U of I to lead study on interseeding, management strategies on manure emissions

KIMBERLY, Idaho — A planned University of Idaho-led research project aims to maximize the nutrients from dairy manure applications that remain in farm soils for use by crops while minimizing the loss of nutrients as air and water pollutants.

Farm fields surrounding dairies often receive the heaviest applications of dairy manure, which is bulky, heavy and costly to transport.

In excess, manure can pose environmental challenges, leaching nutrients into streams through runoff and emitting greenhouse gases such as nitrous oxide.

The researchers will test several irrigation and manure application rates and timings, in addition to trials with corn and alfalfa grown simultaneously in the same field, known as interseeding, to develop management recommendations that will help farmers use manure more effectively.

The greatest potential for nutrients to be lost from manure as pollutants occurs following harvest, when soil lacks cover and living roots. The interseeding trials should eliminate that period of bare soil. Corn will grow to a few inches tall before alfalfa is planted in the furrows. The longer established corn roots will draw nutrients from deeper within the soil profile, avoiding competition with the alfalfa. After harvest, alfalfa will continue growing and consuming nutrients, quickly filling in the gaps where the corn rows had been.

Researchers expect to see reduced emissions, improved water infiltration and higher yielding alfalfa, which will have more time to grow, in the interseeded plots.

“Interseeding is something that has been studied but we don’t have many farmers adopting it, so we hope to share more information about it and tell more farmers that this is something that makes sense,” said Gilbert Miito, an Extension air quality specialist who is the project’s principal investigator. “We have studies on water use, we have studies on nutrient use, and we have studies on emissions, but we don’t have a lot of studies that tie everything together.”

The research will be conducted over three growing seasons, funded by an anticipated $1 million collaborative grant — $750,000 to U of I and $250,000 to Utah State University (USU) — from the the Idaho Dairy Environmental Action League Research Foundation. A committee of Idaho dairymen selected the project from several research proposals.

U of I will oversee 62 research plots with varying levels of manure or conventional fertilizer, including control plots with no supplemental nutrients, planted at the USDA Agricultural Research Service’s experimental farm in Kimberly. Dairy forage crops in the study will rotate among corn, alfalfa or interseeding. The team will place sensors and runoff traps in the experimental fields to monitor nutrient loads in runoff, gas emissions and soil moisture throughout the growing season.

USU will track 32 research plots, applying a consistent rate of 12 tons per acre of manure but varying pivot irrigation levels.

U of I modeling experts will use the data to build models to guide irrigation, manure application and intercropping management to avoid significant spikes in nutrient leaching and emissions.

“We have some general nationwide standards, but we don’t have anything that’s specific to the Northwest,” Miito said. “If we can get some numbers and say that if you increase your manure by this much, this is how much more nitrous oxide you’ll emit, then we’re getting some answers.”

The team will comparing its findings with outcomes from a commercial field in Wendell, where the farmer will interseeding a half pivot of his field with corn and alfalfa, using a separate funding source. Magic Valley food processing companies, including Chobani, have expressed strong interest in the research.

The U of I research team also includes Jared Spackman, Idaho Barley Commission endowed barley agronomist; Emily Bedwell, Extension irrigation specialist; Erin Brooks, a professor in the Department of Soil and Water Systems (SWS); Meetpal Kukal, assistant professor of hydrologic science and water management; Pramod Acharya, Extension specialist of forage agronomy; and Johnny Li, an assistant professor in SWS.

Media contact  

Gilbert Miito
Assistant professor and Extension specialist
208-736-3600
gmiito@uidaho.edu