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Ammonia Volatilization from Surface Applications of Ammonium Compounds on Calcareous Soils: II. Effects of Temperature and Rate of Ammonium Nitrogen Application¹

ABSTRACT

The effects of temperature and rate of application on NH₃-N volatilization from NH₄⁺ salts applied to the surface of a calcareous soil were investigated in the laboratory. Total NH₃-N losses were only slightly influenced by temperature over a broad range of NH₄⁺-N application rates with a precipitate forming NH₄⁺ compound such as (NH₄)₂SO₄ in a calcareous soil. The rates of NH₃-N loss were highly influenced by temperature. High temperatures increased the initial rates of NH₃-N loss although they were proportionally reduced at later stages. The lowest temperature resulted in the lowest initial NH₃-N loss rate but became highest for the last 76 hours. Total ammonia nitrogen losses were dependent on the rate of NH₄⁺-N application. The quantity of NH₃-N loss varied from 19 to 50% of the applied NH₄⁺-N at 33 to 550 kg NH₄⁺-N/ha, respectively.

The increasing temperature increased losses of NH₃-N from NH₄NO₃ which does not form precipitates with CaCO₃ or appreciable (NH₄)₂CO₃. In 100 hours, NH₄NO₃ lost 14, 18, and 26% of the applied NH₄⁺-N at 12, 22, and 32C, respectively. Both the total 100-hour NH₃-N losses and rates of NH₃-N loss were increased by increased temperatures; however, the percent of NH₃-N volatilized was unaffected by rates of NH₄⁺-N application.

Ammonium sulfate losses from a noncalcareous Wilson clay loam buffered to the pH of the calcareous soil produced NH₃-N losses equivalent to NH₄NO₃ at 12C and lower than NH₄NO₃ at 32C. Ammonia nitrogen losses, both total NH₃-N and rates of NH₃-N loss, were similar to losses of NH₄NO₃ from the calcareous soils. Therefore in the calcareous Houston Black clay the NH₃-N loss caused by reaction of (NH₄)₂SO₄ with CaCO₃ ranged from 0 to 70 or 80%.

Regression equations were developed that predict NH₃-N losses at certain temperatures, time, and rate of NH₄⁺-N application.

¹ Contribution from Texas Agr. Exp. Sta., Texas A&M Univ., College Station, Texas 77843, in cooperation with the ARS/USDA, Temple, Texas.

² Assistant Professor and Associate Professor, respectively, Texas Agr. Exp. Sta., Temple, Texas 76501. Senior Author now at Texas A&M Univ. Agr. Res. Center, El Paso, Texas 79927.

Received for publication November 26, 1973. Accepted for publication March 26, 1974.