Evaluation of fecal contamination indicators (fecal coliforms, somatic phages, and helminth eggs) in ryegrass sward farming

Abstract

The effect of soil supplementation with biosolids at various ratios on fecal-origin microorganism activity was evaluated in a ryegrass sward farm. Fifteen plots with 3 different soil and biosolid mixture ratios were assessed. Soil and grass were sampled over a period of 4 months (days 0, 30, 45, 60, 75, and 120) for soil and on days 75 and 120 for grass, corresponding to first and second grass harvest periods. We analyzed fecal coliforms, somatic phages, helminth eggs, and environmental factors, such as rainfall, temperature, and moisture. The fecal coliforms decreased by 2 logarithmic units (LU) in all soils containing biosolids and by 1 LU in the soil alone and in biosolid control plots alone. The concentration of somatic phages decreased to 2 to 3 LU in the soil containing biosolids and to 1 to 2 LU in the control plots. In contrast, however, there was a noticeable increase in helminth eggs on days 75 ad 120, but not in the soil control alone. Maximum concentrations (102 CFU/g TS; colony forming units per gram total solids) of fecal coliforms were found on the grass and in other samples, but the concentrations of phages and helminth eggs were below detection limits. Environmental factors did not significantly influence the results, and grass production increased from 35 to 50 Ton/Ha (tons per hectare) with biosolid supplementation, as compared with controls (14 Ton/Ha).