Apparent balance of nitrogen in organic and conventional dairy farms in Tuscany (Central Italy). ).

Data obtained by a survey conducted on 36 organic and conventional dairy farms in Mugello (Tuscany, Central Italy) are reported. The apparent balance of nitrogen was calculated for each farm in order to evaluate the efficient utilisation of this element, comparing all inputs and all outputs of different forms of nitrogen entering or leaving the farm. The surplus of the element was then referred to the surface to compare farms of different size. Organic farms are located at an higher altitude and they present a larger surface than conventional ones. Large differences were found concerning land use, with a higher use of maize (16.1% vs. 2.4%, P<0.05) and a reduced presence of natural pastures (5.9% vs. 15.7%, P<0.05) in the conventional farms. Organic farms produced somewhat lower surplus compared with conventional farms (not significant), and this was mainly due to purchase of fertilisers (P<0.05). The efficiency in nitrogen utilisation was comparable in organic (27.3%) and conventional farms (22.5%). Results show that stocking rate was the factor that mainly affected nitrogen surplus and there were no significant differences in nitrogen surplus between organic and conventional farms. Therefore, it can be concluded that conventional dairy farms in Mugello are managed in an extensive manner with no high environmental risks, particularly concerning nitrogen pollution.