The No. 1 question Scott Wohltman gets asked by growers using cover crops is: How much nitrogen (N) am I getting from cover crops, and when will it be available?

The answer isn’t cut and dry, says the certified crop advisor and agronomist with La Crosse Seed. But in a recent No-Till Farmer webinar, Wohltman explained how much N growers can expect from different cover crop species, what influences the amount of N they fix and release to the cash crop, and how no-tillers can help maximize a cover’s N production.

A Moving Target.

During the webinar, Wohltman presented a slide that listed several legume cover crop species and the amounts of N they can fix (Table 1).

“You can see a huge difference not only from one legume to another, but also with the range given to each species,” he says. “The obvious reason for this is because there are so many factors at play.”

That’s because the rate of N fixation by a cover crop is directly related to the cover crop’s growth rate, he explains.

“You…