Use center pivots to spoon-feed N to your cornfields
After above-normal spring rain in 2011, Doug Ziemke of Waco noticed yellowing in several cornfields. Tissue samples verified his suspicion that some of his preplant nitrogen had leached below crop roots.
That prompted the York County farmer to equip two center pivots to apply nitrogen, the first time he had ever used his irrigation systems to do so. He made one pass with each pivot to apply 0.30 of an inch of water and the nitrogen solution. For 2012, he intends to apply less anhydrous ammonia preplant on these two circles and possibly a third one, and instead spoon-feed the remaining nitrogen by fertigation.
“I was real satisfied with the results in 2011,” he adds.
Practice used before
The practice of chemigation — the overall term for applying pesticides or fertilizers through center pivots — peaked in the 1980s and early 1990s when farmers treated for corn borer infestations. The practice subsided with the introduction of transgenic hybrids with Bt traits for corn borer control.
Richard Ferguson, University of Nebraska soils specialist, believes more farmers ought to consider applying nitrogen through pivots to spoon-feed N, especially since 80% of Nebraska’s 8 million irrigated acres is watered by sprinklers. “We should be taking more advantage of fertigation. We are in a good position in Nebraska to do so,” he says.
“It is an efficient method of supplying part of the nitrogen needed by the crop near the time of maximum nitrogen uptake,” Ferguson says. “It’s also a stewardship practice by preventing nitrate leaching to the groundwater.”
While it varies by hybrid, the most rapid period of uptake is between the eight-leaf stage and tasseling, a time when a steady supply is critical for optimum yield.
Bill Kranz, UNL irrigation engineer who coordinates the chemigation certification training each year, has seen a moderate increase in the number of farmers or other operators the past two years taking the two- to three-hour course to become certified chemigation applicators.
The Upper Big Blue Natural Resources District, based in York, encourages use of fertigation, says Rod DeBuhr, district water department manager. Nebraska’s NRDs, under the 1987 Nebraska Chemigation Act, are charged with inspecting irrigation sysems that are equipped with several mandated safety components when applying pesticides or fertilizer.
Ziemke opted to have the United Farmers Co-op, based in York, do the actual chemigating through a new service it started in 2011 to foster use of fertigation. Eight of UFC’s employees became certified by taking the UNL course, eliminating the need for farmer/customers who sign on for the service to become certified themselves.
UFC built two mobile trailers, each of which carried a nitrogen tank, injector pump and a couple of safety components to the pivot site. And one of UFC’s employees certified in chemigation managed the actual fertigation application.
Farmers pay a fee for the service, and they also are responsible for purchasing the main check valve that prevents backflow from the pivot to the well in case of a system shutdown. Another component required of farmers is a simultaneous interlock system.
“When we frontload most of our nitrogen through preplant and starter, there are too many things we can’t control,” says Andy Bowman of UFC. “Fertigation is one of the solutions to this problem.”
This article published in the February, 2012 edition of NEBRASKA FARMER.