A minor thing, but it will increase flexibility down the road. If you have Excel 2007 or later, use SUMIFS instead. For example:

=SUMIFS($B$3:$B$29,C$3:C$29,"Farm1",D$3:D$29,"Field1")

B column is the data to add, C column contains farm names, and D contains field names. Note the order of items inside the formula are slightly different than SUMIF.

You can later get into limiting things such as dates when you do this. Take it further, and maybe you only want to sum records where you delivered the loads to an elevator, or maybe variety, or whatever you are tracking.

But, to make the multiple criteria work, you need to start with SUMIFS. It's easy to add more criteria later this way.

COUNTIFS and AVERAGEIFS work in similar ways.