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Craig E. Kallsen, Dan E. Parfitt, and Brent Holtz

method developed by Hoblyn et al. (1926) and reviewed by Pearce and Dobersek-Urbanc (1967) as follows: where, I = the alternate bearing index, n = number of years for which the alternate bearing index is calculated, and a i = yield in the

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Michael W. Smith

annually at 1.4-m height while trees were dormant. An alternate-bearing index was calculated for each tree using the equation: where I was the alternate-bearing index; n was the number of years; and a 1 , a 2 , and a n were yields of corresponding years

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M. Lenny Wells

kernel, pecan tree yield efficiency, and alternate bearing. Materials and Methods Study site, experimental design, and soil sampling. Studies were conducted at the University of Georgia Ponder Research Farm located near Tifton, GA, at lat. 31°51′N and

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Ashley K. Brantley, James D. Spiers, Andrew B. Thompson, James A. Pitts, J. Raymond Kessler Jr., Amy N. Wright, and Elina D. Coneva

temperature. The mean temperature inside the bags was 23.5 °C with 16 cumulative h >30 °C 1 to 6 DAA in year 1 compared with 17.3 °C with 0 h >30 °C in year 2. It is also plausible that the discrepancy between the 2 years was due to alternate bearing

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Zlatko Cmelik* and Stanislav Tojnko

The trial was conducted in a `Elstar'/M9 orchard (2500 trees/ha) and the experiment was designed as a split-block comprising five treatments (fertigation with 45 kg·ha-1 N, 60 kg·ha-1 N, 120 kg·ha-1 N, irrigation without fertilizers, and control—without irrigation and without fertilizers), and two timing variants (treatments during vegetation period from 1 May to 20 June—variant A, and treatments from 1 May to 1 Aug.—variant B). The treatments were imposed beginning in the second year after planting and lasted five years. Fertigation with different amounts of nitrogen had no consistent effect on tree growth, cumulative yield and yield efficiency, however, treatments had a significant influence on regularity of bearing. The index of alternate bearing varied with treatment, but in both variant was significantly higher in control and in treatment with irrigation without application of fertilizer. These results demonstrated that the natural tendency of `Elstar' to alternate bearing could be broken by the different rates of nitrogen applied by fertigation.

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Martin J. Bukovac, Paolo Sabbatini, and Philip G. Schwallier

The effect of ethephon on flowering and cropping of strongly alternate bearing spur-type `Delicious' apple (Malus domestica Borkh.) was evaluated in a 6-year study. Ethephon (200 mg·L–1), applied at 3, 3 + 6, and 3 + 6 + 9 weeks after full bloom in “on years,” increased flowering in “off years” by 33% and reduced flowering in “on years” by 17% compared with the control. The mean yield per tree for ethephon-treated trees over three “on years” and three “off years” was almost identical to that of the controls (82 vs. 80 kg/tree). However, the distribution of yield between “on” and “off” years was changed, 24% greater in “off years” and 10% less in “on years.” Ethephon reduced both the variation in yield, particularly in “off years,” and the magnitude of alternation. Ethephon had a direct effect on flower initiation because 1) it did not reduce shoot growth or yield in the “on years” (years of ethephon application) and 2) ethephon-treated trees initiated more flowers per kilogram of fruit produced than did the controls. The additional flowers initiated were functional because the amount of fruit produced per unit bloom density did not differ between control and ethephon-treated trees. Harvest maturity indices, namely internal ethylene concentration, firmness, starch index, soluble solids, and color, were not significantly affected, although internal ethylene concentration and starch index tended to be higher in fruit from treated trees.

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Neusa M.C. Stenzel, Carmen S.V.J. Neves, José C. Gomes, and Cristiane C. Medina

This study reports the performance (yield, tree size, and fruit quality) of 'Ponkan' mandarin (Citrus reticulata Blanco) on seven rootstocks, evaluated for 11 years under Southern Brazil conditions. Trees on C13 citrange had higher cumulative yield for seven harvests than those on trifoliate orange. Cleopatra mandarin, rough lemon, Rangpur lime, Sunki mandarin, and Volkamer lemon rootstocks maintained their values at an intermediate position and did not present any significant difference regarding C13 citrange, and trifoliate orange. Trees on C13 citrange and on trifoliate orange exhibited the lowest alternate bearing index. Cleopatra mandarin induced the greatest canopy volume, but it was not significantly different from Sunki mandarin and rough lemon. The smallest trees were those on Volkamer lemon and trifoliate orange. The highest yield efficiency came from trees on C13 citrange and the smallest on Cleopatra mandarin. Rootstocks did not significantly affect fruit weight.

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Charles T. Rohla, Michael W. Smith, Niels O. Maness, and William Reid

cluster, and number of current season's shoots with female flower clusters were determined. Total yield per tree was measured annually and the alternate-bearing index ( I ) was calculated ( Pearce and Dobersek-Urbanc, 1967 ) for each cultivar. Values of

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Leonardo Lombardini

Twenty-five-year-old `Cape Fear', `Desirable', and `Kiowa' pecan [Carya illinoinensis (Wangenh.) C. Koch] trees were either not pruned, or subjected to single selective or mechanical pruning using a mechanical hedger [or hedge pruning (HP)] in the dormant season 2003. Canopy light interception, yield, and nut quality were monitored during a period of three years. Leaf area index and light interception were significantly affected during the first growing season after treatment application, but after three years canopies grew back to control levels. In general, there were small positive effects observed on yield and nut quality after pruning. Minor improvements were recorded for `Desirable', in which yield was affected positively by both pruning strategies in 2004. However, most effects disappeared by the third year. `Desirable' responded better than `Cape Fear', whereas no beneficial effects were recorded on `Kiowa'. In 2005, yield was significantly reduced in HP trees of `Cape Fear' and `Kiowa'. Alternate bearing index was unaffected by pruning treatment or cultivar. Kernel percentage increased only in HP `Desirable' trees in 2003 and 2004. Kernel quality was improved in HP `Cape Fear' and `Desirable' in the first growing season after treatment application, but not in 2004. In 2005, quality was again improved in HP `Desirable'. The results of the current study indicate that one-time pruning of pecan trees induce positive short-term effect on light, but not necessarily an increase in productivity and nut quality.

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Darrell Sparks

A multiple regression model was developed from historical data, 1945-92, to predict pecan [Carya illinoensis (Wangenh.) C. Koch] production in a humid climate. Variables were production trend (year of production), previous year's production, and climatic indices for the previous and current year. Production trend was used to measure change in production with time. Previous year's production was the index of alternate bearing. Variables for previous year's climate were heating degree-days for April-October and cumulative rainfall during May-July and 1-15 Sept. Variables for current year's climate were cumulative rainfall during April-August and 1-15 Sept. The indicator used for scab [Cladosporium caryigenum (Ell. & Langl.) Gottwald] infection was the highest cumulative sum of 2 or more days of consecutive rain occurring in May, June, or 1-15 July. The R 2 for the model was 0.908. Production trend was the most important factor influencing production during the 1945-92 study period. Importance of the other variables in decreasing order were previous year's rainfall in May-July, consecutive rainy days, previous year's production, current year's 1-15 Sept. rainfall, previous year's heating degree-days, previous year's rainfall for 1-15 Sept., and current year's rainfall during April-August. Previous year's conditions had a greater effect on production than current year's. The recent decline in pecan production in the southeastern United States is due to an unfavorable change in climate.