Loss of expensive nitrogen is undesirable from both an environmental and economical perspective. That’s why you need to delay fall nitrogen applications until soil temperatures remain below 50 to 55 degrees. Each fall, some producers get the urge to apply anhydrous ammonia as soon as the soybean crop is harvested. But if soil temperatures are too warm, there is a good probability that there will be some loss of the applied nitrogen. The potential for loss of fall applied nitrogen decreases substantially as soil temperature drops below 50 to 55 degrees. Frequently, soil temperatures drop to this level for a few days, and then warm up. Fall nitrogen applications should be delayed until soil temperatures remain below 50 to 55 degrees. As prices for nitrogen fertilizers increase, there’s no common sense in using management practices that are likely to result in some loss of the fertilizer nitrogen that is applied. So stop and think about early application of fertilizer nitrogen. Using a little common sense can pay big dividends when planning for the 2005 crop. George Rehm is a soil scientist with the University of Minnesota Extension Service.
