Split nitrogen applications for management of yield and protein of wheat grown in dryland
The feasibility of using split-N applications for managing yield and protein of wheat grown on dryland was studied in a field experiment initiated on a sandy loam and silt loam near Swift Current. Spring wheat was grown on wheat stubble and was fertilized at seeding with 0,20,40, 60, and 80 kg N/ha. In addition, five N topdressing treatments were applied at the five-leaf, flagleaf, and anthesis to the plots receiving 0 and 80 kg N/ha at time of seeding. Topdressing treatments were 5 kg N/ha as urea-ammonium nitrate solution (UAN) foliar applied; 10 kg N as urea broadcast or UAN dribble banded onto the soil surface; 20 kg N/ha as urea broadcast; and 20 kg N/ha as UAN dribble banded. One set of plots received no topdressing treatment (Check). In general, because of the low soil NOJ-N and high soil moisture in the spring, and adequate rains during the growing season, grain yields had large responses to N applied at seeding. Grain protein decreased with the first 20 to 40 kg N/ha applied at seeding due to yield dilution, and increased above that of the unfertilized check at fertilization rates of 60 or more kg N/ha. Nitrogen topdressing early in the growing season to unfertilized crops increased both protein and yield, and increased protein only when applied later in the growing season. Nitrogen topdressing the crops that were fertilized with N had no effect on grain yield and caused a small increase on grain protein. Soil applied N topdressings tended to be less effective than foliar application because they did not receive timely rains and adequate surface soil moisture to make the fertilizer available to the crop. Foliar applied UAN, although effective in increasing protein, may produce leaf burn, which in turn may reduce grain yields and protein.
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