# Add sulfur without impacting PH?



## Matthawk7 (Apr 5, 2019)

Hey guys and gals,
Just looking for any suggestions on my soil test. I can manage the npk part (i think) but my sulfur and boron levels have continued to drop from last year and need to be addressed. My Ph fell from 6.7 last year to 6.2 as well. From what I've read adding sulfur will lower the Ph further. How should I address this? Add lime? Would gypsum be better? Any other thoughts would be welcomed! I'd like to add Ca and Mg too and get the ratio up as well. Thanks in advance!


----------



## tommyboy (Aug 20, 2019)

Following. Similar issue here.


----------



## CarolinaCuttin (Sep 6, 2019)

@Matthawk7 Use sulfate containing nutrient sources like potassium sulfate, magnesium sulfate, iron sulfate, etc.


----------



## Lawn Whisperer (Feb 15, 2021)

Gypsum, it has calcium and sulfur, but will not affect PH.


----------



## Matthawk7 (Apr 5, 2019)

Thanks for the inputs! Any idea how much sulfur is needed to bring me up to a normal range? I see that gypsum is about 23% sulfur so I can do the math there, i'm just not sure if i need 1lb/k or 50lb/k.

On the boron question, am I correct in thinking I can just use borax at a very low rate? Like 1/2 tsp/k?


----------



## Matthawk7 (Apr 5, 2019)

Well duh. Waypoint recommended .69lb/k. I went ahead and put out some this morning before I realized this at 1/3 bag rate. So 13lb/k @16% sulfur... Roughly 2lb of sulfur/k. Seems high compared to their recommendations but low compared to the bag rate. I dunno... Guess it won't hurt


----------



## Lawn Whisperer (Feb 15, 2021)

It won't hurt your lawn if your sulfate-sulfur is high, additionally epsom salt will do the same wirh sulfur and magnesium. 
Do you have sandy soil? Recommend keeping your Ca:Mg lower to hold your soil together.
Your CEC is extremely low so it won't take much to raise them.
I was curious how your PH went down. Did you intend to lower it? What type of nitrogen have you been using?


----------



## Matthawk7 (Apr 5, 2019)

Yes the soil is a loamy sand. I used mainly carbonx last year. I didn't intend to lower it and didn't do any strange amendments... other than some gcf humic late in the season. Seems like a big drop to me too


----------



## Lawn Whisperer (Feb 15, 2021)

Since your soil is so low in OM and CEC, in addition to loamy sand, it's gonna be hard to maintain PH and keep any nutrients. Have you considered adding OM like compost? I've added between 1/4 to 1/2 inch of compost on my yard, it raised OM% and CEC. I'd imagine that you've been spoon feeding/splitting apps in such a low OM/CEC. Sulfur and other nutrients will also leach easily in that type of soil, you'd almost have to treat it like a golf course green. Wishing for a green season this year, good luck.


----------



## Ridgerunner (May 16, 2017)

Matthawk7 said:


> Well duh. Waypoint recommended .69lb/k. I went ahead and put out some this morning before I realized this at 1/3 bag rate. So 13lb/k @16% sulfur... Roughly 2lb of sulfur/k. Seems high compared to their recommendations but low compared to the bag rate. I dunno... Guess it won't hurt





Matthawk7 said:


> Thanks for the inputs! Any idea how much sulfur is needed to bring me up to a normal range? I see that gypsum is about 23% sulfur so I can do the math there, i'm just not sure if i need 1lb/k or 50lb/k.
> 
> On the boron question, am I correct in thinking I can just use borax at a very low rate? Like 1/2 tsp/k?


You're almost there with your analysis (disregarding that S is nearly as transient as N). Here's another way to look at it. Calculate the theoretical change in ppm. Calculate the amount of the elemental nutrient added t one thousand square feet. Multiply that by 43.5 (the number of thousand square feet plots in an acre) and divide by 2. That will result in the ppm that will theoretically result from the application.

Wayside recommends .69 lbs per thousand square feet of sulfur in its elemental form. .69 times 43.5, divided by 2 equals an increase of 15 ppm. Your soil contains 6 ppm, Waypoint is suggesting you raise it to 21 ppm (6 + 15).

