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FAQs About Ammonium Sulfate

Get answers to common questions about ammonium sulfate and how it compares to one of its alternatives.

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Get answers to your soil management and crop yield questions

Curious about how to get the most out of your fertilizer investment? AdvanSix’s resident agronomy expert is available to answer your questions. With more than 20 years of experience overseeing agronomic research at AdvanSix, Mercedes Gearhart shares a wealth of knowledge about using fertilizer efficiently and improving crop yields.

I’m in the Northeast part of Texas in Commerce. For pecan trees when would you recommend application for ammonium sulphate and is there anything special I need to know about or tell the place I get it from? I’m assuming like a feed and seed store would carry it. Or would I have to go somewhere else? And how much would you recommend per application or per tree? Thanks for the help.

In Texas and other regions with calcareous soils, ammonium sulfate (AMS) is often used not only as a source of nitrogen (N) and sulfur (S), but also to increase phosphorus and micronutrients availability to the roots.  In such cases, mature trees may get as much as 150 to 200 lb N/acre/year in the form of AMS, or about 750 to 1,000 lb AMS/acre/year.  In the case of non-calcareous soils, AMS may be blended with urea to a N:S ratio closer to 9:1 (instead of the 1:1 ratio in AMS).  Given that AMS is a very common fertilizer in Texas, you should have no trouble finding it at your local fertilizer or home and garden store.

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What is the recommended timing for using ammonium sulfate as a starter fertilizer on soybeans?

For a starter effect on soybeans you may broadcast ammonium sulfate anywhere between a few weeks before planting and the V4-V5 stages.

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Does soluble grade ammonium sulfate change the pH of the solution water?

Yes. When dissolving incremental amounts of ammonium sulfate (AMS) up to 17 pounds per 100 gallons (covering typical AMS recommended rates as herbicide adjuvant) water pH went gradually down from 7.67 to 6.30.

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What is the best time to apply sulfur?

It depends on the crop in question as well as the form of sulfur used. While small grains need sulfur early in the season to promote tiller formation, in the case of canola sulfur is more critical at the time of flowering and seed set; and in the case of modern corn hybrids and soybean varieties, sulfur needs are significant both early in the season as well as post-flowering. Regarding sources, elemental sulfur sources may need up to three seasons to oxidize, depending on environmental conditions, while sulfate sources, like ammonium sulfate, are readily available. At-planting applications of sulfate sources tend to be more efficient than pre-plant applications, since the latter provide more chances for leaching loss. As for in-season applications of sulfate sources, they can be more or less efficient depending on the amount and distribution of rainfall relative to timing of application and crop uptake pattern.

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Would you have any concerns about blending pelletized calcitic lime together with granular MAP and ammonium sulfate?

While the blended product should not have any issues during storage, it could face problems once applied to the soil, due to potential ammonia volatilization (from the ammonium-N in both MAP and ammonium sulfate), as well as possible Ca-P precipitation (from Ca-lime and MAP), and gypsum precipitation (from Ca-lime and ammonium sulfate). Having said that, the concern would not be nearly as much as if it were the case of granulated product, since bulk blends allow for physical separation of granules upon application.

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What is a safe rate of ammonium sulfate applied with the drill on wheat?

It will depend mainly on soil texture and whether it is applied straight or in a blend. A 50 pound per acre rate of straight ammonium sulfate would be safe to apply next to the seed across soils, yet you could double that amount on a heavy soil.

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Can a small amount of nitrogen applied with the drill make sense for wheat?

It can certainly make sense, particularly under no-till conditions. Just stay away from urea-containing fertilizers which, due to potential ammonia toxicity, are not recommended for applications in direct contact with the seed. Ammonium sulfate is a common and safe starter option which also supplies sulfur to the young seedling.

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What’s the leaf burn potential from streaming 10 to 20 pounds per acre of ammonium sulfate solution onto wheat straw with young soybeans growing?

Ten to 20 gallons of ammonium sulfate solution per acre would equate to 8 to 16 lb N/acre. Assuming that the fertilizer solution covers 20% of the row width, then the ammonium sulfate rate per wetted row would be equivalent to 40 – 80 lb N/acre, which should not cause a significant salt effect.

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With the wet weather, I’m seeing a lot of slug damage in my region. Can ammonium sulfate help with slug control?

I’m not aware of any formal ammonium sulfate recommendation for slug control, although I have seen it listed as a home remedy option. The idea here would be to burn slugs upon contact, rather than a residual effect.

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How much rainfall is needed to move surface-applied sulfate into the root zone?

It is hard to tell, because it depends on several factors. Most notably, with the same amount of rainfall, the sulfate ion can move faster from surface to root zone through a sandy soils than through a heavier soils. On the other hand, the sulfate ion could also move down below the root zone of a sandy soil, for example, so rainfall could be too little or too much…

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