Nitrogen Management of Forage Winter Cereals

Jason Hartschuh, Extension Educator, Agriculture and Natural Resources, Crawford County, Ohio State University Extension

Winter annual cereal crops for forage are greening up very nicely, thanks to the warm weather over the last several weeks. Over the next several weeks before stem elongation, you will be deciding how much nitrogen to apply, and by the end of April, checking fields to select a harvest date. Nitrogen rates and harvest timing greatly effects forage yield and quality.

Nitrogen is not only a driving factor of yield but an even bigger driver of crude protein (CP) content but has little effect on digestibility. A study from New York found on average cereal rye removes 121 lb/acre of nitrogen with an average dry matter (DM) yield of 2.37 tons/acre. Selection of the most economical nitrogen rate revolves around yield potential, species planted, manure application history, and soil drainage. When a fall application of manure was made containing over 120 lb/acre of nitrogen on well drained soils and the crop was planted before October 1st, multiple studies have found little yield benefit to spring applied nitrogen at green up. A linear increase was found though in CP content from about 12% CP at zero nitrogen to 20% CP when 120 lb of spring nitrogen was applied. Even though CP greatly increased with nitrogen fertilization, the economic return was often negative. With current nitrogen price of a $1/lb or more, the 120 lb/acre of nitrogen would need to increase CP from 12 to 16.8%. If it was really increased to 20%, the fertilizer dollar value as CP to replace soybean meal would be about $196, making it a positive investment. This investment though can be quickly lost if the rye matures too much prior to harvest.

On poorly drained soil with a history of manure applications, a spring nitrogen application of 50 of 60 lb/acre at green up improved both yield and CP. When the field did not have a fall manure application, the most economical spring nitrogen rate was 70 lb/acre, but some fields had positive returns with nitrogen rates as high as 120 lb/acre. On average, winter annual cereal crops need 15.5 lb of spring nitrogen per ton of forage DM produced. Utilizing higher rates than required may leave nitrogen in the soil for the following crop, but also increase the potential for lodging, which will cause harvest challenges. Lodging is also affected by harvest timing and species. Rye is the most likely to lodge, followed by triticale and then wheat.

Manure is an excellent source of nitrogen. Liquid manure can be applied before jointing. The thickness of your liquid manure should be considered though. Thick straw manure may still be present at harvest time and be harvested with the forage. This can be a concern with disease transfer from the manure to the livestock eating the forage. When looking at manure nitrogen, the ammonia and nitrate nitrogen fractions are available for the cereal grain forage crop. While the organic nitrogen will probably not be available for the current crop, it will be released over time to future crops. If you have swine manure available, applying it to your cereal grain forage can be a great synergy between your two operations. The swine manure has more nitrogen, is thinner, and will not transmit Johne’s Disease or Bovine Leukosis Virus if some of the manure resides in the harvested forage. If more manure nitrogen is applied than the crop utilizes, this nitrogen can be calculated into your corn nitrogen budget. This can be done by calculating how much nitrogen was applied minus removed nitrogen by the cereal forage crop. Also, a pre-sidedress nitrate test is suggested to determine how much nitrogen is in your soil at corn sidedress time.   

When selecting the correct nitrogen rate and harvest timing, knowing your livestock’s nutrient requirements is important. For lactating cows, higher CP and digestibility is the goal. Applying 50 to 70 lb/acre of nitrogen at green up and planning to harvest all species between feeks 9 (last leaf is emerged but head is still down in the plant and stem in not fully elongated) and 10 (grain head is in the boot at the top of the plant but is not visible yet) will allow you to have the best forage possible. For heifer and dry cow rations, a delayed harvest at feeks 10 to 10.5 (head fully emerged and flowering has begun) may provide more tonnage and high enough quality feed. If harvest is delayed further, forage value will peak again when the grain is in soft dough stage. At this point, you are maximizing non-fiber carbohydrates instead of CP and digestibility. Late harvest forages will store much better as silage since it is very hard to get the soft dough grain dry enough at this point for dry hay and fermentation as baleage is often poor.