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Time to top dress wheat in TexasBy Miles Dabovich Texas Cooperative Extension agent, agriculture, Wichita County Time is drawing near for producers to consider top dressing their wheat in order to increase yields. This is also one of the hardest years to make that decision. The local wheat conditions right now is from poor to fair with a small amount that looks good. As we all know soil moisture at planting time has been very short and therefore we have stands of wheat in very patchy conditions. Producers will really have to evaluate their situation to determine if they should spend the additional money. Below is some interesting info on top dressing wheat from Todd Baughman our District Extension Agronomist. Top dressing wheat is an efficient fertility practice for two reasons. The first is that it allows a producer to evaluate crop conditions before spending additional money on nitrogen fertilizer. The second is the closer time N fertilizer 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 at jointing, or the time when the spike or head is forming. N uptake 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. If 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 productions cost by not applying this N. Top dressed N should be applied prior to the jointing stage (the stage where stem elongation occurs). Applications after this stage will most likely increase grain protein, but may not contribute to a profitable increase in grain yield. Until or unless wheat price is based on grain protein, late applications (after jointing) of nitrogen are not usually economical. Producers who are planning to harvest wheat on which cattle are grazing should remove cattle prior to jointing, as well, since removal after jointing can reduce grain yield. Wheat will usually start jointing anywhere between Feb. 15 and March 1 in the Rolling Plains of Texas. If you are planning to fertilize wheat between these dates is may be best to inspect the fields to determine what growth stage the wheat is in prior to fertilization. If a field does not have an adequate amount of soil N available for the wheat plant, properly timed applications of supplemental nitrogen can increase yields. The only way to know the actual amount of nutrients you need to produce a high yielding wheat crop is through a soil test. If you're wondering about how much N to apply this year, consider taking a soil test this summer after harvest. This will allow you to adequately fertilize your crop next year. (Producers should consider a soil test now prior to preplant fertilizer applications on summer cropland). 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. Another consideration once we determine the amount of N we need is the source of N fertilizer to use. 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. Finally, we would like to emphasize the importance of soil testing for future consideration on fertilizer needs. You can contact your local county agricultural agent for information on soil test procedures, soil test forms, and soil sample bags. 1/21/08 Date: 1/17/08
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