Nitrogen values of liquid dairy manure and dry broiler litter as affected by preservation treatment

Five liquid dairy manures and five dry broiler litters were tested in the laboratory to determine the effects of four preservation techniques on the forms and concentrations of nitrogen. 300 ml samples of fresh manure from five Virginia dairy and five poultry farms were analyzed for total Kjeldahl, ammonium, and nitrate/nitrite nitrogen within 24 hours of farm sampling, and at the end of seven days. Samples of the fresh manure were analyzed immediately as a control. The four preservation techniques were storage of the samples: at ambient temperature (26°C), by freezing (-22°C), by refrigeration (4°C), and by acidification with sulfuric acid (H₂SO₄) to pH < 2 plus refrigeration (4°C).

Concentrations of nitrogen fractions were tabulated on a dry-weight basis and statistically analyzed using a randomized block design, with subsampling of each treatment × farm combination. Organic and inorganic nitrogen concentrations from the preserved manures were compared to the corresponding fresh concentrations of nitrogen in each manure control. Ambient storage, freezing, and refrigeration did not significantly affect (α=.05) the 7-day nitrogen concentrations of the ten manures. Acidification reduced most N concentrations due to the aggressive physical action of the acid, which accelerated both mineralization of organic N and volatilization of ammonia. Ambient storage was recommended as the most practical preservative technique because, of the three successful preservation methods, ambient storage provided the simplest procedure for 7-day preservation of nitrogen in liquid dairy manures and dry broiler litters.