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Nirit Bernstein, Marina Ioffe, Moshe Bruner, Yair Nishri, Gideon Luria, Irit Dori, Eli Matan, Sonia Philosoph-Hadas, Nakdimon Umiel, and Amir Hagiladi

The form of N supplied to the plant (NH4 + or NO3 ) affects growth, morphology and a range of physiological processes in the plant. Little information is available concerning the effects of N form on development, production or quality of cut-flowers. The present study investigated for the first time the effects of N form and quantity on growth, flower production and flower quality of Ranunculus asiaticus L. The plants were cultivated in an inert mineral soilless medium (perlite) and were exposed to two levels of nitrogen fertilization (50 or 100 ppm) and three levels of NH + 4 (10%, 20%, or 30%, under 100 ppm nitrogen fertilization). Larger shoots and increased shoot/root ratios were obtained in the lowest (50 ppm) N treatment. This treatment also excelled in flower yield production, resulting in higher numbers of total flower produced as well as higher numbers of long flowers. The results demonstrate an effect of N ferlilization treatments on cut-flower quality. Flowers grown under 50 ppm N application characterized by almost double vase life duration compared to flowers grown under the various 100 ppm N treatments. However, flower quantity and quality were not affected by the level of NH4 applied. The R. asiaticus L. root was less sensitive to the N fertilization treatments than its shoot. Contents of organic N, NO 3, P, K, Ca, Mg, Na, Cl, Fe, Cu, Zn, B, and Mo in the leaves were not affected by the fertilization treatments. Taken together, our results suggest a low requirement of R. asiaticus L. for N fertilization, and insensitivity to ammonium concentrations in the range of 10 to 30 ppm, 10% to 30% of the total N supplied. Detrimental effects in terms of growth, production and cut flower quality were apparent already under 100 ppm N supply.

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Carmen Feller and Matthias Fink

The objective was to provide results to optimize the production of table beet (Beta vulgaris L.) with respect to yield and quality. Field experiments were carried out over 2 years, where the effects of nitrogen (N) supply, sowing date, and cultivar were tested in a block design with four replications. In addition to yield, soluble solids and nitrate N contents of roots were measured to assess quality. Sowing date was an important factor for determining yield and quality of table beet. Sowing dates later than June at the experimental site are not recommended because they resulted in an increase in nitrate N content in fresh weight of up to 3027 mg·kg-1 and an average yield loss of 46% compared to sowings in April. Soluble solids content (SSC) was only slightly affected by planting date. Nitrogen supply did not affect SSC, but increasing N supply led to a major increase in nitrate N content, especially if combined with late sowing dates. It was concluded for early sowing dates that N supply be determined to achieve the maximum yield. With an early sowing date, nitrate N content in fresh weight at harvest was <563 mg·kg-1, even with a high N supply of 250 kg·ha-1. Late sowing dates required a reduced N supply to keep harvest nitrate contents below the 2500 mg·kg-1 required by the processing industry. Recommendations for optimizing N supply, sowing date, and cultivars for table beet should always take into account strong interactions between these factors.

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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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Desmond G. Mortley and Walter A. Hill

The influence of Azospirillum inoculation on sweetpotato Ipomoea batatas (L.) Lam.] was evaluated in combination with fertilizer N rates of 0, 40, and 80 kg·ha-1. Plants were inoculated with 5 ml of the inoculant at 2, 4, and 6 weeks after transplanting. Inoculation increased total and marketable yield by 12% and 17%, respectively, in 1984 and 5% and 22%, respectively in 1985. Higher storage root yields were accompanied by lower foliage yields, which suggested the inoculant may enhance storage root growth at the expense of foliage growth on soils with low to moderate N levels (40 to 80 kg·ha-1). Storage root N (1984 and 1985) and leaf N (1985) were higher for 40 kg N/ha with inoculation than with inoculation alone (treatments 4 vs. 2), which suggested that Azospirillum plus fertilizer N increased the N content of the plants.

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Silvia Jiménez Becker, Maria Teresa Lao, and Mari Luz Segura

+ and N-NO 3 – are important nitrogen sources for plant growth ( Marschner, 1995 ). Most plants can use either, or both, ammonium and nitrate, and the effects of the applied N form depend on the ontogenic development of the plant, the plant species

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Timothy K. Broschat

effects on cold tolerance have concentrated on nitrogen (N), which can have positive ( DeHayes et al., 1989 ; Proebesting, 1961 ; Smith and Cotton, 1985 ), negative ( Kelley, 1972 ), or no ( Pellett, 1969 , 1973 ; Smiley and Shirazi, 2003 ) influence

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Frederick S. Davies and Glenn Zalman

citrus trees in Florida. Adequate nutrition is essential for production of high-quality citrus nursery trees, but application rates, frequencies of application, and nitrogen (N) sources vary greatly among citrus nurseries worldwide. For example, annual N

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T.K. Hartz and R.F. Smith

resulted in a significant N pollution problem affecting groundwater and surface water. Many bodies of water in this region have a nitrate-nitrogen (NO 3 -N) concentration in excess of the Federal drinking water standard of 10 mg·L −1 . Regulatory pressure

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W.G. Harris, M. Chrysostome, T.A. Obreza, and V.D. Nair

senior author by V. Carlisle, F. Sodek, and various other scientists who contributed to the Florida Cooperative Soil Survey Program; 1 m = 3.2808 ft. The poorly drained conditions of flatwoods soils affect the fate of nitrogen (N) as well as P. There is a

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Laura L. Van Eerd

content data were converted to kg N/ha based on above-ground plant vegetative (leaves and vines) and reproductive tissues dry weights. Soil mineral nitrogen measurements. Soil inorganic N concentration [NO 3 – -N and ammonium-N (NH 4 + -N)] was determined