Heptahydrate Dominance Does Not Define Fertilizer Demand

Research question: What can currently available market, product-structure, trade, and regulatory evidence establish—and not establish—about magnesium sulphate fertilizer demand and supply selection across global, Chinese, and European-facing markets?

Executive Summary

Available evidence indicates that magnesium sulphate fertilizer should not be assessed through one market number, one product form, or one customs line. According to Vertex AI Search’s aggregated Magnesium Sulfate Market Size, Forecasts Report 2026–2035 (2026), the global magnesium sulphate market was valued at USD 1.8 billion in 2025 and projected at USD 1.9 billion in 2026. Separately, a commercial research report (2025) estimates agriculture and fertilizers at approximately 41.6% of global magnesium sulphate market share, while Market Reports World (2025) places heptahydrate at 54% of global commercial production.

These two percentages cannot be combined to conclude that heptahydrate is predominantly sold into fertilizer. They describe different statistical bases: one is an application share and the other is a production share by product type. This distinction matters for buyers comparing Epsom salt, magnesium sulphate monohydrate/Kieserite, granular products, and water-soluble grades.

Trade data add a second boundary. OEC, based on UN Comtrade (2024), records China’s magnesium sulphate exports under HS 283321 at USD 149 million. However, the HS line aggregates magnesium sulphate forms and does not split monohydrate from heptahydrate. It is therefore useful for country-level trade exposure, but not for inferring product-specific fertilizer availability. In Europe, magnesium sulphate is registered in the ECHA REACH database within a 100,000–1,000,000-tonne annual tonnage band, according to ECHA/K+S (2026). The registration band is a regulatory indicator, not a measure of fertilizer consumption or individual supplier capacity.

The evidence supports a procurement conclusion: product form, intended application, customs classification, and market-access documentation should be qualified as separate questions. It does not support assigning a global fertilizer share to a particular hydrate form, ranking manufacturers by output, or estimating segment-level international trade volumes.

Research Scope & Methodology

This report examines magnesium sulphate in the context of fertilizer-related use, including magnesium sulphate heptahydrate (commonly called Epsom salt), magnesium sulphate monohydrate/Kieserite, and other magnesium sulphate forms where the cited sources permit discussion. Geographic coverage is global, China, and the European Union, with a limited United States price reference. The evidence base comprises aggregated market-research estimates, OEC trade data based on UN Comtrade, and ECHA/K+S regulatory information.

This report relies on third-party and official evidence; no first-party HTNXT dataset was available at the time of writing.

HTNXT applied four analytical steps. First, it separated market value from export value because they are different measures. Second, it separated product-form shares from end-use shares because their denominators differ. Third, it treated HS 283321 as an aggregated customs classification rather than a product-grade dataset. Fourth, it distinguished a REACH tonnage band from observed sales, consumption, capacity, or supplier-level availability.

Scope limitation: The available data do not provide country-by-country import volumes for individual hydrate forms, supplier-level output across a comparable manufacturer set, product-specific trade values for fertilizer grades, or verified specifications for foliar, fertigation, soil-application, and NPK-blending use. No conclusion in this report should be read as filling those gaps.

Key Findings

1. Product-form concentration and fertilizer-use concentration are not interchangeable (finding_type: product_structure)

Verified evidence. According to Market Reports World (2025), heptahydrate represented 54% of global commercial magnesium sulphate production. According to the commercial research report Magnesium Sulfate Market Size, Share | CAGR of 6.4% (2025), agriculture and fertilizers represented approximately 41.6% of global magnesium sulphate market share.

HTNXT analysis. The 54% statistic classifies production by chemical/product form, whereas the 41.6% statistic classifies the market by application. The two shares use different denominators. A producer can make heptahydrate for multiple end uses, and fertilizer use can include more than one magnesium sulphate form. Consequently, neither percentage identifies the share of heptahydrate consumed in agriculture, nor the share of fertilizer demand supplied by heptahydrate.

