The No. 1 question Pennsylvania No-Tiller Lucas Criswell gets about planting green is how the practice affects nitrogen (N) requirements for corn.

For Criswell, it technically starts at cover crop green-up, when he applies 1,500 gallons of hog manure per acre. That provides about 25 pounds of N an acre, since only half of the N in hog manure is available the first year. But he doesn’t count that toward his N for corn.

“My goal is to grow a healthier cover, so in turn that cover breaks down to feed the corn crop,” he explains.

Criswell has been using Ag Leader’s OptRx crop sensors the last 2 years to maximize his N needs. In doing so, he noticed he wasn’t seeing a big difference in N credit when he was applying higher levels of manure, which is why he decided to go to the lower rate of 1,500 gallons.

The 1,500-gallon rate allows him to feed more of his covers. Last fall, he was able to apply manure to 100% of his acres going to corn this year, and he’ll likely make another 1,500-gallon application in the spring.

He begins applying N for corn at planting, and says his rule of thumb is at least 45-50 pounds down with the planter. For Criswell, that’s 10 gallons of 30% and 5 gallons of ammonium thiosulfate applied with his Kinze planter.

But he notes that since every soil and field is different, the right amount is a moving target.

“The more mature your cover is, like your cereals, wheat and ryes, the more tied up the N is going to be,” Criswell says, adding that it’s one of the reasons why he’s trying to ramp up the amount of legumes in his cover crop mix.

He sidedresses additional N later using the OptRx sensors to determine the appropriate rate. Since adopting the crop-sensing technology, he’s applying less N on higher-producing field areas and more N on poorer-producing areas.

To learn more about how Criswell manages his farm using cover crops, read Laura Barrera’s article “The Next Step in No-Till: Planting into Living Covers” on Cover Crop Strategies.