Distribution and Nitrification of Anhydrous Ammonia in a Nicollet Sandy Clay Loam1
- T. H. McIntosh and
- L. R. Frederick2
A roughly cylindrical distribution of NH3 centered at the knife openings was found when anhydrous ammonia was applied with a field applicator at a depth of 4 inches, by sampling an 8- by 8- by 2-inch cross section perpendicular to the applicator row. NH4-N, NO3-N and pH were determined on each 1-inch square subsample. NH4-N decreased from a maximum concentration of 1,300 to 2,000 ppm. (pH 9.5) at the center to less than 200 ppm. (pH 8) in the area about 1½ inches away from the center of the retention zone. After 2 weeks, the maximum concentration of NH4-N was about 800 ppm. (pH 8.8) in the center decreasing to less than 100 ppm. (pH 7.0) in the area about 2½ inches away from the center of the retention zone.
Nitrification initially proceeded more rapidly in the outside 2 inches of the retention zone where the concentration of NH4-N was less than 400 ppm. Later in the original ammonia retention zone, nitrification appeared to be limited by low pH and nitrate concentration; at the end of 4 weeks the pH had decreased to a value of 5.0 to 5.5 and NO3-N had increased until 200 to 300 ppm. were present. Ammonia applied in November just prior to freezing showed little nitrification by March. Rapid nitrification began in mid-April when soil temperatures rose above 40° F. Approximately 8 weeks were required to completely nitrify the ammonia.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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