coco ph, what am i doing wrong

Discussion in 'Sick Plants & Problems' started by buzzkillz, Jan 26, 2020.

  1. Jan 26, 2020 #1

    buzzkillz

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    i have 6 plants in 3 gallon fabric pots under a 675 watt led.temps are around 72 lights on and 68 off, light is on 18-6, feeding sensi grow coco at 13 mls per 4 1/2 gallons, using ro water.

    im having problems with keeping my medium at 5.8.-6.0, i stick my soil pen in and ph is around 5.0- 5.4. when i water with 5.8 the ph does not go up, so i watered at around 7 ph and got my medium to 5.9 - 6 but then the next day its back down. why is it drifting down and not up? pretty much my waterings have been of ph of 6.5 or higher. what am i doing wrong.
     

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  2. Jan 26, 2020 #2

    2RedEyes

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    I grow in coco chips, I feed usually at 5.8 or so...I never check the ph in the pot, just the reservoir...I run a recirculating system where the nute solution is pumped to each plant through a feeding ring around each stalk...I feed 15 minutes every 3 or 4 hours and then it drains back into the reservoir...my res stays at 5.8 To 6 in ph...I change or refill the res once a week or so...but I have never check the ph of the actual coco...
     
  3. Jan 26, 2020 #3

    St_Nick

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    Ok here's the thing as I understand it. You are putting in chow for the plant at a perceived ideal ph. The plants are stripping out what they need and you find your runoff is much lower. Where's the problem? Are the plants green and bushy? Now later on, say in about a month, you are gonna notice the ph levels rising in your runoff due to a buildup of "residue" in your medium. Then its time to flush. Coco drove me nuts. I went back to soil. My medium starts out at a ph of 8.1
     
  4. Jan 26, 2020 #4

    buzzkillz

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    Not the runoff but the medium itself. So then I should just water at 5.8 then?
     
  5. Jan 26, 2020 #5

    St_Nick

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    I water at 6.3
     
  6. Jan 26, 2020 #6

    buzzkillz

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    @dd
     
    Last edited: Jan 27, 2020
  7. Jan 27, 2020 #7

    stinkyattic

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    Why are you using RO water, is your tap water really that bad? And as an addendum to the first question, what are you doing to replace the minerals taken out in the purification process? When I ran coco, I was even adding calmag to my TAP water just to jack it up!
    I used to precondition my coco with a soak in mild vinegar solution set to 6ish, rinse, then always give calmag.
    Listen to Nick and Redeyes on feeding routine, they won't steer you wrong.
     
  8. Jan 27, 2020 #8

    umbra

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    Presoaking the fibers in an alkali treatment has been shown to increase the tensile strength of coco fibers by almost 30%. Check to see if the manufacturer of your preferred coco brand is buffered with calcium.

    As a rule of thumb, be cautious when selecting bales and bricks of coco. The drying and compressing of the fibers creates dust, and it is a lot of work to decompress coco coir. Most bales of dried coco are compressed in a 6:1 ratio. Too often, waste-grade coir and coir dust is pressed into these bricks. The medium needs to be sieved to remove the small particulates. A high-quality coco should not contain any dust or tiny coco particles, as it can be compacted easily, thereby depriving the roots of oxygen and water.

    The pH of coco coir is naturally between 5 and 6.5—an ideal range for most plants. This gives the medium a distinct advantage over other mediums that need pH conditioning before use. Coco works best with 10% recycled glass stones or perlite added to it to aerate it further and prevent compaction. Earthworm castings can also be added to stimulate the microbial community.

    Coco can be reused for a total of three full indoor runs. Between each run, additional glass stones or perlite should be added. After harvest, you can add enzyme and flush solutions to pretreat the medium and remove any leftover salts and organic matter
     
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  9. Jan 27, 2020 #9

    umbra

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    Soil particles and organic matter have negative charges on their surfaces that attract cations. The total of these negative charges are collectively referred to as the CEC.
    The CEC is significant in growing media because it is a measure of the quantity of nutrients the media is able to hold on to before nutrients start leaching out. Plants are able to access the cations attached to the cation exchange capacity.
    Coco often has a CEC in the range of 90-100 meq/100 g of media. The CEC of coco is naturally loaded with potassium (K) and sodium (Na), with little or no calcium (Ca) or magnesium (Mg). These are the four cations that are most important when buffering coco.
    The goal is to significantly lower the percentage of CEC sites that have K and Na on them and increase the percentage of CEC sites that have Ca and Mg attached. Potassium can be attached to up to around 40% of the sites and sodium can be attached to up to around 15% of the sites.
    This is significant because if 40% of the exchange of un-buffered coco is holding potassium, then that equals 40 meq/100 g of media of the single-charge K molecule.
    The 100 g of weight in the above equation is the dry weight of the coco, not the weight of the coco straight out of a bag when it is moist. Hydrated coco should make 12-15 L (3-4 gal.) of coco growing media per kilogram of dry coco and of course 100 g is one-tenth of a kilogram.
    This does not sound like much, but would be as much as 1.56 g of potassium per 100 g of media. This is a lot of potassium, most of which will be slowly released into the aqueous solution around a plant’s roots. Compare this 1.56 g to 0.22 g of potassium per liter of nutrient solution (which is feeding potassium at 220 ppm, the amount that one would have in a well-balanced feed).
    If you have a 4-gal. pot and give it 1 gal. of feed per day, you would be feeding about 0.9 g of potassium and the CEC may be holding 15.6 g of potassium.
    Sodium may be present in up to 0.35 g per 100 g of media. With these numbers, an unbalanced nutrient solution will quickly result, as I explain in more detail below.

