What Is EDDHSA-Fe 6%? Complete Guide to Chelated Iron Fertilizer

Written by: ALEN | Chemical Engineer, MOSINTER | 15 years in "vitamin manufacturing" and "pharmaceutical APIs"

A few weeks ago, a long-time client from Spain called me with an urgent problem. Their citrus orchard was showing severe iron chlorosis symptoms-yellowing leaves, stunted growth, and poor fruit development. They had tried conventional iron fertilizers with little success. The soil was alkaline (pH 8.2), and the irrigation water wasn't helping either. This scenario is more common than you might think. Iron deficiency affects crop yields worldwide, particularly in calcareous soils. That's where EDDHSA-Fe 6% chelated iron fertilizer comes in.

EDDHSA-Fe 6% (CAS 84539-54-8) is a highly stable chelated iron fertilizer containing 6% water-soluble iron chelated with EDDHSA (ethylenediamine-di(2-hydroxy-5-sulfophenylacetic acid)). It maintains iron availability in soils with pH 3-11, making it particularly effective for alkaline and calcareous soils where conventional iron fertilizers fail.

Table of Contents

1. What Makes EDDHSA-Fe 6% Different from Other Iron Chelates?

2. How Does EDDHSA-Fe Work in Alkaline Soils?

3. Application Rates and Methods for Different Crops

4. EDDHSA-Fe vs EDDHA-Fe: Which One Should You Choose?

5. Frequently Asked Questions

6. Where to Buy EDDHSA-Fe 6% Chelated Iron Fertilizer

1. What Makes EDDHSA-Fe 6% Different from Other Iron Chelates?

If you've been in agriculture or horticulture for any length of time, you know that not all iron fertilizers are created equal. The key difference lies in the chelating agent-the organic molecule that binds to iron and keeps it soluble and available to plants.

EDDHSA-Fe 6% stands out because of its exceptional stability across an extremely wide pH range (pH 3-11). While EDTA and DTPA chelates become ineffective in alkaline conditions, EDDHSA maintains iron solubility even at pH 9 and above. This makes it the go-to choice for calcareous soils and high-pH irrigation water commonly found in arid regions.

Research published in the European Journal of Agronomy demonstrated that EDDHSA-Fe was as effective as EDDHA-Fe in correcting iron chlorosis in sunflower, peach, and pear crops, but with some notable advantages. The study found that EDDHSA-Fe has significantly higher solubility-3.4 times greater than EDDHA-Fe-which means better mixing and distribution in fertigation systems.

2. How Does EDDHSA-Fe Work in Alkaline Soils?

Understanding soil chemistry is crucial to appreciating why EDDHSA-Fe excels where other fertilizers fail. In alkaline soils (pH > 7.5), iron naturally occurs as insoluble ferric oxides and hydroxides that plants cannot absorb.

EDDHSA-Fe works by encapsulating the iron ion in a stable molecular structure that prevents precipitation. The sulfonate groups (-SO3H) on the EDDHSA molecule provide additional negative charges, enhancing water solubility while maintaining iron in its bioavailable chelated form. Even when soil pH reaches 8.5 or higher, the chelate structure remains intact.

What most suppliers won't tell you is that the effectiveness of iron chelates isn't just about stability constants. The EDDHSA molecule has a unique structure that allows for better mobility through the soil profile. Unlike some chelates that get adsorbed by soil particles, EDDHSA-Fe remains mobile, reaching plant roots more efficiently.

A field study on crimson grapes in Australia found that EDDHSA-Fe increased soil iron levels by 99.7% after just two weeks, compared to 60.3% with EDDHA-Fe. The chlorophyll content in leaves increased by 19.4%, indicating rapid recovery from iron deficiency.

3. Application Rates and Methods for Different Crops

Proper application is key to getting the most from your EDDHSA-Fe investment. The method and rate depend on your crop type, soil conditions, and whether you're treating existing chlorosis or preventing it.

For soil application, EDDHSA-Fe 6% can be applied through fertigation at rates of 5-25 kg per hectare, depending on crop sensitivity and severity of deficiency. Foliar applications using 0.1-0.2% solutions provide rapid green-up for severely affected plants. Always apply in spring before growth begins for preventive treatment.

Based on our experience supplying over 500 agricultural operations across 20 countries, we've compiled the most effective application rates. Citrus and grape crops typically require higher rates due to their sensitivity to iron deficiency, while stone fruits like peach and pear respond well to moderate applications.

Important: These rates are general guidelines. Always conduct soil tests and consult with local agricultural extension services for crop-specific recommendations in your region.

