iowa department of revenue review statutory sales and use tax exemptions november 2006 1 on july 2004 streamlined sst law was implemented in a new category explaining the changes due to implementation has been added this list for your reference citations listed below have both prior code sections under agriculture commercial fertilizer agricultural limestone 422 42 3 1937 423 4 materials including used control disease weeds or insects promote health plants livestock market most exempt items farming fall exemption 1957 redrafted 1985 include breeding stock domesticated fowl herbicide pesticide insecticide food medication 5 fuel consumed implements husbandry production 6 grain drying 1969 sale rental certain farm machinery equipment