This study concerns the phytotoxicity test of a compost prepared with calcined Tahoua phosphate in order to increase its solubility. To do this, a test was carried out on two crops: corn and peanuts. For each crop, four treatments were carried out: control To made up of sand, T1 containing 1/4 compost and 3/4 sand, T2 made up of 3/4 compost and 1/4 sand, T3 made up of compost alone. The experiment was carried out in pots arranged in blocks with three repetitions. After 10 days of incubation, the maturity of the compost was evaluated according to the percentage of germination of the treatments compared to the control. The results made it possible to obtain a germination rate of 100% with maize and 122% with peanut for the T1 treatment. For the T2 treatment, the germination rate is 100% with maize and 88.89% with peanuts. As for the T3 treatment, the germination rate is 111% for maize and only 22.22% with peanuts. These results show that the calcination of merchant phosphate from Tahoua does not lead to the formation of phytotoxic products for plants.