4. EDDHSA-Fe vs EDDHA-Fe: Which One Should You Choose?

This is probably the most common question I get from growers. Both EDDHSA-Fe and EDDHA-Fe are excellent iron chelates, but they have distinct characteristics that make each better suited for specific situations.

Choose EDDHSA-Fe if you're dealing with extremely high pH soils (pH > 8.5), need maximum water solubility for fertigation systems, or want better compatibility with other fertilizers in tank mixes. Choose EDDHA-Fe if you prefer the most established chelate with decades of research backing, or if cost is your primary concern and soil pH is moderately alkaline (7.5-8.5).

From a chemical engineering perspective, I find the molecular differences fascinating. EDDHSA has sulfonate groups that EDDHA lacks, giving it three negative charges compared to EDDHA's single negative charge. This higher charge density increases water solubility but also means it moves faster through soil. For perennial crops with deep root systems, this can be an advantage. For shallow-rooted crops, you might need more frequent applications.

5. Frequently Asked Questions

What is the CAS number for EDDHSA-Fe?

The CAS number for EDDHSA-Fe chelated iron fertilizer is 84539-54-8. This identifier is recognized in chemical databases including PubChem and is used for regulatory compliance and quality verification. You can find more details in the PubChem database maintained by the National Library of Medicine.

How long does EDDHSA-Fe remain effective in soil?

EDDHSA-Fe typically remains effective for 2-4 months in soil, depending on soil conditions, temperature, and microbial activity. Research published in Molecules journal indicates that both Fe-EDDHA and Fe-EDDHSA chelates are classified as not readily biodegradable, which means they persist long enough to provide sustained iron availability to plants. In cooler soils or soils with lower microbial activity, effectiveness can extend to 6 months.

Can EDDHSA-Fe be mixed with other fertilizers?

Yes, EDDHSA-Fe has excellent compatibility with most water-soluble fertilizers, including NPK blends, calcium nitrate, and micronutrient mixes. Its high water solubility (over 1000 g/L) makes it ideal for tank mixing. However, always perform a jar test before large-scale mixing, especially with products containing high levels of phosphate or carbonate, which could potentially cause precipitation.

Is EDDHSA-Fe suitable for organic farming?

EDDHSA-Fe is a synthetic chelate and typically not approved for certified organic production. Organic farmers usually prefer iron fertilizers based on natural chelating agents like lignosulfonates, amino acids, or siderophore-producing bacteria. However, EDDHSA-Fe is highly effective in conventional agriculture and can be part of integrated nutrient management programs.

What crops benefit most from EDDHSA-Fe?

Iron-sensitive crops growing in alkaline soils show the greatest benefit from EDDHSA-Fe. This includes citrus, grapes (especially in calcareous regions), kiwi (actinidia), peach, pear, and many vegetables. Crops like avocado, mint, and soybeans are also highly responsive to iron chelate applications. If your crops show interveinal chlorosis (yellowing between leaf veins) on new growth, EDDHSA-Fe is likely an excellent solution.

6. Where to Buy EDDHSA-Fe 6% Chelated Iron Fertilizer

At MOSINTER, we've been supplying high-quality chelated iron fertilizers for over 21 years. Our EDDHSA-Fe 6% is manufactured under strict quality control, ensuring consistent 6% iron content with optimal ortho-ortho isomer levels. We supply agricultural cooperatives, fertilizer blenders, and commercial growers across 50+ countries.

We offer flexible packaging options from 1kg samples to full container loads, with delivery within 7 days for standard orders. Our technical support team can help you determine the optimal application rates for your specific crops and soil conditions.

Ready to solve your iron deficiency problems?

Contact us today for specifications, pricing, and samples:

• WhatsApp: +8618989305995

• Email: info1@mosinterchem.com

• Website: www.moschemical.com

Last Updated: January 2026

References

1. Álvarez-Fernández, A., García-Marco, S., & Lucena, J. (2005). Evaluation of synthetic iron(III)-chelates to correct iron chlorosis. European Journal of Agronomy, 22(2), 119-130. https://doi.org/10.1016/j.eja.2004.02.001

2. Klem-Marciniak, E., et al. (2021). Chemical Stability of the Fertilizer Chelates Fe-EDDHA and Fe-EDDHSA over Time. Molecules, 26(7), 1933. https://doi.org/10.3390/molecules26071933

3. PubChem Database - CAS 84539-54-8. National Library of Medicine. https://pubchem.ncbi.nlm.nih.gov

4. Hershkowitz, J.A., et al. (2025). Fertigation with Fe-EDTA, Fe-DTPA, and Fe-EDDHA Chelates to Prevent Iron Chlorosis. HortScience, 60(3), 404-410. https://doi.org/10.21273/HORTSCI17892-24