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Ben A. Faber, A. James Downer, Dirk Holstege, and Maren J. Mochizuki

commercial floriculture crops, cultural practices and production programs Cornell University Ithaca, N.Y Knepel, K. 2003 Determination of nitrate in 2M KCl soil extracts by flow injection analysis QuikChem Method 12-107-04-1-B. Lachat Instruments Loveland

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Giedrė Samuolienė, Akvilė Urbonavičiūtė, Pavelas Duchovskis, Zenonas Bliznikas, Pranciškus Vitta, and Artūras Žukauskas

An important nutritional quality factor of vegetables is low nitrate content. Although data on potential long-term health risk of nitrate are contradictory ( Gangolli et al., 1994 ; Walker, 1990 ), some national and international regulatory

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Joan R. Davenport, Robert G. Stevens, Kelly M. Whitley, and Tanya Winkler

used as a tracer for mobile anionic plant nutrient movement (e.g., nitrate, chloride) in the soil ( Fisher and Healy, 2008 ; Green et al., 2005 ; Izadi et al., 1993 ; Logsdon, 2007 ; Schuh et al., 1997 ; Seo et al., 2005 ) as well as in studies

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Subhrajit K. Saha, Laurie E. Trenholm, and J. Bryan Unruh

turfgrass ( Killian et al., 1966 ). Brown et al. (1982) observed nitrate losses of 8.6% to 21.9% in golf course greens (bermudagrass, perennial ryegrass, Kentucky bluegrass, tall fescue, and creeping bentgrass) fertilized with ammonium nitrate. When slow

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Pietro Santamaria and Antonio Elia

In a growth chamber, endive (Cichorium endivia L. var. crispum Hegi) plants were grown using a solution culture method to evaluate the influence of four ammonium : nitrate (NH4-N : NO3-N) percentage ratios (100:0, 70:30, 30:70, and 0:100) on growth (leaf area, dry mass, crop growth rate, relative growth rate, and net assimilation rate), yield characteristics (head and root fresh mass and root length), quality (dry matter, nitrogen, and nitrate), and inorganic ion content. No symptoms of NH4 + toxicity were detected in endive plants 8 weeks after beginning nutrient treatments. Moreover, by feeding N in mixed form, the growth indices increased compared to indices from feeding with any of the two N forms alone. Ammonium-fed plants produced nitrate-free heads with a fresh mass (171 g) similar to nitrate-fed plants. Compared to the other treatments, the heads of NH4 +-fed plants were darker green and more succulent. Mixed N improved yield but caused a remarkable accumulation of nitrate in heads. Following an increase in NO3-N from 30% to 70% in the nutrient solution, head fresh mass rose from 196 to 231 g and NO3 - concentration more than doubled (from 2.4 to 6.1 g·kg-1 fresh mass). With 100% of NO3-N, NO3 - concentration was 5.5 g·kg-1 fresh mass. With higher NO3-N percentages in the nutrient solution, the difference in the concentration of inorganic cations and anions increased, but K+ concentration was also high in ammonium-fed plants (on average 77 g·kg-1 dry mass). Head total N accumulation was increased by the presence of NH4 + in the nutrient solution and decreased with 100% NO3-N. From the commercial viewpoint, the produce obtained from 100% NH4-N was good, with the value-added factor of the absence of nitrate. This may be an extremely remarkable factor because of the commercial limits on the allowable nitrate content in leafy vegetables already enforced by many European countries and those the European Union is going to adopt in a directive.

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Katherine Kreuser, William C. Kreuser, Gautam Sarath, and Keenan L. Amundsen

overcome dormancy in all seeds. Salt marsh grass, Distichlis spicata , is similarly treated with nitrate to overcome hormonal control of seed dormancy ( Amen et al., 1970 ). Also, for some species, initial promotion of germination rates induced by external

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Yuki Sago and Airi Shigemura

culture systems. However, this method can lead to excessive nitrate absorption by roots and high nitrate concentrations in vegetable leaves. Furthermore, surplus solutions from ECM systems with relatively high EC are drained into the environment, resulting

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P. Chris Wilson and Joseph P. Albano

Nitrogen applications are essential for producing quality ornamental plants. Nitrogen commonly is applied as nitrate (NO 3 − ) or ammonium (NH 4 + )-N in commercially available soluble and/or controlled-release fertilizer formulations. Ammonium-N is

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Mary C. Stevens, Rui Yang, and Joshua H. Freeman

overabundance of ammonium ( Simonne et al., 1992 ). Furthermore, ammonium is converted to nitrate in the soil by nitrifying bacteria. Under conditions that predominate in Florida, most of the soil N is quickly converted to NO 3 − , regardless of the originally

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Aaron Heinrich, Richard Smith, and Michael Cahn

Concern over nitrate contamination in drinking water has led to increased regulatory scrutiny of N fertilizer use by regional water quality agencies. A recent assessment of nitrate in groundwater for two of the most intensive agricultural production