translate English to French: In lab tests, addition of urea (112, 280, and 448 kg N/ha or 875, 2187, and 3500 ppm N) stimulated the endogenous respiration of each layer.
En laboratoire, l'addition d'urée (112, 280 et 448 kg N/ha ou 875, 2187 et 3500 ppm N) stimula la respiration endogène de chaque couche.