The objective of this work was to evaluate the effects of triple superphosphate, magnesium thermophosphate and their mixtures in the agronomic and bromatological characteristics of black and white oats. The experiment was conducted in a 2 × 6 factorial scheme, constituted by the two forages: black and white oats; and two sources of phosphorus (P): triple superphosphate and magnesium thermophosphate, at a dose of 70 kg ha -1 of P 2 O 5 , in the proportions: 0:0, 100:0, 0:100, 50:50, 75:25 and 25:75. The effect of fertilization and P source on the total dry matter of black and white oats (p < 0.05) ranged from 0.21 ± 0.03 to 10.83 ± 0.33 and from 0.14 ± 0.00 to 13.79 ± 0.60 g pot -1 , respectively. Greater forage production was observed in black and white oats fertilized with triple superphosphate (p < 0.05), even when used in a mixture up to 50%. Due to the different responses observed and the variation in the levels of P and crude protein in the forages, it was not possible to determine the effect of the fertilization and the sources of P in these variables. It was verified that black and white oats presented better responses in their productive characteristics when