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Steven C. Wiest

Digitized photographic images of turf plots composed of bermudagrass, buffalo grass, tall fescue, and zoysiagrass were taken at a height of about 150 cm with a 28-mm lens. Fast Fourier transforms of these images were performed, and a radial plot of the power spectrum was obtained from each image. Hurst plots (log frequency vs. log intensity) were used to subtract “background” from the power spectra, so peaks would be more evident. The peak of the power spectrum occurs at the average spacing between leaves (more precisely, between areas of the canopy that reflects a significant amount of light) and defines the characteristic dimension. Zoysiagrass had the lowest characteristic dimension, while tall fescue had the highest. The width of the power spectrum is indicative of the variability of the characteristic dimension within the canopy. The minimum characteristic dimension (occurring at the highest frequency) was less than 1.7 cm, whereas all the other species had about the same minimum characteristic dimension of ≈1.9 cm. The maximum characteristic dimension was greatest for fescue (6.9 cm), followed by buffalo grass (3.8 cm), bermudagrass (3.3 cm), and zoysiagrass (2.8 cm). These results indicate that the characteristic dimension can be a useful tool for discriminating between turfgrass species in digitized images.

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Steven C. Adams

Seed vigor has a very subtle effect on the productivity of greenhouses producing vegetable transplants, celery, cauliflower, lettuce, etc. and on todays highly mechanized automatic or semi-automatic transplanting operations. As greenhouse production technology moves from traditional bare root to plug/tray growing systems and as automatic and semi-automatic transplanting operations increase in number, the impact of poor seed vigor is realized.

Measures to mitigate the impact of poor seed vigor in the nursery are: Seed density grading; increased growing cycle in the nursery, hand culling or replanting. Measures to mitigate the impact of poor seed vigor in automatic transplanting operations: increase the number of people following the planter to replace poor vigor plants; use hand fed transplanters.

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Steven C. Wiest

A system for the digital analysis of photographic prints of turfgrass plots is being developed. The 3-year-old turfgrass plots included Meyer zoysiagrass, Midlawn bermudagrass, Prairie buffalograss and Mustang tall fescue. The plots were photographed by a camera with a small dual bubble level on the camera back and a 28-mm-wide angle lens. Photographs were digitized with flatbed scanners. The images can then be analyzed in a variety of ways. For example, a series of photographs were taken from mid-Sept. through late Oct 1995 and spectral analysis of the resultant digital images were made. The initial RGB (red-greenblue) format of the images was converted to HSI (hue-saturation-intensity) for analysis. The results indicate, obviously, that hue changed from 104 (i.e., green) to 75.7 degrees (i.e., brownish) between the beginning and end of Oct. 1995. Similarly, intensity changed from ≈0.12 to ≈0.16 during the same time period, indicating that the images became darker over time. These phenomena were observed in all four species examined. However, the saturation value evoked a significant species * date interaction. The three warm-season species showed a decrease in saturation, while Mustang had no significant decrease during Oct. Spectral as well as textural analysis are likely the two most useful techniques in the digital analysis of turfgrass plots. Examples of both will be presented.

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V. A. Khan and C. Stevens

Staminate and pistillate flower production and fruiting characteristics of `Crimson Sweet' watermelons were evaluated under VisPore row cover plus clear polyethylene mulch (VCM), VisPore row cover plus black polyethylene mulch (VBM), clear polyethylene mulch (CM), black polyethylene mulch (BM) and bare soil (BS). VCM produced significantly higher numbers of pistillate and staminate flowers than other treatments. All mulched and mulched plus VisPore treatments were significantly different from BS with regards to the 1st nodal position of the staminate and pistillate flowers. Fruit-set among the treatments between 53-55 days after transplanting were: 100%, 75%, 59% and 32% for VCM, VBM, CM and BM, respectively. Average number of fruits per plant were: 4, 3, 3, 3 and 1 for VCM, VBM, CM, BM and BS, respectively.

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Steven C. Blank and Raymond Venner

This study develops a method of estimating wind machine effectiveness. The method captures the important variables affecting cost-effectiveness and can be applied at little cost. The present-value method outlined may be applied when evaluating frost protection for other crops and other risk-reducing inputs, such as irrigation equipment. Oranges in California are presented as a case study. The empirical results presented indicate that wind machines are generally not cost-effective for California orange producers. However, when the nonfinancial benefits of yield risk reduction are included, it is possible that wind machines are cost-effective for some growers.

