There is another thing you can do to defer income.  You can start the plan year in, for example, November and fund 2 years
of the pension, and expense it all in one tax year. 
This is really helpful if you have a machinery auction, or sell multiple years of grain in one year. 
You need an experienced retirement specialist to do this.  This is not your local bank or financial advisor. 
Fees vary, and your CPA should be able to advise you.  Some advisors in farm states work a lot with farms and small businesses.