Nitrogen concentration variability in dairy-cattle slurry stored in farm tanks
1991
Patni, N.K. | Jui, P.Y.
Spatial and temporal variability in the concentration of total Kjeldahl and ammonia (NH3 + NH4+) nitrogen (TKN and AMN, respectively) was studied in 8 to 10% total solids content dairy-cattle manure slurry and its centrifuged supernatant during undisturbed storage in covered, reinforced concrete, farm storage tanks. Slurry was stored in two winter-filled tanks for 285 days, and in two additional summer-filled tanks for 146 days. Although concentration variability with time and space was small relative to the initial concentrations, slurry at depths of less than 1 m had consistently lower concentrations than at greater depths, particularly after the initital two months of storage. Mass balance for nitrogen (N) indicated a 9% loss in three of the four tanks. A lower loss (4% N) in the fourth tank was accompanied by a decrease in acetic acid concentration and a rise in slurry pH, at all depths, which was not observed in the other tanks. The lower loss of N from this tank than from the other tanks probably occurred to satisfy chemical equilibria that required a greater retention of ammonia (NH3) by the carbon dioxide (CO2) release from acetic acid breakdown. Considerations other than TKN and AMN concentration changes and equilibrium relations may also be important factors for N retention in slurry stored in farm tanks.
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