Nitrogen Fertilization of Spring Pastures or Hay Land

Richard Taylor, Extension Agronomy Specialist;

Good quality hay was not only hard to find this past fall and over the winter, but expensive as well. Livestock managers may be looking at their pastures and thinking about how to kick start them this spring. Researchers have found that mid- to late fall nitrogen (N) applications can help get pastures and hay fields off to a quick start in the spring although the benefit is not always consistent. In some cases, not enough N is stored in the grass to really trigger early and vigorous spring growth; or where fall N applications do not take place, an early spring N application will be necessary to jump start spring growth. If your operation is short of hay and you are hoping for an early spring to get feed for your livestock, you may want to consider an application of N at this time.

This year, although we’ve had a relatively mild winter, many of our fields are not yet actively growing. I would suggest applying about 30 lbs of N broadcasted over the pasture to stimulate the grass to begin growth as soon as the temperature reaches the minimum for the grass species dominating your pasture or hay field. I know a number of growers have in the past used products such as poultry litter or liquid dairy manure or other manure or composted organic source for N. At this time of year, however, you should be applying either granular or liquid inorganic fertilizer supplying ammonium, nitrate, or urea since the soil temperature is much too low for mineralization to take place in order to free the N contained in the organic N sources listed above. Using the pelletized poultry litter, regular poultry litter, compost, or other organic sources is best done once the soil has warmed above 50 to 55°F, or around late-April to mid-May. Before this timeframe, mineralization of N will be so slow as to not be of value to the producer when trying to jump start a pasture or hay field.

Generally an actively growing pasture can use about a pound of N per day, but be sure to scout your pastures about 20 to 30 days after you apply the inorganic N fertilizer to see when the next shot of N will be needed. Since potash (K) tends to be released over the winter, I recommend waiting until mid-May to mid-June to apply the recommended phosphorus (P) and K using soil test recommendations for maintenance fertilizer application rates. If clovers are present add about 1 lb boron/acre with the required maintenance P and K and adjust later N application rates based on the amount of clover in the pasture. If half or greater of the biomass (dry matter) comes from clover, additional N will not be needed. If from 25 to 50 percent of the dry matter comes from clover, the N rate can be cut in half; but if the clover contributes less than 25 percent to the dry matter available, a full rate of N should be used.