You applied 13 lbs/M of gypsum which is 16% S. You calculate that to be 2 lbs of elemental S/M. So, 2lbs of S/M times 43.5, divided by 2 equals an addition of 44 ppm. Total S = 50 ppm of sulfur. Recommended sufficiency levels vary, but commonly fall between 15 and 40 ppm but some suggest as high as 60. Fortunately, excessive amounts of sulfur (in the form of sulfate) have not been found to be toxic. No worries.


----------



## Ridgerunner (May 16, 2017)

Plants need sulfur as a nutrient, but can only take it up in the sulfate form.
Adding elemental sulfur will acidify the soil. (microbes convert S to sulfuric acid which quickly disassociates into H+ and sulfate)
Ammonium sulfate will also acidify while providing N and sulfate.
Iron sulfate will also result in acidification and provide iron and sulfate and a number of other sulfate compounds will acidify while providing sulfate
Potassium sulfate will not acidify and will provide potassium and sulfate
Other materials that will not acidify have been mentioned by others in the above posts but remember, they will add whatever cation (Ca, Mg) that is bound to the sulfate into the soil, so best to use a product with a cation the plant will use in relatively high quantities-that's why most use AMS and SOP)


----------



## RichS (Jan 28, 2019)

Regarding the Boron - I've applied it at 3-4 tbsp/K (4Tbsp=1/4 cup) every 45 days or so over the last three seasons, raising it from around 0.5 to about 1.5ppm. It didn't move quickly but it also has the lowest headroom to reach toxicity.

Fwiw, the same rate of Copper Sulfate knocked my Cu shortage up to Very High in two years. One year probably would have done it.

As noted in my thread, I've pounded my lawn with Potassium Sulfate (SOP) over two years and added 200ppm of Potassium but my Sulfur somehow dropped.


----------



## Matthawk7 (Apr 5, 2019)

All great info guys!

@Ridgerunner Thanks for the help on the math part of it... that makes it much easier in the future to determine how much to add (assuming I can find the target rates). I haven't added any micros other than what's been in carbonx in the past so that will be implemented into the plan this year. I'll be trying some feature along with some andersens PGF for part of the program. I think that switching to liquids may make more sense going forward.

@Lawn Whisperer The OM and CEC dropped this year along with the PH (from 6.7 to 6.2). The turf is 3 years old and I ammended the original soil with mushroom compost so it may just be that it's washing away. I am unsure of how/why the PH dropped so much but I may have been heavy handed on the N for the first two years. Or it could be that I did the soil test right after a month of rain here in SC. I'm not sure if this is a problem yet but I'll need to pay attention to those levels too.

@RichS Thanks for the details. Did you just use Borax (laundry powder) or some other form? I added 1 app of SOP @ 3lb/k and will probably do another in the fall. I should probably do the math on how much to truly add to reach target levels (up for debate but I'm guessing ~100ppm of k2o.) I know @thegrassfactor mentioned a calculator that would give you target application rates using a growth probability model, but I'll be darned if I can find it anywhere.

Jeez, what started out as just enjoying mowing grass sure has escalated quickly.


----------



## RichS (Jan 28, 2019)

Sorry, I should have been more explicit. Yes, the amounts I provided were for Borax which, iirc, is about 11% Boron.

If you use other sources, do the conversion on that percentage. Certainly don't apply that amount of actual Boron.

From my related post


> I put about 22lbs/K SOP over two years, so that should be ~160ppm K20, which is in the ballpark of the +110ppm increase I saw, given annual consumption (~10ppm per year from the Soil Growth Potential spreadsheets)


Note that this amount of SOP should have caused an 80ppm increase in S and I saw a decrease, still in the teens. Sulfur is apparently difficult/transient in measurement (though mine has been 10-20 for multiple years).

I'm trying elemental Sulfur this year. Most sources I've read indicate ~10lbs/K to reduce pH by 0.5pts. To get the calculated ppm I seek, I only need 2-3 lbs/K, so I'm not worried about the tenth or so of pH change. If you are, 10lbs/k of lime should knock it back. (There are also studies that show Sulfur is ineffective at lowering pH).


----------

