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E.H. Simonne, J.N. McCrimmon, H.L. Scoggins-Mantero, and H.A. Mills

With recent advances in N analyzers, the Dumas method becomes more attractive as a replacement for Kjeldahl N. Kjeldahl N (K_N):Dumas N (D_N) ratios were determined for anthurium (A), orchid (O), fern (F) and turf (T). Dry tissues were ground to pass a 20-mesh seive. D_N was determined using 0.2 g of sample and a Leco FP-428. K_N was determined by digesting 0.4 g tissue with a CuO/TiO/K2SO4 catalyst and 10 mL H2SO4 at 450°C for 2 hr. Ammonium in the digest was assayed by colorimetry (Lachat analyzer). Overall (n=397 obs.), D_N was a good estimator of K_N: K_N = 0.90(p<0.01) D_N + 0.09(p=0.03), R2=0.93, over the 0.4-6.6 N range. K_N:D_N ratio was significantly (p<0.01) affected by plant type. Ratios of 0.85 for A, 0.92 for T, 0.99 for O, and 1.00 for F may be used to estimate K-N from D-N for the diagnosis of N nutrition, along with existing interpretative data.

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Shahrokh Khanizadeh, Deborah Buszard, and Constantinos G. Zarkadas

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Laura Elisa Acuña-Maldonado, Michael W. Smith, Niels O. Maness, Becky S. Cheary, Becky L. Carroll, and Gordon V. Johnson

Nitrogen was applied to mature pecan (Carya illinoinensis Wangenh. C. Koch.) trees annually as a single application at 125 kg·ha-1 N in March or as a split application with 60% (75 kg·ha-1 N) applied in March and the remaining 40% (50 kg·ha-1 N) applied during the first week of October. Nitrogen treatment did not affect yield, and had little effect on the amount of N absorbed. Nitrogen absorption was greater between budbreak and the end of shoot expansion than at other times of the year. Substantial amounts of N were also absorbed between leaf fall and budbreak. Little N was absorbed between the end of shoot expansion and leaf fall, or tree N losses met or exceeded N absorption. Pistillate flowers and fruit accounted for a small portion of the tree's N; ≈0.6% at anthesis and 4% at harvest. The leaves contained ≈25% of the tree's N in May and ≈17% when killed by freezing temperatures in November. Leaves appeared to contribute little to the tree's stored N reserves. Roots ≥1 cm diameter were the largest site of N storage during the winter. Stored N reserves in the perennial parts of the tree averaged 13% of the tree's total N over a three year period. Current year's N absorption was inversely related to the amount of stored N, but was not related to the current or previous year's crop load.

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Emily G. Tenczar and Vera A. Krischik

661 nm were measured and used to determine the amounts of chlorophylls A and B and anthocyanins ( Sims and Gamon, 2002 ). Total nitrogen and Kjeldahl (usable) nitrogen were measured from five plants for each treatment. Leaves were dried in an oven at

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Ronnie W. Schnell, Donald M. Vietor, Richard H. White, Tony L. Provin, and Clyde L. Munster

Oct. 2005. Fresh CMB [n = 4; 51% dry matter, 21.4 g·kg −1 total Kjeldahl nitrogen (TKN), 11.5 g·kg −1 total P (TP), and 6.5 g·kg −1 total K] was spread with buckets and raked into a 5-cm soil depth (0.25 m 3 CMB/m 3 of soil; 89.6 Mg·ha −1 ) before

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Amy L. Shober, Kimberly A. Moore, Nancy G. West, Christine Wiese, Gitta Hasing, Geoffrey Denny, and Gary W. Knox

Res. Dev., U.S. Environ. Protection Agency, Cincinnati, OH U.S. Environmental Protection Agency (USEPA) 1993c Method 351.2. Determination of total Kjeldahl nitrogen by semi-automated colorimetry. Environ. Monitoring Systems Lab., Office Res. Dev., U

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David G. Himelrick and W. A. Dozier Jr

`Chandler' strawberry plants were grown in a nutrient flow hydroponic systems with six solution N treatments (35, 70, 140, 210, 280, 350 ppm). Total N was determined in leaf blade and petiole samples using Kjeldahl procedure and by LECO CHN analyzer. Nitrate-N was extracted with KCl and analyzed using a LACHAT ion analyzer. Correlations for total N in leaf blades with hydroponic N levels were r7 = 0.79 for Kjeldahl, r2 = 0.25 for LECO, and r2 = 0.60 for LACHAT while petiole samples were r* = 0.57 for Kjeldahl, r2 = 0.55 for LECO and r2 = 0.41 for LACHAT. Vegetative characteristics of the plants were affected with the 210 ppm treatment producing both the most crowns and runners and 350 ppm the least.

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Gitta Shurberg, Amy L. Shober, Christine Wiese, Geoffrey Denny, Gary W. Knox, Kimberly A. Moore, and Mihai C. Giurcanu

(fertilizer N + soil inorganic N) when planted in St. Augustine fine sand subsoil fill in U.S. Department of Agriculture hardiness zone 9a. Table 3. Regression derived optimum and annual nitrogen (N) rates for shoot biomass and tissue total Kjeldahl N

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Luther C. Carson and Monica Ozores-Hampton

organic-N and NH 4 –N may be measured using TKN. Total Kjeldahl N costs more to conduct than the prill weight loss or the ion-specific electrode method. Total Kjedahl N does not measure NO 3 –N, but modified methods are available to measure NO 3 –N along

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Laura E. Acuña-Maldonado and Michael W. Smith

A study was conducted to compare a single nitrogen application in March (125 kg N/ha) vs. a split application in March (75 kg N/ha) and October (50 kg N/ha) on 15-year-old `Maramec'. After one season, N application time did not affect return bloom. A split N application increased trunk wood Kjeldahl-N but decreased Kjeldahl-N in the current season's reproductive shoots and 1-year-old branches compared to a single application in March. Kjeldahl-N concentration was not affected by treatment in current season's vegetative shoots, trunk bark or roots. Nitrate-N concentration was not affected by treatment in any tissue sampled. Between the first week of October and the first killing frost in November, Kjeldahl-N increased 29% in current season's shoots, 21% in trunk bark, 32% in roots >1 cm in diameter, and 15% in roots <1 cm in diameter but decreased 42% in trunk wood and 5% in 1-year-old branches. Roots <1 cm in diameter accumulated more nitrate-N than other tissues during November.