Diet manipulation is a promising way for reducing phosphorus (P) content in manure and subsequently in surface water. The objective of this study is to clarify the effects of dietary fiber content on P distribution in fresh and stored liquid hog manure. Ten, 25 L liquid manure storage tanks were constructed and operated to simulate farm-based manure storage lagoons. Fifteen pigs were randomly grouped into three pens and the pigs in each pen were fed with a diet of different fiber contents (12%, 16%, and 21%). For 20 weeks, one litre of liquid manure from each pen was fed to each storage tank once a week with 3 replicate storage tanks per diet treatment. The samples of fresh and stored manure, each representing a diet treatment, were analyzed for P distribution along the fractions of dissolved organic, dissolved inorganic, particulate organic, and particulate inorganic. The results showed that fresh manure derived from the high fiber diet contained lower total P concentrations. Of the four fractions of total P, particulate organic P and particulate inorganic P composed 95.3% to 97.5% of total P in the fresh manure. After storage, the dissolved P concentration increased from around 25 ppm to 30–60 ppm. Inorganic P was the main fraction in dissolved P and composed 80% of the dissolved P in stored manure. The dissolved inorganic P, and therefore the total dissolved P were speculated to increase with manure storage time, indicating microbial activity through digestion. It was concluded that a higher fiber diet yielding manure with higher fiber content resulted in enhanced anaerobic degradation during manure storage. This, in return might promote the destruction of organic materials, resulting in the release of P and subsequent formation of inorganic dissolved P.
Caged Layer Performance in Pens with Oxidation Ditches and Liquid Manure Storage Tanks