Apparent balance of nitrogen and phosphorus in dairy farms in Mugello (Italy).

The aim of the present work is to evaluate the differences in the surplus of nutrients at farm level and the risk of pollution related to farm management between the two areas of Mugello (Tuscan Apennines, Italy): Basso Mugello (LM) and Alto Mugello (HM). Data of a survey on 36 farms of dairy cows in the area of Mugello (FI) are reported. In each farm the apparent balance of nitrogen and phosphorus was estimated in order to evaluate the equilibrium of these elements within the farms. The operative procedure, already used in Italy, is based on the estimation of fluxes of these elements entering and leaving the farm, and the difference between them represents the surplus of this element, which refers to the surface of the farm. Two typologies of farms were identified, differing in altitude: farms in the lowlands (LM) and in the uplands (HM) of the area. Farms belonging to LM showed N surplus of 136 kg ha-1, while in HM the N surplus amounted to 53 kg ha-1. Surplus of P were 73 kg ha-1 and 27 kg ha-1 for LM and HM, respectively. Results are related to the different productive systems, with 31.7% of surface of permanent fodder crops in HM (instead of 1.5% in LM). Moreover, the LM raises maize crops in a very intensive way utilising it for animal feed together with feedstuff coming from outside the farm. Results showed that the main factors affecting the surplus of the elements are the purchase of animal supplements, fertilisation and animal stocking rate.