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  • Author or Editor: Robert H. Stamps x
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Abstract

Rising fuel, labor, and materials costs and concerns about possible geophysical and political effects of withdrawing large quantities of water from aquifers have prompted growers and researchers to consider methods to reduce the amount of water necessary to protect crops from cold. For crops grown in shadehouses, there is a need for an inexpensive method to seal these structures to reduce convectional and radiational heat loss during freezes. A method that shows promise is the use of water to form a thin layer of ice to seal openings in shade fabric (1, 4, 5).

Open Access

One of the most difficult times to balance crop nitrogen (N) requirements with concerns about nitrate-N leaching occurs during crop establishment, when root systems are poorly developed and not widely distributed in the growing medium. This dilemma can be exacerbated when producing a slow-growing plant such as leatherleaf fern (Rumohra adiantiformis [Forst.] Ching) on sandy soils in shadehouses in areas with significant rainfall. Rhizomes were planted in 36 drainage lysimeters containing Tavares fine sand located in a shadehouse. Nitrogen fertilizer was applied at nine rates using liquid and/or controlled-release fertilizer. Nitrogen application rates were varied as the rhizomes became established and spread into unplanted areas of the lysimeters. Irrigation and rainfall were monitored and the amount of water not lost to evapotranspiration was determined. Nitrogen (ammoniacal, nitrate/nitrite, total Kjeldahl) concentrations in leachate collected below the rootzone were determined. Stipe sap nitrate and frond total Kjeldahl nitrogen (TKN) were determined to try to develop a production monitoring technique. Initially, only leachate samples from controlled-release fertilizer plots treated at 21 and 42 kg of N/ha per year and liquid fertilizer at 28 kg of N/ha per year were consistently below the maximum contamination level (MCL) of 10 mg·L–1. As the fern became established, leachate nitrate/nitrite-N concentrations from higher N application rate treatments also remained below the MCL. Leachate N concentrations decreased as rainfall increased. Fern growth increased with increasing N application rate. Stipe sap nitrate-N and frond TKN concentrations were not well-correlated during establishment.

Free access

Impatiens `Dazzler Violet', Petunia × hybrida `Carpet Blue', and Spathiphyllum `Ty's Pride' plugs were planted in 10-cm pots containing a commercial peat-based soilless growing medium composed of Canadian 60 peat: 20 vermiculite: 20 perlite (by vol) not treated with surfactant. Growing medium was treated, or not treated, 1) at planting, 2) during production, and/or 3) preshipment with experimental surfactants. The production phase consisted of growing plants on raised benches in a greenhouse until they reached marketable size. Phytotoxicity, plant water use and growth were determined. At the beginning of the postproduction phase, growing medium in all pots was brought to container capacity. Plants were then dried to wilting three times. Water loss and water retained on rewatering and times to wilt and recovery were recorded. Surfactant treatments caused no foliar phytotoxicity and did not delay flowering for petunia or spathiphyllum. However, surfactant treatments delayed flowering for impatiens by ≈4 days. Surfactant treatments increased top growth of petunia but not of the other crops. Postproduction, water retention at rewatering, and times to wilt were increased for petunia and spathiphyllum when they were in surfactant-treated medium. For impatiens, treatments had no effects on water retention or wilting, probably due to the small root systems and limited attendant medium dewatering for this crop. Generally, all three experimental surfactants performed similarly and weekly and preshipment surfactant applications were of no additional benefit compared to a single initial application at planting.

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Abstract

Kodak Vericolor slide film SO-279 and 5072 (formerly designated as SO-372) is an easy and fast means for making colored reverse text slides (1, 2, 4, 5). However, recommendations have dealt only with photographing black copy on a white background using hard-to-find and easily scratched Wratten gelatin filters. Additionally, the use of this film for making colored transparencies from black and white negatives, such as those produced using scanning electron microscopes (SEM), or directly from monochromatic video display monitors has not been reported.

Open Access

Microenvironmental conditions in a shadehouse covered with shade fabric designed to exclude 70% of incoming light were monitored and compared to those in an adjacent field to quantify differences related to plant water use. Radiant flux density and photosynthetic, photon flux inside the shadehouse varied seasonally between about 18% to 28% of outside values. During the day, leaf and air temperatures around the crop canopy were generally lower and relative humidities higher inside the shadehouse than outside. Leaf-to-air vapor pressure gradients inside the shadehouse averaged about half those outside. Wind run inside was <10% of wind run outside. Differences between reference ET (ETo) values, calculated using Penman's equation), inside and outside the shadehouse were greatest during summer months. Outside evaporatory pan (Epan) water losses ranged from 205 mm in July to 95 mm in Nov. For the same months, Epan losses inside were about 80% lower. Monthly ETactual, as determined for Rumohra adiantiformis growing in lysimeters in the shadehouse, ranged from around 40% to 80% of inside Eo.

