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Recycled feedlot nutrients help second crop

Rye silage is more than just another feed option for thousands of beef cattle in northwest Iowa feedlots. The silage also solves issues of utilizing surplus nitrogen, preventing erosion and runoff, and effectively utilizing nutrients and land.

When good northwest Iowa farmland sells for more than $20,000 an acre, it makes sense to figure out a way to grow crops nine months out of the year instead of four, says Joe Lally, an Iowa State University nutrient management specialist. In the past five years, he and Tom Moorman and Jeremy Singer with USDA Agricultural Research Service have worked with feedlot owners, who have more than 1,000 animals and are dealing with surface runoff pond requirements by the EPA.

“Most of the feedlot owners hated the regulation to create surface ponds for the effluent. They thought it was an extra management chore and a huge capital expense,” Lally says. “Now, they see it as an advantage in crop production and increasing feed inventory.”

The recipe for success includes center pivot irrigation, short-season silage corn, and a rye cover crop harvested in spring that utilizes nutrients in the effluent.

“Irrigation isn’t very common here. We haven’t needed it, but we’ll probably see more systems built to manage water from feedlots,” Lally says. 

Ingredients for success

The solution begins by selecting 110-day high-yield silage corn varieties so the crop can be harvested early enough to plant a cover crop of rye – preferably by October 1 and no later than November 1. Next, it’s important to establish good rye seed germination by applying .5 inch of effluent through irrigation and then applying additional effluent and water as needed in a timely manner with fall and spring applications. 

In spring, instead of killing rye as is common in the area, it is allowed to grow and then harvested as silage. If the spring is wet and the harvest is late, corn might be planted as late as June 10, which is why short-season varieties are necessary.

Late planting in 2012 actually benefited feedlot owners in northwest Iowa. Though the area only received 20.5 inches of rain from October 1, 2011, to October 1, 2012, compared to a 30-inch average, the timing of the rains was perfect in August when corn was pollinating. 

An added 4½ inches of effluent was applied to corn, and yields were impressive for 2012: 10 tons per acre of rye (13.5% crude protein) and 180 bushel-per-acre corn. 

“We are utilizing extra nitrogen to grow rye that we have available through the effluent and not cutting our corn crop short,” Lally says. The rye uses most of the nitrogen and holds the rest in the root zone for corn. 

“Producers are getting value, and they’re recycling nitrogen into their cattle that they’d otherwise be losing,” Moorman says. “They’re getting an economic benefit and saying their soil has improved. The soil is better aggregated, and because the cover crop uses moisture, they’re getting better infiltration.”

The cover crop also prevents erosion and helps use excess effluent and water in wet years. 

Setting up a system and learning how to manage the effluent and water through irrigation takes some trial and error, notes Lally. The timing and amount of effluent/water applied varies each year based on rainfall and the amount of effluent available in the storage ponds. 

“There are huge variations in Iowa. With a system like this, we have a better opportunity to manage water,” Lally says.

Scope of potential

It’s something feedlots throughout the Upper Midwest and as far west as Kansas can incorporate, as well as anyone interested in double cropping or grazing newly calved pairs on spring grazing. Lally recommends seeking advice from land-grant university Extensions and engineers to come up with the right formula.

For example, one producer with 7,000 cattle has a 42-acre feedlot in northwest Iowa. About 120 irrigated acres seem to be about the right amount to deal with effluent (and rain water) that flows into the surface pond. 

“A 40-acre center pivot runs about $1,000 an acre, which is cheap compared to buying more dirt,” Lally notes.

It’s a worthwhile investment that takes growing cover crops to the next step, which is growing a second crop of feed. Besides rye, wheat and triticale have also worked well, Lally adds. 


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Joe Lally


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