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S. Shukla, C.Y. Yu, J.D. Hardin, and F.H. Jaber

Continuous monitoring of hydraulic/hydrologic data for managing water for horticultural crops has been a challenge due to factors such as data loss, intensive resource requirements, and complicated setup and operation. The use of state-of-the-art wireless spread spectrum communication technology and wireless data acquisition and control (WDAC) systems for agricultural water management is discussed in this paper. The WDAC technology was applied to a research project where lysimeters were used for water quantity and quality studies for vegetables. Two types of WDAC networks, master–slave and peer-to-peer WDAC networks, are discussed. The WDAC system linked the wireless dataloggers to a network to make real-time data available over the Internet. The use of WDAC made it possible to collect real-time data and control the experiment (e.g., frequency of data collection) remotely through the Internet. The WDAC system for the lysimeter study was compared to a commonly used manual system with regard to potential instrument damage, data loss, ease of data collection and analyses, and total cost of monitoring. The advantages of the WDAC include: reduced equipment losses from natural disasters (e.g., lightning), improved equipment maintenance, reduced data loss from faulty equipment, higher project personnel efficiency, and real-time involvement by a dispersed team. The total cost of the WDAC system ($65,750) was about half that of the manual system ($130,380). The WDAC system was found to be an effective tool for agricultural water management projects.

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J.W. Buxton and Wenwei Jia

The controlled water-table irrigation (CWT) system was evaluated for vegetable seed germination and transplant growth. The system is a modification of capillary mat irrigation except that the mat along one side extends over the edge of the bench into a narrow trough running along the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn by capillarity from the trough upward to the bench surface and then moves by capillarity to the opposite side of the bench. The system automatically maintains a constant air: water ratio in the growing media. Seeds of broccoli, tomato, and pepper were germinated in a 96-cell plug tray and grown to transplanting stage with the CWT system. A factorial experiment consisted of two growing media combined with CWT treatments of 2 and 4 cm. Excellent germination and high-quality seedlings were produced with all treatments. No differences were observed in growth of seedlings at 2 vs. 4 cm or between the two growing media. The CWT system is capable of maintaining a constant uniform water: air ratio in all plug cells on a commercial growing bench. Nutrient solution does not run off the bench. The CWT potentially is an excellent system for the irrigation of vegetable transplants.

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Marc van Iersel and Ron Oetting

Ebb-and-flow systems can be used to apply systemic pesticides to greenhouse crops without worker exposure or runoff. However, there is little information on the efficacy of pesticides applied with ebb-and-flow systems. We are using silverleaf whitefly (Bemisia argentifolii) control on poinsettia (Euphorbia pulcherrima) with imidacloprid as a model system to study pesticide efficacy in ebb-and-flow systems. The objective of this study was to determine the effect of the amount of insecticide taken up by the pot on the efficacy of whitefly control. Different amounts of imidacloprid uptake were obtained by not watering the plants for 0, 1, 2, or 4 days before the imidacloprid application. The imidacloprid (132 g·L–1) was applied once when the roots of the cuttings had reached the side of the pots. These treatments were compared to an untreated control on ebb-and-flow and a standard drench application (100 mL) to hand-watered plants. Pots in the different subirrigation treatments absorbed 12 to 175 mL of imidacloprid solution. Four days after the application, leaf tissue of the hand-watered plants contained 8 to 20 times more imidacloprid than the subirrigated plants. Efficacy was determined from the percentage of surviving mature whiteflies after 2 days on the plants and by counting the number of immatures after 2 weeks. Surprisingly, imidacloprid efficacy was better in the subirrigated imidacloprid treatments than in the hand-watered treatment. Whitefly control in all subirrigated imidacloprid treatments was excellent, irrespective of the amount of imidacloprid solution taken up by the pots.

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Sven E. Svenson, Dave Adams, and R.L. Ticknor

Roots growing out of container drainholes, and weeds growing on the sandbed surface, are the two major problems associated with the use of sandbed subirrigation systems for nursery crop production. Adjusting the water level within the sandbed, application of herbicides to the sandbed surface, placing weed barriers on the sandbed surface, and placing copper hydroxide-treated weed barriers on the sandbed surface were tested to control rooting-out and weed growth. Coppertreated barriers provided the best control of rooting-out and weed growth without reducing the shoot growth of heather, forsythia, or weigela. Several herbicides provided good control of rooting-out and weed growth without reducing the shoot growth of daphne.

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Derek M. Law, A. Brent Rowell, John C. Snyder, and Mark A. Williams

A 2-year field study in Lexington, Ky., evaluated weed control efficacy and influence on yields of several organic mulches in two organically managed bell pepper (Capsicum annuum) production systems. Five weed control treatments [straw, compost, wood chips, undersown white dutch clover (Trifolium repens) “living mulch,” and the organically approved herbicide corn gluten] were applied to two production systems consisting of peppers planted in double rows in either flat, bare ground or on black polyethylene-covered raised beds. In the first year, treatments were applied at transplanting and no treatment was found to provide acceptable season-long weed control. As a result, bell pepper yields in both production systems were very low due to extensive weed competition. First year failures in weed control required a modification of the experimental protocol in the second year such that treatment application was delayed for 6 weeks, during which time three shallow cultivations were used to reduce early weed pressure and extend the control provided by the mulches. This approach increased the average weed control rating provided by the mulches from 45% in 2003 to 86% in 2004, and resulted in greatly improved yields. In both years, polyethylene-covered raised beds produced higher yields than the flat, bare ground system (8310 lb/acre compared to 1012 lb/acre in 2003 and 42,900 lb/acre compared to 29,700 lb/acre in 2004). In the second year, the polyethylene-covered bed system coupled with mulching in-between beds with compost or wood chips provided excellent weed control and yields. When using the wood chip mulch, which was obtained at no cost, net returns were $5587/acre, which is similar to typical returns for conventionally grown peppers in Kentucky. Net returns were substantially decreased when using compost due to the purchase cost. Results from this study indicate that shallow cultivation following transplanting, combined with midseason mulch application, resulted in high yields in an organically managed bell pepper system that were comparable to yields of most varieties grown conventionally in a variety trial conducted on the same farm.

