Changes in the properties of pig manure slurry.

The paper presents the results of analyses of samples of manure from a pig farm located near Piła, Poland performed between June 2011 and May 2012 using a single sampling system. The statistical analyses of the average content of chemical and biological oxide demands, nitrogen, phosphorus, potassium, calcium and dry mass in the slurry in various seasons allowed us to draw conclusions concerning the changes in the chemical composition of the manure in specific seasons and to determine the correlations between the chemical parameters. The average content of N, BOD, P, and dry mass content tended to decrease systematically from the spring until the winter. The highest correlation coefficient, which indicates significant interdependency among the variables tested, was consistently found for COD and BOD, whereas the smallest correlation coefficient was found consistently for K and Ca and once for Ca and N.