Influence of Dolomite Application on Forage Productivity of Andean Grass–Legume Mixtures in Slightly Acidic Soils

This study evaluated the effects of three mineral amendments—calcitic lime, dolomite, and agricultural gypsum—and three cropping systems—Lolium multiflorum monoculture, Trifolium pratense monoculture, and a mixed grass–legume cropping system—on biomass production, forage nutritional quality, and soil chemical properties in Cajabamba, Peru. A 4 × 3 factorial arrangement within a completely randomised block design was implemented and analysed using generalised linear mixed models. The grass–legume association amended with dolomite achieved the highest biomass production, outperforming both monocultures and the calcitic lime treatment, even though calcitic lime produced the greatest increase in soil pH. Dolomite increased exchangeable magnesium and improved the soil Ca:Mg balance, whereas agricultural gypsum enhanced potassium availability without substantially modifying soil pH. The findings indicate that, under the evaluated slightly acidic high-Andean soil conditions, dolomite may represent an agronomically viable amendment for improving forage productivity. Nevertheless, the results correspond to a single-site, single-season experiment and require further validation before broader recommendations can be made.