Gage County
1115 West Scott St.,
Beatrice NE 68310
Phone: (402) 223-1384
FAX: (402) 223-1370

News Column

Paul C Hay, Extension Educator

Life Goes On After 50 (Soil Temperature)

Fall is an incredible time of color and beauty in Nebraska. The fall leaf colors are spectacular. The sun being lower on the horizon adds reds and oranges to every sunrise and sunset. The cooler weather is a refreshing change from the blistering heat of summer. Every plant and animal is in a transition preparing for the winter season. Even the soil bacteria are in preparation for the change of season.

Life still goes on after the soil has reached 50 degrees and below. The is important to farmers because as we finish harvest they are preparing for the crop in 2003. The white anhydrous ammonia tanks will soon be on the road again.

Anhydrous ammonia remains as the most economical choice of nitrogen fertilizer for many farmers. The University of Nebraska recommendations are to delay anhydrous ammonia applications until soil temperatures fall below 50 degrees. Soil temperatures from the Plymouth weather station are reported to farmers in the weather report section of the Beatrice Daily Sun and on KWBE Radio. I would additionally recommend that producers would be wise to wait until those soil temperatures are below 50 degrees for an entire week, before beginning ammonia applications. I do not recommend the application of any other form of nitrogen fertilizer, like UAN or urea, in the fall.

Anhydrous ammonia needs to be converted from the ammonium form to the nitrate form via bacteria activity in order to be available to plants and in order to be in a form which is leachable by water movement in the soil. Since bacterial activity slows down below 50 degrees so does the conversion of ammonium to nitrate. Life still goes on however and it would be a wrong assumption to believe that all transformation stops.

Farmers should know that nitrogen fertilizer efficiency is increased when applications are made closer to the maximum uptake months of June and July. When farmers can control the situation fully like under center pivot systems they can spoon feed the crop and achieve considerable nitrogen efficiency improvements.

Recent Iowa State University research done by Dr Al Blackmer and his graduate students, has been showing that bacteria activity is not quite as low as was previously thought. There are two parts to this research that are not surprising and are business as usual. There is one part which is of interest and needs further investigation.

The two usual parts show that in 2001-2002 we had considerable ammonia conversion. If you remember how warm it stayed last fall, that should be of no surprise. Also, much of Iowa receives more rain and has more tile drained fields. Both situations can result in more nitrogen movement and loss than we are likely to see in Nebraska.

In the Iowa State studies conversion speed and field losses were greater in fields with higher pH levels. Soils with pH values greater than 6.5 had significantly greater potential for quicker ammonia conversion to nitrate and possible loss from the field. This is valuable information to guide farmers in efficient use of nitrogen.

View other Gage County News Columns & News Letters: http://gage.unl.edu/news/news.htm

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