Potassium qty & timing

Discussion in 'Pesticide & Herbicide Application' started by HBFOXJr, May 30, 2002.

  1. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Posts: 1,712

    Many of us have heard of and practice nitrogen management in our programs. We vary type and qty as we go through the season. We also know that a lot of cool season and transition turf like the 4-1-2 or 3-1-2 NPK ratio.

    But what about the qty and timing of the K side of the fert operation? There has been talk here about how K is better absorbed when its ratio .6-.8 to 1 of N. However some are putting down a 5-10-31 in early to mid summer. How good is that going to really perform.

    Should out K amounts be managed independent of N rather than just as a percentage of N each time or a big chunk of the annual amount before stress time?
     
  2. tremor

    tremor LawnSite Bronze Member
    Posts: 1,476

    Harold,

    This is a subject near & dear to me. I work for the outfit that is producing that product. So I might just shoot myself right square in the foot with what I'm about to say here.

    The best use of higher potash levels for stress management involve the use of anywhere from 3-1-2 to 1-0-1 type ratios APPLIED IN ADVANCE OF STRESS PERIODS TO ACTIVELY GROWING TURF. I do NOT advocate the use of that product DURING periods of stress. While elevated K levels will promote more durable & well rooted plants, this change cannot take place while stress is upon the turf. That blend should, in my (sometimes) humble opinion, be used well in advance of stress as a true "pre stress conditioner".

    One other issue. Check the source of that potash. It's KCL or potassium chloride (aka muriate of potash). The salt (chloride) content of KCL is high so it's best suited for periods of cool wet weather. If drought conditions are present or appear shortly after application, a full 1lb of K from this material would make the drought symptoms worse. Watch the weather & adjust rates accordingly if this material is now part of your program.

    We produce plenty of better summer blends that would be easier on the turf. Sulphate of Potash (k2So4) is the more desirable K source for summer use. I often sell a custom (10 ton minimum) 20-3-20 75% PolyPlus SCU 4.5% Iron that's made with all K2So4. There's also the very popular 21-3-21 75% PPSCU with 2% Iron ( I helped develope this one) that is a blend of KCL & K2So4. This is a more cost effective approach than a straight K2So4 blend and still has lower salts than the 5-10-31.

    The very low N & the 10% Iron could give the applicators a false sense of security that this blend can't burn & will promote a deep rich green without any top growth. It can burn & probably won't be a very efficient utilization of the agronomic potash value much later into summer. Around here (coastal CT/Metro NY), I'd like to see this material applied befor the middle of June to get the most out of it. Much later than that and we'll lose the benefit of the elevated potash and possible cause salt related stress to the turf if we're starting to get dry.

    Now I'll probably have to dodge a few bullets, but I'll stand but what I've just said regardless. So have at it. LOL

    Steve
     
  3. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Posts: 1,712

    My mix for the rest of the year will run about 3-1-2, 50% Muriate and 50% SOP. Just varying the N qty to suit. Also running 65% CRN currently in the product. I'm having everything custom blended except pre/fert for spring. Maybe next year I'll go 3-1-3 on the current round (starts May 1) and possibly the 3rd round (late June-July 1 start) and back off a little in the fall.

    What do you know about Uflexx?
     
  4. lawnstudent

    lawnstudent LawnSite Senior Member
    Posts: 472

    Two things that I would like to add to Tremors fine response is:

    1) any single K app should not exceed more than 1lb. K/M

    2) Sulfate of Potash is a good K source but also adds sulfur. Sulfur will lower your pH. If your turf has a low pH you may not want to use Sufate of Potash. Another good source of K is Potassium Nitrate (44% k2o). Adds N (13%) and will not lower pH like Sulfate of Potash.

    jim
     
  5. tremor

    tremor LawnSite Bronze Member
    Posts: 1,476

    Harold,

    Uflexx is (I think) Simplot's trade name for Urea thats been stabilized with dicyanimide (DCD) and nitrapyrin. It's usually dyed blue for no reason at all. Most applied urea nitrogen is used by plants as ammonium ions, which resist leaching & to a lesser extent, nitrate ions that will readily leach. Nitrification inhibitors prevent the conversion of ammonium ions to nitrate ions. This is 20 year old agriculture technology. These Nitrification Inhibitors seem to come up once in a while in Pro Turf. Usually when an ag coop runs long (usually due to weather or bad ordering disciplins) and needs to sell the stuff quick. DCD can be useful for row crop treatments where the prills are disced under the soil. When left near the surface, the UV in sunlight destroys the DCD pretty fast. This is too bad, since DCD was originally engineeered to reduce nitrogen volatility (not create a slow release N). DCD is also known to leach out of soils before the urea has released.

    I don't want to get into it in detail here. But the new catch phrase in some areas is "soil biology". The soil microbes that so benefit plants, are often destroyed by the DCD since they're the same ones that cause nitrification to take place.

    There are much cheaper ways to make urea last longer than the 2-3 week extension we'd expect to see from DCD. (Uflexx is good for 6-8 weeks) The other ways are somewhat more predictable, last longer, & cost less. I wouldn't bet the farm on this one.

