The fertilizer value of pig slurry. I. Values depending on the type of operation

151 samples of pig slurries were taken from 83 operations in the Castile-Leon region of Spain. Analysis of them enabled comparison of slurries coming from pig farming operations located in different Spanish and European regions. These operations were classified into three groups, namely maternity (64 samples), closed cycle (35 samples) and fattening (52 samples). For each sample 27 parameters were analysed. Data obtained from each kind of operation were compared. Finally, the fertilizer value of slurries was determined with regard to the relationship between their major elements, N/P2O5/K2O (1/0.6/0.4).