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Calcium Product 98G


Sulfur, Part 2: Application Rates & Timing

 By: Glen Howell

In Midwestern agriculture, there are primarily 4 fertilizers that are actively used for meeting sulfur nutritional needs. They are listed from highest to lowest sulfur concentration.  Also listed is their overall analysis & type of product composition:

Elemental Sulfur-90%S; (0-0-0-90S); dry product; sulfur is not in plant available form
Ammonium Thiosulfate (ATS)-26% S; (12-0-0-26S); liquid product
Ammonium Sulfate (AMS)-24% S; (21-0-0-24S); dry product
Potassium Magnesium Sulfate (langbeinite)-21% S; (0-0-21-21S-11Mg); dry product
Calcium Sulfate (SuperCal SO4; CaSO4; gypsum)-17%S; (0-0-0-17S-21Ca); dry product
Potassium Sulfate (SOP)-17% S; (0-0-50-17S); dry product

Crop need for sulfur

Crops need varying amounts of sulfur to complete their life cycle.  Much of what is needed for growth is recycled to the soil with plant residues, but there is a net loss with the crop removed. Organic matter (O.M.) in soil is a great sulfur source—each 1% contains 140# of sulfur—but it may not always be available when the crop needs it. 

Crop         Unit of Measure        # Sulfur/Unit of Measure        Yield-# Sulfur Removed                                                                 (Crop removal)

Corn (grain)        Bushel                   0.08#                               200 Bushels-16# S

Corn (silage)      Ton                        1.1#                                 30 Ton-33# S

Soybean (grain)  Bushel                   0.18#                                60 Bushels-10.8# S

Alfalfa/Forages  Ton                        5.4#**                   &nb


Sulfur-Part 1: Solubility & Leaching

 By: Glen Howell


I have received several calls this week on sulfur.  They focused on solubility/leaching potential, application rates, application timing, and product comparisons.  We will discuss solubility & leaching potential in this part.

The solubility of any fertilizer or soil amendment is critical to a successful outcome.  In order for plants to utilize a nutrient, it must be in soil solution (the water surrounding the soil particles).  Until a nutrient dissolves & goes into this solution, it is unavailable for plant growth.  This is why applying fertilizer does not immediately result in improved plant growth, but takes time (usually days) for the material to dissolve, go into soil solution, & be taken up by plant roots, before 

Corn showing sulfur deficiency

resulting crop growth occurs.  Leaching can happen if a product is too soluble, & unfavorable weather conditions occur.  This is typically associated with heavy rains, especially during the growing season, but is possible at other times also.  We are most often concerned about leaching nitrogen, but sulfur can leach almost as easily.  

Soil particles have both positive (+) and negative (-) charges on their exchange sites.  Younger, unweathered soils, such as those found in the Midwest, have a prevalence of positive sites, referred to as cation exchange capacity (CEC), while older, highly weathered soils have more anion exchange capacity (AEC).  Opposite charges are attracted to each other, so Midwestern soils with good CEC values, can hold significant quantities of beneficial nutrients such as Calcium (Ca++), Magnesium (Mg++), Potassium (K+) & the ammonium form of Nitrogen (NH4+). Unfortunately, nitrogen does not stay in the ammonium form for long, & instead changes to the nitrate form (NO3-), which is why nitrate leaching is such a huge concern (; Sulfur must be in the sulfate form (SO4--) for plants to use it, so conditions favorable for nitrate leaching will also favor the loss of sulfates.

In the next part, we will look at application rates for sulfur fertilizers.

Other references:


Glen Howell is a contributing writer to Yield Starts Here, a blog for farmers, focusing on increasing yield and profitability by focusing on the soil.  His other interests include severe weather & old farm tractor


Sulfur Deficiency

In an e-letter I received from there is a good article on alfalfa response to sulfur. Trials conducted by Iowa State are confirming what Calcium Products' customers have always known.

This summer we will be teaming with Dr. Sawyer, and Extension Agronomist Mark Wuebker to continue their sulfur research on corn.

"We are excited at Calcium Products to team with Dr. Sawyer and his staff." stated Larry Moore, President of Calcium Products. "It will be of great importance to Iowa farmers to finally quantify the impact of sulfur on production. I have seen a yield increase from sulfur on the farms I own and for many of our customers, SuperCal SO4 is the last thing they would cut from their fertility programs in tight years."

