COLLEGE STATION — Plant nurseries and greenhouses — two of the state’s largest consumers of water — are stepping up and responding to the challenge of conserving water. A study at Texas A&M University may help the owners decide which of these systems is the best and most efficient for them.
Subirrigation systems allow plant growers to apply water to a trough or moist mat that the plant is sitting on or in. Moisture is absorbed from the bottom of the plant; excess water drains out of the tray and is recycled back through the system. It is a system already used extensively in greenhouse production in Holland where water is at a premium, said Dr. Dave Reed, associate head, department of horticultural sciences, Texas A&M University.
Here in the United States, Texas A&M is studying fertility and salinity problems that commonly occur with this type of system. Growers have to totally readjust their fertility programs. However, Reed estimated that growers can cut their water and fertilizer use in half, depending on how much water they used before installing the system.
Since the water is often recycled back through the system in a greenhouse, “we have to be very careful in the amount of salts and fertilizers that get in the water, because if we over-fertilize, the salts in the recycled water would get (too) high.”
Reed found the problems are best dealt with by using good- to moderate-quality water, cutting fertilizer rates in half and by periodic leaching. Another restriction is the size of plants that can be watered with the system — large plants do not grow well. The plants can only be flooded to about 1 inch deep, so it cannot be used on a plant that is greater than 6 to 8 inches in height.
The major drawback of the system is the cost of materials and installation, since it is still such a new industry in the United States.
However, Kevin McGuckin of Indian Creek Nursery near Brenham is sold on the system. When he first started his wholesale nursery business in the early 1990s, he and his workers watered all of the plants by hand or with drip tubes.
After visiting with Texas A&M horticulture professors and horticulturists with the Texas Agricultural Extension Service, he decided to put in his first ebb and flood system — a type of subirrgation — in a 3,000-square-foot house in 1995. He then began building another house the same size and then came down with infectious mononucleosis. His wife and workers had to take on all the work.
“I saw how much easier it was to take care of the house with the ebb and flood system,” he said. “And I made the decision to go all ebb and flood.”
He designed the system for the new greenhouse while he was still recuperating in bed.
Since then, he has added another 15,000 square foot house. That system paid for itself in added production in four and a half years.
“Efficiency and production were the reasons to go with it, but water savings and runoff reduction are added benefits,” he said.