diff --git a/django/contrib/gis/db/backends/postgis/operations.py b/django/contrib/gis/db/backends/postgis/operations.py
index 2d27be14ca..7e1712bc7f 100644
--- a/django/contrib/gis/db/backends/postgis/operations.py
+++ b/django/contrib/gis/db/backends/postgis/operations.py
@@ -15,7 +15,7 @@ from django.utils.version import get_version_tuple
 
 from .adapter import PostGISAdapter
 from .models import PostGISGeometryColumns, PostGISSpatialRefSys
-from .pgraster import from_pgraster, get_pgraster_srid, to_pgraster
+from .pgraster import from_pgraster
 
 # Identifier to mark raster lookups as bilateral.
 BILATERAL = 'bilateral'
@@ -297,8 +297,6 @@ class PostGISOperations(BaseSpatialOperations, DatabaseOperations):
         # Get the srid for this object
         if value is None:
             value_srid = None
-        elif f.geom_type == 'RASTER' and isinstance(value, str):
-            value_srid = get_pgraster_srid(value)
         else:
             value_srid = value.srid
 
@@ -306,8 +304,6 @@ class PostGISOperations(BaseSpatialOperations, DatabaseOperations):
         # is not equal to the field srid.
         if value_srid is None or value_srid == f.srid:
             placeholder = '%s'
-        elif f.geom_type == 'RASTER' and isinstance(value, str):
-            placeholder = '%s((%%s)::raster, %s)' % (tranform_func, f.srid)
         else:
             placeholder = '%s(%%s, %s)' % (tranform_func, f.srid)
 
@@ -376,10 +372,6 @@ class PostGISOperations(BaseSpatialOperations, DatabaseOperations):
     def spatial_ref_sys(self):
         return PostGISSpatialRefSys
 
-    # Methods to convert between PostGIS rasters and dicts that are
-    # readable by GDALRaster.
     def parse_raster(self, value):
+        """Convert a PostGIS HEX String into a dict readable by GDALRaster."""
         return from_pgraster(value)
-
-    def deconstruct_raster(self, value):
-        return to_pgraster(value)
diff --git a/django/contrib/gis/db/backends/postgis/pgraster.py b/django/contrib/gis/db/backends/postgis/pgraster.py
index 555fc17f1e..ff06f11895 100644
--- a/django/contrib/gis/db/backends/postgis/pgraster.py
+++ b/django/contrib/gis/db/backends/postgis/pgraster.py
@@ -30,18 +30,6 @@ def chunk(data, index):
     return data[:index], data[index:]
 
 
-def get_pgraster_srid(data):
-    """
-    Extract the SRID from a PostGIS raster string.
-    """
-    if data is None:
-        return
-    # The positional arguments here extract the hex-encoded srid from the
-    # header of the PostGIS raster string. This can be understood through
-    # the POSTGIS_HEADER_STRUCTURE constant definition in the const module.
-    return unpack('i', data[106:114])[0]
-
-
 def from_pgraster(data):
     """
     Convert a PostGIS HEX String into a dictionary.
@@ -112,10 +100,6 @@ def to_pgraster(rast):
     """
     Convert a GDALRaster into PostGIS Raster format.
     """
-    # Return if the raster is null
-    if rast is None or rast == '':
-        return
-
     # Prepare the raster header data as a tuple. The first two numbers are
     # the endianness and the PostGIS Raster Version, both are fixed by
     # PostGIS at the moment.
diff --git a/django/contrib/gis/db/models/fields.py b/django/contrib/gis/db/models/fields.py
index 9f8c5a1e16..a69c10b6b4 100644
--- a/django/contrib/gis/db/models/fields.py
+++ b/django/contrib/gis/db/models/fields.py
@@ -361,13 +361,6 @@ class RasterField(BaseSpatialField):
     def from_db_value(self, value, expression, connection, context):
         return connection.ops.parse_raster(value)
 
-    def get_db_prep_value(self, value, connection, prepared=False):
-        self._check_connection(connection)
-        # Prepare raster for writing to database.
-        if not prepared:
-            value = connection.ops.deconstruct_raster(value)
-        return super().get_db_prep_value(value, connection, prepared)
-
     def contribute_to_class(self, cls, name, **kwargs):
         super().contribute_to_class(cls, name, **kwargs)
         # Setup for lazy-instantiated Raster object. For large querysets, the