public decimal GetAmmoniaRetention(int manureid, int seasonapplicationid) { decimal ammoniaRention = 0; FarmManure myManure = _ud.GetFarmManure(manureid); AmmoniaRetention myAmmoniaRetention = _sd.GetAmmoniaRetention(seasonapplicationid, myManure.dmid); ammoniaRention = myAmmoniaRetention.value.HasValue ? myAmmoniaRetention.value.Value : 0; return(ammoniaRention); }