Changes and Interactions between Grassland Ecosystem Soil and Plant Properties under Long-Term Mineral Fertilization

Grasslands intensification by use of mineral fertilization has contributed substantially to the increase in forage production. Intensification, however, can degrade the other beneficial functions or soil properties. The effects of mineral fertilization on soil and plant chemical qualities of a permanent wet grassland (Festucetum pratense association) were investigated in Slovakia. The grassland was treated using 3 different N, P, and K rates of mineral fertilizers in kg. ha−1. yr−1 plus the Control (0NPK) almost over 60-year period (1961–2017). The N, P, and K rates in low NPK treatment (LNPK) were N50, P15.4, and K 41.5, in the medium NPK treatment (MNPK) were N100, P30.8, and K83, and in the high NPK treatment (HNPK) were N200, P 61.6, and K 166, respectively. Overall, soil variables (pH, soil organic carbon, plant-available K) showed the most significant changes. A more balanced development was observed in case of soil total nitrogen, C:N ratio, and plant-available P. ANOVA revealed a significant effect between treatments only on plant-available P. In the case of plant functional group development, long-term mineral addition significantly disfavors legumes and forbs. However, analyses of the botanical composition over the last 5 years showed that legume cover significantly differs only in the HNPK treatment. Plant C:P, N:P, and N:K ratios were significantly reduced when fertilizers were added. In terms of grasslands yields, the highest biomass and content of macronutrients were obtained under the HNPK rates. However, with regard to the quality and quantity of the soil organic matter, the most appropriate treatment has been with the MNPK rates. Our findings demonstrate that medium fertilization seems to be an acceptable compromise to meet both productivity and environmental aspects and to connect ecological benefits with social benefits in the long term.