diff --git a/facho/model/__init__.py b/facho/model/__init__.py
index 13d7c13..33cd824 100644
--- a/facho/model/__init__.py
+++ b/facho/model/__init__.py
@@ -1,3 +1,4 @@
+from .fields import Field
 
 class ModelMeta(type):
     def __new__(cls, name, bases, ns):
@@ -19,7 +20,15 @@ class ModelBase(object, metaclass=ModelMeta):
         obj._fields = {}
         obj._text = ""
         obj._namespace_prefix = None
-        
+
+        # forzamos registros de campos al modelo
+        # al instanciar
+        for (key, v) in type(obj).__dict__.items():
+            if isinstance(v, fields.Attribute) or isinstance(v, fields.Many2One):
+                if hasattr(v, 'default') and v.default is not None:
+                    setattr(obj, key, v.default)
+
+
         return obj
 
     def __setitem__(self, key, val):
@@ -32,10 +41,12 @@ class ModelBase(object, metaclass=ModelMeta):
         pass
 
     def __default_set__(self, value):
-        return str(value)
+        return value
     
     def _set_content(self, value):
-        self._text = str(self.__default_set__(value))
+        default = self.__default_set__(value)
+        if default is not None:
+            self._text = str(default)
 
     def _hook_before_xml(self):
         self.__before_xml__()
@@ -63,7 +74,6 @@ class ModelBase(object, metaclass=ModelMeta):
 
         for name, value in self._fields.items():
             if hasattr(value, 'to_xml'):
-                print(self._fields)
                 content += value.to_xml()
             elif isinstance(value, str):
                 content += value
diff --git a/facho/model/fields/__init__.py b/facho/model/fields/__init__.py
index 77d3bef..4e35a11 100644
--- a/facho/model/fields/__init__.py
+++ b/facho/model/fields/__init__.py
@@ -3,5 +3,6 @@ from .many2one import Many2One
 from .model import Model
 from .function import Function
 from .virtual import Virtual
+from .field import Field
 
-__all__ = [Attribute, Many2One, Model, Virtual]
+__all__ = [Attribute, Many2One, Model, Virtual, Field]
diff --git a/facho/model/fields/attribute.py b/facho/model/fields/attribute.py
index e8fd7a0..e89268a 100644
--- a/facho/model/fields/attribute.py
+++ b/facho/model/fields/attribute.py
@@ -4,6 +4,7 @@ class Attribute(Field):
     def __init__(self, tag, default=None):
         self.tag = tag
         self.value = default
+        self.default = default
 
     def __get__(self, inst, cls):
         if inst is None:
diff --git a/facho/model/fields/function.py b/facho/model/fields/function.py
index 2294041..20ba6e9 100644
--- a/facho/model/fields/function.py
+++ b/facho/model/fields/function.py
@@ -14,6 +14,7 @@ class Function(Field):
         # si se indica `field` se adiciona
         # como campo del modelo, esto es
         # que se serializa a xml
+        self.field.name = self.name
         inst._fields[self.name] = self.field
 
         if self.getter is not None:
diff --git a/facho/model/fields/many2one.py b/facho/model/fields/many2one.py
index 0ead219..d75e03b 100644
--- a/facho/model/fields/many2one.py
+++ b/facho/model/fields/many2one.py
@@ -1,11 +1,12 @@
 from .field import Field
 
 class Many2One(Field):
-    def __init__(self, model, name=None, setter=None, namespace=None):
+    def __init__(self, model, name=None, setter=None, namespace=None, default=None):
         self.model = model
         self.setter = setter
         self.namespace = namespace
         self.field_name = name
+        self.default = default
 
     def __get__(self, inst, cls):
         if inst is None:
diff --git a/tests/test_model.py b/tests/test_model.py
index b42b473..c965649 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -314,3 +314,44 @@ def test_field_virtual():
     person.age = 55
     assert person.age == 55
     assert "<Person/>" == person.to_xml()
+
+
+def test_field_inserted_default_attribute():
+    class Person(facho.model.Model):
+        __name__ = 'Person'
+
+        hash = fields.Attribute('hash', default='calculate')
+
+
+    person = Person()
+    assert '<Person hash="calculate"/>' == person.to_xml()
+
+def test_field_inserted_default_many2one():
+    class ID(facho.model.Model):
+        __name__ = 'ID'
+
+        key = fields.Attribute('key')
+        
+        def __default_set__(self, value):
+            self.key = value
+
+    class Person(facho.model.Model):
+        __name__ = 'Person'
+
+        id = fields.Many2One(ID, default="oe")
+
+    person = Person()
+    assert '<Person><ID key="oe"/></Person>' == person.to_xml()
+
+def test_field_inserted_default_nested_many2one():
+    class ID(facho.model.Model):
+        __name__ = 'ID'
+
+    class Person(facho.model.Model):
+        __name__ = 'Person'
+
+        id = fields.Many2One(ID, default="ole")
+
+    person = Person()
+    assert '<Person><ID>ole</ID></Person>' == person.to_xml()
+