I'm not sure of farm work is allowed for a western foreigner. I'd say it isn't. Your only option might just be to idly sit there and watch your wife, as even handing her a tool could be considered violating the terms of your visa.
What do you do for a living, Ben Ji? It might be easier to get a long-term (business) visa on the grounds of work. Though I take it you are retired if you have an elite visa. In that case, you should just be patient and try to get back the normal way.