To help answer this question, the cost of stockpiling was compared to the cost of feeding hay on a per day basis. Each additional grazing day resulting from nitrogen applications will save the farmer from feeding hay. However, this needs to be compared against the cost of the nitrogen applications. The trick is to figure out at what point adding additional grazing days would become more expensive than feeding hay.
The price of nitrogen was evaluated on an elemental basis between $.40-.60 per unit ($270-400 per ton ammonium nitrate), with application rates of 40 and 80 units/acre. Three response rates (low, medium, and high) were evaluated corresponding to various soil moisture conditions. The application cost for spreading the nitrogen was set at $5/acre.
Farm size and management practices were set at typical Kentucky conditions: 30 cow herd with late winter/early spring calving. Waste rates were estimated at 35% for both hay feeding and grazing. Machinery and labor costs were estimated at $.06 and $.25 per cow-day for grazing and hay feeding respectively. P and K from the hay were assumed to be recycled back into pastures at a 50% rate at $.40/lb for P2O5 and $.40/lb for K2O.
A range of hay prices were evaluated to determine which prices, if any, would result in profitable nitrogen applications this year. In general, good opportunities for applying nitrogen and stockpiling exist in mostly pure fescue stands (stands with few weeds and clover). Significant savings are possible where hay is priced at $60/ton in areas with average soil moisture conditions (medium response rate), and $40/ton in areas with ideal soil moisture conditions (high response rate).
Few cost saving opportunities exist in the mixed fescue-clover stands. Assuming a $.60/unit effective price, hay prices need to be above $60/ton before significant savings occur in these stands with ideal soil moisture conditions (high response rate). Applying Nitrogen with a low or medium response resulted in a loss with all the price scenarios evaluated. Additionally, any potential savings in the fescue-clover stands need to be balanced against the potential loss of clover due to N applications. As a consequence, the general consensus among agronomists that reviewed these results is that mixed fescue-clover stands would not be good candidates for N applications this summer.
Producers should also be aware that, even with volatilization losses factored, there may be instances where urea will be a better option than ammonium nitrate this year depending on their relative prices. For more detailed results, consult the publication "Profitability of Nitrogen Applications for Stockpiling Tall Fescue Pastures – 2010 Guide" http://www.ca.uky.edu/cmspubsclass/files/extensionpubs/departmentseries/ext-2009-09.pdf (Greg Halich)