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Study digs into manure

Previous studies have been shorter, involved fewer crops


Capital Press

The Idaho Barley Commission has made a sizable funding commitment toward an eight-year study that should provide the first long-term analysis of how manure affects crops commonly used in southern Idaho rotations.

IBC will award University of Idaho Extension soils specialist Amber Moore $16,000 for each year of the project, which should cost about $90,000 per year to complete.

Moore has also approached the Idaho Dairymen's Association and the state's sugar beet, wheat and potato commissions seeking financial assistance. Her study will address lingering questions among growers about long-term manure use including: optimal manure application rates, the need to supplement with fertilizer, the effects on crop diseases, weeds and insect pressure, improvements in soil organic matter, the potential accumulation of excess levels of copper sulfate and salt and nitrate leaching.

Moore said her past manure studies have been conducted on a much shorter term and focused on more specific issues.

"Some of these changes take four, or five or even six years before you start to see them," Moore said. "My hope is with this research, people will get more faith with using manure as a fertilizer and they'll use it more wisely and effectively. Right now we have a lot of growers who put it on and they don't have a strong sense of what it's going to contribute."

On a 5-acre USDA field in Kimberly, Idaho, Moore will plant control plots that receive no fertilizer, plots that receive traditional fertilizer applications and plots that receive 8, 16 or 24 dry tons of manure applied every year or every other year. Each scenario will be planted in two different crop rotations with wheat, potatoes, barley and sugar beets so data for each crop is available every other year. Ten other USDA Agricultural Research Service and UI scientists will help investigate specific questions.

"My expectation is the overall soil microbial health will improve, and with increased activity of soil microbes, you should have decreased disease pressure," said UI Extension cereals pathologist Juliet Marshall, one of the collaborators.

Moore also hopes to address growers' concerns that excess late-season nitrogen caused by the nutrient's slow release from manure could lead to undesirably high proteins in malting barley or low sugars in sugar beets. Another concern is that manure may spread weed seeds consumed by cattle.

IBC Chairman Dwight Little said manure is abundant from dairies in Magic Valley, and Miller-Coors contracts heavily in that area for malting barley.

"There's been a year or two-year study but never a longtime rotational effect study on manure being used in rotation with barley," Little said. "I think some of the growers are already using it, but they don't know the consequences of long-term use."

Idaho Dairymen's Association executive director Bob Naerebout said his organization will give careful thought to the study before making an eight-year commitment.

Moore said sugar beet growers suggested the study. The Snake River Sugar Beet Research Committee and the Idaho Potato Commission both have meetings scheduled for later this month during which they'll discuss the project.


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