Surface runoff pollution by cattle slurry and inorganic fertilizer spreading: chemical oxygen demand, ortho-phosphates, and electrical conductivity levels for different buffer strip lengths

As a way of dealing with the removal of pollutants from farming practices generated wastewater in the EU, we investigate the effect of spreading cattle slurry and inorganic fertiliser on 8×5 m² and 8×3 m² areas, referred to surface runoff chemical oxygen demand (COD), ortho-phosphates (o-P) and electrical conductivity (EC) levels, and the efficiency of grass buffer strips of various lengths in removing pollutants from runoff.

The experimental plot was a 15% sloped Lolium perenne pasture. Surface runoff was generated by means of a rainfall simulator working at 47 mm h^-1 rainfall intensity. Runoff was sampled by using Gerlach-type troughs situated 2, 4, 6 and 8 m downslope from the amended areas.

During the first rainfall simulation, COD, o-P and EC levels were consistently higher in the slurry zone, more evidently in the larger amended area. During the second and third rainfall simulations, concentration and mass levels show a downslope drift into the buffer zones, with no clear buffer strip length attenuation.

Correlation between runoff and mass drift is clearly higher in the slurry zone.

Percentage attenuation in COD and o-P levels, referred to initial slurry concentrations - including rainfall dilution - were higher than 98%, and higher than 90% for EC.