Nitrogen Mineralization of Dairy Manure in a Calcareous Soil Under Field Conditions.

Understanding N transformations in fields receiving dairy manure applications is an important component of managing this nutrient source to maximize crop profitability and reduce environmental damage. The objective of this study was to determine the net N mineralization from field applied dairy cow manure to a Portneuf silt loam as affected by application rate, application frequency, and naturally fluctuating temperatures throughout the growing season. This study was conducted in a field located at the USDA Agricultural Research Service (ARS) Northwest Soil Research Laboratory (NWISRL) station in Kimberly, Idaho. Soil treatments included three manure rates (17.3, 34.7, 52.0 Mg ha^-1, dry weight basis) applied at two recurrence intervals (annual or biennial fall applications). The field was sprinkler-irrigated under spring barley (Hordeum vulgare L.) in 2013 and sugar beets (Beta vulgaris L.) in 2014. Nitrogen mineralization was monitored in the 2013 and 2014 growing seasons, with amended soils from the 0-30 cm and 30-60 cm soil depths placed in polyethylene tube shaped bags and incubated in the field of origin at the same soil depths. Bags were removed every 4 weeks in March, April, and May, and every 2 weeks in July, August, September, and October. Soil from removed bags were analyzed for ammonium-N and nitrate-N concentrations. Zero-order models were fit to net N mineralization. Sugar beet N uptake was correlated with nitrate accumulations in the buried bags (r-square = 0.75).

Key words: dairy manure, nitrogen mineralization, calcareous soil, in-situ, buried bag method

Acknowledgments

This study was made possible by the Idaho Dairymen’s Association, Idaho Barley Commission, USDA Agriculture Research Service, and the University of Idaho.