Improperly applied fertilizer to newly placed sod may result in nutrient runoff into the water supply, but just when is the best time to apply fertilizer and what kind is the best for new turf?
Aiming to answer those questions is a team of scientists from Texas A&M AgriLife Research: Dr. Jacqui Aitkenhead-Peterson, assistant professor of urban nutrient and water management; Dr. Ben Wherley, assistant professor of turfgrass science and ecology; Dr. Richard White, professor of turfgrass physiology and management; and Jim Thomas, senior research associate, all with the department of soil and crop sciences at Texas A&M University.
"We are looking at the establishment of turf and what nutrients are coming off of that turf in the water runoff after irrigation or rain events," Peterson said.
The study, sponsored by The Scotts Miracle-Gro Company, is being conducted at the Texas A&M Urban Ecology Field Laboratory on F&B Road, College Station.
The runoff facility used in the study took a year to construct and consists of 24 individual plots, each 13 feet wide by 27 feet long on native soil that has not been disturbed until planting, all on a 3.5 percent slope. The plots are isolated with vertical plastic barriers between them so that water applied either infiltrates into the ground or runs down the hill where it can be sampled for nutrient content.
"We have the capability of irrigating where we can force a 'rainfall event' but the equipment is always on to also record any naturally occurring events," Peterson said.
The study was planted on Aug. 8 and the first event measured was the following day, they said. The plots are planted to St. Augustine grass, which is most commonly used in new construction in Central Texas, Thomas said.
They will test and compare runoff from plots with no fertilizer to those receiving several different nitrogen sources, applied either immediately or weeks after sod has been laid and rooted in, Thomas said. After a month or two, they will be able to gather conclusions and information on the results.
"This will be the largest runoff facility of its kind in Texas, if not in the country," Peterson said. "We hope to have a lot of long-term projects looking at management practices, water conservation and nutrient conservation."
Turfgrass, she said, is the largest irrigated crop in the country. It is important to have recommendations for the industry.
"Considering the amount of sites that are sodded during new construction, it is important to understand what nutrients are coming off in runoff that could impair surface water quality," she said. "Hopefully we can make recommendations towards science-based best management practices for sod establishment after our study."
Thomas said if turf is managed properly, the fertilizer won't run off and the lawn will still be green. So there is no reason to over-apply. At the same time, he said, abandoned lawns can have as much or more erosion and nutrient loss than a well-maintained lawn.
"Our goal at the end of the day is to understand how these different manipulations of fertilization and irrigation affect the runoff volume and nutrient load and provide recommendations and best management suggestions," Peterson said.