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

Idaho had a standing herd of 573,000 dairy cattle in 2013, with 92% of the herd concentrated in 11 counties in southern Idaho. It is estimated that 6-7 billion kilograms of manure (dry basis) are produced annually containing 102-119 million recoverable kilograms of N. Understanding N transformations from manure applications is an important component of managing this nutrient source to maximize crop profitability and reduce environmental damage. This study determined the net N mineralization produced from annual vs. biennial stockpiled dairy-manure applications to a sprinkler-irrigated field under barley in 2013 and sugar beets in 2014. Treatments to a calcareous soil included three manure rates (dry basis) (17.2, 34.5, 51.7 Mg/ha) applied at two recurrence intervals (applied either each year vs. every other year). Manure was applied to annual and biennial plots in fall 2012 and to annual plots only in the fall of 2013. We monitored cumulative N mineralization in the 2013 and 2014 growing seasons using the buried bag incubation method. Bags were exhumed throughout the growing season and soils were analyzed for nitrate and ammonium.