A crowd of farmers took time from busy fall harvest schedules to attend a manure field day in Washington County, Maryland, and they weren’t disappointed. Retired dairy extension agent Stan Fultz opened the day with an introduction to the featured topic — manure injection.
“Many of you have been incorporating manure,” said Fultz. “What we were looking for was a piece of equipment that could be used on continuous no-till ground. For this grant, we worked with a farmer who has been continuous no-till for 40 years. When the injection requirement came along, he was upset because it would have required tillage. He didn’t want to do that but still wanted to maximize nutrients.”
Manure injection is becoming a viable option for Maryland farmers who are required to either inject or incorporate manure within 48 hours of application. However, farmers in other states are realizing the benefits of manure injection.
Fultz noted that the farmer had highly erodible land and wasn’t required to incorporate quite yet, so he started looking for alternatives. That’s where the Veenhuis came in. Fultz described the Dutch-made injector as a machine that results in very little soil disturbance, and compared it to going through the field with a no-till grain drill or a no-till corn planter. Fultz added the Veenhuis is one of several brands of equipment that can accomplish good injection.
The Veenhuis, which is widely used in Europe, was one of the injectors demonstrated during the field day and impressed everyone who watched it work on both corn stubble and alfalfa. The machine was purchased with the help of a grant through the Catoctin & Frederick Soil Conservation District, Sustainable Chesapeake, University of Maryland Extension and Maryland Department of Natural Resources. It’s available for use through cost-share programs.
Although nutrient management regulations vary from state to state, the goals concerning land application of manure are consistent: to use valuable nutrients in manure efficiently without jeopardizing water quality. Dr. Trish Steinhilber, extension associate with the University of Maryland department of Environmental Science and Technology, says injection is one good option for getting manure into the ground and preserving nutrients.
“If we leave manure on the surface, a certain portion of that manure is in the form of ammonium, which can transform to ammonia, and if it’s on the surface, it can be lost,” said Steinhilber. “If we inject, we can capture more available nitrogen.” Steinhilber has looked at the analysis of hundreds of dairy manure samples over the years, and she can give a fairly good estimate of how much nitrogen a farmer would save with injection.
Why not chisel manure in like farmers have been doing for years? Steinhilber says recent emphasis on soil health and the biological and chemical complexities that occur in soil have changed the thinking on how to most efficiently use manure to preserve soil structure. “If you’re disturbing less, you’re doing less damage to the residue cover,” she said. “So you’re protecting the soil surface. You aren’t breaking up soil aggregates as much, and the overall effect is minimal erosion. You also minimize disturbance below the soil that contributes to disturbance of soil microbes and breaking up of macropores. Over time, the less soil volume that’s being torn up, the closer you are to no-till in terms of infiltration rate and preservation of soil organic matter, soil structure and stable aggregates.”
There’s also the issue of odor, which can be an issue for farms located near development. “Injecting minimizes odors significantly,” said Steinhilber. “Work with olfactometers (equipment that measures what odors humans can detect) shows that there’s only slightly more odor with injection than with spreading and incorporation.”
In addition to than keeping neighbors happy and capturing nitrogen, there’s another reason to inject. “There’s less phosphorus per pound of nitrogen,” said Steinhilber. “A lot of manures have more phosphorus in relation to nitrogen in terms of what crops need and will take up, so if you inject and capture more nitrogen, there is less phosphorus per pound of nitrogen. That’s something we should be concerned about with the new rules (for Maryland) that will be phased in over the next five or six years. By injecting and capturing nitrogen, we are extending the amount of time we can use manure on that field without running into phosphorus restrictions. If soils are not phosphorus restricted now (fertility index values less than 150), work to keep it that way to make your life easier. Injecting helps accomplish this.”
Injecting manure also reduces the phosphorus in runoff. “Leaving manure on the surface leaves it open to soluble phosphorus being dissolved during a rainfall event,” said Steinhilber. “If it’s under the surface, you’ve eliminated that.”
Steinhilber says if someone who has available dairy manure wants to supply all plant available nitrogen from manure, if that manure is injected, there would only be 110 pounds/acre of phosphate applied. “If you surface apply, you’re applying 170 pounds of phosphate/acre,” she said. “If you realize that 150-bushel corn will only take off 60 to 65 pounds of P2O5, I’d rather have the lower application than the higher, because it’s going to cause the phosphorus soil test level to go up at a much slower rate and give me more years I can use that field for its nitrogen value without running into phosphorus restriction.”
Although research shows clear benefits of injection, it’s difficult to place a value on the process. Steinhilber says some farmers are applying liquid manure themselves, and others are having it custom applied. For those who are having it custom applied, it’s important to communicate the appropriate application rate to the applicator. “You are just as responsible for the rate that is applied as the custom applicator is,” she said. “If you don’t communicate to the operator what the rate in your plan is, you can’t expect it to be applied accurately. She suggests providing a copy of nutrient management recommendations to the custom applicator.”
The topic of manure injection goes hand in hand with soil health and reduced tillage. “We know there are benefits to leaving the soil as undisturbed as we can,” said Steinhilber. “Not only are we losing nitrogen when we let it volatilize, but it’s also going next door on the wind. We also want to keep phosphorus so we don’t get into phosphorus issues.”