    Lawn Student,

    Potassium Nitrate is pretty salty in it's own right. It also makes a mean bomb! The FBI finally convinced our legal dept that we didn't really need this one after all!. The military enjoys potassium nitrate. They can't make gunpowder without it. The army also used it as an assistant to abstainence (saltpeter). It's also found in Sensodyne toothe pasted for old guys like us that have worn little holes in our teeth via the elimination of enamle by brushing. The PN blocks up the holes I guess. But knowing why the Army used it, I won't!
    Sulfur is a required nutrient by all plants. We have a competitor that has recently "introduced" the lawn care industry to the wonders of Ammonium Sulphate. It contains (I think) 26% Sulfur. And thet're hocking it as the salvation of turfgrasses everywhere! LOL. Since all the N sources have at least some degree of acidifying effect on soils, I suppose this isn't really such a big deal. Bottom line: some sulfur is very good for turf.

    Steve
     
  6. lawnstudent

    lawnstudent LawnSite Senior Member
    Posts: 472

    Sulfur is an crucial nutrient. Several turf proteins require sulfur and sulfur is needed to produce chlorophyll. 70 - 90% of the soil sulfur is in organic matter. Acid rain adds sulfur to the soil. Leached or low-organic matter soils are your most likely soils to require additional sulfur. But sulfur is the primary element used to lower pH and a low pH ties up nutrients. If your turf shows signs of sulfur deficiencies, then use sulfur. Just under stand that you are lowering the pH. That was my point.

    The nitrification process lowers the pH. Also, a growing plant will, over time lower the pH of the soil. Everytime the plant up-takes a cation (k+, Ca++, nh4+, Mg++, Cu++, Fe++, Mn++, Zn++, Ni++) the turf plant root hair gives back to the soil solution a hydrogen cation (H+). The balance of hydrogen cations and hydroxyl anions determines the pH level. The more hydorgen ions than hydroxyl ions, the lower the pH. Not much that we can do about the nitirification process or the nutrient up-take process, but we should be aware of our own fertilizer selection process and it's impact on the health of our turf.


    jim
     
  7. tremor

    tremor LawnSite Bronze Member
    Posts: 1,476

    Jim,

    I agree. If everyone was aware of the reactions caused by our efforts and those that occurr naturally, it would take a lot of the "guess work" out of turf maintenance.

    I've seen the need for Lime around here exceeding 200 lbs/M. I've also seen soil (that had just been indiscriminately treated with Lime without a soil test) that later came back from the lab with a 7.4 Ph. The applicator looked like a fool in this case. That's about as high as it gets around here though. That soil was carted into a new mall in Westchester Co, NY by the developer from New Jersey. (?!?!) I still can't figure out how the carting, Tappan Zee Bridge tolls, & permit fees made good economic sense.

    Since Sulfur is so rarely needed around here, we don't advise that applicators use acidifying fertilizers. (sometimes for Summer Patch management) We do however, stock limited quantities of pelleted or split pea sulfur for those rare occasions that a customer does need it. It's not uncommon to use these products on ornamentals though. The so called "acid loving fertilizers" don't often have enough impact on Ph to be of significant value when real corrective need issues develope. Especially on broadleafed evergreens. But I suppose where conditions are mild yet routinely encountered, these products are of genuine value.

    Have a great weekend, it's time for some boating!

    Steve
     
  8. lawnstudent

    lawnstudent LawnSite Senior Member
    Posts: 472

    tremor,

    enjoy the weekend boating.

    I live and work in an area of Illinois that was covered by the last great glacier. So a large portion of our soils are calcareous (derived from limestone glacial tills). What this means is we see pH ranges well above 7.0 (7.4 -7.8). Liming is the absolute worse thing to do yet we have services around here selling liming! I guess the message for this tread is that it is OK to talk about potassium needs, but they really are specific to the localized needs of your turf. Kentucky Bluegrass stands have a different requirement for potassium then a warm season grass or even another cool season grass like tall fescue. The soil type of your turf will require you to modify your fert. program. People need to stop thinking that one fert routine will fit all sites. Recognize your specific site's needs and modify your program to those needs and you will offer your customers a unique service, one probably not offered by anyone else in your area.

    jim
     
  9. paul

    paul Lawnsite Addict
    Posts: 1,625

    I think you are all missing one very important cation, Magnesium.
    Think of the 2 main cation that should be in balance are Calcium and Magnesium. Ideally they should = 68% Calcium and 12% Magnesium, with others as minor %'s. Think of Calcium as a mild flavor and Magnesium as a wild one, both will raise the pH of the soil, but Magnesium will raise it much faster. But Magnesium can't be lowered with Sulfur, you need to lower the Magnesium with High calcium lime or gypsum.
     
  10. lawnstudent

    lawnstudent LawnSite Senior Member
    Posts: 472

    Paul,

    the pH scale is actually stating the concentration of hydrogen ions. Liming a soil cause two things to happen: 1) Calcium (from the limestone and Magnesium if present) replaces the hydrogen ions at the cation exchange sites. The displaced hydrogen ions are now in soil solution and can be easily leached through the soil. 2) Liming converts the hydrogen ions at the cation exchange sites to water. The result is fewer hydrogen ions in the soil exchange sites. If the number of hydrogen ions are reduced relative to the number of hydroxyl ions, the soil pH rises. Yes, the calcium (or Magnesium) has displaced the hydrogen ions at the cation exchange sites, but pH is still measuring the hydrogen ion concentration. Is this correct? Is this what you were saying?

    jim
     

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