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  • Author or Editor: Mary M. Peet x
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“Sustainable Practices for Vegetable Production in the South,” 174 pages long, including 250 references, was written as a traditional college textbook. I will be discussing my experiences converting it to a web document and simultaneously releasing web and print versions. I will also discuss some of the issues we will confront if we depend on the web for delivering and receiving information. These issues are: 1)There are no conventions for websites comparable to those that have evolved for print documents. At the same time, users expect sites to function certain ways. 2) Consistency between parts of the website is more difficult to maintain than in a print document, but is critical in order to correctly orient the user. 3) The optimal size and structure of the information “chunk” or subdivision is unclear—Should it be a whole chapter or article, a single paragraph, or a functional unit of facts that does not have a name or correspond to anything in print media? 4) How do you let a person accessing any one part of your website know about all the other parts and how they fit together—You can flip through a book to view it, but a person following a link to a page on your site is like the blind person touching the elephant's trunk—they can not visualize the whole. 5) There is no one intuitively obvious or logical place to put references and footnotes because of the subdivision of information into “chunks” or functional facts. 7) There is no obvious starting or stopping point in making revisions. 8) People accessing the site will send messages and ask questions. 9) Meaningful evaluation of usage and usefulness is difficult.

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It is often difficult to obtain information on producing vegetables using `sustainable' practices such as reduced inputs of pesticide and commercial fertilizers. Lack of such information is often cited by conventional farmers and extension agents as a reason for not adopting or assisting others in adopting sustainable techniques. As part of a Southern Region Low Input Sustainable Agricultural (LISA) Program, we are compiling a database which will include techniques for vegetable production acceptable to `organic' farmers as well as those acceptable to conventional farmers. This information source will include information on 17 specific vegetables and well as chapters on general topics such as cover crops and weed control. We hope to make this information available both as a production manual and by way of an electronic information retrieval system. Steps in the development of this project include initially soliciting input from farmers and extension workers on the preferred content and format and conducting an on-going evaluation by these groups as segments are developed. The database should be available within 2 years in both electronic and hardcopy versions.

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`Grace' tomatoes were grown utilizing three different growing methods: organic, conventional, and biorational (IPM and use of reduced-risk pesticides). There was one treatment per greenhouse per growing season. Treatments were rotated for each crop. Inputs for the organic system were allowable according to the Carolina Farm Stewardship Materials List for organic certification or the Organic Material Review Institute (OMRI). Organic methods were compared to conventional and biorational methods in a total of two spring and two fall crops. The conventional and biorational substrates consisted of a commercial peat/perlite blend containing a “starter” nutrient charge. The organic substrates were a coir pinebark blend and a peat/perlite/vermiculite commercial substrate without non-organic “starter nutrients” and wetting agents. Organic substrates were amended with 15% by volume vermi-compost and dolomitic lime. Organic nutrient amendments were bloodmeal, bonemeal, and potassium sulfate to provide an initial nutrient charge. Organic post-transplant fertilization practices included three commercial blends used at several application rates. Fertilizers were applied by “mixing and pouring” in Spring 1998, but were injected into the drip irrigation system for the remaining three growing seasons. Data was collected on harvest yield, fruit quality, and plant development. In the first two growing seasons, organic production resulted in the highest percentage of number1 quality fruit, but in Spring 1998, these plants were developmentally slow, resulting in lowest total yields. In the Fall 1998 and Spring 1999 crop, all measurements of growth and yield for organic production were comparable to those in conventional and biorational controls. We feel however, that additional development work is required in the organic treatments to optimize transplant production, post-plant fertilization regimes and biocontrol application.

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Global temperature increases are predicted over the next several decades. Earth surface temperatures in 1995 were the highest ever recorded. At day temperatures above 30C or night temperatures above 21C, tomato fruit production decreases. However, the temperature dependence of fruit production has not been described in terms of whether day temperatures, night temperatures, or mean temperatures are the most limiting. The process or tissue most sensitive to heat and most limiting to fruit production is also not known. The objectives of this experiment are to establish the temperature dependence of fruit set in tomatoes and to determine the importance of post-pollen production effects. We imposed a total of nine temperature treatments in a series of four separate experiments. Each experiment consisted of a 30/24C treatment and two other day/night temperature combinations with differing means and/or day/night temperature differentials. As mean daily temperature increased from 25 to 29C, fruit set, fruit number, total fruit weight, and seediness index (a quantitative rate of fruit seed content) declined. Temperature treatments did not affect average fruit weight. Higher mean temperatures promoted flowering except at the highest temperature. Mean temperature was more important than day/night temperature differentials or the specific daytime or nighttime temperature treatment.

