1040 Schedule F Line 18

Line 18 on 1041 Schedule F is for "Freight".  I've been using this to report only freight paid to ship my farm products out.  I've been advised that I should also include freight paid on items (fertilizer, etc.) I purchase and have shipped to me.  Is this true?  Up to now I have been including that as the cost of the incoming item.  Schedule F instructions say I should do that for purchased livestock so I figured it should apply to all purchases.