Can humic acid be mixed with fertilizers and pesticides?
A practical compatibility guide for humic acid, seaweed and amino acids with NPK, urea, micronutrients, calcium, fungicides and biofertilisers, with a jar test method.
Humic acid can be mixed with most fertilizers, including NPK, urea, micronutrients and seaweed extract. Avoid mixing it with strongly acidic products or concentrated calcium solutions, which can make it settle out, and always run a jar test before tank-mixing with pesticides. Keep biofertilisers away from chemical fungicides and bactericides.
On this page
Quick guide
| Mixing humic acid with | Usually | Note |
|---|---|---|
| NPK and urea | Compatible | Common practice in soil and drip |
| Micronutrients | Compatible | Humic can help keep them available |
| Seaweed extract and amino acids | Compatible | Often sold as ready blends |
| Calcium nitrate and high-calcium solutions | Caution | Can flocculate; jar test or apply separately |
| Strong acids and acidic products | Avoid | Humic acid precipitates at low pH |
| Fungicides and insecticides | Jar test | Depends on the formulation |
| Trichoderma and biofertilisers | Generally compatible with humic | Never mix biologicals with chemical fungicides |
How to do a jar test
- Fill a clear jar with water from the source you will spray with, in the same proportion as the tank.
- Add products in the label order, mixing after each.
- Wait 15 to 30 minutes.
- If you see clumps, a layer, sludge or heat, do not mix them in the tank.
Tips
- Fill the tank half with water before adding products
- Spray the mix the same day
- Follow label directions of every product
Frequently asked questions
Can I mix humic acid with NPK?
Yes. Humic acid is commonly applied with NPK fertilizers.
Can I mix humic acid with urea?
Yes. Humic acid is commonly applied with urea in soil and drip programmes.
Can I mix humic acid with fungicide?
Sometimes. It depends on the fungicide formulation, so always run a jar test first.
Can I mix humic acid with micronutrients?
Yes, and humic acid can help keep micronutrients available.
Can I mix humic acid with calcium nitrate?
Use caution: high calcium can cause humic acid to flocculate. Jar-test or apply separately.
Can humic acid be mixed with Trichoderma?
Humic acid is generally compatible with Trichoderma and biofertilisers; chemical fungicides are not.
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