The phosphorus (P) balance represents the difference between the input of P on agricultural land and the uptake of P from agricultural land with harvested crops. The total input is the sum of P, which is applied to the agricultural land with livestock fertilizers, mineral fertilizers, other organic fertilizers (sewage sludge, compost, digestates) and P, which comes to agricultural land with seeds and planting material. Uptake of P represents P in harvested crops. Long-term balance surplus P leads to an increase in P stocks in the soil and poses a potential risk for water, whereas the long-term balance deficit of P poses a potential risk for declining of soil fertility. It should be pointed out that this is a potential risk, as the actual risk depends on many factors, such as soil supply with P, meteorological conditions, the ability of the soil to bind P, farming methods, etc. Unlike nitrogen (N), which is characterized by a relatively rapid transfer from soil to water and air, P is relatively stable in the soil. Long-term surpluses/deficits of P can be problematic, whereas the surpluses/deficits in the individual years do not have a significant impact on the environment and soil fertility.

The P balance was expressed in tonnes at the national level and in kilograms of P per hectare of utilized agricultural area. Data for the period 1992–2023 are presented. The structure of input and output is also presented and the comparison with the countries of the European Union (EU-28) is given.

The main source of phosphorus (P) input to agricultural land in the last five years (2019–2023) represents livestock manure (60%), followed by mineral fertilizers (38%), other organic fertilizers (2.1%) and seeds and planting material (0.6%). The main source of P output represents fodder from permanent grassland (60%), followed by grain (25%) and green fodder from fields (13%). The trend analysis shows that during the period 1992–2023, the total input of P decreased from 14580 t P to 7914 t P, or by 46%. In the period 1992–2023 the input of P with mineral fertilisers decreased for 68% and with livestock fertilizers for 18%. The uptake of P by agricultural crops increased during the considered period. The trend analysis shows an increase from 6811 t P to 8690 t P, or by 26%.

The phosphorus surplus shows a clear decreasing trend. For the period up to 2003, surpluses were typical between 11 and 16 kg P per hectare. Thereafter, the surpluses decreased and reached an average value of + 1 kg P per hectare in the last five-year period. The trend analysis shows that the phosphorus budget during the period 1992–2023 decreased by 107% (from 14,9 to -1,0 kg P per hectare), which translates to about 0.5 kg P per hectare annually. The phosphorus budget is characterized by significant fluctuations between years. The large differences are mainly due to different weather conditions, which influence P uptake by the plants.

In the period 2005-2014, the phosphorus budget (+4.6 kg P per hectare) was above the average of the EU member states (+2.1 P kg per hectare).

The results on phosphorus budget should be interpreted in connection with the soil content of P. A potential risk for water pollution is represented by excessive P content in the soil and thus also in the soil solution. The results of the soil analyses show that Slovenia has more problems with a lack of phosphorus in the soil than with excesses. On average, 79% of meadow and 44% of arable soils do not reach the optimal supply of phosphorus, and the optimal supply is exceeded in 9% of meadow and 26% of arable soils (Babnik et al., 2011). It is favorable that livestock farms, which dispose of large amounts of P in livestock manure, are also characterized by a large output of P by crops (73% of total output represent fodder from permanent grassland and green fodder from fields). Further reduction of P surplus at the national level is therefore not desired.