Fertilizing hayfields and pastures might still be a paying proposition given today’s high hay prices, says Eric Peterson, a University of Wyoming extension educator in Lincoln, Sublette, Sweetwater, Teton and Uinta counties. Hay growers have asked if it makes sense to apply high-priced fertilizer to hay meadows, he says.

“You will nearly always see an improvement in productivity when supplemental nitrogen is provided,” says Peterson. The law of diminishing returns will dictate when fertilizing is no longer profitable. Returns should increase until inputs cancel out any returns. “The trick is in knowing the point at which you are no longer getting a satisfactory return on the investment.”

A bulletin describing hayfield and pasture responses to fertilizer and a spreadsheet to help make fertilizer decisions are available online through the university’s extension service. The normal responses to fertilizer from native, improved and grass-alfalfa forages are summarized in “Fertilizing Wyoming Hay Meadows: How Much Fertilizer Can You Afford?” at agecon.uwyo.edu/agecon/whatwedo/publications/B828r.pdf. The spreadsheet, which includes fertilizer cost, value of hay, and the added cost of harvesting the additional production resulting from fertilization is at fp1.centurytel.net/sublette/anr.html.

“When you run some numbers through the spreadsheet, you’ll see that, although fertilizer is very expensive, the value of the additional hay you get from that input offsets the cost, making the decision to fertilize hay meadows a rational decision at reasonable application rates,” says Peterson.