The study of the influence of deficient dose of potassium on the mineral nutrition of sorghum (Sorghum dochna, F.) does not any modification in calcium distribution. On the other hand, the quantity and percentage of magnesium increase proportionally with the decrease of potassium. The quantity of magnesium doubles in the deficient lots compared with the reference solution. This observation shows a strong interaction between potassium and magnesium, and a much weaker one between potassium and calcium.