Why savings? It makes tham less competitive with the Chinese prison labor.
Ooops, someone forgot the sarcasm tag ;-)
How about the "carrot and stick" ploy? If you volunteer for working the fields, you will have money put into a savings account. If you do well and cooperate, you will also get a good job recommendation upon your release. If you choose not to participate, or screw up your assignment, expect to spend every lasting minute of your sentence behind bars.
It could work, and perhaps even rehabilitate certain types of criminals. We won't know unless we try.