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• Author or Editor: Kent D. Kobayashi*
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Crop modeling encompasses the use of mathematics, statistics, and equations to describe quantitatively crop growth and development. It can be useful tool to describe, quantify, and predict crop growth, development, and phenology. Crop models fall into two general classes—statistical (empirical) or mechanistic (physiological)—or they may be a combination of the two. The model type depends upon several factors including the objectives of the modeler, understanding of underlying physiological processes, and availability of data. Model development proceeds from a preliminary conceptual model through formalization into a mathematical model. Models are later verified, and validated, if possible. Model development is an iterative process with continual refinement as more data becomes available and understanding increases. Simulations are dynamic models that follow the growth and development of crops over time. They are more mechanistic in nature and involve changes in measurable quantities of the crop as affected by changes in rates of physiological processes.

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A shade experiment for pruned coffee trees was conducted on Maui, Hawaii, in 1996. Nine-year-old Guadalupe' trees were stumped at 70 cm above the ground, and three main verticals were allowed to remain on the main trunk. Each stumped tree was randomly selected and covered with shade cloth. The shade cloths were 30%, 50%, and 70% shade, and each shade structure had a length × width × height of 1.5 × 1.5 × 2.5 m. Data were collected in 1997. In general, the basal diameters of the verticals were similar in all treatments, as were the lengths of the verticals. The total number of laterals in the full-light treatment was slightly more than that of the other treatments. The numbers of flowering laterals were similar in all treatments. The numbers of fruit per tree in the full light, 30%, 50%, and 70% shade treatments were 1876, 3434, 2399, and 403, respectively. Fruit per flowering node was the best index relating to yield. Fruit per node was highest under 30% shade, followed by full light and 70% shade. At the beginning, fruit ripened faster in the full light treatment than in the other treatments, but at the end of September, fruit in 70% shade ripened slower than the other treatments. Therefore, after stumping, coffee trees grew best under 30% shade. For coffee, pruning under the field condition, stumping every other row of trees may be a satisfactory way to obtain the best yield in the future.

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It is difficult to estimate the total leaf area of coffee plants with accuracy due to the large number of leaves and the high leaf density of the plant canopy. In 1996, on Maui, Hawaii, 98 leaves of various sizes were randomly collected for each of five cultivars of Coffea arabica L. The cultivars used were Guadalupe', Guatemalan', Mokka', Red Catuai', and Yellow Caturra'. Leaf length, width, and area were measured. Seventy-five leaves were used to develop leaf area models, and the remaining leaves were used to test the accuracy of the models using a 1:1 line. We then developed leaf area devices (LADs), which were made of sheet plastic and shaped to resemble coffee leaves. There were three groups of areas in the leaf area devices, based on leaf sizes. Total leaf area (TLA) contained three components. Each component related to the mean leaf area (k) and the number of leaves (n) in that group. The model for the total leaf area was: TLA = k1n1 + k2n2 + k3n3, where k is a constant in each group. The estimation errors for the different cultivars ranged from 5.6% to 12.3% for 1-year-old plants (four cultivars) and from 1.9% to 7.8% for mature plants (five cultivars). By using the LADs and counting the number of leaves, we can obtain the total leaf area for coffee plants in the field.

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Turfgrass is grown under a wide range of environmental conditions, especially light conditions. In residential and commercial applications, selecting the appropriate turfgrass depends, in part, upon its performance under differing light conditions. This study was conducted to determine the growth habits of four turfgrasses under different shade treatments. Common Bermuda', Tif dwarf Bermuda', Seashore Paspalum', and Z-3' were grown outdoors in pots. Z-3' is an attractive new variety of turfgrass for residential lawns. Benches were covered with shade cloth to provide different shade conditions (0%, 30%, and 50% shading). Clippings were taken every 2 weeks and dried to determine growth. Turfgrass growth under the three shade treatments were significantly different. In the 0% and 30% shade treatments, Common Bermuda' and Seashore Paspalum' had similar growth with their dry weights being greater than that of Tif dwarf Bermuda' and Z-3'. Under 50% shade, Seashore Paspalum' grew significantly greater than the other turfgrasses. Common Bermuda' grew significantly less under 50% shade than under 0% and 30% shade. Common Bermuda' does well on golf courses because of its fast growth and attractiveness. With its vigorous growth and shade tolerance, Seashore Paspalum' can be used for residential lawns. Z-3' turfgrass, a relatively new variety for residential lawns, shows slow growth but is desirable because of its tolerance to different shade conditions.

