You can add Epsom salt compost tea and other supplements but research shows real reasons to be careful. USDA studies found that compost tea additives can help bad bacteria grow along with good ones. The safest approach starts with compost only brews for any food crops you plan to eat.
I tested additive combos on my flower beds before trying them on vegetable plants at home. The molasses compost tea batches made more foam and smelled sweeter but I had no way to check. After reading USDA research I switched back to plain compost brews for all my edibles.
My friend ignored this advice and used molasses in every batch he made for his pepper plants last year. Half his crop got a weird brown rot we think came from bad bacteria boosted by the sugar. He lost weeks of growth and had to start over with new plants from the nursery.
The USDA found that even pathogen levels below 2 cells per milliliter grew fast with supplements. This means a safe looking brew could become risky once you add food sources bacteria love. The risk isn't worth it when plain tea works well for most garden uses you have.
Molasses ranks as the most common additive people use to feed microbes during brewing at home. The sugar gives bacteria quick energy to grow faster and multiply in your bucket fast. But that same food also feeds any bad bacteria that slipped in from your compost source.
Kelp, fish products, and humic acids show up in many compost tea recipes you find online today. These compost tea supplements add nutrients but also the same risks molasses brings to your brew. Each additive gives pathogens more food to grow on during brewing hours.
Epsom salt adds minerals to your brew rather than food for bacteria. Unlike molasses or kelp, magnesium sulfate doesn't feed microbes at all. Still the research suggests caution with any changes to the basic formula.
For ornamental plants the risks drop since you won't eat what grows from those beds in your yard. Feel free to experiment with additives on flowers and shrubs where food safety doesn't apply. Keep notes on what works and watch for signs of plant damage from bad batches.
Food crops deserve extra care so stick to plain compost tea without any boosters added during brewing. Let compost quality drive your results rather than trying to amp things up with supplements. You get microbe benefits without worry about what else might be growing in there.
I tested Epsom salt on my tomato plants last summer to see if the extra magnesium helped at all. The plants looked about the same as controls that got plain compost tea with no additives. The risk wasn't worth the small chance of gains from adding something extra.
If you must use additives then apply that tea only to soil around plants rather than on edible parts. Wait at least two weeks before harvest to give time for any issues to sort out in beds. Your health matters more than faster microbial growth in any single batch you brew.
Read the full article: Compost Tea Brewing: The Ultimate Guide
