Increasing doses of Si interfered with the nutrition of forage crops under conditions of aluminum toxicity, with positive results for leaf concentrations of Si, K, Ca, Mg, Cu, and Zn. From the first to the second cut of the grasses, there was a decrease in Al concentration in the aerial part, demonstrating that Si doses were beneficial over time. Increasing Si doses under conditions of aluminum toxicity had a positive effect on the number of leaves and tillers, with repercussions on the dry matter production of Mombaça and Tanzania grasses. In the second cut of forage crops, the supply of silicon resulted in higher dry matter production of Tanzania grass. The supply of silicon reduces aluminum absorption and toxicity in the two Panicum maximum cultivars without causing a loss in the quality of these forage crops (FDN and FDA).