Well, I surely don't know where Deere is going. However, your short calls are faced with 2 probable scenarios:
1) Stock goes up and volatility goes down. You loose because of delta effect but win some on vega.
2) Stock goes down and volatility goes up. You win, but not so much, because of the inverse relationship of volatility to stock price. It will prop up the value of the call options.
Is there a win/win? Is it likely that price and volatility simultaneously go up? Extremely unlikely unless it's biotech or oil exploration faced with a new discovery.
Btw, are you making use of special, home-grown knowledge of these industries? As an Aussie, you should be diversifying away from these industries. Your economy is incredibly concentrated in the materials sector.
Show us your map O' Tassie!