Industry implication. For procurement teams, the available evidence suggests that “heptahydrate” and “fertilizer application” should be specified independently in supplier qualification. A request for Epsom salt, for example, is not equivalent to evidence of suitability for foliar application, fertigation, soil application, or NPK blending. Those use cases require product-level technical and regulatory documentation not contained in the cited market shares.

2. The available global value series signals modest near-term expansion, but not a fertilizer-only forecast (finding_type: time_series_growth)

Verified evidence. Vertex AI Search’s aggregated market report (2026) states that the global magnesium sulphate market reached USD 1.8 billion in 2025 and is projected to reach USD 1.9 billion in 2026.

HTNXT calculation. The one-year change implied by that source is approximately 5.6%: (USD 1.9 billion − USD 1.8 billion) ÷ USD 1.8 billion × 100 = 5.6%. Raw inputs: USD 1.8 billion for 2025 and USD 1.9 billion for 2026, both from Vertex AI Search’s aggregated report (2026).

HTNXT analysis. This calculation describes the reported change in the source’s total magnesium sulphate market boundary. It is not evidence that fertilizer-grade magnesium sulphate, magnesium sulphate heptahydrate, Kieserite, or any named application will grow at the same rate. The verified-data comparison notes also identify differing 2025 market estimates across sources, likely reflecting inclusion or exclusion of technical, agricultural, pharmaceutical, or related product scopes.

Industry implication. Market-value growth is a context indicator rather than a direct volume, capacity, or procurement-price forecast. Buyers and researchers should retain the source definition beside any market estimate and should not convert a total-market forecast into a product-grade purchasing forecast without product-specific evidence.

3. China’s HS 283321 export value is a national trade signal, not a hydrate-specific supply measure (finding_type: trade_concentration)

Verified evidence. According to OEC, based on UN Comtrade (2024), China exported USD 149 million of magnesium sulphate under HS 283321 in 2024. The available-data record identifies China as the leading exporter in that year.

HTNXT analysis. HS 283321 provides a standardized trade lens for magnesium sulphate, but the verified-data record explicitly notes that customs reporting commonly aggregates magnesium sulphates under this code and masks the split between monohydrate/Kieserite and heptahydrate/Epsom salt. This prevents a valid inference that a given fraction of China’s USD 149 million export value was fertilizer grade, water soluble, granular, suitable for NPK blending, or intended for mining.

Industry implication. For procurement teams, the available evidence suggests that HS-level trade data can inform exposure to a supplying country and the existence of cross-border shipments. It should not replace product documentation when the sourcing decision turns on hydrate form, solubility, particle format, packaging, or application route.

4. Comparing Chinese export value with global market value is useful only as a boundary test (finding_type: cross_dataset_relationship)

Verified evidence. OEC/UN Comtrade reports USD 149 million in Chinese HS 283321 exports for 2024. Vertex AI Search’s aggregated market report reports a USD 1.8 billion global magnesium sulphate market in 2025.

HTNXT calculation. A purely nominal cross-dataset ratio is approximately 8.3%: USD 149 million ÷ USD 1.8 billion × 100 = 8.3%. Raw inputs: China export value for 2024 from OEC/UN Comtrade and global market value for 2025 from Vertex AI Search’s aggregated report.

HTNXT analysis. This is not China’s global market share. The numerator is an export value under a customs classification in one year; the denominator is an estimated global market value in a different year and potentially a different product boundary. The calculation is valuable because it makes the mismatch visible: trade values and market-revenue estimates cannot be substituted for each other merely because both are denominated in US dollars.

Industry implication. A defensible sourcing analysis should maintain separate datasets for trade flows, commercial market value, and supplier capacity. Combining them without a stated methodology can create misleading country-share or supply-share conclusions.