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Increasing flower production and manipulating the flowering season of potted ornamental plants would help provide a competitive edge for floriculture producers in Hawaii. Photoselective shadecloths that modify the light spectrum may be an approach to achieve these aims. The objective of this study was to determine the effects of photoselective shadecloths on the flowering of potted orchids. At the University of Hawaii Magoon Facilities (Oahu), two kinds of orchids were grown in a saranhouse in chambers built with PVC pipe covered with the four shadecloths—black (control), gray (diffusive), red, and blue—each providing 30% shading. With M-10973 Rhv. Herbert Kurihara Flori' orchid plants, more buds and flowers were produced under the black and red shadecloths than the other two shadecloths. The black and red shadecloths resulted in similar earlier starting dates of bud appearance (4 Aug.2005) and flower appearance (4 Aug. 2005). Whereas, under the blue shadecloth, bud appearance (18 Aug. 2005) and flower appearance (31 Aug. 2005) were delayed. Under the black and red shadecloths, flowering ended earlier (27 Oct. 2005). When flower production resumed, new spikes were produced earliest under the red shadecloth (1 Dec. 2005). No new spikes were produced under the black shadecloth. For M-10878 Colmanara Sphacetante Evelyn' AM/AOS orchid plants, spike formation occurred later than with the M-10973 plants. Spike formation occurred on the same date for all shadecloth treatments (10 Feb. 2006), with similar numbers of spikes. Thus, photoselective shadecloths influenced flowering, but their effects varied with the orchid.

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The objective of this study was to develop a computerized personal information management system for use by extension agents and growers. Agents and growers need an easy-to-use computer information system to access quickly information about specific topics for different crops. An information system helps agents provide faster, better service and up-to-date information to their clients. Using the software LinkWay (IBM Corp.) on an IBM personal computer, we developed such a system called the “Farmer's Bookshelf for the IBM.” This information system uses “index cards” with information stored on separate screens called “pages.” Both textual and graphical information may appear on a page. Using a mouse, the user navigates from one page to another by clicking on a “button” on the page. This easy-to-use system requires no typing except to enter a word for the computer to search. The user can easily browse for the desired information and then print it. The “Farmer's Bookshelf for the IBM” provides an easy, fast tool for agents and growers to obtain vitally needed information.

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Four turfgrasses (Z-3, Seashore Paspalum, Common Bermuda, and Tif dwarf Bermuda) were grown outdoors in pots under different shade conditions (0%, 30%, and 50% shade) from August to December 1995. Dry weight of clippings taken every two weeks was determined. Turfgrass growth in the three shade treatments were significantly different, and the growth of the turfgrasses were highly significantly different. In the 0% and 30% shade treatments, Common Bermuda and Seashore Paspalum grew similarly, and their dry weights were significantly greater than those of Z-3 and Tif dwarf Bermuda. However, under 50% shade, only Seashore Paspalum grew significantly greater than the others. Comparing growth among the shade treatments for each turfgrass, we found no significantly differences. Only Common Bermuda grew significantly less under 50% shade than under 0% and 30% shade. Common Bermuda is good for golf courses because of its fast growth and attractiveness. Seashore Paspalum can be used for home lawns because of its vigorous growth and shade tolerance. Z-3 turfgrass, an attractive new variety for home lawns, despite its slow growth, is tolerant of different shade conditions.

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Premature fruit drop of Macadamia integrifolia is a major limitation to yield. This study investigated the effects of raceme thinning and branch girding on find fruit set of macadamia nut 'Ikaika' and 'Keaau'. Eleven-year old grafted trees grown near Hilo, Hawaii were used. Racemes were thinned to 1, 2, or 4 racemes per branch two weeks after anthesis. The base of half these branches was girdled when the racemes were thinned.

Premature fruit drop occurred during the 97 and 151 days following anthesis for Keaau' and Ikaika', respectively. Peak fruit drop occurred within 70 days after anthesis for both cultivars. Raceme thinning and girdling had no effect on final fruit set (nuts/branch) of Ikaika' 151 days after anthesis. There was a significant interaction between raceme thinning and girdling on final fruit set of Keaau'. Branches with four racemes set more fruit than branches with one or two racemes. Raceme thinning and girdling had no effect on fruit retention (% of initial fruit set retained through final fruit set per branch) of Ikaika'. There was a significant interaction between girdling and raceme thinning on fruit retention of Keaau'. Branches with four racemes had greater fruit retention than branches with one or two racemes. Premature fruit drop may be altered on individual branches by altering raceme load and limiting phloem transport of assimilates into the girdled branch.

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Extension personnel and growers need up-to-date information on crops to make sound management decisions. The Farmer's Bookshelf™, a hypermedia information system based on the software HyperCard®, was developed for Macintosh® computers. Since clientele who use IBM-compatible computers could not use the Macintosh version of the Farmer's Bookshelf, we looked into several DOS/Windows™ hypermedia software. Spinnaker PLUS™ (Spinnaker Software Corp.) suited our needs, primarily because it required a minimum of reprogramming. PLUS (Macintosh) converted HyperCard files into PLUS (Macintosh) files. Some programming, fonts, and icons required modifications. PLUS (Macintosh) files were then edited using PLUS (widows). Again, minor editing was necessary. Currently, the PLUS (Windows) files and a runtime version of PLUS (Windows) are distributed to clientele who use IBM-compatible computers. PLUS enables our supporting the Fanner's Bookshelf without having to develop a DOS or Windows version that requires completely new programming and extensive modifications. HyperCard files are readily converted to run under Windows, thus helping us to serve clientele who use either platform.

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