# Do You Need to Topdress Winter Pasture?

Posted Jan. 1, 2006

When someone asks me, "Do I need to topdress my winter pasture?," my answer is, "It depends." Two things happened this growing season that will affect the need for topdressing winter pasture with nitrogen (N) fertilizer in the spring. First is the severe drought we experienced this fall, and second is the amount of N fertilizer applied at or since planting.

First, let's assume there was enough moisture to get a stand last fall, but, due to dry weather, little or no fall forage was produced. If 80 pounds of actual N per acre or more was applied, and spring forage demand for livestock is light, you may not need to topdress with additional N. Due to the lack of small grain forage production last fall, it is likely that most of the N applied will be carried over and used by the crop this spring.

Second, let's assume there is a stand, but no fertilizer has been applied to the crop, or there is going to be a high demand for small grain pasture this spring. If this is the case, then apply a topdress application of 60 to 80 pounds actual N per acre to enhance spring forage production.

Now, if you have determined there is a need to topdress with additional N, your next question might be, "Can I afford the fertilizer?" If you were to visit a local ag dealer or co-op and price urea fertilizer (46-0-0), you would learn that it is high (about \$370 per ton). Both urea and UAN (32-0-0) are recommended N sources this time of year because of their cost per unit N and the low risk of N loss through the winter. Obviously, the cost of fertilizer right now is higher than usual, but will it pay? Let's take a look at a scenario that shows the economics of topdressing winter pasture this spring for grazeout. In this scenario, we are going to use a few proven assumptions in a winter pasture enterprise.

Assumptions:

1. Cost of urea (46-0-0) fertilizer = \$370/ton (\$0.40/unit N)
2. Fertilizer rate = 60 lbs. actual N per acre
3. 1 lb. N yields 25 lbs. of small grain forage (spring phase)
4. 10 lbs. of winter pasture equates to 1 lb. of beef gain
5. 90% forage utilization by stockers
6. Custom care rate = \$0.35/lb. gain

Example:

• \$0.40/ unit N x 60 lbs. N per acre = \$24/acre
• 60 lbs. N per acre x 25 lbs. forage/pound N applied = 1,500 lbs. total forage/ac
• 1,500 lbs. total forage/ac x 90% utilization by stockers = 1,350 lbs. available forage/ac
• 1,350 lbs. available forage/ac / 10 lbs. of forage consumed = 135 lbs. beef gain/ac
• 135 lbs. beef gain/ac x \$0.35/lb. gain = \$47.25

Of course, every situation is different, but this example points out the advantage of fertilizing that winter pasture this spring. A \$24 per acre investment in N fertilizer can return almost \$50 per acre if the weather cooperates for the rest of the growing season. If you have questions while trying to determine if you should topdress winter pasture this spring, contact a Noble Research Institute soil and crops specialist at (580) 224-6500.