“Improvement Technologies” in Campos Grasslands: Effects on Soil Chemistry and Botanical Composition and Implications for Ecosystem Persistence

Background and Aims Pasture improvement practices such as liming, fertilization, and overseeding with exotic cool-season species have been adopted to increase forage production and reduce land conversion to agriculture; however, their long-term effects on soil chemical properties and plant community structure remain insufficiently understood across contrasting environments. Methods This study evaluated unimproved natural grassland (NG) and improved natural grassland (NG + X, where X represents years under improvement) across five physiographic regions in southern Brazil. Improvements consisted of surface liming, annual fertilization with N, P, and K, and overseeding with ryegrass and legumes. Soil samples were collected at four depths (0–5, 5–10, 10–20, and 20–40 cm) to assess pH, exchangeable cations, Al saturation, and available P and K. Botanical composition, species richness, diversity indices, and forage production were also quantified. Results Improvement technologies generally increased soil fertility, especially by raising pH and increasing available P and K, although effects were largely restricted to the surface layer due to limited mobility of lime and P. In contrast, long-term nitrogen fertilization without liming promoted soil acidification in some environments. Pasture improvement altered plant community composition, favoring fertilization-responsive forage species but, in some locations, reducing species richness and diversity, particularly under long-term ryegrass establishment. Responses varied among sites and were strongly influenced by initial soil fertility. Conclusion Overall, targeted pasture improvement in low-fertility soils can enhance forage production and ecosystem services, but strategies must be carefully managed to avoid long-term biodiversity losses and excessive nutrient stratification.