Abstract
Nitrogen leaching in croplands is a worldwide problem with both human health and environment pollution implications. Efforts should be taken in order to increase nutrient use efficiency and minimize N losses from terrestrial to water ecosystems. Soil-applied biochar has been reported to increase soil fertility, improve nutrient retention and decrease nutrient leaching in tropical soils and lab conditions. The aim of the present experiment was to evaluate the effect of biochar soil addition on N leaching in a mature apple (Malus domestica Borkh.) orchard located in the Po Valley (Italy). In spring 2009, 10 Mg of biochar per hectare were incorporated into the first 20-cm soil layer by surface soil ploughing. A similar soil perturbation was applied to control plots. Cumulative nitrate and ammonium leaching was measured during a 4 months period after biochar addition and in the following year, using ion-exchange resin lysimeters installed below the ploughed soil layer. Cumulative nitrate leaching was not affectedby biochar 4 months after application, while a significant reduction of nitrate leaching was observed during the following year in biochar treated soil. Conversely, ammonium leaching was very low and unaffected by the treatment. We speculated that the higher efficacy of biochar observed in the second year of the experiment might be due to a change in biochar properties with time.