Comparison of the phosphorus balance results based on 'field surface' and 'farm gate' methodology in large-scale farms

The aim of the study was the comparative analysis of the results of the phosphorus balance calculated by two methods, in the field scale and the farm scale, and assessment of usefulness of the application of balances in monitoring the agricultural production. Twenty-six large-scale farms were selected for studies with the area from 204.0 to 11391.5 ha. The analyses used data from the years 2002-2006. The spatial scope included the farms located in 33 municipalities, which administratively belonged to three provinces. Twenty six municipalities were located in 7 areas particularly nitrate vulnerable zones (NVZ’s). The evaluation of phosphorous load of the selected farms in different regions was performed based on the calculation of the balance with two methods – field surface and farm gate. As research has shown although the balance of the phosphorus calculated with the field surface method was on average higher by 7.2 kg P2O5·ha-1 AL, the results obtained based on two different methodical approaches indicate similar trends. The higher balance was mainly affected by manures produced in the own farm. Maximal values of the balance in both methods remained at a similar level, reaching approx. 60 kg P2O5·ha-1 AL. In case of the field surface balance, 7 farms fitted in the standard, and in case of the farm gate balance 5 met recommendations concerning the acceptable balance for the analysed region.