Closing ADO Objects

I know it's "best practice" to dispose ado.net objects, but does it make a big difference if just the connection is closed?
 In other words, is the code below good enough or should the DataAdapter & Command be explicitly closed?

using (SqlConneciton  cn = new SqlConnection(connstr))
{
 SqlDataAdapter da = new SqlDataAdapter(sql,cn);
DataSet ds = new DataSet();
da.Fill(ds); 
SqlCommand cmd = new SqlCommand(someOtherSql,cn);
cmd.ExecuteNonQuery();

 
}