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How Much Nitrogen for Ryegrass and Small Grain?

Posted Dec. 1, 1998

By the time you read this many of you will have realized the ryegrass or small grain you planted in August, September or October did not produce much forage. There were many reasons such as: it came up and was killed by excessive heat, the grasshoppers ate it or the army worms killed it. Some of you replanted in late October or waited until late October to plant the first time.

At this time you may be wanting spring forage as early as possible. Proper nitrogen fertilizer management will determine both spring production and the cost of production. Some soils contained significant amounts of nitrogen when you planted in the fall and many fields had nitrogen fertilizer applied. What should you do about applying nitrogen? Our normal recommendation for small grain planted to be up and growing by early October is to have 70 to 80 pounds of actual nitrogen available (soil plus fertilizer) as soon as plants begin to grow. Ryegrass that is growing by late September could also utilize similar amounts. Then, if good forage yields are produced and utilized we recommend additional nitrogen in late January or early February for small grain and in February for ryegrass.

How much nitrogen should you apply? As you expected it depends. Whether you had good fall production or not, you need to estimate the amount of nitrogen available for the crop in early January. The amount of nitrogen in the soil near planting time, amount applied as fertilizer, amount removed by grazing and amount lost by leaching will all influence the soil and plant nitrogen status in early January. Records such as soil test levels, fertilizer applied, production (measured by animal grazing days and average weight of the animals) and rainfall will help estimate nitrogen status. Soil type can also influence leaching potential.

Soil nitrate nitrogen levels may be determined by soil testing, but other information such as size of plants, color of plants and possibly nitrogen content of the plants may be needed to properly estimate nitrogen need. Soil test values alone may not be enough. If you collect soil samples for nitrate nitrogen analysis, in ryegrass or small grain, collect them the last of December or the first week of January (a good project for the kids - if properly instructed).

Collect samples from the 0-6 and 6-12 inch soil zones. Either air dry the samples immediately after collection (do not leave them wrapped up in an air-tight bag in a warm place) or immediately ship the moist samples to the lab for analysis. We have sampling instructions available in video or printed form.

Many other factors will help determine whether or not you should apply nitrogen and how much you should apply. Stands, other available feeds, class of livestock, cost of nitrogen, cost of other feeds, your financial situation, etc. will all affect your decision. Noble Research Institute Specialists and many other agricultural professionals can help you evaluate potential nitrogen needs.