Introduction. The transformation of nitrogen in horse dung (BC) and in vegetal stubble with cow dung (VR) in all stages of the composting of these residues. Objective. Evaluate the behavior of nitrogen in the compost of the horse dung, comparing it with what happened in the compost of the vegetable stubble with cow dung. Materials and methods. Use of open-air compost piles and the chemical evaluation of these. Results. In both composting piles the temperature reaches its highest value in the thermophilic phase within the first week. The pH values are regulated by the formation and volatilization of the ammoniacal nitrogen. The electrical conductivity of the compost produced by the BC reaches a maximum value of 5 ΜS /cm and that produced by the VR of 4 ΜS/cm, this is related to the formation of ammoniacal nitrogen in the thermophilic phase and nitrates in the cooling phase. The C/N ratio at the end of composting for BC is increased, because only the remains of non-degraded rice husk remain. The decrease in the concentration of N-NH4 is due to volatilization and formation of N-NO3. Conclusions. The compost of the BC presented higher concentration of nitrogen than the compost of the VR.