Nitrogen Fertilization Studies in Dryland Winter Wheat and Potential Nitrogen Losses from the Soil at the Blue Creek Experimental Station in Northern Utah

This study compared the effects of nitrogen sources on the available inorganic soil nitrogen, nitrogen movement, nitrogen losses, and wheat yields when nitrogen fertilizers were applied to soil planted to dryland winter wheat at the Blue Creek Experimental Station in northern Utah. In the fall 1973 soil samplings, the fertilizers producing the largest mineral nitrogen contents in the 0-30 cm soil depths were ammonium nitrate \u3e ammonium sulfate \u3e S-coated urea, when they were broadcast at the practical rate of 56 kg N/ha. There was no increase in the mineral nitrogen at the deeper depths in the fall or at any depth in the following spring. Statistically, the three nitrogen sources did not increase grain yield significantly but did increase grain protein content and nitrogen content in grain. Ammonium nitrate and potassium bromide at the rates of 400 kg N and 200 kg Br/ha were broadcast to soil planted to winter wheat in October 1974. Nitrate-nitrogen and bromide distribution patterns in the soil profile looked alike in May 1975. These showed that their movements were similar. Considerable nitrate-nitrogen (35 percent of the added nitrogen) had moved down below the 120 em depth. The highest nitrate-nitrogen concentrations were found at the 45 to 90 cm depth. There seems to be evidence that nitrate-nitrogen and bromide had moved deeper than the 150 cm depth. Ammonia- nitrogen losses from nitrogen fertilized soils were conducted in the laboratory. Ammonium sulfate, ammonium nitrate, or urea applied to the soil surface lost ammonia-nitrogen differently. From noncalcareous soil, the ammonia-nitrogen loss was greatest from urea. From calcareous soil or soils receiving carbonates or high soil pH by the addition of sodium hydroxide solution, the greatest losses were from ammonium sulfate. High losses were favored by high temperatures and longer periods of moist soil. The total amounts of water lost from the soil was not closely related to the total ammonia-nitrogen loss during two weeks. No loss of ammonia-nitrogen occurred when nitrogen fertilizers were applied at a 2.5 cm depth or deeper. The ammonia-nitrogen losses were also greatly reduced when nitrogen fertilizers applied to the soil surface was followed by irrigation or heavy rainfall. In the field, the higher temperatures increased the ammonia-nitrogen losses from ammonium sulfate, ammonium nitrate, and urea when applied to both a noncalcareous and a calcareous soil. However, the loss from calcareous soil was reduced by irrigation following fertilizer application. No ammonia-nitrogen was observed when ammonium sulfate was applied at a 2. 5 cm soil depth, despite of the high soil temperature during the day time in moist soil. Rapid drying of the moist soil surface quickly reduced the losses per day