Ammonia Volatilization from Dairy Manure Spread on the Soil Surface
1976
Lauer, D. A. | Bouldin, D. R. | Klausner, S. D.
Volatilization of ammonia from manure spread in the field was measured in five experiments carried out over a period of 2 years in spring, summer, and winter. The rates of manure application were 34 and 200 metric tons/ha (15 and 90 tons/acre). Ammonia volatilization was determined after spreading by periodically measuring the total ammoniacal N (TAN) content of manure samples collected from the soil surface. Corrections were made for increase in ammoniacal N in the soil. Time spans of the experiments ranged from 5 to 25 days with total losses of NH₃ ranging from 61 to 99% of the TAN content. Quantities of N volatilized as NH₃ ranged from 17 to 316 kg N/ha depending on the application rate and TAN content of the manure. In the winter trial, NH₃ volatilization was precluded by subfreezing temperatures, snow cover, and a rapid thaw which leached the ammoniacal N into the soil. In the other experiments, for a period of 5 to 7 days after spreading, rates of NH₃ loss are represented by mean half-lives of 1.86 to 3.36 days, respectively, for the low and high rates of manure application. After the initial period of loss, the rate of NH₃ volatilization slowed in most cases. The 34 metric tons/ha manure application dried more rapidly because of its thinner ground cover, which increased the rate of NH₃ loss from the manure. Volatilization of NH₃ was optimum under sustained drying conditions. Effects of drying on the manure in relation to the chemistry of NH₃ in aqueous solution in the manure aided in understanding the process of NH₃ volatilization from the manure.
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