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Cover Crops' N Benefit Is Tough To Calculate

Cover Crops' N Benefit Is Tough To Calculate
Cover crops can build N levels, but it takes time and effort to see results.

Improved soil health, reduced compaction, increased water holding capacity … there are a lot of great reasons for implementing cover crops. But, will any of them actually boost profit?

Dan Towery says most farmers immediately think of cover crops' nitrogen benefits as the quickest route to payback. And, yes, an N boost does pay dividends.

After using cover crops for five years, Towery says farmers can typically cut N rates by an average of 50 lbs per acre for the crop year.

"That will pay for your cover crop seed easily," he adds.

EXPERIENCE PAYS: Walton, Ind. farmer Cameron Mills has been cover cropping since 2005 on his 3,500-acre farm.

Walton, Ind. farmer Cameron Mills has been cover cropping since 2005 on his 3,500-acre farm. The last few years, he's started running the numbers to see if he can reduce N rates.

This year, he reduced his annual N application from 200 lbs to 170 lbs per acre. He'd like to go even further.

"This year, we put out check plots where we sidedressed 100%, 75% and 50% of the normal rate to see what the yield response looks like," he adds.

If Mills is happy with the results, he wants to shave another 20-25 lbs of N off his program.

"I think we can get down to 140 lbs, but we're not there yet," he adds.

After years of improving the soil with cover crops, Towery thinks farmers will be able to cut N rates even more drastically. He expects after 15 years or so, some folks may be able to put a 200-bushel corn crop in the bin with only 50 to 75 lbs of total N.

Scavenging for N
After last year's drought, Mills saw even more evidence that cover crops were pulling their weight in the crop rotation.

For 2012, Mills layered in 170 lbs. of N per acre. Thanks in large part to his healthy no-till/cover-crop soil, he harvested a 165 bushel corn crop despite the severe drought.

To test cover crops' nitrogen-holding abilities, Mills set up numerous plots following the 2012 harvest. His goal was to see if cover crops held left-over N for the 2013 crop.

One plot had 116 lbs of N left over in December 2012. Without a cover crop, the plot's N level had dropped to 30.6 lbs by April 13.

In the same field, Mills aerial seeded annual ryegrass. The December soil test revealed only 12 lbs of N per acre. However, tissue tests on the annual ryegrass came in at 78 lbs/acre.

The following spring, soil tests came back at 10 lbs, while tissue tests increased to 93 lbs.

 "That told us that the annual ryegrass scavenged the nitrogen and held it all winter long," Mills says. "In the one plot, we lost about 100 lbs of nitrogen by the time we planted corn. With the annual rye, we were able to hold onto that nitrogen."

Mills calculates the nutrient storage alone netted him $97.81 per acre. So, yes, cover crops can contribute to the bottom line.

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