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Bernadine C. Strik and Amanda J. Vance

cultivar on nutrient allocation to fruit, as it is hypothesized that high yield and or fruiting season may affect leaf nutrient concentration. Materials and Methods Study sites. The study was conducted at two mature northern highbush blueberry sites

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Michael V. Mickelbart

Table 1 . Table 1. Range of soil characteristics (top 15 cm) under the canopy of trees from which samples were obtained for determination of leaf nutrient concentrations in leaves of different ages and positions in the canopy (n = 7). z

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Patrick H. Brown

Concentrations of N, P, K, Ca, Mg, B, Fe, Cu, Zn, and Mn in mature commercial fig (`Calimyrna'; `Sari Lop') leaves are presented throughout the growing season. These data can be used as preliminary norms for the interpretation of tree nutrient status for high-yielding commercial fig orchards. In comparison with other deciduous tree crops growing in the same regions {almond [Prunus amygdalus Batsch syn. P. dulcis (Mill) D.A. Webb], walnut (Juglans regia L.), peach [Prunus persica (L.) Batsch]}, productive fig trees have relatively low leaf N, P, and K concentrations (2.1%, 0.1%, and 1.0% dry weight, respectively) in July, although tissue Mn and Ca concentrations often exceed those typically found in other deciduous species growing in the same soils. Seasonal variations in fig leaf nutrient concentrations are similar to those of other tree crops. Marked declines in tissue K and N concentrations toward the end of the season may indicate a need for supplemental N and K fertilization in highly productive orchards. The potential for K deficiency in fig also is indicated by the generally lower leaf K concentrations in the low-vigor orchards examined.

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Mehdi Sharifi, Julia Reekie, Andrew Hammermeister, Mohammed Zahidul Alam, and Taylor MacKey

crops, or mixtures, using a modified SSS on apple yields, tree growth, and leaf nutrient concentrations in an organic apple orchard in Nova Scotia, Canada. Materials and Methods The study was conducted at Boates Farms Limited, a 10 ha certified organic

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Ricardo Goenaga, Heber Irizarry, David Jenkins, Debbie Boykin, and Angel Marrero

other rootstock seedlings. Fig. 1. Average leaf nutrient concentration of major elements [nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg)] in ‘Prolific’ sapodilla grafted onto seedlings of 16 sapodilla rootstocks sampled (A

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Haytham Z. Zaiter, Dermot P. Coyne, Ralph B. Clark, and James R. Steadman

Nine bean cultivars/lines (Phaseolus vulgaris L.) were grown in three soils/rooting media at pH values of 7.9, 6.5, and 5.8 in greenhouse, growth chamber, and field experiments to evaluate the leaf reaction of the plants to a Nebraska bean rust [Uromyces appendiculatus (Pers.) Unger var. appendiculatus] isolate US85-NP-10-1. Significant differences were observed for rust pustule diameter between cultivars/lines grown in the three growth media. Plants grown in the medium at pH 5.8 showed significantly larger rust pustule diameters than those of plants grown at pH 6.5 or 7.9. A significant interaction occurred between growth medium and cultivars/lines for the rust reaction. Concentrations of Cl and Mn in leaves were positively correlated with rust pustule diameter. In contrast, concentration of K in leaves was negatively correlated with rust pustule diameter. Plant breeders attempting to improve beans for rust resistance must consider the growth medium pH in evaluating intensity and severity of rust symptoms on leaves.

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James M. Dangler and C. Wesley Wood

Collards (Brassica oleracea L. Acephala Group) were grown in spring and fall to evaluate the effects of N fertilizer rate (0, 56, 112, 168, and 224 kg·ha -1), cultivar (Blue Max and Vates), and within-row spacing (15, 23, and 30 cm) on yield and leaf mineral nutrient concentrations. Season, cultivar, and N rate interacted in their effects on yield. In spring, `Blue Max' yield increased linearly with N rate to 10.4 t·ha-1, whereas the highest `Vates' yield (7.0 t·ha-1) was obtained with 112 kg N/ha, and yield remained similar with additional N. In fall, `Blue Max' and `Vates' yields were highest (14.5 and 9.9 t·ha -1, respectively) with 112 kg N/ha. Leaf N and P concentrations increased quadratically and linearly, respectively, in response to N rate. Maximum yields were obtained with the 15-cm within-row spacing. Leaf N concentration increased linearly with increased plant population. The adequacy of the present sufficiency range for leaf Ca concentrations of field-grown collards is discussed.

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John M. Smagula and David Yarborough

Experimental plots in a commercial lowbush blueberry (Vaccinium angustifolium Ait.) field deficient in N and P received preemergent 33.6 and 67.2 kg/ha rates of N (urea), P (23 % phosphoric acid), N+P (DAP), N+P+K (S-10-5) or N+P+K (fish hydrolysate, 2-4-2). A RCB design with eight replications of 12 treatments was used. Fertilizer containing N alone was as effective in raising N leaf concentrations, as those containing N and P. However, leaf phosphorus concentrations were raised more by fertilizer providing N and P than only P. Fish hydrolysate fertilizer was as effective as 5-10-5 in raising leaf N, P and K concentrations in prune and crop year leaf samples.

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Lenny Wells

The prolonged period from tree planting to first commercial harvest of pecan [Carya illinoinensis (Wangenh.) K. Koch] provides incentive for many growers to intensively manage young trees to induce commercial production as soon as possible. This management includes high nitrogen (N) application rates with or without fertigation. However, there remains little data regarding the effect of N fertilization or fertigation on young pecan trees grown under southeastern U.S. orchard conditions. The objectives of this study were to compare the effects of fertigation with more commonly recommended forms of fertilization on growth and leaf N, phosphorous (P), potassium (K), and zinc (Zn) concentrations of first- through third-leaf pecan trees irrigated with microsprinklers. An optimal growth rate of young pecan trees was obtained as easily with a balanced granular fertilizer application using significantly less N compared with fertigation applications. The minimal treatment differences observed along with the fact that leaf N concentration never fell below the minimum recommended level in any treatment throughout the study supports the supposition that first-year pecan trees require no N fertilizer during the year of establishment. Only modest N application rates are required during the second and third growing seasons. This practice helps to promote optimal tree growth while minimizing excessive losses of N to the environment.

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Timothy K. Hartz, P. R. Johnstone, E. Williams, and R.F. Smith

analysis. Minimal differences in leaf nutrient concentrations between lettuce types were found ( Fig. 1 ). Therefore, DRIS analysis was performed on the combined iceberg and romaine data. Leaf nutrient concentrations varied between growth stages