As producers plan for winter topdressing wheat or another small grain cereal, they should be conservative in the amount of nitrogen (N) credit they count as coming from a preceding legume crop, a Kansas State University agronomist said.

For example, if the small grain is following alfalfa that was destroyed during the summer, producers typically should figure on getting about one-half the N credit that row crops planted the following spring would get, said Dale Leikam, nutrient management specialist with K-State Research and Extension.

“The reason winter cereals get a smaller N credit than would summer row crops in this situation is that there has been less time for the alfalfa residue to decompose and the N to be mineralized,” Leikam said.

“If the alfalfa stand was killed in late fall, rather than summer, it’s best to allow little or no N credit for winter cereals planted into the residue.

“For soybeans harvested only a few days or weeks before wheat planting, we also would expect little N mineralization over the winter. So, no N credit should be given for the wheat in that case, either.”

More information about nutrient management in crops and crop production in general is available at any county or district K-State Research and Extension office, as well as on the Web at http://www.oznet.ksu.edu.