Which Natural Substances Are Prohibited in Organic Crop Production?

1What § 205.602 actually says

The section is one sentence and a list:

The full list, quoted from the regulation:

2Reading the list — flat bans vs conditional bans

Most entries are flat bans: arsenic, lead salts, strychnine, tobacco dust, manure-burning ash, sodium fluoaluminate, and rotenone (the old-school botanical insecticide — natural, historically common, and prohibited). Three entries are conditional — prohibited unless the annotation's condition is met:

• Calcium chloride: prohibited except "as a foliar spray to treat a physiological disorder associated with calcium uptake" (think blossom-end rot). Ground application as a fertilizer is not what the exception covers.
• Potassium chloride: allowed only if "derived from a mined source and applied in a manner that minimizes chloride accumulation in the soil" — a sourcing and a practice condition, and your records need to show both.
• Sodium nitrate (Chilean nitrate): the annotation as written restricts use to "no more than 20% of the crop's total nitrogen requirement." If you use it at all, be ready to show the nitrogen budget math that keeps it under that line — and ask your certifier how they interpret and verify the 20% cap, because certifier practice on sodium nitrate varies. (The spirulina clause in the quoted text refers to a date long past; it's quoted verbatim because that's what the current text says.)

3Why such a short list matters so much

Ten entries versus the hundreds of allowed synthetics on §205.601 — but this list does different work. Every other natural substance is allowed by default, so §205.602 is the only thing standing between "natural" and "approved." Inspectors know these entries; a rotenone product or a casual sodium nitrate application is exactly the kind of finding that turns into a noncompliance. And like the rest of the National List, this section changes through rulemaking — check the current text1 before relying on any summary, including this one.

4Substance vs product, one more time

§205.602 speaks to substances. A "natural" branded product can still fail organic review because of what else is in the formulation — which is why the three-step input check (substance → product → certifier approval) applies to naturals just as much as to synthetics.

5How to document this on your farm

The conditional entries are the recordkeeping trap: mined-source documentation for potassium chloride, the calcium-uptake justification for a calcium chloride foliar, the nitrogen-budget arithmetic for sodium nitrate. OrganicAssistant logs each input with its product name and checks it against the National List and OMRI data as you go, so a prohibited or conditional natural gets flagged when you log it — not when your inspector reads your input records in the fall.

6The bottom line

Natural is the default, not the verdict. Ten nonsynthetic substances are prohibited or tightly conditioned in organic crops — and the conditional ones (calcium chloride, potassium chloride, sodium nitrate) are only as allowed as your documentation makes them. Verify the substance, then the product, then confirm with your certifier.

This explainer summarizes federal regulation in plain language; it is not legal advice or a compliance determination. Your certifier makes the final call on your operation. Reviewed against the eCFR text of 7 CFR § 205.602 current as of 2026-07-02.