Gaseous nitrogen losses and ammonia volatilization measurement following land application of cattle slurry in the mid-Atlantic region of the USA

摘要

To provide locally-determined field data for extension and environmental management purposes, gaseous N losses were measured following cattle slurry application to an arable silty-loam soil in the mid-Atlantic region of the USA. The field had been cropped to no-till maize. NH3 volatilization was measured with the micro-meteorological, integrated horizontal flux (IHF) method, and denitrification with a core incubation method using acetylene inhibition. An early-winter surface application (5 December 1996; 88 m3 ha−1 supplying 91 kg NH 4 + -N ha−1) was either unincorporated or immediately incorporated. NH3 volatilization was measured from the unincorporated application, and denitrification from both slurry treatments and appropriate control soils. Total NH3 loss from the unincorporated slurry application was 19% of applied NH 4 + -N; temperatures were cool (4–6 °C), and 25 mm of rain fell within 24 h of application. For 3 months, enhanced denitrification occurred from the two slurry treatments, with generally higher rates from the incorporated slurry. Total net denitrification loss from the surface-applied and incorporated slurry treatments was, respectively, 11 and 17% of applied NH 4 + -N. Denitrification loss over the winter/early-spring period was appreciable but not substantial, even where NH3 volatilization was restricted by immediate incorporation. From the spring application (30 April 1997, 39 m3 ha−1 supplying 51 kg NH 4 + -N ha−1), total NH3 loss was 71% of applied NH 4 + -N. These NH3 volatilization loss data and the similarity of climate suggest that NH3 loss factors from recent NW European work are likely to be generally applicable in the mid-Atlantic region. NH3 volatilization from the spring application was also measured using the Z-instrument (ZINST) approach, and with a system of small wind tunnels. A comparative assessment of the three methods is reported.