5 when treated with WSF containing either 50%, 25%, or 3% NH4 +-N, respectively, between 8 and 17 weeks after planting. The accumulation of NH4 +-N and NO3 --N in the root medium was different for treatments receiving the same WSF and depended on root-medium pH. The critical root-medium pH for NH4 +-N accumulation was between 5.4 and 5.7, and for NO3 --N, accumulation was between 5.3 to 5.9. Above this pH, minimal NH4 +-N concentrations were measured in the medium, even with 50% or 25% NH4 +-N WSF, while below this pH, NH4 +-N began to accumulate in the medium with a corresponding decrease in the NO3 --N concentration. The NH4-N: NO3-N ratios in the WSF had minimal effect on shoot fresh and dry weights. Tissue N concentration was higher with the higher NH4-N : NO3-N ratio WSF at all four sampling dates. There was a linear relationship between higher tissue N and lower root-medium pH with the same WSF, possibly due to differences in the ratio of NH4-N: NO3-N actually taken up by the plant.

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D.M. Glenn and W.V. Welker

We determined how differences in peach tree water use and shoot and root growth due to ground cover treatments are affected by tree response and soil conditions in the adjacent soil environment. Ground cover combinations of bare soil (BS), a killed K-31 tall fescue sod (KS), a living Poa trivialis sod (PT), and a living K-31 tall fescue sod (LS) were imposed on 50% of the soil surface in greenhouse studies. The ground cover on 50% of the soil surface influenced root and top growth of the peach trees [Prunus persica (L) Batsch], water use, and NO3-N levels in the opposing 50%, depending on the competitiveness of the cover crop (LS vs. PT and KS) and characteristics of the soil (BS vs. KS). Tree growth was allometrically related to root growth.

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H. C. De Roo

Abstract

The water economy of plants often is seriously unbalanced by root destruction or vascular occlusion induced by various rot organisms. Water absorption by the roots and water transport within the plants is impeded and wilting follows. Beckman (1) reviewed the literature on the histological and physiological changes in host plants infected with pathological wilts. Dimond and Edgington (2), studying the mechanics of water transport in healthy and Fusarium-vrilted tomato plants, pointed out the tremendous pressure deficits that are required to maintain normal water flow into leaves through partially plugged vessels.

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C. S. Tan and J. M. Fulton

Abstract

Root systems were studied to determine if differences in utilization of soil moisture were associated with the extent and number of roots produced by corn and tomato. Growth room studies for both crops indicated that the reduction in transpiration when the upper portion of the root zone was dry was greater than when the lower portion was dry. Total root length of corn was about twice that of tomato roots. However, no direct relationship between the total amount of root length and transpiration was found. Roots of corn and tomato in the field extended beyond the maximum depth measured (100 cm) between 42 – 46 days after establishment. The spatial density of corn roots was much greater than that of tomato roots, especially as depths increased. This difference possibly explains the use of stored soil moisture by corn. On the other hand, the capacity of tomatoes to extract large amounts of water from the soil cannot be explained by the density and rooting depth. Perhaps this capacity is due to total root surface area differences or high absorption capacity of tomato root system.

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Mark Rieger

Abbreviations: A, net CO 2 assimilation; g, stomatal conductance; L p , root hydraulic conductivity; NUE, nitrogen-use efficiency; RH, `Redhaven'; WUE, water-use efficiency; Ψ water potential. A contribution of the Georgia Agricultural Experiment

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Carolyn F. Scagel, Guihong Bi, Leslie H. Fuchigami, and Richard P. Regan

. The influence of water and N management on uptake of other nutrients during production for many crops has not been evaluated fully. With some woody perennial plants, growth is enhanced more by minimizing water stress than by increasing fertility ( Rose