Rongqing Chemical –the China Kieserite source manufacturer shares the differences between Synthetic and Magnesium Sulfate.
Synthetic Kieserite VS Magnesium Sulfate(Espsom Salt)
1. Composition & Form

| Property | Synthetic Kieserite | Magnesium Sulfate (Epsom Salt) |
| Chemical Formula | MgSO₄·H₂O (Monohydrate) | MgSO₄·7H₂O (Heptahydrate) |
| Magnesium Content | ~27% MgO (16% Mg) | ~16% MgO (10% Mg) |
| Sulfur Content | ~22% S | ~13% S |
| Hydration Level | 1 water molecule (low moisture) | 7 water molecules (high moisture) |
2. Physical Properties
| Property | Kieserite | Magnesium Sulfate(Epsom Salt) |
| Appearance | White or gray | White crystalline crystals |
| Water Solubility | Soluble but slower to dissolve | Highly soluble (instant in water) |
| Moisture Sensitivity | Low — storage stable | High — can cake and absorb moisture |
| Bulk Density | Higher | Lower (fluffier) |
3. Origin & Production
Synthetic Kieserite
— Made by thermal dehydration of magnesium sulfate heptahydrate or by reacting magnesium oxide/hydroxide with sulfuric acid, then crystallizing into monohydrate form.
— Can also occur naturally in salt deposits (natural kieserite).
— Granulated forms are common for agriculture.
Magnesium Sulfate (Epsom Salt)
— Usually crystallized from natural brines or seawater, or made by reacting magnesium carbonate/hydroxide with sulfuric acid.
— Primarily used in medical, bath, and garden applications.
4. Agricultural Application
| Factor | Kieserite | Magnesium Sulfate(Epsom Salt) |
| Release Speed | Medium — dissolves gradually in soil moisture | Fast — dissolves instantly in water |
| Best Use | Base fertilizer, blending in NPK, bulk spreading | Foliar spray, fertigation, quick correction of Mg/S deficiency |
| Soil Suitability | Acidic & neutral soils | Any soil (fast correction) |
| Application Frequency | Longer residual effect | Needs more frequent application |
5. Cost & Handling
· Kieserite is usually cheaper per unit of Mg in bulk agriculture and better for large-scale field application because of its granule stability.
· Epsom salt is more expensive per Mg unit, better for small-scale or emergency nutrient correction, and often sold in finer crystal form.
Quick Summary
Choose Kieserite → If you want a slow-to-medium release, high Mg content, bulk-spread fertilizer that stores well.
Choose Epsom Salt → If you want instant dissolution for quick Mg/S correction via foliar spray or fertigation.
· Need more Info. about China Kieserite and Magnesium Sulfate, welcome to contact with Rongqing Chemical the China Kieserite/Magnesium Sulfate manufacturer.
www.rqkieserite.com
Rongqing Chemical Co. Ltd, established in 1991, is a China-based kieserite Manufacturer & Exporter. Located in Yingkou Liaoning -the China magnesium We focus on kieserite,magnesium sulfate
E-mail :
marketing@rqsulfates.com info@rqsulfates.comWhatsapp:
86-15111400823Office Tel:
86-731-85864603 86-731-85864624
Moble Tel/Wechat:
86-18670090463 86-15111400823QQ:1265626382
Address:
Headquarters:Yuelu District,Changsha, Hunan, ChinaKieserite Factory:
Dashiqiao,Yingkou,Liaoning,ChinaWebsite
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