Premium mined agricultural gypsum delivering calcium and sulfur to improve soil structure, reclaim sodic soils, and loosen compacted clay—without changing soil pH.
Unlike lime, gypsum supplies calcium without raising soil pH, making it ideal when soil is already neutral to alkaline. Use it as a calcium sulfate soil amendment wherever pH correction is not needed.
Provides both 23% calcium and 18% sulfur in a single application. Calcium strengthens cell walls and supports root development; sulfur is essential for protein synthesis and enzyme activation.
Calcium ions from gypsum bind clay particles together (flocculation), creating pore space for improved drainage, aeration, and root penetration. Improvements in infiltration and workability may begin within weeks under suitable moisture and soil conditions, while larger structural benefits typically develop over months.
One of the most widely used and practical amendments for reclaiming sodic and many saline-sodic soils. Calcium ions replace excess sodium on soil exchange sites where leaching and drainage are possible, allowing sodium to move through the profile and restoring soil structure and fertility.
Gypsum is moderately soluble, so calcium and sulfur become available with moisture and move into the root zone more readily than many less-soluble calcium sources—no waiting for microbial breakdown.
In some soils, gypsum can improve subsoil conditions that restrict deeper rooting. Deeper roots access more water and nutrients, supporting drought resilience and overall plant health.
Gypsum supplies readily available calcium to the root zone, helping reduce the risk of blossom end rot in tomatoes, peppers, and squash when low available calcium is a contributing factor. Consistent watering and balanced nutrition are also essential.
Gypsum carries no burn risk at recommended rates and can be applied any time of year. Compatible with most fertilizers, organic amendments, and standard irrigation programs.
Mined gypsum is generally allowed in many certified organic systems, subject to certifier review. CDFA registered and processed without synthetic additives.
Sourced to agricultural quality standards and tested for compliance with applicable safety requirements, ensuring consistent purity for crop applications.
Our gypsum is mined from high-purity natural deposits and processed to agricultural specifications—the same mineral that has been used to improve soil for centuries. Minimal processing preserves the natural dihydrate form (CaSO₄·2H₂O), which provides optimal solubility for crop applications.
Calcium sulfate dihydrate from natural mineral deposits. Approximately 23% calcium and 18% sulfur. pH neutral with no synthetic binders or additives.
Gypsum works through ion exchange chemistry. When calcium ions (Ca²⁺) enter the soil solution, they displace sodium ions (Na⁺) and bridge clay platelets together—a process called flocculation. This electrochemical mechanism is what makes gypsum uniquely effective at improving structure in both sodic and heavy clay soils, without the pH shift associated with other calcium sources.
Calcium is the primary structural nutrient in cell walls and membranes. It's largely immobile in the plant, so a steady soil supply is essential. Gypsum's calcium is in soluble sulfate form—readily available without requiring soil acidification.
Sulfur is required for the synthesis of the amino acids cysteine and methionine, chlorophyll formation, and enzyme function. It is the fourth most limiting macronutrient in many soils, particularly those with low organic matter or heavy leaching.
| Product | Supplies Calcium | Supplies Sulfur | Raises pH | Best Use |
|---|---|---|---|---|
| Gypsum (Calcium Sulfate) | Yes — 23% | Yes — 18% | No | Clay soils, sodic soils, calcium without pH change |
| Dolomite Lime | Yes | No | Yes | Acidic soils needing pH correction + calcium |
| Calcium Nitrate 15.5-0-0 | Yes | No | Minimal | Fast soluble calcium for fertigation or hydroponics |
Results vary with soil type, application rate, irrigation, and initial sodium or clay levels.
