Measurements of gaseous emissions from denitrification of applied nitrogen-15, 2. Effects of temperature and added straw
1995
Avalakki, U.K. (Griffith Univ., Brisbane (Australia). School of Environmental Studies) | Strong, W.M. (Queensland Wheat Research Inst., Toowoomba (Australia)) | Saffigna, P.G. (Griffith Univ., Brisbane (Australia). Graduate School of Environmental Sciences and Engineering)
Gas emissions of applied 15N were measured beneath a soil cover daily following saturation of Vertisol and Alfisol soils repacked in pots to the original field bulk density and held at 3 temperatures (5, 15 or 30 deg. C) with or without addition of wheat straw. Loss measured by gas emissions (15N2 and 15N2O) ranged from 36 percent and 152 percent of the denitrification loss as determined by 15N mass balance. In the absence of added straw, measurement by gas emissions was consistently less than loss by 15N balance. Where straw was added, 15N loss by gas emissions was overestimated, probably because of a smaller headspace than considered desirable for emission measurements. Potential denitrification rates, in the presence of added straw, were similar for the Vertisol and Alfisol. Decreasing temperature slowed potential rates of denitrification. Straw addition (10.5 t per ha) to the Vertisol, which contained no visible plant residues from previous crops, more than doubled the losses of applied 15N. The N2O emissions generally represented the smaller fraction of denitrification emission, becoming smaller as temperature was increased. As a proportion of emissions due to denitrification, N2O emissions were very low in the presence of added straw.
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