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Influence of Soil Temperature on Urea Hydrolysis and Subsequent Nitrification¹

ABSTRACT

Nitrogen as urea was added to soil samples at rates equivalent to 100 and 200 pounds of N per acre. These samples were placed in temperature-controlled chambers maintained at 10°, 20°, and 30°C. The soil moisture was maintained near field capacity and duplicate samples were analyzed at the end of 1, 2, 3, and 5 weeks for ammonia and nitrate nitrogen.

The results show that there was generally an increase in the rate of urea hydrolysis and subsequent nitrification with increase in soil temperature. The higher rate of urea application increased the average amount of hydrolysis and nitrification at all temperatures except 10°C. The 10°C. temperature had very nearly a constant rate of nitrification, about 25 pounds of N per acre per week, at both rates of urea application. The initial soil pH was 6.8 and there was no great change in the soil pH during this study.

Contribution from the Department of Agronomy, University of Tennessee Agr. Exp. Sta., Knoxville. This work was supported in part by a grant from Grace Chemical Company. Presented before Div. III, Soil Science Society of America, Nov. 20, 1957, at Atlanta, Ga.

² Graduate Assistant and Agronomist, respectively.

Received for publication January 22, 1958. Accepted for publication February 25, 1958.