First Split Nitrogen Application to Small Grain

Richard Taylor, Extension Agronomist;

Many wheat and barley fields that were not fertilized with manure or poultry litter last fall have looked poor for much of the winter. Even those fields that received some fall nitrogen (N) fertilizer but as commercial fertilizer have been yellow since mid-winter or earlier. Recently, the date when spring fertilizer can be applied was moved to earlier in February to help those with wheat that was showing signs of N stress and was trying to start spring growth. Since then, some cooler weather has settled over the region and slowed greenup in small grains.

For those who have not yet applied the first shot of N to their wheat, it is time to apply it. In fields that did receive fall manure or litter, the need is not as critical. In wheat, we have often seen about a 5 to 7 bu/acre yield increase when N applications are split into early greenup and then just before or at Feekes growth stage 5 when the first node is visible or can be felt above the soil surface. In work that Bob Uniatowski and I conducted a number of years ago, this response to splitting N applications was fairly consistent across locations and years. The largest response to a split application comes when significant rainfall occurs between the two splits causing some of the applied N to be loss either through leaching or denitrification. We also found that if all N was applied at one time, the early application date was the best choice although if the wheat had adequate tiller numbers in early spring even a Feekes growth stage 5 single application could produce excellent yield potential.

For those who may be growing barley, we did find that this crop is very sensitive to the rate of N applied because the straw strength seemed to be most affected at high rates of N. Whenever we applied much more than about 80 pounds of N per acre, we started seeding significant lodging which can not only make harvest difficult but can cause yield reductions, especially when lodging occurs early in the grain fill period.

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