use of both water and fertilizers; however, the initial cost of automated subirrigation systems is high ( Ferrarezi et al., 2015a ; Thomas, 1993 ). Ebb-and-flow subirrigation is relatively cheap and easy-to-use compared with other subirrigation
, 1977 ). The runoff of water, fertilizer, and pesticides resulting from these irrigation methods is a potential risk to the quality of the environment in proximity to a greenhouse operation. Subirrigation, and in particular ebb and flow, systems are more
plants were sprayed with 0.4 g·L −1 of 8.5% acetamiprid (TriStar; Cleary Chemicals LLC, Dayton, NJ) to exterminate caterpillars. Plants were grown on 10 ebb-and-flow benches with 1.52 m length × 0.91 m width × 4 cm height (MidWest GroMaster, St. Charles
products to reduce algae while limiting effects on growth, including plant height, flower number, net CO 2 assimilation, SPAD, and fresh and dry weight of pepper ( Capsicum annuum L.) and tomato plants using an Ebb and Flow hydroponic system
Univ. of Georgia. Mention of brand names is for informational purposes only and does not imply its approval to the exclusion of other products that may also be suitable. We would like to thank Sunbelt Greenhouses for their donation of plant material and
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.
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.
The root rot fungus Phytophthora parasitica is known to be very destructive to annual vinca (Catharanthus roseus). Phytophthora produces motile zoospores which swim freely in water, posing a special threat to crops grown using a recirculating water supply. Vinca were transplanted into 7 cm square pots containing a sphagnum peat:perlite medium. The medium was inoculated with the pathogen and plants were then placed in one row on each ebb and flow bench. Untreated vinca were placed in six additional rows on the benches. Separate benches were used to space plants at a distance of either 1 cm or 4 cm between pots. Plants were harvested biweekly over a six week period and tested for presence of Phytophthora. Cumulative results of root sampling revealed pathogen movement to 60% of untreated plants spaced at 1 cm, and to 30% of those spaced at 4 cm. Severe root injury (injury to root system ≥ 25%) was exhibited in 36% of the closer spaced plants, compared to 13% of those spaced at 4 cm. Phytophthora zoospores were detected in one tank which was used to irrigate plants spaced at 1 cm. Closer plant spacing enhanced the pathogen's ability to infect healthy plants.
The negative effects of nutrient runoff on the environment has come more to the forefront of greenhouse issues in the past few years. Alternative irrigation systems that reduce or eliminate runoff that are widely used in Europe have not yet gained much popularity in the southeastern United States, in part due to a lack of available information on their use. One such system is ebb-and-fl ow, which is a completely closed recirculating system, having no runoff whatsoever. In order to learn more about optimum growing practices using the ebb-and-fl ow system for bedding plants, marigolds and sunflowers were grown under a variety of conditions. After a 6-week period, pH of growing media of both marigolds and sunflowers decreased by 1, while EC increased by ≈1 dS/m. There were also significant differences in EC due to the different media types. The soilless medium with the highest percentage of vermiculite and lowest percentage of pine bark had the highest EC. Different types of fertilizer and fertilizer rates will be discussed, as well as interactions between fertilizer and media.
; however, studies have shown over-watering by 10% to 30% is recommended to prevent salinity buildup in the root medium ( Mastalerz, 1977 ). By comparison, subirrigation, and in particular ebb and flow, systems use water more efficiently ( Dole et al., 1994