The objective of this work was to verify the effect of the calcium and magnesium ratio in the fertility of a dystrophic Dark Red Latosol (Oxisol), phase savanna, cultivated with alfalfa (Medicago sativa L.). The used experimental design was a randomized split-plot with four replicates. The treatments consisted of five Ca:Mg ratios 1:0; 1:1; 2:1; 3:1 and 4:1 at a recommended dosage of 3.9 t ha-1 and an additional treatment with the same ratio of 3:1, however with the double of the applied amount (7.8 t ha-1). Four soil samples were collected during the experiment consisting in the subtreatments. The results showed that with an increase of the relationship K/(Ca+Mg) a reduction of the Ca and Mg content of the aerial dry matter and of the exchangeable Ca and Mg content happens. The saturations of K, Ca and Mg are directly related with the total dry matter production and the increase of the relationship K/(Ca+Mg) reduces the pH index and increases the potential acidity of the soil.
Medicago sativa; K/Ca+Mg; K saturation; Ca saturation; Mg saturation; soil fertility
