Fertilizer recommendations without a soil test are guesswork. Say so.
Well established It is settled without a trial. If you skip this, it still grows, just less well. The planner suggests it.
How it works
Whether a soil has enough nitrogen, phosphorus and potassium (N-P-K) depends on the site, and there's no way to know it without a test.
What to do about it
We will not invent an NPK number. A soil lab will test this soil, and the soil card shows how to find one where you garden. Until then, feed heavy feeders, do not feed root crops, and add compost.
The evidence
Evidence: settled without a trial (epistemics).
Folklore it answers
Read next
- What to do with last year's raised bed soilYour raised bed soil isn't used up at the end of the season. Here's why it settles, how to refresh it with compost, and why replacing it is almost never the answer.
- The soil test, the best buy in gardeningA soil test replaces guessing with knowing. Here's what it measures, why no tool should hand you fertilizer numbers without one, and how to take one. The rare piece of garden advice that saves money.
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Advice on what to do added
- Wording made clearer
- Added to the rules
Burying banana peels feeds plants potassium (roses in particular). · What can I plant now?
More ways Milpa can help
When do I plant? · What grows well together? · Plan my garden · What can I plant now? · Something wrong in the garden? · Keep a garden diary · Heard a tip?
Cite this page
Milpa Gardens. “Fertilizer recommendations without a soil test are guesswork. Say so.” Evidence grade: Well established. https://milpa.garden/rules/fertilizer-recommendations-without-soil-test-guesswork-say/
A garden planner built on graded evidence. Every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.