Abatement of NO3–N concentration in agricultural waters by narrow buffer strips

The performance of narrow buffer strips in abating the NO3–N concentrations in the water coming from cropland was tested in an experiment carried out on the low plains of the Veneto Region (northeast Italy). The buffer was composed of a 5-m wide grass strip and a 1-m wide row of trees. Maize and wheat were cultivated in the neighbouring field during the monitoring period (December 1997–June 1999). Four experimental conditions were monitored, deriving from a combination of two levels of crop N fertilisation and two sizes of buffer trees. The narrow buffer was very effective in abating NO3–N concentrations, allowing water to be discharged with a concentration always below 2 ppm. Its zone of influence might be bigger than its simple width. The abatement was also efficient during winter. Tree size showed no evident effect on the reduction of the concentration.