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Yasutaka Kano, Hiroshi Nakagawa, Masami Sekine, Hideyuki Goto, and Akira Sugiura

Given that increasing the amount of nitrogen fertilizer is a relatively simple method for increasing the yields of leaf vegetables, growers are often inclined to apply more nitrogen fertilizer than is necessary. This increased application of

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M. Lenny Wells

., 2005 ; Wood, 2001 ). In all other years there was no source × rate interaction ( Table 2 ). Table 2. Effect of nitrogen fertilizer source (NFS) and nitrogen fertilizer rate (NFR) on pecan leaf nitrogen concentration, 2015–18. Leaf K was reduced in 2015

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Vincent M. Russo

described ( Kanton et al., 2002 ; Leskovar and Vavrina, 1999 ; Russo, 2004 ). In Michigan, when there were two seedlings in each cell in the seedling tray, and increased nitrogen fertilizer was used during seedling production, yield of plants developed

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Travis Wayne Shaddox and Joseph Bryan Unruh

-release nitrogen fertilizers Agron. J. 89 491 496 10.2134/agronj1997.00021962008900030020x Carrow, R.N. Waddington, D.V. Rieke, P.E. 2001 Turfgrass soil fertility and chemical problems: Assessment and management Ann Arbor Press Chelsea, MI

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Kris L. Wilder, J. M. Hart, Arthur Poole, and David D. Myrold

Little work has been done to establish the rate and timing of nitrogen fertilizer applications to optimize return from fertilizer expenditures and minimize potential for ground and surface water pollution in Oregon cranberries (Vaccinium macrocarpon Ait.). Predicting cranberry N requirements is difficult because cranberries require little N and soil tests for N are not helpful for perennial crops, especially when grown in shallow sandy soils. We used 15N-labeled ammonium sulfate to measure both plant uptake and movement of fertilizer N in a south coastal Oregon cranberry bed. A bed planted to the Stevens variety was fertilized with 15N-labelled ammonium sulfate at two rates (18 kg/ha and 36 kg/ha) applied at five phonological stages: popcorn, hook, flowering, early bud, and late bud. Plant N uptake and translocation were measured throughout the growing season in uprights, flowers, berries, and roots, Initial results indicate that when N was applied at popcorn stage approximately 12% of the N was present in the above-ground vegetative biomass at harvest. Incorporation of fertilizer N into the duff and mineral soil was measured. An estimate of fertilizer N leaching was made by trapping inorganic N below the root zone using ion exchange resin bags.

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Joan R. Davenport and Nicholi Vorsa

Cranberry (Vaccinium macrocarpon Ait.) has the opportunity to partition resources into sexual and/or asexual (stolons) modes of reproduction. Nitrogen status has been shown to impact the degree of stoloniferous growth. To determine whether there is a genotypic response to varying nitrogen levels, six hybrid and four native cultivars were treated with three annual rates of nitrogen fertilizer (17, 34, or 67 kg·ha-1) for 4 years. Fruit yield was determined each year and asexual vegetative growth (stolons) weight was removed and measured in all but the first year of the experiment. Cultivars exhibited different patterns of yield and stolon weight response over the three nitrogen rates. Not all cultivars exhibited significant yield decreases at the high N levels. Vegetative growth (stolon weight) generally increased with increasing N, however, not all cultivars responded similarly over three N rates. Partitioning between yield and stolon production favored fruit yield at the lower N rates in three of the four native cultivars studied (`Cropper', `Early Black', and `Howes'). Yield over N rates was more stable for four of the six hybrid cultivars, which may be the result of greater heterozygosity in hybrids than natives, and/or genetic gain from one breeding and selection cycle, offering increased tolerance to nitrogen stress. This study indicates that genetic variation exists for yield, yield stability, and stolon production relative to nitrogen level, and that genetic gain in cranberry is possible for these traits. Future studies involving cranberry physiology and nutrition should consider the genotypes used.

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E.A. Guertal

A brief review of slow-release fertilizer technology Slow-release nitrogen fertilizers can be separated into three broad categories. The first is “natural” organic fertilizer, with the N contained as a part of crop residue, animal waste, or other

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David R. Bryla, Bernadine C. Strik, M. Pilar Bañados, and Timothy L. Righetti

., Ore. State. Univ., Corvallis, OR Bañados, M.P. Strik, B.C. Bryla, D.R. Righetti, T.L. 2012 Response of highbush blueberry to nitrogen fertilizer during field establishment—I. Accumulation and allocation of fertilizer nitrogen and biomass HortScience 47

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Robyn Rufner, A. V. Barker, J. P. Boucher, W. Kroll, and Trina A. Hosmer

Abstract

Studies concerning the use of the nitrification inhibitor, 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin), have indicated that at least one site of action of nitrapyrin is associated with leaf chloroplasts. Leaves from radish (Raphanus sativus L. cv. Cherry Belle) grown with 10 ppm nitrapyrin in combination with 6 nitrogen fertilizers exhibited symptoms of nitrapyrin toxicity which ranged from reduced leaf size to marginal chlorosis and chlorotic mottling of leaves. The incorporation of nitrapyrin with nitrogen fertilizers, particularly organic sources of N, significantly reduced the number of chloroplasts per cell and significantly altered the structural integrity of radish chloroplasts relative to mesophyll cells and chloroplasts from plants grown at 0 ppm nitrapyrin.

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Brian A. Kahn and Judith L. Schroeder

Field experiments were conducted in Oklahoma in 1993 and 1994. Cowpeas [Vigna unguiculata (L.) Walp.] were grown using either non-inoculated seed and 23 kg·ha–1 of preplant nitrogen fertilizer (conventional) or inoculated seed and no preplant nitrogen fertilizer (reduced input). Sample plants were excavated at first pod set and analyzed for nodulation and root morphology. Additional plants were excavated at the green-shell stage and were analyzed for nitrogen concentration. Conventional and reduced input cowpeas did not differ in nodule distribution among root morphological components, total nodule fresh weight, total root dry weight, or nitrogen concentration. Most nodules generally were located on the basal and lateral roots. Results indicate that cowpea root characteristics are not necessarily altered by differing cultural systems at a given location.