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  • Author or Editor: J. Benton Storey x
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The influence of temperatures during nut filling on nut size, kernel percentage, kernel color, percent oil, and fatty acid composition were evaluated over 3 years in `Cheyenne', `Mohawk', and `Pawnee' pecans [Carya illinoenensis (Wangenh.) C. Koch]. Nuts were harvested at shuck split at 14 sites located in Texas, Oklahoma, Kansas, Nebraska, Arizona, and California and Coahuila, Mexico. Weather data for 12 weeks before shuck split at each site were used to determine degree days by the formula: degree days = summation n(m–t) where n = number of days, m = (max + min temperature) ÷2, and t = 10°C. The degree days ranged from 996 to 1675. The oleic: linoleic ratios in all three cultivars were positively correlated with degree days in 2 of 3 years. `Mohawk' nut size was positively correlated with degree days all 3 years and `Cheyenne' and `Pawnee' were larger 2 of 3 years in the warmer climates. `Pawnee' kernel percentage and oil content was higher in the warmer climates. Warmer developmental temperatures had no influence on `Cheyenne' kernel color. `Mohawk' kernels were not affected 2 of 3 years, but `Pawnee' developed darker colors 2 of 3 years.

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Stumps remaining after tree removal during orchard thinning will characteristically produce extensive shoot growth in response to the massive root systems that previously supported large trees. A 38-year-old pecan orchard was thinned from 15 × 15 m to 21 × 21 m. Stumps ranging from 45 to 65 cm in diameter were treated in seven replications with 0.19, 0.37, and 0.75 kg KNO3, respectively, per stump in drilled holes. Two controls consisted of stumps with drilled holes and intact stumps with no holes. Eight holes per stump were drilled with a 2.54-cm-diameter power auger to a depth of 15 cm. The number and weight of regrowing sprouts was measured annually. The 0.75 kg KNO3 rate significantly reduced the number and weight of sprouts regrowing the first year. The drilled stumps showed a significant decrease in new sprouts over the undrilled control. The low KNO3 rate stimulated regrowth. The key to regrowth suppression is to use a high rate of KNO3 in sufficient holes to allow penetration. KNO3 stump treatment should be a safe practice because no more than, perhaps, 2.25 kg of KNO3, depending on trunk diameter, will be used per site, which will then provide nutrients to existing trees as it dissipates.

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In 1990, a randomized design was set up in a 33 year old orchard on Westwood silty clay loam with 4 main treatment factors: 1990 nut size, chiseling, aeration, and cultivar. Location for this experiment was the Adriance Orchard on the Texas A&M Plantation – Brazos River flood plain. Nut quality was determined by the % kernel and # nuts / kg. Yield was measured per tree and calculated for g/cm2 cross-sectional trunk area. The soil bulk density for each treatment was 1.53 g/cm3 and found to be statistically uniform at the start of the experiment. Results after one year showed that aeration increased the nut size and % kernel of `Mahan' but not of `Desirable' and `Stuart'. Chiseling increased the yield of `Stuart' and `Desirable' and nut size of all 3 cultivars but not % kernel. Aeration increased the % kernel from a mean 48.6% to 56.8% and nut size from 129 nuts/kg to 102 nuts/kg of the 1990 small-nut-size trees but did not significantly increase nut quality for the 1990 normal-nut-size trees.

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Four cultivars of pecan [Carya illinoinensis (Wangenh.) K. Koch] were selected for the study (`Cheyenne', `Mohawk', `Pawnee', and `Osage'). The influence of total climatic heat units, during nut filling, on nut quality was compared from 14 geographic locations over a 3-year study. Nut quality parameters included nut size by weight, kernel percentage by weight, kernel color by Hunter Color Difference Meter, fatty acid profile by GC, and total oil by NMR. Nuts were harvested at shuck split, dried to 3% moisture, and stored at –20C prior to analysis. Monounsaturated fatty acids (MUFA) and total oil increased, and polyunsaturated fatty acids (PUFA) decreased in `Mohawk' 2 out of 3 years with increased heat units. Fatty acids in `Pawnee' responded the same as in `Mohawk' in 1992, but were variable in 1991. In 1993, `Pawnee' kernel whiteness and total oil decreased with increased heat units. Higher heat units caused the testas of `Cheyenne' to be darker in all 3 years. MUFA of `Cheyenne' increased with increased heat units 1 out of 3 years. The PUFA content of `Cheyenne' decreased with increased heat units in 1993. `Osage' showed a reversal of MUFA and PUFA with increased heat units. High negative correlation between oleic and linoleic acid were obtained for all cultivars.