SuperCal SO4 is high quality natural gypsum finely crushed then pelletized. It contains 17% sulfur and is one the least costly sulfur products on the market today.

Additional Information

Sulfur is a structural component of amino acids, proteins, vitamins and enzymes and is essential to produce chlorophyll. It imparts flavor to many vegetables. Deficiencies show as light green leaves. Sulfur is readily lost by leaching from soils and should be applied with a nutrient formula. Some water supplies may contain Sulfur.



The Blogronomist is maintained by Craig Dick, head blogronomist and VP of Sales and Marketing. Here you will find a wide array of blog articles from Craig and expert guests on topics related to soil and crop health, farming, and so much more. If it’s not here, ask us!


Cost of sulfur, ammonium sulfate vs. calcium sulfate

While visiting with a dealer last week, I (Glen) discussed the attributes of different sulfur fertilizer sources.  The final choice between ammonium sulfate and calcium sulfate came down to the cost for a unit (#) of sulfate sulfur.  Here is what my calculations showed (these prices are not suggested to be indicative of every particular situation, but only an example):

Ammonium sulfate (AMS), 21-0-0-24S, was costing $0.75 per unit of sulfur (nitrogen value set to 0).

Calcium sulfate (SO4), 0-0-0-17S-22Ca, was costing $0.59 per unit of sulfur (calcium value set to 0).

If the sulfur requirement for 5 Ton alfalfa removal is 30# (6# sulfur per Ton), the cost for sulfur nutrition from AMS was $22.50 per acre, with the SO4 providing the same 30# of sulfur, but for a cost of $17.70 per acre.  Net difference (savings) to the grower of $4.80 per acre.

Not a huge difference, but still a 20% decrease in cost.  With the economic challenges of livestock production today, every little bit helps.

SuperCal SO4, the right fit, right now.



The Blogronomist is maintained by Craig Dick, head blogronomist and VP of Sales and Marketing. Here you will find a wide array of blog articles from Craig and expert guests on topics related to soil and crop health, farming, and so much more. If it’s not here, ask us!


What does all this rain mean to your field?


Obviously, it’s been a cool, cloudy and wet spring. So much so that corn planting, as of last week, stands at only 88%, 11% behind the five-year average of 99%. Only 44% of the soybean crop has been planted, way behind the 99% we experienced last year at this time. The stark weather contrast between this year and last has not only limited farmers’ ability to get into their fields, but also may have consequences in regards to soil fertility.

During drought conditions, it is normal for a ‘bank’ of nitrogen to be stored in the soil as there isn’t sufficient moisture to move it in the soil, so it stays put. Soil samples taken by Iowa State last fall indicated that it may be possible to have upwards of 100 lbs N/A carryover to this season, which is roughly double what may normally carry over from year to year. However, with all of the moisture that has fallen this spring, a significant amount of that nitrogen may have already leached out of the soil.

My suspicion is that the same thing may be happening with sulfate as well. Observations that I’ve made as I drove past corn fields last week generally show a yellowish, chlorotic plant that is starved for nutrition, at the V3-V6 stages on average.

The Iowa Soybean association is recommending farmers do a late-spring, pre-sidedress soil nitrate analysis in early June when the plants are 6-12 inches tall. The benefit of this test is that it predicts the amount of nitrogen available before the corn plant begins taking up more nutrients as it matures. ISA is recommending that if the test shows less than 21ppm nitrate, there is a high probability that the cost of an additional nitrogen application would be covered by the increase in yield you will see from that application. It’s completely up to the individual, but it may also be worthwhile to consider a sulfate source to sidedress along with additional nitrogen.

There are other compounding factors when soil is waterlogged for prolonged periods. Not only does the saturated soil predispose corn and other plants to disease pressure, it depletes the soil of oxygen, which has many negative impacts on plants. One of which tends to be exacerbated when it happens early in the season is restriction of root growth and development. Fortunately, we are not dealing with temperature extremes along with the saturated soil which would make the situation even worse. Things look to warm up this week; hopefully the soil will start to dry out a bit so we can all get back to our regularly scheduled growing season!




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