Nutrient Balances and Forage Productivity in Permanent Grasslands Under Different Fertilisation Regimes in Western Poland Conditions

Effective nutrient management in grassland ecosystems is essential for maintaining soil nutrient balance and ensuring high forage productivity. A field experiment was conducted between 2022 and 2024 on a permanent dry meadow at the Experimental Station in Poznań-Strzeszyn, western Poland. The trial, established in autumn 2021, was carried out under production conditions on large plots (140 m² each). Plots were assigned to different fertilisation regimes, varying in both type and dosage. The treatments included an unfertilised control, three levels of annual mineral NPK fertilisation (NPK1, NPK2, NPK3), three levels of annually applied farmyard manure (FYM1, FYM2, FYM3), and three levels of mineral and organic fertilisers applied every two years (NPK1/FYM1, NPK2/FYM2, NPK3/FYM3). Throughout the study, botanical composition, annual dry matter yield (DMY), nitrogen (N), phosphorus (P), and potassium (K) content in the plant biomass were assessed. A simplified nutrient balance was calculated based on nutrient input from fertilisers and nutrient output with harvested yield. The average N balance across three years ranged from −12.17 kg N ha⁻¹ in control to +20.6 kg N ha⁻¹ in FYM3. For phosphorus, average balances ranged from −7.2 kg P ha⁻¹ in the control to +9.8 kg P ha⁻¹ in FYM3. In contrast, potassium balances were mostly negative: from −51.7 kg K ha⁻¹ in FYM1 to −7.4 kg K ha⁻¹ in NPK1. The most balanced nutrient budgets were observed under alternate NPK/FYM fertilisation, with moderate surpluses of N and P and a smaller K deficit compared to FYM applied alone. In contrast, inorganic and organic fertilisation applied separately resulted in greater nutrient surpluses or a pronounced potassium deficit. This study emphasises the importance of balanced nutrient management in permanent meadows, showing that moderate fertilisation strategies, such as alternating FYM and mineral NPK, can maintain productivity, and reduce environmental impacts. These findings provide a practical basis for developing sustainable grassland management practices under variable climatic conditions.