Soil Denitrification and Nitrification Potentials during the Growing Season Relative to Tillage
- T. E. Staley ,
- D. G. Boyer and
- W. H. Caskey
Soil management practice, through the alteration of various biological processes, can have a profound effect on nutrient availability to crops. During the growing season, the effect of no-tillage (NT) or conventional tillage (CT), location (between or within row), and N rate (0 or 56 kg N ha−1) on soil potential denitrification activity (PDA) and potential nitrification activity (PNA) was investigated. A Gilpin silt loam (fine-loamy, mixed, mesic Typic Hapludults) was selected and maize (Zea mays L.) was planted. For both PDA and PNA, most of the activity was concentrated in the soil surface (0–3.8-cm) layer, especially under NT, and decreased to barely detectable levels in the deepest (15–30-cm) layer examined. Significant main effects were found for tillage, season, and location for PDA in the soil surface layer. Tillage interacted only with season, resulting in an increase in PDA under NT, and a lack of response under CT, during the growing season in both the soil surface and the 3.8- to 7.6-cm layers. For PNA in the soil surface layer, significant main effects were found for all treatments. Only location interacted with tillage, resulting in a 50% increase in PNA from within rows to between rows under NT, and a lack of response under CT. In the 3.8- to 7.6-cm layer, the lowest order interaction was significant. In the 7.6- to 15-cm layer, PNA increased more rapidly under CT than NT during the growing season. These results demonstrate the importance of considering spatial distribution and time when these microbial activities are examined in tillage studies, and suggest that N losses under NT should exceed those under CT.
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