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Previous greenhouse studies in Raleigh have shown that nighttime cooling increases tomato fruit weights from 11% to 53%, depending on planting dates. The physiological mechanism was unclear, except that temperatures during fruitset were most critical We report here on a phytotron experiment comparing pollen characteristics and in vitro pollen germination of plants grown at night temperatures of 18, 22,24 or 26°C in a 12-hour photoperiod with 26°C day temperature in all treatments. There was considerable variability between sampling dates in pollen characteristics and % germination. The most consistent and significant effects were a decrease in total pollen and an increase in % abnormal pollen at high night temperatures. Number of seed present in the fruit also decreased with increasing night temperatures, indicating that the changes in pollen characteristics adversely affected seedset. Night temperatures of 22C appeared optimal for many of the pollen and growth characteristics measured, but fruit developed most rapidly at the higher night temperatures.

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Environmental restoration of streams and wetlands in North Carolina is creating a growing demand for commercially available native plant material. Recent changes in the tobacco industry have resulted in decreased production leaving some tobacco greenhouses, once utilized for a few months, empty year-round. Identifying alternative crops that can be grown in tobacco greenhouses will provide valuable income to economically distressed tobacco growers. The floatation system (sub-irrigation) employed in the production of tobacco transplants in greenhouses is similar to that utilized by some native plant nurseries to produce wetland and riparian species. Local production of this plant material can enhance restoration project goals by increasing utilization of regional germplasm in this industry and reducing the risk of importing exotic pests with material shipped from out-of-state. To research these possibilities, we constructed a demonstration tobacco greenhouse with multiple float beds. Three commercially available media, including a tobacco seedling mixture, were tested. No differences were observed among the plants grown in different media. After one growing season, we have identified close to 20 species, woody and herbaceous, that can be successfully grown in a traditional tobacco greenhouse with minimal input or alternation to the structure or normal production practices. Additional research is needed, however, to address optimal production criteria.

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In the southern U.S. and other mild winter areas, the length of the harvest season for greenhouse tomatoes is limited by high night temperatures. The purpose of this study was to determine the extent of this limitation by installing mechanical refrigeration to provide nighttime cooling in two of four computer-controlled greenhouses. For three crops of greenhouse tomatoes, nighttime temperatures in cooled houses were not allowed to rise above 20°C. Sixteen-week old transplants were placed in greenhouse treatments starting Mid-April ('91), mid-July ('90) and mid-August ('89). Fruit weights were significantly increased by nighttime cooling on all three planting dates, with weights increasing 11%, 28% and 53%, respectively. For the mid-July and mid-August plantings, fruitset, fruit size and % uncracked fruit were also increased significantly by nighttime cooling. Data collected in '90 showed that plants in the cooled houses required only an additional 2.4 days to mature and were only 10-15% taller, suggesting there were no significant plant-related disadvantages to nighttime cooling. Lack of stored heat and nighttime heat load in the greenhouses resulted in low cooling costs and refrigeration requirements, so nighttime cooling may also be commercially feasible.

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Peet et al. (1997) demonstrated that in male-sterile tomato plants (Lycopersicon esculentum L. Mill cv. NC8288) (MSs) provided with pollen from male-fertile plants (MFs) grown at 24°C daily mean, percent fruit set, total number and weight of fruit, and relative seediness decreased linearly as mean daily temperature rose from 25 to 29°C. The primary parameter affecting these variables was mean temperature, with day temperature at a given night temperature, night temperature at a given day temperature, and day/night temperature differential having secondary or no effect. To compare the effect of temperature stress experienced only by the female tissues with that experienced by the male tissues or both male and female tissues, MSs and MFs were grown in 28/22°C, 30/24°C, and 32/26°C day/night temperature chambers. Fruit yield and seed number per fruit declined sharply when increased temperatures were experienced by both male and female tissues (MFs). There was no fruit set in any of the MSs assigned to the 32/26°C pollen treatment, mostly because of the limited amount of pollen available from MFs. Both fruit production and seed content per fruit were also greatly reduced in MSs receiving pollen from 30/24°C grown MFs for the same reason. For plants experiencing stress only on female tissues (MSs grown at high temperatures, but receiving pollen from MFs grown at the lowest temperature), there was also a linear decrease in fruit yield as growth temperatures increased, as previously seen by Peet et al. (1997), but the temperature effect was less pronounced than that on pollen production. Thus, for this system, temperature stress decreased yield much more drastically when experienced by male reproductive tissues than when experienced only by female reproductive tissues.

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