Howdy,
perhaps they are treating the loan as commercial due to the commercial farming scenario, rather than residential,
 Commercial vs residential rates differ by roughly 2.25%.
We pay 9.75% to Bankwest on a big commercial bill, and  I pay 6.61% on my personal line of credit with Bankwest.
 NAB used to be our bankers but they wouldn't finance us again when we bought an additional commercial property, 65% LVR was too much for them to consider. Bankwest LVR is 82%, maybe we got lucky, we got a fantastic bank manager and the $!
Also check your credit rating in case something has gone askew.
And I guess the most important question the bank will want to know is how are you going to fund your repayments?
Perhaps loan 100k, then some more $ later?

Good luck!