Manage irrigation, you’ll control pollution


In the face of a new government-imposed pollution diet to regulate nitrogen, phosphorus and sediment entering the Chesapeake Bay and all its tributaries, growers will want to make sure all of their efforts are recognized and accounted for. Dr. John Lea-Cox, professor and nursery research and Extension specialist at the University of Maryland, offered updates on water and nutrient management during the second day of the Chesapeake Green symposium in Linthicum, Md., Feb. 10.
After reviewing the extent of the Chesapeake Bay watershed, the definition of TMDL (Total Maximum Daily Load) and the efforts so far to clean up the bay, Lea-Cox said "We are now at Phase II." Loading is now divided by smaller geographic areas, with allocation of nitrogen, phosphorus and sediment down to the county level. Maryland recently filed plans with the EPA, but the counties, according to Lea-Cox, are saying "That's well and dandy, but we cannot comply without federal assistance."
Lea-Cox noted in the allocations by county that agriculture is divided into agronomic and nursery categories. He's wondering how nurseries got segregated out. "We're giving information to them and educating them as to what a nursery is, because their data is based on the ag census data." With woody ornamentals grown in both field and containers, there is a disconnect, he suggested, between the data and what growers are actually doing.
"It is my job and John (Majsztrik)'s to ensure the Chesapeake Bay Modelers have that granularity in their models. There's a huge disparity in rates. I don't mind being (held) accountable, but let's have the right numbers," Lea Cox said.
"They have no idea of the (best management practices) we apply in the nursery. They know nothing about grass strips, control release fertilizer, riparian buffers or drip irrigation. Our job is to make sure all these BMPs are associated, down to the county level if we can."
As researchers, their futuristic strategy is to get a handle on water management, "then we won't need to work about nutrient management. It's all about the runoff and leaching. Control those and you'll reduce the downstream issues from there."
He noted that small growers make up the majority of growers in Maryland — 60 to 70 percent of them — but manage only 30 to 40 percent of the acreage. "Most are constrained by labor; almost all are limited by time.
"We want to provide the most time- and cost-effective systems for providing detailed information to growers for their own operations."
To that end, he and his colleagues are working on sensor networks. Few growers are monitoring practices; many consider that they are already implementing best practices. One grower in the audience said he travels 10 miles per day in monitoring.
"Growers won't change their practices unless you convince them that it will improve current practice and profitability," Lea-Cox said.
The sensor network consists of a battery powered box which logs data from sensors. Installed on different parts of the farm, they transmit data to a local computer or, more recently, making use of an Internet-based approach, information is sent to a server in "Cloud" which can be accessed online.
Several growers in the session acknowledged they had a sensor system on their farm.
A new development is the ability to use the data to make a decision to turn irrigation on or off.
Lea-Cox emphasized the importance of growers cooperating with the researchers. "We aren't doing stuff without running it by them and conducting tests in a commercial environment. Sometimes there is a disconnect between the researcher and reality." He noted there were also teams in Colorado and Georgia doing similar research.
One tree grower in Maryland has been cooperating with the university for four years. They are working to optimize the amount of water applied so as to increase the water available for other plants. Knowing what tree uses how much water, he can allocate water to trees that need more and cut back on others. Trees growing in the ground will slow their growth rate if they don't get enough water. "We want trees to be as happy as can be," he said.
Using sensors, he was able to cut back one block of trees from two hours per day to much less and allocate the water to another block of trees during a drought.
A container nursery in Georgia was accustomed to a 30 percent loss of its gardenias to pytophera. The cost was built into the company's price. By fine-tuning irrigation, the whole production schedule was moved forward by six months and the increase in profits, due to reduced production time and elimination of the disease problem, amounted to $1.06 per square foot per production cycle. Lea-Cox said, "All they did was irrigate based on sensor data. The water manager (then) watered all the other blocks based on the research plot."
For more information, Lea-Cox recommended visiting