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W.P. Cowgill Jr., M.H. Maletta, and S.A. Johnston

Two disease forecasting systems - FAST, Pennsylvania State University and CUFAST, Cornell University - were used to generate spray schedules for controlling Alternaria solani Ell. and Mart. on `Celebrity' tomato (Lycopersicon esculentum Mill.) at The Rutgers Snyder Research and Extension Farm in Northwest New Jersey. Disease control was compared to that obtained following standard weekly spray schedules. Chlorothalonil, 1.5 lb/A, was used for disease control for all treatments. Disease ratings of the FAST and CUFAST plots were significantly lower than that of the unsprayed control and were not significantly different from the plots sprayed according to standard spray schedules. A total of 10 fungicide applications were made following FAST recommendations; 7 applications were made following CUFAST recommendations; 13-15 applications were made following standard recommended schedules. Using CUFAST resulted in an estimated $200 per acre savings in spray costs. Chemical name used: tetrachloroisophtalonitrile (chlorothalonil).

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Robert L. Wample, Guy Reisenauer, Andy Bary, and Fred Schuetze

A computerized system capable of controlling the freezing rate and collecting, storing, and analyzing data from multiple samples to determine their freezing point using low-temperature exotherm analysis is described. Details include electrical diagrams of modifications to the multiplexer/amplifier interface to provide additional signal amplification and permit control of the freezer's compressor. Computer software is described that permits variable temperature decline rates. Data analysis consists of a program in “C” that sequentially compares each data point in a low-temperature exotherm profile. Low-temperature exotherms are identified by a user-specified minimum differential between sequential data points. Examples of exotherm output and data analysis are given.

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Angela K. Tedesco, Gail R. Nonnecke, John J. Obrycki, Nick E. Christians, and Mark L. Gleason

Field plots of four production systems of `Tristar' dayneutral and `Earliglow' Junebearing strawberry (Fragaria xananassa Duch.) were established in 1993. Productions systems included conventional practices (CONV), best-management practices including integrated crop management (ICM), organic practices using corn gluten meal, a natural weed control product, (ORG-CGM), and organic practices using a natural turkey manure product (ORG-TM). `Earliglow' plants grown with ORG-CGM showed the highest number of runners and total vegetative biomass. Plots with CONV and ICM systems using standard herbicide treatments had lower total weed numbers (11 and 18, respectively) than ORG-CGM (63) and ORG-TM (58). `Tristar' plant growth, yield and berry number were reduced when plants were grown under straw mulch in ORG-CGM and ORG-TM compared to CONV and ICM plots with polyethylene mulch.

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Marsha Ann Bower, David H. Trinklein, and John M. Brown

Recent trends in greenhouse container production suggest using ebb and flow irrigation for water conservation and pollution control. A major problem in this system is management of soil borne pathogens. Some species of Trichoderma, a beneficial fungi, are known to control Pythium and Phytopthora in container production. This study investigates the potential of applying a Trichoderma conidial spore suspension in an ebb and flow irrigation system. Trichoderma conidia were collected from culture and placed in 101 l stock solution tanks at 10-2 and 10-4 colony forming units (CFU) per ml. Six inch container grown Dendranthema grandiflora `Delano', were irrigated as needed. To determine Trichoderma density in the root environment, soil samples were acquired from the container at 7 day intervals. Results showed that initial population densities of 10-4 CFU/ml were required to achieve adequate container populations to control disease after one irrigation. This study successfully demonstrated that Trichoderma could be dispersed through irrigation water into container plants in an ebb and flow system.

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Jay Frick, Manette A. Schonfeld, Paul H. Williams, and Cary A. Mitchell

The short time to flower and rapid production cycle of dwarf Brassica lines make it a promising candidate as an oilseed crop for NASA's Controlled Ecological Life Support Systems (CELSS) program. Breeding lines provided by Paul H. Williams are being screened at Purdue University for productivity and yield rate using soilless culture techniques under controlled-environment conditions. The small, irregularly-shaped Brassica seeds did not respond well to conventional methods of germination above the batch hydroponic systems, even when a variety of capillary ticking materials were used. At best, attaining uniformity of seedling stands required transplants, which compromised potential yield rates in terms of mechanical damage and inhibited seedling establishment. Present emphasis is on solid substrate soilless mixtures using passive ticking hydroponics systems. Crop growth rate, harvest index, and overall yield are being compared as a function of planting densities ranging from 117 to 1423 plants/m2 of growing area. Yield parameters are also being evaluated as a function of growth medium and level of ambient CO2 in the growth chamber atmosphere. Research sponsored by NASA Cooperative agreement NCC 2-100.