Hi there, I have only ever been paid by the hour and per bin, so will explain that.
The farmer at the start of the job will tell you how much you will be paid and in what way. So when I was picking pears the farmer would pay me $16 per hour. I picked apples on another farm and was paid per bin I filled and they are large bins. I filled 4 bins in 8 hours, I was paid $27 a bin. The farmers always paid me what they said because I was going through the working backpacker hostel who supplied the local farm with labour.