Nitrate leaching during a 4-year period in a maize monoculture trial in Friuli-Venezia Giulia.

This paper presents the results of a multi-annual experimental trial carried out in the Friulian plains (N-E Italy), to compare the environmental impact on water and nitrate leaching of the most important crop system of the region (Maize-Maize succession) with a rotation system using cover crop (Maize-Ryegrass). Field lysimeters were used to collect leached water, which was then analysed for evaluating the amount of percolation, the nitrate concentration and the nitrate load of leaching. The results indicate good efficiency of the rotation system to limit nitrate leaching of 5 to10 times compared to maize monoculture, at values of about 20-30 kg/ha per year. The effect of cover crops resulted also when both systems were set-aside for two consecutive years, with a reduction of nitrate leaching of 50-60%. Because of the high temporal and spatial variation of the leaching data, it is anyway stressed that, for monitoring purposes, some other techniques, like diffused suction cups integrated by territorial models, could be more effective.