Have you ever stopped to think what your annual nitrogen (N) fertilizer cost is per cow? I am certain that you are aware that fertilizer prices are at a historic high, and, with the amount of corn acres predicted in 2008, the outlook is that prices will climb even higher next spring. So, at what N fertilizer price is it no longer economical to fertilize bermudagrass in a cow/calf enterprise?
First, I will use urea (46-0-0) as the N fertilizer source at a price of $475 per ton or 52¢ per pound N (2,000 lbs. x .46 = 920 lbs. N/ton; $475/920 lbs. N/ton).
Second, it takes 9,490 pounds of dry matter forage to support a 1,000-pound cow for one year, but who has 1,000-pound cows? An average cow weighs closer to 1,200 pounds. As a result, 11,388 pounds of dry matter forage will be needed to support a 1,200 pound cow for one year (9,490 lbs. dry matter forage x 1.2 animal unit equivalent).
Third, adjust for grazing efficiency. Under very good grazing management, a cow will consume 70 percent of the bermudagrass forage grown. A total of 16,270 pounds of forage (11,388 lbs. dry matter forage/70 percent) is needed annually to support one cow.
Fourth, the "natural" forage production (without any N fertilizer applied) on an average upland soil will produce 2,000 pounds dry matter forage per acre. Under somewhat normal weather conditions, 30 pounds of additional forage can be produced for each pound of N fertilizer applied. Assuming a stocking rate of one cow per 4 acres, a total of 275 pounds N fertilizer is required to produce 16,270 pounds of forage [(2,000 lbs. natural production x 4 acres) + (275 lbs. N x 30 lbs. dry matter forage/lb. N applied)].
Fifth, now we can calculate the N fertilizer cost per cow by multiplying the cost per pound N (52¢) by the amount of actual N to be applied (275 pounds). The cost per cow is $143.
During 2003-2006, the Standardized Performance Analysis (SPA), a national cow database that records cow economics and performance, marginal input costs to maintain one breeding female averaged $175. When additional marginal costs and N fertilizer costs are added together, the total is $318. If the producer is profitable with their current production system, then they can justify the application of N fertilizer as long as calf revenue per cow is higher than $318. Due to the variability of land and other input costs, each producer should figure their individual production costs for their cow/calf enterprise.
It is important to remember that this article only discussed N fertilizer cost. It does not include any costs associated with other fertilizer inputs, such as phosphorus, potassium and/or lime. This is why it is critical to always soil test to determine what nutrients may be deficient and those which may already be at acceptable levels.