Can I plaster Straw Bale walls with cement?

With finishes, it is critical that the straw walls / earthen walls should breathe. It has been found that walls can get wet provided they are able to dry out again. As such cement plasters are to be avoided, as they tend to trap moisture within the walls, which ultimately leads to the destruction of the wall. A traditional lime sand plaster is therefore used, either onto an initial coating of mud plaster or straight onto the straw. Clay sand lime plasters and lime sand dung plasters can also be used. Earthen plasters alone can also be used, provided lots of finely chopped/shredded straw or cellulose fibre (soaked shredded newspaper) is added to the mix and that weather walls are sufficiently protected with good roof overhangs or verandas. In all cases it is advised to protect the plaster with a good breathable paint.

Also see "With what can I plaster my walls?"