N and P Farmgate Balances in Arable and Mixed Bulgarian Farms Before EU Accession

Increasing nutrient loads in European agriculture was the reason for theapplication of farm gate nutrient balance approach and improvement of nutrientmanagement by re-examining the routine agricultural practices. Before EuropeanUnion (EU) accession the nutrients loads in Bulgarian agriculture were very low onaverage. Applied chemical fertilisers in last years at country scale were as follows N -31 kg.ha-1, P2O5 - 5.6 kg.ha-1 and K2O - 0,6 kg.ha-1. Regardless the low fertiliser’sutilisation in vegetable farms and in mixed farms nutrients loads are significant andconditions of environment pollution could be observed. Other source of pollutions arethe non-intensive farms on acid soils where low fertiliser rates are applied, but the lowyield and nutrients uptake are causing positive nitrogen balance. This paper reports onthe farm gate nitrogen (N) and phosphorus (P) balances of typical Bulgarian arableand mixed farms calculated for 2007 and 2008. The farm gate nutrientsurpluses/deficits varied significantly between the farm type within one year andbetween the different years. This could partly be explained by the different level ofutilisation of chemical fertilisers and reutilisation of available farmyard manures.Calculated N and P balances clearly reflected the lower grain crop yields in 2007 dueto the dry weather conditions in the active season, which strongly affected the arablefarms from the Central part of Bulgaria. Nitrogen surplus was observed in vegetablefarms, mixed farms and in the larger farms which were fertilising with adequatefertiliser rates. Surplus of P was observed only in intensive vegetable farms and mixedfarms. The farm gate P deficit in most of the selected farms indicated a soil mining and is a warning for possible future crop deficiencies and yield reduction. Some of thefertiliser application tendencies are also valid for the current time.