@Ahmed, generally the recommended rate of FYM for maize varies between 5,000 and 20,000 kg/ha depends mainly on soil fertility and the preceding field management.
The FYM depends upon soil to soil generally 10 Ton FYM per ha, 10-15 days prior to sowing supplemented with 150-180 kg N, 70-80 kg P2O5, 70-80 kg K2O and 25 kg ZnSO4 per ha is recommended.
Your question is not answerable without stating the basis for the application and the nutrient profile of the FYM. what are you applying the FYM for? - to supply total N requirement of corn or the P requirement or other pre-determined requirement? also, what is the guaranteed analysis (nutrient profile) of the FYM? You'll need to provide these in order to calculate the rate of application.
Depends on the quality of nutrients in the FYM and recommended nutrient requirement of the maize variety as well as soil nutrient status. Another important factor when calculating the amount of FYM is the moisture status of the organic material/FYM