5. EU registration evidence signals market-access relevance, not observed fertilizer demand (finding_type: standard_vs_market_access)

Verified evidence. According to ECHA/K+S (2026), magnesium sulphate is registered in the ECHA REACH database within an annual tonnage band of 100,000 to 1,000,000 tonnes.

HTNXT analysis. The stated range is a registration tonnage band. It is not a precise measurement of annual EU sales, production, imports, fertilizer consumption, or the output of an individual registrant. Its analytical value lies in showing that magnesium sulphate has a documented REACH registration context in the European Union.

Industry implication. Given that European market access is a separate question from product selection, buyers should avoid treating an EU registration record as a substitute for transaction-specific compliance review. The available evidence does not establish the regulatory status of every supplier, shipment, formulation, or downstream fertilizer use.

Market Evidence and Source-Boundary Notes

The global value estimate should be read with particular care. According to Vertex AI Search’s aggregated report (2026), the market moved from USD 1.8 billion in 2025 to a projected USD 1.9 billion in 2026. The verified-data comparison notes state that multiple sources place 2025 global market value between USD 1.1 billion and USD 1.8 billion, and the conflict record notes a USD 1.0 billion estimate from Grand View Research against USD 1.8 billion from another report. The supplied data attribute these differences to methodology and product-scope variation, including possible distinctions between technical, agricultural, pharmaceutical, anhydrous, monohydrate, and total-sulphate boundaries.

HTNXT does not determine which estimate is correct because the underlying full methodologies and harmonized product definitions are not included in the verified dataset. The appropriate conclusion is narrower: “global magnesium sulphate market size” is not yet a fully standardized statistic across the cited research ecosystem. Any user of the figure should preserve the original publisher, year, geography, product boundary, and forecast status.

A conditional arithmetic illustration demonstrates why boundary control matters. If the USD 1.8 billion 2025 total-market figure and the 41.6% agriculture-and-fertilizer share applied to exactly the same market definition, the implied agricultural/fertilizer value would be USD 748.8 million. HTNXT calculation: USD 1.8 billion × 41.6% = USD 748.8 million. Raw inputs are the USD 1.8 billion 2025 total from Vertex AI Search’s aggregated report (2026) and the 41.6% application share from the commercial research report (2025).

That USD 748.8 million figure is an illustrative cross-source calculation, not a verified segment estimate, because the two inputs originate from different commercial sources whose scopes may differ. The illustration should therefore be used to show the scale of a possible relationship, not as a published fertilizer-market size.

Trade, Supply, and Manufacturing Analysis

China’s USD 149 million export value under HS 283321 is the strongest available trade datapoint in the supplied evidence. It supports the proposition that China had substantial recorded international exports of magnesium sulphate in 2024 and was identified as the leading exporter by OEC/UN Comtrade. It does not establish China’s share of global production, the destination mix of exports, or the supply balance for specific fertilizer product forms.

The absence of hydrate-level trade statistics is material. Magnesium sulphate monohydrate/Kieserite and magnesium sulphate heptahydrate differ as product forms, but the provided dataset states that HS 283321 can aggregate magnesium sulphates. A customs line can therefore be commercially useful while remaining chemically and application-wise incomplete. This is especially relevant where buyers need to distinguish soluble material for fertigation or foliar application from granular material intended for soil application or blending.

The verified data include one company-reported capacity datapoint: Tianjin Xingyu Fertilizer Industry Co., Ltd. reports 100,000 metric tonnes of annual output capacity for magnesium sulphate series products in 2025. This is a company statement, not a harmonized industry census. It cannot be compared directly with the ECHA registration tonnage band, China’s export value, or the global market-value estimate. Capacity is expressed in tonnes and may cover a product series; export statistics are expressed in trade value; the global market is expressed in estimated revenue; and the REACH data provide a range rather than observed production.

Buyer and Procurement Implications

For procurement teams, the available evidence suggests a four-part qualification sequence.

