Walt's Organic Fertilizer Co. Gypsum (10 LB) - Soil Amendment - Modern Style - 1E+1 liters

Why I reached for this gypsum

Tomatoes are the crop that forces me to keep a tighter handle on calcium than any other plant I grow. In a season with erratic irrigation, I started seeing the telltale puckered, leathery ends on some early fruits—classic blossom end rot. I wanted a fast, soil-based calcium source that wouldn’t mess with pH, and I didn’t want anything made from recycled drywall. That’s what led me to this 10-pound bag of pure mined gypsum from Walt’s. It’s straightforward: calcium sulfate dihydrate, relatively water soluble, and nothing extra.

What stood out right away

This is a very fine powder—closer to flour than grit. That’s both the main virtue and the main quirk. The fine texture dissolves and moves into the root zone quickly when you water it in, which is exactly what you want if you’re trying to supply calcium in a hurry. The flip side is that it’s dustier than pelletized or granular gypsum. I apply it on a still morning or lightly mist the bed first, then water it in immediately. A simple dust mask is worth using.

The other thing that stands out is the purity. Mined gypsum has a consistent feel and lacks the odd additives or binders you can run into with recycled sources. It’s just calcium and sulfate, which is the point.

How I used it

I trialed this gypsum in a few scenarios:

• Tomatoes in raised beds: I side-dressed midseason at about 1/4 cup per plant, lightly scratched it into the top inch of soil, and watered deeply. I also mixed a tablespoon or two into the planting hole for late-season transplants.
• Sodic patch in a compacted side bed: I broadcast roughly 2 pounds per 100 square feet and watered in over several cycles to see whether infiltration and surface crusting would improve.
• Seedling mix refresh: I added a teaspoon per gallon of potting mix to boost calcium without pushing pH up.

For reference, gypsum doesn’t change soil pH the way lime does. That’s a key reason I like it for crops that prefer neutral to slightly acidic soil; you get calcium without turning the dial on pH.

Performance in the garden

On the tomatoes, the turnaround was noticeable. Existing BER spots don’t heal, but within about a week of the side-dress and steady irrigation, the new fruit set came in clean. It’s worth emphasizing: calcium availability is only half the battle—consistent soil moisture is the other half. Paired with drip and mulch, this gypsum gave me the quick push I was looking for, and the fine texture likely helped it get to work fast.

In the compacted bed, I wasn’t expecting miracles, but I did see an improvement in surface crusting after a few thorough waterings. Gypsum can help flocculate clay particles in sodic soils, improving structure and infiltration. The effect depends heavily on your starting soil (and sodium levels), so it’s not a cure-all. Still, water penetration improved enough that I could establish a cover crop without the usual patchy germination.

As a calcium bump in potting mix, it blended easily and didn’t create gritty hot spots the way some granular amendments can. Seedlings were sturdy, and I didn’t see the minor tip burn I sometimes get in fast-growing brassicas.

Handling and application tips

Because it’s a fine powder, a few small changes to handling go a long way:

• Apply on a calm day or after lightly dampening the soil surface.
• Water in right away—drip or a gentle shower is fine.
• For tomatoes, 1–2 tablespoons in the planting hole or 1/4 cup as a side-dress per mature plant is a practical starting point.
• For bed-wide applications, 1–2 pounds per 100 square feet is a conservative rate for general calcium supplementation; remediation for sodic soils often requires more and should be guided by a soil test.
• If you prefer to avoid dust altogether, make a slurry in a watering can and drench the root zone.

Gypsum is relatively water soluble compared to many minerals, but it’s not instant like a liquid. Expect days—not hours—for effects to show up in plant tissue.

Where it fits—and where it doesn’t

• Great fit:

  • Supplying calcium without raising pH, especially in neutral or alkaline soils where lime would be counterproductive.
  • Addressing calcium-related disorders like blossom end rot in tomatoes, as part of a strategy that also stabilizes watering.
  • Helping with soil structure where sodium is a problem, improving infiltration and reducing crusting over time.
  • Adding sulfate-sulfur in a gentle, plant-available form.

• Not a magic wand:

  • It won’t correct pH issues. If your soil is acidic and calcium-deficient, lime is the right tool.
  • It won’t fix blossom end rot if irrigation is erratic; calcium transport hinges on steady moisture.
  • It’s not the most convenient format for broadcast applications in wind-prone areas; pelletized gypsum is cleaner to spread, though slower to act.

Comparisons and context

I’ve used both granular and pelletized gypsum in the past. Those forms are tidy to broadcast but slower to break down, which is fine for pre-plant applications and general maintenance. This gypsum’s fine texture makes it better for midseason corrections, especially for targeted applications around individual plants.

Liquid calcium products exist, but they’re frequently pricier per unit of calcium and can come with extra components you may not need. For a straightforward, soil-applied calcium source that won’t alter pH, mined gypsum remains hard to beat.

Quality and packaging

The 10-pound size is a sweet spot for small gardens and raised beds: enough for a couple of beds and a tomato row, not so much that it lingers open for months. The product itself is consistent in texture and free of debris, which matters for uniform application and predictable results. I didn’t encounter caking, though with any fine mineral, sealing the bag and storing it somewhere dry is smart.

Environmental and safety notes

• Wear a simple dust mask when handling; it’s a fine powder.
• Avoid applying right before heavy rain; let it settle into the soil.
• Soil testing pays off, particularly if you’re tackling high sodium or suspect micronutrient imbalances.

Pros

• Pure mined gypsum; no recycled wallboard or binders.
• Fine powder dissolves and moves into the root zone quickly.
• Supplies calcium without affecting soil pH.
• Useful for both calcium nutrition and addressing sodic soil issues.
• Convenient 10-pound size for small gardens and raised beds.

Cons

• Dusty to handle; not ideal for breezy conditions.
• Not as tidy to broadcast as pelletized forms.
• Effects on soil structure vary with soil chemistry; best results come with a soil test.

Bottom line

This is a no-frills, fast-acting gypsum that does what I want a gypsum to do: deliver calcium quickly without nudging pH and help nudge troublesome soils in the right direction. The fine texture demands a little care in handling, but it’s exactly why it works so promptly for midseason corrections. If your focus is tomatoes, it’s a practical addition to your toolkit; if you’re remediating sodium issues, it’s a sensible piece of a soil-test-driven plan.

Recommendation: I recommend this gypsum for gardeners who need a reliable, fast-acting calcium source that won’t alter pH, particularly for managing blossom end rot in tomatoes and for incremental improvements in sodic or crust-prone soils. It’s clean, effective, and cost-efficient, provided you’re comfortable handling a fine powder and pair it with good watering practices and, ideally, a soil test.