Frances Gould, McClure, Olivia J. | 8/14/2015 2:14:06 AM
As concern about the future of water resources grows, researchers at the LSU AgCenter’s Red River Research Station in Bossier City are identifying ways to help farmers improve irrigation efficiency.
Agricultural irrigation has steadily increased in recent decades, reaching about 1.1 million irrigated acres in Louisiana in 2013, which is the most recent data collected by the U.S. Department of Agriculture. While irrigation helps good crop yields, it can also cause runoff of valuable soil nutrients, which cost farmers and the environment in the long run.
Stacia Davis, AgCenter irrigation engineer, is studying how to schedule irrigation applications using two types of sensors – one that provides a percentage of the water volume per unit of soil and one that measures water pressure.
Sensors are not common in Louisiana, Davis said. But scheduling irrigation based on water needs identified by the sensors has benefits over irrigating on a calendar schedule regardless of moisture in the field.
"You can save money and save water by running the pump less and potentially improve your water quality and soil health," Davis said.
Over-irrigating with poor quality water can lead to accumulation of salts that create soil salinity issues and lower fertility, said Syam Dodla, AgCenter agronomist. He is trying to find out how farmers can irrigate less but still reap the benefits.
Most farmers in Louisiana use furrow irrigation, where water is pumped onto the field and floods the furrows between rows. To save water, some farmers irrigate every other row middle. While this can minimize runoff, it can also affect nutrient uptake, which could affect yields.
Soil type also affects nutrient uptake because water seeps through clay soils at a different rate than through sandy soils. Depending on the soil type, rows may need to be narrower to ensure enough water and nutrients reach the crop roots, Dodla said.
Dodla is also studying how organic fertilizers such as poultry litter can be integrated with inorganic fertilizers and irrigation practices.
"North Louisiana has excess animal waste from poultry and cattle," Dodla said. "Some farmers use it already. The benefit is that it’s cheap and has to be disposed of anyway, and it has many beneficial plant nutrients that can be used as a source of fertilizer for crops."
One of those nutrients – phosphorus – can move readily with irrigation. It can run off the fields and create water quality issues downstream, so farmers should apply poultry litter carefully and incorporate it into the soil soon after application, Dodla said.
Because poultry litter holds water, it’s also important to make sure enough water is still available for crops. Dodla wants to find out how irrigation should be altered for farmers who use organic fertilizers.
Changyoon Jeong, an AgCenter water quality specialist, is examining how water quality can affect soil salinity and overall soil health.
Some farmers in the Shreveport area irrigate using water from Red Bayou, a Natural Resources Conservation Service project that pumps water from the Red River into smaller pools. While Red River water isn’t known for high salt concentration, Jeong said, Red Bayou collects the runoff from nearby farms. Farmers then irrigate with that water, which is often laden with salts and plant nutrients.
"High salinity levels in soils make it harder for roots to uptake nutrients, which could decrease yields," Jeong said.
He wants to find out how the water from Red Bayou is affecting different soil types, crop yields and soil fertility in northwestern Louisiana.