NET Nitrogen Mineralization From Dairy Manure in Eroded and Noneroded Calcareous SOILS.

Efficient recycling of abundant manure resources from regional dairy industries in the semiarid West requires a better understanding of N availability in manure-amended soils.  We measured net N mineralization using buried bags, and crop biomass, N uptake, and yields for sprinkler-irrigated, whole (non-eroded) and eroded Portneuf soils subject to a one-time manure application.  Treatments included a control, fertilizer, two rates of composted dairy manure (12.7, 28.7 Mg ha^-1, dry wt.), and two rates of stockpiled dairy manure  (10.4, 20.4 Mg ha^-1, dry wt.) applied in the fall prior to the year 1 cropping season.  Plots were planted to sugarbeet, winter wheat, and spring barley during the 3-yr study.  Overall, net N mineralization rates were low to moderate during winter through spring, decreased in early summer due to N immobilization, then increased to a maximum in late summer, followed by a decrease in fall.  The mean mineralization rate (as a % of the added organic N) for 3-yr period was 1.6% for compost, and 15.3% for manure.  Relative to controls, compost and manure treatments as a group increased total 3-yr net N mineralization more for eroded (1.77x) than for whole soils (1.55x).  At higher rates, manure also increased immobilization and mineralization in 30-to-60-cm soil depths (below the zone of incorporation).  To optimize the use of N mineralized in southern-Idaho’s manure-amended soils, one should consider the type manure employed and the erosion status of the soil receiving the amendment.