Soil nitrogen leaching from tree row strips and grassed alleys in a pear orchard

A study was carried out to evaluate nitrogen losses between October 2004 and February 2005 in a pear (Pyrus communis cv. Abbé Fètel) orchard, in the eastern Po Valley (Northern Italy). NO3- concentration was determined in the soil solution extracted with suction lysimeters in the tree rows and in the grassed alleys. Nitrate losses were calculated multiplying N concentration in the soil solution by the amount of water drainage out of the soil profile, estimated by a meteorological approach. Two treatments (with or without N supply – 48 kg N ha-1 - by fertigation) were compared. Nitrate-N concentration in soil solution and N losses were highest in the tree row strips of fertilized plots and lowest in the grassed alleys. Results indicate that localised addition of nitrogen through the irrigation system at rates used in this experiment increased the N losses through leaching by 3.8 kg N ha-1, accounting for about 8 % of fertilizer N. Negligible amounts of nitrate-N were lost from grassed alleys, suggesting a beneficial role of the extension of grass presence along tree row strip during autumn-winter.