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Ricardo Fernández-Escobar, Miguel A. Sánchez-Zamora, Jorge M. García-Novelo, and Concepción Molina-Soria

nutrient to be applied. Predicting such amount is not simple. The performance of leaf analysis annually may reflect the response to fertilizer application ( Fernández-Escobar et al., 2009b ) and provide a good approach to determine the amount of nutrient to

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William Reid

The nuts of 10 pecan cultivars were used to produce rootstock trees for the propagation of two scion cultivars—Posey and Pawnee. Seed sources included: `Chickasaw', `Colby', `Dooley', `Giles', `Greenriver', `Major', `Mohawk', `Peruque', `Posey', and `Shoshoni'. Leaf analysis performed in 1994 and 1996 revealed that rootstock influenced K and Zn concentrations. Scions propagated on `Posey' seedlings contained the greatest amount of K, while scions propagated on `Greenriver' seedlings contained the least. Zn levels were highest in trees with `Chickasaw' seedling rootstocks and the least in `Major' seedlings. Yield and nut quality was influenced by a major drought during the late summer and fall of 1995. Nuts produced by trees with `Chickasaw' and `Colby' rootstocks had the highest kernel percentage, while trees grown on `Major' and `Posey' had the lowest. The greatest yields, during the drought year, were produced from scion cultivars grafted on `Giles' and `Chickasaw' seedling rootstocks. `Major' and `Greenriver' seedlings produced trees with the smallest yields.

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Ray E. Worley and Benjamin G. Mullinix

Yield and quality of pecan nuts were as high when 50 pounds N/acre was applied through a dripirrigation system as with 100 pounds/acre (112 kg·ha−1) applied either all broadcast or half broadcast-half fertigated. All N treatments kept leaf N well above the 2.50% (dry weight) lower threshold recommended for pecans. The 50 pounds N/acre-all-fertigated treatment resulted in less soil pH reduction and less loss of K, Ca, and Mg from soil in the nonwetted zone underneath the tree canopy than broadcast treatments. Soil pH, K, and Mg were slightly lowered in the 6- to 12-inch (15 to 30 cm) soil layer when all of the N was fertigated. Higher leaf Ca and Mg from the low rate of N fertigated reflected the higher concentrations of these elements in the soil in the nonwetted zone rather than the lower concentrations in the wetted zone. There was no evidence of a detrimental effect on the tree from lowering the N application to only 50 pounds/acre and applying it in four monthly applications through the drip irrigation system beginning 1 Apr.

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Shirin Shahkoomahally, Jose X. Chaparro, Thomas G. Beckman, and Ali Sarkhosh

concentrations, and to interpret the leaf analysis, orchard nutritional status, and the amount of soil nutrient removal ( Nachtigall and Dechen, 2006 ) as it relates to the physiological status of the tree. The results are essential for the accurate application

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M. Lenny Wells

is of value to recognize the status of pecan tree and orchard soil nutrition typical of a region. Leaf analysis is widely regarded as a reliable index for many of the nutrient elements of pecan trees. Critical ranges for leaf nutrients have been

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M. Leonard Wells and Bruce W. Wood

growth, and leaf analysis of pecan J. Amer. Soc. Hort. Sci. 99 49 57 Worley, R.E. 1990 Pecan leaf scorch in response to various combinations of nitrogen and potassium fertilization HortScience 25 422 423 Worley, R.E. 1994 Long-term performance of pecan

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Ray E. Worley

A threshold of 2.75% N was most practical for the low end of the sufficiency range when lower thresholds of 2.25%, 2.50%, 2.75%, and 3.00% were tested on old `Stuart' pecan [Carya illinoensis (Wangenh.) C. Koch] trees. Application of 224 kg N/ha annually reduced nut size when compared with application of 112 kg/ha made only when leaf N dropped below 2.25%, 2.50%, 2.75%, or 3.00%. Yield and tree growth were similar when 112 kg·ha-1 was applied only when leaf N dropped below 2.75% and when 224 kg·ha-1 was applied annually. No N application was necessary to meet the 2.75% threshold for 3 of the 16 years.

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Michael W. Smith, Becky S. Cheary, and B. Scott Landgraf

A low leaf Mn concentration was detected in bearing pecan (Carya illinoinensis Wangenh. C. Koch) trees growing in an alluvial soil with an alkaline pH. Trees lacked vigor and leaves were pale in color, but there was no discernible leaf chlorosis or necrosis. Three foliar applications of MnSO4 beginning at budbreak, then twice more at 3-week intervals at rates of 0 to 3.3 kg·ha-1 of Mn increased leaf Mn concentration curvilinearly, and alleviated leaf symptoms. Results indicated that three foliar applications of MnSO4 at 2.15 kg·ha-1 of Mn plus a surfactant were adequate to correct the deficiency.

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Yin-Tung Wang and Elise A. Konow

Research was conducted to investigate the interaction of water-soluble fertilizer and medium composition on vegetative growth and the concentration of mineral nutrients in media and in leaves of a hybrid moth orchid (Phalaenopsis Blume.). The vegetatively propagated `TSC 22' clone of the hybrid Phalaenopsis Atien Kaala plants 15 cm in leaf spread were potted in a medium consisting of either 100% fine grade douglas fir [Pseudotsuga menziesii (Mirb.) Franco] bark or a mixture of 7 fir bark: 3 sphagnum peat (by volume). Plants were fertigated at each irrigation with a soluble 10N-13.1P-16.6K, 20N-2.2P-15.8K, or 20N-8.6P-16.6K fertilizer, or a 2N-0.4P-1.7K liquid fertilizer at a common N rate of 200 mg·L-1. After 1 year in a greenhouse, plants grown in the bark-peat medium produced more leaves, greater fresh weights (FW), and larger total leaf areas than those in 100% bark. In the bark medium, the 20N-2.2P-15.8K fertilizer resulted in plants of the highest quality, despite its low P concentration (22 mg·L-1). When grown in bark-peat, the two fertilizers (20N-2.2P-15.8K and 20N-8.6P-16.6K) containing urea as part of their N source (10% and 52%, respectively) resulted in plants with 40% to 50% heavier shoot FW and 40% larger leaf area than the other fertilizers without urea. With any given fertilizer, plants had similar root FW in both media. Media and fertilizers had limited or no effect on the concentrations of mineral nutrients in the second mature acropetal leaves, except P, which nearly doubled in leaves of plants grown in 100% bark. High leaf Mg concentration was associated with low Ca. Water extracts from the bark-peat medium had lower pH, higher electrical conductivity, and much higher levels of NH4-N, Ca, Fe, Na, Cl, B, and Al than those from 100% bark. Extracts from the bark medium did not have detectable levels of NO3-N, whereas extracts from the bark-peat medium all had similar levels of NH4-N, regardless of which fertilizer was applied. Levels of P and K were not different between the two media.