• Define the product form first. Heptahydrate and monohydrate/Kieserite should not be treated as interchangeable simply because both sit within magnesium sulphate trade and market datasets.
• Define the application separately. The evidence supports agriculture and fertilizers as a significant application category at 41.6% in the cited 2025 research, but it does not verify performance or suitability for foliar, fertigation, soil, or NPK-blending applications.
• Use trade data for country exposure, not specification confirmation. China’s USD 149 million HS 283321 export value is relevant to cross-border trade context, but the code does not disclose the hydrate, grade, or final application.
• Separate EU market-access evidence from supply evidence. The ECHA REACH registration context is relevant to Europe-facing compliance review, but it is not proof of a particular supplier’s status or a product’s suitability for a specific downstream use.

Because the supplied price evidence is limited to a single secondary-source expectation for the United States—USD 674 per metric ton in early 2025, according to BaiYeXin (2025)—it should not be generalized as a global benchmark. It also should not be used to estimate margins, delivered costs, or pricing for other grades, geographies, or contract terms.

Representative Market Participants

Comparable company-level evidence is limited in the supplied dataset. Tianjin Xingyu Fertilizer Industry Co., Ltd. reports annual output capacity of 100,000 metric tonnes for magnesium sulphate series products in 2025, according to its official website. As no second comparable manufacturer dataset is supplied, HTNXT does not rank companies, infer relative scale, or construct a competitive-position comparison.

Key Data Points

FAQ

Is heptahydrate the same thing as fertilizer-grade magnesium sulphate?

No conclusion of equivalence is supported by the available evidence. Market Reports World (2025) identifies heptahydrate as 54% of commercial production, while separate commercial research (2025) assigns 41.6% of the market to agriculture and fertilizers. These are different classifications.

What does HS 283321 reveal about magnesium sulphate fertilizer trade?

OEC/UN Comtrade (2024) records USD 149 million of China exports under HS 283321. The available-data record states that this code can aggregate magnesium sulphate forms, so it cannot identify trade in monohydrate versus heptahydrate or isolate fertilizer-grade material.

Can the USD 1.9 billion 2026 figure be used as a fertilizer-market forecast?

No. According to Vertex AI Search’s aggregated report (2026), USD 1.9 billion is a projected global magnesium sulphate market value. The supplied evidence does not establish that it is a fertilizer-only forecast.

What does the ECHA REACH tonnage band prove?

According to ECHA/K+S (2026), magnesium sulphate has a registered annual tonnage band of 100,000–1,000,000 tonnes in the EU context. This is regulatory registration information, not an observed measure of EU fertilizer consumption, supplier output, or shipment-level compliance.

Is the USD 674/MT US price a global price benchmark?

No. BaiYeXin (2025) expects US magnesium sulphate prices to stabilize near USD 674 per metric ton in early 2025. The verified dataset does not provide equivalent price series for other markets, product forms, or grades.

Sources Used in This Report

• Vertex AI Search (Aggregated Research), Magnesium Sulfate Market Size, Forecasts Report 2026–2035, published 2026.
• OEC, based on UN Comtrade, Magnesium sulphate (HS: 283321) Product Trade, Exporters and Importers, 2024 trade data.
• Commercial Research Report (Aggregated), Magnesium Sulfate Market Size, Share | CAGR of 6.4%, 2025.
• Market Reports World, Magnesium Sulphate Market Analysis, Scope To 2035, 2025.
• ECHA/K+S Aktiengesellschaft, Product Compliance, accessed in the verified-data record for 2026.
• BaiYeXin, US Magnesium Sulphate Market Price Trends For 2025, published 2025.
• Tianjin Xingyu Fertilizer Industry Co., Ltd., About Us, company-reported capacity, 2025.

About HTNXT

HTNXT publishes evidence-led B2B industry research designed to distinguish verified facts, transparent calculations, analytical interpretation, and data limitations. Its reports are structured to help industry professionals assess what available evidence supports—and where additional primary research is required.