Section 179 is limited by business income on the return.  So if spouse farm losses out do K1 income, wages, and guaranteed payment; then the 179 is limited.  Use F1 on line 11 of the 4562 from P'ship to see what is considered business income.

Also on the K1 worksheet right after line 12 where you enter the 179 deduction, there is a quickzoom.  Tap that sucker and then you scroll down just a bit to the question "Check this box to reduce self-employment income (guaranteed payments) by UPE and 179 deduction?"  A yes answer to this question will allow milage to reduce self-employment tax.