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Douglas C. Needham and Steven Dobbs

Twenty-three students of HORT 2212: Herbaceous Ornamental Plants divided into five teams, each selecting one of the ground beds at the television studio gardens of Oklahoma Gardening to design with the aid of MacDraw II and Macintosh computers. The team approach promoted cooperative learning, where those who were skilled in design worked cooperatively with those individuals more skilled at developing the theme gardens' cultural pamphlets. This project encouraged individual students to develop various communication skills to support their team's thematic garden-visual, in the form of a CAD plot of the garden design; written, in the form of a garden pamphlet; and telecommunication, in the form of Oklahoma Gardening television segments.

The students and OBGA Ambassadors started the seeds and, then, planted the gardens, resulting in a very practical experience. This design and installation project not only prepared students for the cooperative efforts that they are likely to encounter in the ornamental horticulture and landscape design and maintenance industries, but also imparted pride in their work, which was viewed by over 150,000 television viewers and visitors weekly.

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Steven C. Wiest and Roth E. Gaussoin

The following model simulates hourly temperature fluctuations at 6 Kansas stations:
\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[T_{h}=\frac{(T_{x}-T_{n})}{2}\left[\mathrm{exp}\left(\frac{0.693h}{DL_{M}}\right)-1\right]+T_{n};{\ }0{\leq}h{\leq}DL_{M}\] \end{document}
\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[T_{h}=\frac{(T_{x}-T_{n})}{2}\left[1+\mathrm{sin}\frac{{\pi}(h-DL_{M})}{2(23-DL_{M})}\right]+T_{n};{\ }DL_{M}{\leq}h{\leq}23\] \end{document}
where h = time (hours after sunrise), DLM = 20.6 - 0.6 * daylength (DL), Th = temperature at time h, and TX and Tn = maximum and minimum temperature, respectively. Required inputs are daily TX and Tn and site latitude (for the calculation of DL). Whereas other models have been derived by fitting equations to chronological temperatures, this model was derived by daily fitting of hourly temperatures sorted by amplitude. Errors from this model are generally lower, and less seasonally biased, than those from other models tested.
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Steven C. Blank, Karen Klonsky, and Kim Norris

We address whether it is better for a producer to own harvesting equipment or hire a custom harvester to perform the job. A comparison of calculated purchase costs with the cost of hiring a custom operator leads to an estimate of the break-even acreage, which is used as a decision criterion. However, two risk factors must be included in the decision process: the date of harvest and the efficiency of the harvest operation. The affect of these factors may significantly alter the “real” costs of owning vs. hiring a custom operator and, therefore, change the decision reached by an individual grower.

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Steven J. McArtney and David C. Ferree

Grapevines (Vitis vinifera L.) were covered with an 80% neutral shade cloth from flowering until harvest to investigate effects of shade on early season vegetative development in the year after treatment. Shading reduced root dry weight, the concentration of soluble sugars, and amino nitrogen in xylem sap at budbreak, and leaf area expansion in the following year. Dry weight of roots on both shaded and nonshaded vines declined by more than 50% in the first 3 weeks after budbreak and then began to increase, but still had not recovered to prebudbreak levels, 10 weeks after budbreak. Total leaf area per shoot was reduced in the year after shading due to both fewer and smaller leaves.

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Steven J. McArtney and David C. Ferree

Early season vegetative development of grapevines was studied in the year after imposing three cropping levels to mature `Seyval' vines in the field or establishing two light levels to potted `DeChaunac' vines growing in the greenhouse. Heavily cropped `Seyval' vines (averaging 90 buds, 15.8 kg fruit per vine over the previous two growing seasons) had 85% fewer count buds and 31% fewer non-count (latent) buds than lightly cropped vines (averaging 25 buds, 9.7 kg fruit per vine). The rate of leaf area expansion was reduced on heavily cropped vines. Covering `DeChaunac' vines in the greenhouse with 80% shade from bloom onwards reduced the leaf area per shoot in the year after treatment by reducing both the rate of leaf appearance and the rate of leaf expansion. The leaf at node four from the base of the shoot had the greatest area on both shaded and control vines; however, the area was reduced 33% on shaded vines. Data from the greenhouse experiment were used to model the effect of leaf size at the transition from sink to source on total source leaf area per shoot. Prior to bloom the total source leaf area per shoot was increased when individual leaves became sources earlier, i.e., at a lower percent of their final size. Whether a leaf became a source at either 30%, 50%, or 80% of its final size had little effect on total source leaf area per shoot after bloom. The proportion of source to sink leaf area at bloom was greater than 90% for both slow- and rapidly growing shoots (those on shaded and control vines, respectively). Expansion of grapevine leaves was reduced by heavy cropping and low light levels in the previous year, greatly reducing the source leaf area per shoot.