| Soil Condition | Application Rate | Purpose | Frequency |
|---|---|---|---|
| Heavy Clay Soils | 1–2 tons/acre (40–80 lbs/1,000 sq ft) | Improve structure & drainage | Annual or biennial |
| Sodic Soils (High Sodium) | 2–4 tons/acre (80–160 lbs/1,000 sq ft) | Sodium displacement | As needed per soil test |
| Compacted Soils | 1–1.5 tons/acre (40–60 lbs/1,000 sq ft) | Improve infiltration | Annual |
| General Maintenance | 0.5–1 ton/acre (20–40 lbs/1,000 sq ft) | Maintain soil quality | Every 2–3 years |
| Crop | Rate | Timing | Notes |
|---|---|---|---|
| Peanuts | 600–1,000 lbs/acre | At pegging | Critical for pod calcium uptake |
| Alfalfa | 1–2 tons/acre | Pre-plant or early spring | High sulfur demand crop |
| Corn | 200–500 lbs/acre | Pre-plant | Band or broadcast |
| Tomatoes | 1,000–1,500 lbs/acre | Pre-plant | Supports calcium availability; pair with consistent irrigation |
| Citrus | 2–4 tons/acre | Spring/Fall | Improves fruit quality & structure |
| Application | Rate | Method |
|---|---|---|
| Lawn (Clay Soil) | 40–50 lbs/1,000 sq ft | Broadcast, water in |
| Vegetable Garden | 2–4 lbs/100 sq ft | Work into top 6 inches |
| Flower Beds | 1–2 lbs/100 sq ft | Top dress or incorporate |
| Potted Plants | 1 tbsp/gallon of soil; up to 2 tbsp for heavy-feeding crops | Mix into potting mix at planting |
Apply 1,000–1,500 lbs/acre (approximately 2–3 lbs per 10 sq ft of bed space) of gypsum pre-plant, then follow with a complete tomato fertilizer program. Gypsum supplies available calcium directly to the root zone, helping support consistent calcium uptake throughout fruit development. Pair with steady, even irrigation for best results.
Refer to the Safety Data Sheet (SDS) for complete safety information.
Build a complete soil health and crop nutrition program with these complementary products.
High-potassium formula for fruit development. Pair with gypsum pre-plant to support calcium availability and feed your crop throughout the season.
Add magnesium to complement gypsum's calcium. Both provide sulfur for a complete secondary nutrient program. Ideal for tomatoes, peppers, and roses.
When soil pH also needs correction, dolomite lime provides calcium and magnesium while raising pH. Use lime for acidic soils; use gypsum when pH is already adequate.
Correct iron chlorosis in alkaline soils alongside gypsum's pH-neutral calcium delivery. DTPA form stays plant-available up to pH 7.5.
No. Gypsum (calcium sulfate dihydrate) is pH neutral and does not raise or lower soil pH. This is the key difference from lime (calcium carbonate), which raises pH as it dissolves. If your soil is already at or above pH 7.0 and you need calcium, gypsum is the correct choice. For acidic soils that need both calcium and pH correction, consider Dolomite Lime instead.
For general maintenance on clay soils, once per year is typical. Sandy soils may only need an application every 2–3 years. For sodic soil reclamation, multiple applications are often needed based on the severity of sodium levels—soil retesting after 6 months will guide subsequent applications. For crops like peanuts or tomatoes with high calcium demand, apply at each planting cycle.
Both provide calcium, but they work differently. Lime (calcium carbonate) raises soil pH as it releases calcium—useful for acidic soils. Gypsum (calcium sulfate) releases calcium without changing pH. Additionally, gypsum contains 18% sulfur, improves clay soil structure through flocculation, and is one of the most widely used practical amendments for reclaiming sodic soils. Use lime to raise pH; use gypsum when pH is fine but calcium, sulfur, drainage, or sodium are the issues. For a deeper look at soil pH management, see our article on Understanding Soil pH and Nutrient Availability.
Yes—this is one of gypsum's primary applications. Clay particles carry a negative charge and naturally repel each other, which compacts the soil and limits water movement. Calcium ions from gypsum bridge these charges and cause clay particles to clump together (flocculate), creating larger pore spaces for air and water. Improvements in infiltration and workability may begin within weeks under suitable moisture and soil conditions, with continued structural improvements developing over months. For more on improving clay soils, see our article on Improving Clay Soil for Better Gardens.
Mined gypsum is generally allowed in many certified organic systems, subject to certifier review. It is a natural mineral without synthetic additives, and it does not contain pesticides or heavy metal contaminants at levels of concern. Always verify specific allowed materials with your certifying agency to ensure compliance with your organic certification requirements.
Blossom end rot in tomatoes, peppers, and squash is associated with localized calcium deficiency in developing fruit tissue. Contributing factors include low available soil calcium, irregular irrigation, root stress, and excessive ammonium nitrogen. Gypsum supplies readily available calcium to the root zone, helping reduce the risk when low available calcium is part of the problem. Consistent, even irrigation and balanced fertilization remain equally important for prevention.
Yes. Gypsum is compatible with NPK fertilizers, organic amendments, and most pesticides. It can be applied simultaneously with other products or as part of a standard amendment program. The calcium from gypsum may improve the uptake of several other nutrients, including potassium and magnesium, by improving root zone conditions.
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Family-owned since 1989. For over 35 years we've been making premium-grade fertilizers, soil amendments, and micronutrients that home gardeners and commercial growers trust. Made in Madera, California.
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