What you are probably seeing is the Partial Pattern. This pattern is added to a field whenever you perform a farming action and enter a number of acres that is less than the entire field's size (in the Acres Farmed box). The reason for this pattern is a way to remind you that you haven't farmed the entire field yet.
You can turn this option off when you record a farming action by clicking on the pattern in the Farming box and turning off the Partial Pattern option. Alternately, after you record the farming action you can right-click on the field (with the Pointer Tool) and choose the Properties menu option. You can then click on the Pattern button and turn off the Partial Pattern option.
I hope this helps! R. Scott Nusbaum CPA Farm Works Software