Top Dressing Wheat Pays Off

With the recent snow and assuming adequate moisture is available before jointing occurs, top dressing wheat is an efficient fertility practice for two reasons. The first is that it allows a producer to evaluate crop condition before spending additional money on nitrogen (N) fertilizer. The second is the closer N fertilizer is applied relative to crop use, the less potential there is for loss due to environmental conditions such as leaching and/or denitrification.
When we are matching N requirements of the grain crop to N availability, top dress can be very important as the peak utilization of this nutrient is jointing, or the time when the spike or head is forming. N uptake and use at this time can be as high as 2 pounds per acre per day. This high demand for N typically continues for about the next 30 to 40 days, with demand substantially decreasing as the plant approaches the boot stage. The time is growing near for wheat producers who are thinking about top dressing their wheat. If we receive rain and the crop has adequate moisture as it approaches jointing, this can be the most efficient time to apply N to the crop. If the crop is short of moisture and stressed, it may not pay to top dress, and the farmer can significantly reduce production cost by not applying this N. Top dressed N should be applied prior to the jointing stage. Applications after this stage will most likely increase grain protein, but may not contribute to a profitable increase in grain yield. Late applications (after jointing) of nitrogen are not usually economical. Wheat will usually start jointing anywhere between February 20 and March 10 in our area. The only way to know the actual amount of nutrients you need to produce a high yielding wheat crop is through a soil test. Other things to consider in making a decision on top dressing wheat are a realistic yield goal, whether the wheat is grazed or not, and how much preplant fertilizer was applied. The source of N we choose should not effect yield. However, if urea is used, there is a greater potential for loss due to volatilization than with other sources of N. As a rule of thumb, 1.5 lbs. of N per acre is required for every bushel of grain expected to be harvested. Remember that grazing wheat will remove about 20 lbs of Nitrogen per acre and that must be taken into account when determining N requirements for grain production.