Annual Ryegrass and Nitrogen Uptake

A recent article by Farm Journal writer Darrel Smith, talked about a nitrogen study with different cover crops, and the importance in managing the burn down so as to maximize nitrogen uptake by corn and beans.

Farm Progress worked with Dan Towery and Ken Ferrie on the project. The following paragraphs are from the article. To read the entire article, click above on the Farm Journal highlight.

Annual ryegrass is a nitrogen scavenger, and has a relatively low C/N ratio—as low as 17/1 if you burn it down early,” Towery says. “Because the annual ryegrass was planted into wheat stubble, it may not have taken up much nitrogen because there wasn’t much in the soil to begin with—possibly less than 20 lb. per acre. I’ve seen annual ryegrass take up much more nitrogen than that—90 lb. to 120 lb. per acre, depending on field history.

“The low C/N ratio of annual ryegrass means that typically 50% to 75% of that nitrogen becomes available to corn plants six to 10 weeks after it is killed in the spring—in late June or early July,” Towery continues. “Often, corn fields following an annual ryegrass cover will be dark green, or even almost black in July. That has to be from the nitrogen mineralized from the annual ryegrass, and the absence of a carbon penalty, resulting from the crop’s low C/N ratio.


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