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Laurence A. Sistrunk

UIsing phosphorus in horticultural crops has been researched for a long time, almost since it was discovered in 1669 by Hennig Brand in Germany. Recent advances in phosphorus application, involving using precision placement of coated fertilizers and by inoculating crops with mycorrhizae, have provided-more efficient uptake and increase in plant yields. By reviewing the key discoveries and current work going on, we can better design our future projects as nutrition scientists. While this approach will not encompass all horticultural crops, results with vegetables and ornamentals should provide concepts for work with other commodities.

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Laurence A. Sistrunk

The use of the Internet and specifically the World Wide Web has grown rapidly in the last 2 years. There are now >60 million web pages on the Internet, each containing information on various subjects and many having very useful information. The text is viewed with a web browser, using a hypertext markup language, enabling formatting similar to word processing. Graphics, sounds, and video are accessed from hot links in the text. While commercial users are struggling with marketing strategies, the web will continue to evolve. We as educators will continue to dominate the rapid growth due to increased needs to reach more students with fewer resources. By adding course materials on-line, instructors can enhance the learning process. Interactive computer teaching modules will give students more one-on-one experience at their own pace. Then, by adding e-mail connectivity to instructors, students can have daily or even hourly access for questions. By careful Web page design, we can hold the interest of our students and disseminate more information than ever before.

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Laurence A. Sistrunk

Horticulturists need to stay abreast of the rapidly changing technology for disseminating research and teaching information. By connecting to the Internet and using the various tools available, horticulturists can gather information needed to communicate with colleagues and other clientele as a means of highlighting our science. The use of network software, such as FTP (file transfer protocol), Gopher, Veronica, Archie, Jughead, WAIS (wide area information servers), Mosaic, Netscape, Telnet, IRC (Internet relay chat), and WWW (World Wide Web) is essential in navigating the super information highway. This largely academically based network will evolve based on needs and politics in the years to come.

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Dan Chapman, Laurence Sistrunk and J. Benton Storey

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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Dan Chapman, Laurence Sistrunk and J. Benton Storey

Objectives of this experiment were: 1) to determine what effect a soil spike aerator had on nut quality and yield, and 2) to determine whether soil compaction influenced nut quality and yield.3) to determine whether tree stress influenced nut quality or yield on pecan trees In 1990, a randomized design was set up in a 33 year old orchard on Westwood silty clay loam with 3 main treatment factors: 1990 nut size (measure of tree stress), 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 in kg per tree. Results after two years showed that aeration increased the nut size of stressed trees in 1991 and non-stressed trees in 1992 Yield was unaffected by aeration in both years but stressed trees produced lower yields in 1992. Aeration increased nut size, but not significantly from 119 nuts/kg to 111 nuts/kg in 1991. There was a significant increase with aeration in 1992 from 121 nuts/kg to 113 nuts/kg. Yield and % kernel were not significantly different for both years with aeration Stress did not increase % kernel in either 1991 or 1992 but nut size was larger on non-stressed trees for both years. Stressed trees produced fewer nuts per tree in 1992.

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Laurence A. Sistrunk and J. Benton Storey

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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Laurence Sistrunk, Dan Chapman and J. Benton Storey

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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Laurence Sistrunk, Dan Chapman and J. Benton Storey

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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Dan Chapman, Laurence Sistrunk and J. Benton Storey

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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Robert Brown, Laurence Sistrunk, William Aldred and J. Benton Storey

`Stuart' pecans were harvested as soon as shucks would split in the fall of 1989 and 45 kg inshell samples were placed in 30 × 30 × 105 cm drying bins. The nuts were dried at air volumes of either 0, 1.27, 1.56, 1.84, or 2.12 m3/min down to 4% moisture. Air temperature in the drying bins was maintained at uniform 35°C with the exception of the 0 air volume treatment which was allowed to dry at room temperature. Four random samples of each treatment were held in frozen storage awaiting fatty acid analysis. Palmitic, stearic, oleic, linoleic, and linolinic fatty acids were separated in a 183 cm × 3 mm packed column using a 10% Silar 10C phase on a Gas Chrom QII, 100/120. The samples dried with a air volume of 1.27 m3/min retained a significantly higher oleic acid content than the 0 and 2.12 m3/min drying volumes. The 1.27 m3/min volume retained 64.55 % oleic acid compared with 61.37'% for the 0 velocity sample and 59.61% for 2.12 m3/min treatment. The more desirable oleic/linoleic ratio of 2.24 was found in the 1.27 m3/min sample compared to a 1.78 ratio in the 2.12 m3/min sample. Increased volume of air in the drying bins was thus deleterious to these samples because of the loss of monounsaturated fatty acid.