August 25, 2011

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Several growers have called about fertilizer requirements for winter wheat going into former CRP land. A good general discussion and some recommendations can be found in NebGuide 1970 Soil Fertility Considerations for Land Coming Out of Conservation Reserve Program (CRP).

UNL strongly recommends soil testing before the wheat crop. For CRP going into winter wheat, sample the top 8 inches for routine tests then deep sample to 3 or 4 feet to determine residual nitrate-N. This is important as soil nitrate levels are influenced by tillage method and length of time since tillage. Follow guidelines for P (broadcast or banded) depending on your preference, equipment, or budget. Nitrogen application is another story because of the amount of residue and its carbon to nitrogen (C/N) ratio, which is high.

We have no recent Nebraska research on fertilizer N required for wheat in recently converted CRP land. Data from Kansas shows that because of high residue and C/N in conventional or no-till systems, over 100 lb N per acre was required for optimum yield and protein. Several growers in the Nebraska Panhandle have had wheat the past two years in both no-till and tilled fields. They have applied “normal” rates of 50 to 60 lb N per acre. Yields have ranged from 40 to 60 bu/ac when conventional adjacent fallow wheat has yielded 50 to 70 bu/ac. Protein levels have been low in the CRP fields with normal N rates.

In a July 12 CropWatch article, N recommendations were given for fallow wheat production. At current wheat and fertilizer prices, and based on grower experience plus the Kansas data, you would probably need to add an extra 40 lb of N per acre to the “standard” N recommendations for good yields and adequate protein. Most dryland growers are reluctant to apply this much N, but the data and farmer information confirms the N need.

One suggestion would be to apply needed P plus 30 to 40 lb N preplant this fall, see how the crop comes through the winter, see what happens with wheat and fertilizer prices, then, put the additional N on early next spring before wheat jointing.

Gary Hergert
Extension Soils Specialist, Panhandle REC, Scottsbluff