Physical characteristics

All piles except number 1 were uniform loaf-shaped piles of approximately 30 ‘ long and 5‘ high. All piles but number 1 were "built" using the front end loader of a tractor. Pile 1 was roughly the same shape, but tapered somewhat at the ends. Pile 1 was dumped directly from the side of the hauling tractor trailer and was minimally smoothed before being instrumented. Building the piles allowed for more precise placement of continuous temperature probes.

We observed pH values ranging from 6.1 to 9.0. The most common values were from 8.2 to 8.9. This range of pH values are within the biological range where coliform bacteria will grow. Mean values for pH, Aw and DM values are listed in Table 1. Notably, Pile 2 had the lowest water activity and dry matter of the 5 piles analyzed. In our visual appraisal of the litter material of pile 2, we noted that it appeared to have a greater proportion of rice hulls versus manure than the other piles we worked with. This may indicate that moisture is necessary to drive the heating reaction in the pile and that perhaps the manure provides this. This hypothesis was later tested in Model 2.

TABLE 1. Range of values for physical parameters, pH, water activity (Aw) and DM for stacked poultry litter piles based on 6 piles.

*data represents 2 seasons (summer-hot/dry; winter-cool/wet)