Cover crops can be beneficial for erosion, nitrate uptake, and even early season grazing. The upper Midwest had one of the warmest falls on record and we saw incredible cover crop growth in most fields. Most cover crops are rye grass which grow at some of the coolest temps. Rye does a good job of taking up free nitrogen in the soil. Research from MN, ISU and Michigan is consistent that it takes several years for this nitrogen to reenter the soil in plant useable forms. Minnesota has found this “penalty” should be accounted for over the first 5 years of using cover crops until the system stabilizes. MN recs call for 40 lbs of extra N be applied each of those years when growing a grass crop like corn. In some cases, the fall growth was so extensive it took 80 lbs extra N to offset all the N uptake by the rye. With the current price of N, one should perhaps compare the cost of a legume-based cover crop. Don’t forget the MN recs that call for killing the cover crop in the spring at least 2 weeks before corn planting to avoid any yield loss. This can be difficult as we usually get into the fields as soon as they are fit to plant. We can spray Roundup to kill the crop earlier, but it doesn’t work very fast in the cool temps of early April.