Total and faecal coliform bacteria persistence in a pig slurry amended soil

The aim of this experiment was to study the effect of the application of pig slurry on potential pathogen (total and faecal coliform bacteria) presence in a Typic Xerofluvent soil. The experiment was conducted in field conditions, in the Segura River valley in the South East of Spain. Four treatments, in a fully-randomised design with three replicates per treatment, were established in experimental plots of 16 m2 each. Fertiliser treatments were: MF, mineral fertiliser (with a complex 16N–16P2O5–16K2O) equivalent to 150 kg N ha− 1; PSF, organic fertilisation with swine manure slurry, at two different rates (supplying 150 and 210 kg N ha− 1), and C, a controlled treatment without fertilisation. A high variability of the concentrations of total and faecal coliforms was observed during the experiment, mainly depends on the time and the treatment. The pig slurry amendment induced the highest initial and also persistent presence of total and faecal coliform bacteria. The higher application rate seemed to induce a long-lasting persistence of the total, but especially the faecal coliform, population in the amended soils compared to the lower rate. In most cases, an increase in the total coliforms content was observed in the soils amended with mineral fertiliser compared to controlled soils, probably due to an increase in soil microorganisms populations. In general, the total coliform bacteria was 2–3 log10 units higher than the faecal ones. Mostly, a tendency to decrease with time was observed in both indicator microorganisms, in all the treatments.