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Michael W. Smith

2 are protogynous. Potassium and P are phloem-mobile macronutrients ( Marschner et al., 1996 ) that are readily translocated from leaves to developing pecan fruit ( Sparks, 1977 , 1988 ). Potassium functions in osmoregulation, carbohydrate

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Simone da Costa Mello, Francis J. Pierce, Rachel Tonhati, Guilherme Silva Almeida, Durval Dourado Neto, and Kiran Pavuluri

Polyhalite is a naturally occurring potassium, calcium, magnesium sulfate mineral with a chemical formula K 2 Ca 2 Mg(SO 4 ) 4 ·2(H 2 O) corresponding to 13.0% K, 13.3% Ca, 4.0% Mg, and 21.3% S. Many horticultural crops including potatoes ( Solanum

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Valdinar Ferreira Melo, Edvan Alves Chagas, Raphael Henrique da Silva Siqueira, Olisson Mesquita de Souza, Luís Felipe Paes de Almeida, Diogo Francisco Rossoni, Pollyana Cardoso Chagas, and Carlos Abanto-Rodríguez

–12,000 mm 3 , distributed up to 0.5 m deep, in response to different increasing doses of K ( Fig. 5 ). Fig. 5. Camu-camu root volume (measured in cubic millimeters) under potassium fertigation doses of 0 ( A ), 40 ( B ), 80 ( C ), 160 ( D ), and 320 ( E ) kg

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Bruce W. Wood, Lenny Wells, and Frank Funderburke

Pecan orchard profitability is potentially influenced by tree potassium (K) nutritional status with deficiency being common in commercial orchard operations, especially in years with heavy crop loads. The earliest visible symptom of K deficiency

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Ran Erel, Arnon Dag, Alon Ben-Gal, Amnon Schwartz, and Uri Yermiyahu

current study concentrated on the importance of the macronutrients nitrogen, phosphorus, and potassium and their specific roles in flowering and fruit set of olive. Olive leaves and stems represent storage organs for N and release it in response to the

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Chenping Xu and Beiquan Mou

plant growth (Crafts-Brandner et al., 1998; Lemaître et al., 2008 ; Wingler et al., 2006 ). Phosphorus is a macronutrient of crucial importance in signaling, photosynthesis, and other metabolism ( Marschner, 1995 ). Potassium is an essential nutrient

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Timothy K. Broschat

soil phosphorus (P), potassium (K), and magnesium (Mg) concentrations in plots mulched with organic mulches or none, but we are unaware of any studies documenting the effects of above versus below mulch applications of fertilizers on soil nutrient

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Carl Rosen, Wenshan Wang, and David Birong

A 2-year field study was conducted on a low- to medium-K testing sandy soil 1) to evaluate the effects of various K management strategies on potato (cv. Russet Burbank) yield and quality and 2) to calibrate a petiole sap test for determining plant K status. Treatments included banded applications of potassium chloride fertilizer at planting with K ranging from 0 to 300 kg·ha–1 in 75 kg·ha–1 increments. Comparisons of preplant broadcast + banded applications and evaluation of in-season applications of potassium nitrate also were made. In both years, tuber yield increased with increasing banded K fertilizer up to 150 kg ha-1 K the first year and 225 kg ha-1 K the second year. In-season applications of potassium nitrate increased tissue K levels, but at equivalent K application rates, timing of K application had no effect on yield. Petiole K concentrations, measured on a dry weight and sap basis, increased with increasing K fertilizer application. Potassium concentrations in nondiluted sap determined with the Cardy K electrode were ≈200 to 2500 ppm lower than those determined by flame emission. The greatest discrepancy occurred at the higher K sap concentrations. Potassium concentrations determined with the Cardy electrode in sap diluted with aluminum sulfate or deionized water were much closer to those determined by flame emission. These results suggest that dilution of the sap is necessary to obtain accurate K concentrations in petiole sap.

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Ada Baldi, Anna Lenzi, Marco Nannicini, Andrea Pardini, and Romano Tesi

root and stolon development ( Pettit and Fagan, 1974 ). Potassium is second only to N in the amounts required to sustain turfgrass quality and growth. Various studies have focused on the importance of adequate K fertilization to maintain turfgrass

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Timothy K. Broschat

Ixoras (Ixora L.) growing in calcareous sandy soils are highly susceptible to a reddish leaf spot disorder. Symptoms appear on the oldest leaves of a shoot and consist of irregular diffuse brownish-red blotches on slightly chlorotic leaves. Symptoms of K deficiency, P deficiency, and both K and P deficiency were induced in container-grown Ixora `Nora Grant' by withholding the appropriate element from the fertilization regime. Potassium-deficient ixoras showed sharply delimited necrotic spotting on the oldest leaves, were stunted in overall size, and retained fewer leaves per shoot than control plants. Phosphorus-deficient plants showed no spotting, but had uniformly brownish-red older leaves and olive-green younger foliage. Plants deficient in both elements displayed symptoms similar to those observed on landscape plants. Symptomatic experimental and landscape ixoras all had low foliar concentrations of both K and P.