Evaluation of Mineralization of Nitrogen in Liquid Dairy Manure during Storage

Abstract. The objective of this study was to conduct a lab-scale assessment of how temperature, manure solids content, using manure seed at the beginning of storage, and storage time affect N mineralization during storage of liquid dairy manure. Manure was scrapped from the barn floor of a dairy barn and diluted to make experimental stocks with high (46 to 78 g/L) and low (19 to 36 g/L) total solids (TS), simulating what was typically transported to the storage pit. The prepared manure was incubated in the laboratory at three temperatures (10, 20, and 30°C) for two incubation tests (seeded and unseeded). Manure samples were taken on selected days of storage for analyses. The results showed that temperature had significant (p<0.05) effects on N mineralization rates for both incubation tests, with the highest (0.096 week-1) and lowest (0.013 week-1) calculated N mineralization rate constants (k) occurring at 30℃ and 10℃, respectively. The concentrations of mineralized N (Nm) with non-sterilized manure were significantly higher than that with sterilized manure (p < 0.05). Compared to that with high TS manure, the concentrations of Nm were significantly higher with low TS manure after 180-d storage (p < 0.05). Raw manure augmented with manure seed had significantly higher Nm than the manure seed only (p < 0.05). The outcome of this study could be used to refine N mineralization input parameter of manure storage submodules of the process-based models such as Manure DNDC and IFSM with the goal to improve their accuracy of estimating or accounting for the fate or cycling of N in dairy manure during storage.