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Since DRIS calculations prove to be tedious for most researchers, a computer pro am was written to use test data from foliar analyses to compile DRIS norms for a population and using these norms, calculate the indices for each of 14 elements.

The data to be tested is first put into a record base format and stored as an ASCII file. When DRISCALC is run on IBM compatible microcomputers, this data is separated into two subpopulations based on the mean yield for the main population. The next procedure calculates the mean, the standard deviation (from the mean), and the variance for each subpopulation as well as the variance ratio (low yield/high yield) and the CV.

The F test for variance and the student's t test selects the norms (high population mean and CV'S). After construction of this temporary database, and unknown sample is entered into the program for testing. DRIS indices are calculated and several statistical options can be selected b the user. Hidden deficiencies can be found by the researcher or DRIS principles can be taught to students.

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Abstract

Nutrient spray residue can be removed from leaflets of pecan (Carya illinoensis (Wang.) K. Koch for nutrient absorption measurement. The residue can be removed by washing the leaflets in 0.1% Alconox, rinsed in running tap water followed by a 7 liter 1% HCl rinse and three separate 7 liter demineralized distilled water baths. The elimination of some of the solutions resulted in erroneously high results in adsorption of the nutrients. Young leaflets absorbed more zinc than did the old leaflets. Nutrient sprayed pecan leaflets washed in 0.1% Alconox, rinsed in running tap water, 7 liters 1% HCl, and three separate 7 liter demineralized distilled water baths prior to tissue analysis gave more consistent and reliable data than leaflets washed by any other method. This leaf washing procedure does not remove biologically significant amounts of any of the elements analyzed.

Open Access

Abstract

Tank mixing Uran (0.5% by weight) with ZnSO4 increased leaflet Zn concentration compared to ZnSO4 alone in pecan [Carya illinoensis (Wang) K. Koch]. Zinc nitrate was more efficient than ZnSO4 in increasing leaflet Zn concentration especially if tank mixed with Uran (0.5%). Zn concentration of spray solutions can be reduced by 1/8 to ¼ of the current recommended rate of Zn at 86 g/100 liters of water as ZnSO4. Use of the lowest rate of Zn(NO3)2, 10.8 g/100 liters of water + Uran, increased yield and income over the recommended rate of ZnSO4.

Open Access

Fall soil treatments of ZnEDTA and ZnSO4 at three increasing rates (32.2, 64.4 and 128.8 g. Zn/tree) and 1, 2 and 3 spring foliar sprays of NZN (0.35 g. Zn/tree/application) were tested to correct Zn deficiency in three year old `Earligrande' peach trees. All Zn carriers increased the Zn leaf content. Peach trees treated with three applications of NZN were equal to the medium or high rates of soil applied ZnEDTA or ZnSO4 respectively, in appearance, chlorophyll content and foliar Zn content. Three applications of NZN at 0.35 g. of Zn/tree (473 ml/378 gal H2O) gave excellent tree response and was cost effective.

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Preharvest germination (viviparity) can be a problem with nuts of pecan [Carya illinoinensis (Wangenh.) K. Koch]. Two southern-adapted cultivars (`Cherokee' and `Wichita') and one northern-adapted cultivar (`Johnson') were paternal parents in controlled crosses with the maternal parent `Wichita'. `Wichita' × `Johnson' seed took much longer to germinate than seed from either the `Wichita' × `Cherokee' cross or the `Wichita' self, therefore indicating that pollen source may influence germination characteristics.

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Analyses of stem cross sections of 97 pecan [Carya illinoinensis (Wangenh.) K. Koch] and 22 post oak (Quercus stellata Wangenh.) trees from seven sites showed tree rings were sensitive to the environment and were datable by tree, among trees within a site, among sites, and between species. Pecan had well-defined annual growth rings averaging from 1.25 to 3.36 mm in width and that varied synchronously among trees. Pecan had a mean sensitivity of about 0.3 compared to 0.4 for post oak, indicating a smaller but adequate response of pecan to reflect climatic variations and to use pecan tree rings in other dendrological studies.

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