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  • Author or Editor: W.J. Lamont x
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Abstract

One of the primary missions of the Agricultural Extension Service in each state is to reach agricultural producers with new technology. One of the best educational resources available to accomplish this mission is the on-farm demonstration program. Demonstrations provide a vital link between the researchers and the agricultural producers. The use of the portable pumping and filtering unit in an extension on-farm demonstration provides growers with the opportunity to observe plastic-mulch–drip-irrigation technology and also allows extension specialists to provide valuable training to county extension personnel.

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On-farm extension demonstrations are one of the best participatory research and educational resources available to extension specialists and county extension staff for presentation of new technology to agricultural producers. On-farm extension demonstration programs for intensive vegetable production, of which drip irrigation is a major component, can range from a complete package [3/4-ton truck, a trailer for transporting equipment, a tractor in the 36 to 42 HP range (i.e., Ford 3910) a plastic-laying machine, a bed press pan, hillers, and drip/overhead irrigation systems] with a price tag of about $40,000 used in a multistate, statewide, or multicounty program, to a small demonstration package using a household well source with a cost of about $250. The demonstration package used will depend on the scope of the program, local conditions, and economic realities.

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Drip irrigation used in conjunction with plastic mulches and other intensive production technologies continues to expand in the Midwestern states. The vegetable crops being produced on the greatest acreages using drip irrigation/plastic mulch are tomatoes, peppers, muskmelons and watermelons. Summer squash, eggplant, cucumbers and some cole crops are also grown using drip irrigation and plastic mulches but to a much lesser extent. The estimated acreage for drip irrigation in the Midwest is 43,209 acres which includes both vegetable and fruit crops.

Special consideration in using drip irrigation in this region of the country are high pH of the water, amounts of calcium salts, and iron levels in the water.

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Research was conducted to determine the optical properties of eight plastic mulches and evaluate their effects on soil, mulch, and air temperatures in the field. Optical properties of the mulches were measured in the laboratory in the shortwave (0.3 to 1.1 μm) and longwave (2.5 to 25 μm) wavebands using a spectroradiometer and Fourier transform infrared spectrophotometer, respectively. Additionally, each mulch was installed on a fine sandy loam soil near Manhattan, Kan. Air and soil temperatures were measured 5 cm above and 10 cm below the surface, respectively. Measurements of longwave radiation emitted and reflected from the surface were used to approximate the apparent temperature of the surface. Shortwave transmittance of the mulches ranged from 0.01 to 0.84, and shortwave reflectance ranged from 0.01 to 0.48, with the greatest reflectance from white and aluminized mulches. Infrared transmittance ranged from 0.87 for a black photodegradable mulch to 0.09 for aluminized material. Air temperatures at 5 cm were similar for all mulch treatments, but were typically 3 to 5C higher than the air at 1.5 m during the day. Midday soil temperatures were highest beneath mulches with high shortwave absorptance (black plastics) or those with high shortwave transmittance coupled with low longwave transmittance. Apparent surface temperatures approached 70 to 80C during midday, with the highest temperatures occurring on mulches with high shortwave absorptance. For some mulches, both, shortwave and longwave optical properties of the plastic governed the level of radiative heating. Our results suggest that conduction of heat between the plastic and the soil surface also affects the extent of soil heating in a mulched field.

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Abstract

Broccoli plants (Brassica oleraceae L. var. italica Plenk) were grown in an air-conditioned, 22°/18°C day/night temperature, greenhouse in the Southeastern Plant Environmental Laboratories in Raleigh, N.C. Seedlings 6 to 33 days from seeding were exposed to cold treatments of −3° to −5° or +1° to +2° for periods of 7 to 34 days, then returned to higher temperatures. Days from seeding to flowering were determined. Plants 13 or more days from seeding and exposed to 14 or more days of cold treatment were induced to flower earlier than untreated plants. The critical stem size for cold inductions was 5 to 8 mm diameter. Susceptible plants weighed 4 to 50 g at the beginning of the cold treatment phase. Plants outside that range were nonsusceptible.

Open Access