Free access

As the area devoted to cut foliage production has increased and residential development has encroached upon these agricultural areas, conflicts between growers and homeowners have increased. Withdrawals of water for cold protection produce severe reductions of local artesian levels which render domestic wells inoperative and lowered lake levels have made some boat docks useless. Overhead sprinkler irrigation has been used for irrigation and cold protection of cut foliage crops since the 1960's. Using water application rates of about 0.84 cm·hr-1 growers were able to reliably supply product on a year-round basis. Water management district developed regulations mandate that certain water saving methods be implemented prior to the issuance or renewal of consumptive use permits and limit water application rates for cold protection to 0.56 cm·hr-1 under certain circumstances. Research on irrigation scheduling and various cold protection strategies have and are being conducted to allow further reductions in water use during the production of cut foliage crops.

Free access

Four spunbonded crop covers were evaluated for use with and without irrigation for cold protection of leatherleaf fern [Rumohra adiantiformis (Forst.) Ching]. Heavier and less porous covers provided the most protection when used without over-the-crop irrigation. However, differences in cover weight and porosity did not affect temperatures under covers when over-the-crop irrigation was applied. Damage to immature fronds was decreased by 75% to 99% when the covers were used alone and by 98% to 99% when the covers were used with over-the-crop irrigation. Covers had no effect on frond vase life.

Free access

Established leatherleaf fern was grown for one year in a glasshouse in intact soil columns (Astatula fine sand, 21 × 61 cm) contained in drainage lysimeters. Columns were fertilized at rates of 224, 448, or 672 kg N ha-1 yr-1 using controlled-release (CR) fertilizer, either 360-day (360CR) or 180-day (180CR) term, or weekly applications of liquid (L) fertilizer. Water use, yield (number of harvestable fronds) and average frond weight increased linearly with increasing fertilization rate and more fronds were produced using L than CR fertilizers. Frond color measurements paralleled yield results. During cool weather when vase life is greatest, fronds from L fertilizer lysimeters lasted longer than fronds from CR treated plots. During warmer weather, treatments had no effect on vase life. Nitrate nitrogen (NO3-N) leaching increased with fertilization rate and exceeded 10 ppm in leachate from the L and 180CR treatments at all application rates. NO3-N in leachate from 360CR lysimeters never exceeded 8 ppm at any application rate.

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Water is an economical source of heat to prevent cold damage to certain crops; however, ways to reduce the quantity of this limited resource required for cold protection need to be developed. Rapidly rotating (6 rpm) wedge-drive impact sprinklers (conventional practice) were compared with a rotary action spray head and patented slow-rotating stream sprinklers for cold-protecting a subtropical crop {leatherleaf fern [Rumohra adiantiformis (Forst.) Ching]} growing in shadehouses. Treatments were applied in a 3 × 3 latin square design to nine 29 × 29-m post- and-cable shadehouses covered with woven polypropylene shade fabric designed to provide 73% shade. Temperatures in each shadehouse were monitored 45 cm above the soil surface using four constantan–copper thermocouples. Ambient temperatures and wind speeds were monitored using additional thermocouples and an anemometer at a nearby weather station. All sprinklers had 2.8-mm orifices, were operated at 0.25 Pa, and applied 0.5 (rotating stream, rotary) or 0.54 (wedge-drive) cm·hr–1 of water. During an advective freeze with windspeeds up to 19 m·s–1 and temperatures to –2°C, there were no temperature differences due to treatments. During a radiational freeze with readings below –2°C for over 12 hr and a low of –5°C, all three irrigation systems maintained thermocouples at about –1°C. No significant damage to mature fronds were detected. Percentage of immature fronds damaged was not affected by treatments and ranged from 11% for rotary to 43% for the wedge-drive sprinkler treatments. The two newer sprinkler designs (rotary action spray head and patented slow-rotating stream) provided satisfactory protection equivalent to the industry standard (wedge-drive) while using about 10% less water.

Free access