    Buffering coco media is accomplished by exposing the cation exchange to a solution of water with a high concentration of the cations that are desired on the exchange sites—in this case, calcium or calcium and magnesium.
    Because the cations on the exchange sites are held reasonably tight, washing coco does little to change the makeup of the cations on the exchange sites. The washing will change the EC but not the CEC. CEC sites have a preference for some cations over others.
    If the cations of Ca, Mg, Na and K are all present in the solution at the same concentration, they will be adsorbed at different levels, with calcium and magnesium being adsorbed at double the rate as they both have a double-positive charge, while potassium and sodium have a single-positive charge (Ca++, Mg++, K+, Na+).
    For example, many coco product manufacturers buffer their coco with 8 kg of calcium nitrate per cubic meter of coco. Calcium nitrate has a value of 19% calcium, which equals 1,520 g of Ca with almost no Mg, K or Na if the water is clean.
    As the process commences, a high concentration of Ca molecules attaches to the media—as each Ca++ molecule is adsorbed, two molecules of K+ or Na+ are released because the Ca has a double-plus charge and K and Na are single-plus charges.
    In the beginning, the exchange goes very quickly, but as the exchange continues, the concentration of the K and Na molecules released into the solution slows the exchange down and it will eventually come into equilibrium. The buffering process can be done in 10-15 minutes—the point at which the exchange slows down enough that the greater exchange is not worth the wait.
    Some coco products have been buffered with a higher treatment of Ca and Mg concentration. This creates a lower K and Na percentage on the exchange and adds the benefit of Mg to the CEC. These more advanced buffering processes involve a much greater amount of time, but result in much lower K and Na levels on the exchange.
    This essentially creates a better coco product from day one, ensuring all of a nutrient mix goes straight to the plant versus amending the coco’s CEC.
    As a grower, your goal is to create and use a well-balanced nutrient solution. If you are using an un-buffered coco product, a well-balanced nutrient solution goes into the coco and starts to buffer the coco as well as feed the plants, instead of all of the nutrients going directly to plants. So, the CEC in the coco is exchanging some of the K and Na for Ca and Mg.
    This exchange is now unbalancing your nutrient solution, increasing the K and Na while decreasing the Ca and Mg. How much unbalancing, you ask?
    Earlier, I mentioned the coco could have as much as 1.56 g of K and 0.35 g of Na per 100 g of coco. Your nutrient mix is not highly concentrated with Ca and Mg, but it is enough to get some of the K and Na released from the CEC.
    About 15 years ago, I was growing roses in coco and we did a weekly chemical analysis of our feed and drain water. The first time we used coco, we noticed the Ca in our drain water was less than 40 ppm (we would have normally expected the Ca to read 100-150 ppm in the drain water), and we were feeding Ca at a rate of about 200 ppm.
    For the next two weeks, we had the same result, so we doubled our Ca to 400 ppm. The analysis of our drain water went up to about 50 ppm of Ca. We watched that for about three weeks and then started feeding Ca at about 500 ppm and still had very little change in the Ca ppm in our drain water. It took about four months for our drain water Ca analysis to read about 100 ppm.
    The loss of the Ca and Mg is one thing, but you also get an increase of K and Na. High levels of K will hinder the uptake of Mg by plants. Sodium can negatively impact plant health even at low levels and is toxic to some plants starting at 50 ppm.
    The widespread use of calcium and magnesium supplements in the indoor gardening industry is an indication that many have experienced the CEC phenomenon in coco that I am talking about here.
    The deficiencies are observed and can be corrected to a certain extent with calcium and magnesium supplements, but there are also coco products out there buffered to a higher level, which don’t need the calcium and magnesium supplements.

    The degree to which a growing media can adsorb and exchange cations. The value of a cation exchange capacity is normally expressed as meq/100 g.
    • Cation – A positively charged ion, such as Ca++, Mg++, K+, Na+, NH4+, H+, Al+++.
    • Milli-equivalent (meq) – A measurement often used in quantifying a cation exchange capacity (meq/100 g = milli-equivalent per 100g of dry media). The milli-equivalent is based on the value of an equivalent. An equivalent is the weight in grams of a molecule divided by its molecular weight multiplied by its charge. For example, hydrogen (H+) has a molecular weight of 1 and a single positive charge, so 1 g of hydrogen is one equivalent. Calcium (Ca++) has a molecular weight of 40 g and a double-positive charge, so 40 g of calcium is two equivalents.
     
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  10. Jan 27, 2020 #10

    2RedEyes

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    I buy compressed bails of coco chips...I like the chips because I feel like my roots are able to breath easier...I use coco coir as a starter mix and then that gets transplanted into the chips...I rinse them as well as I can then use them...i ph my nute to somewhere around 5.8 and let it ride...it usually doesn’t change much over about a week...
     
    Last edited: Jan 28, 2020
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  11. Jan 27, 2020 #11

    stinkyattic

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    I've tried a few forms, from bricks that decompressed into almost a sawdust consistency and drove me batty, to semicompressed long fiber bales which were lovely, also those fancy prefab cubes, and no matter what, I always threw ridiculous amounts of CalMagPlus at the project for exactly the reasons Umbra put in above. Stuff is HUNGRY for cations even before you add the plants! Lolol
     
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  12. Jan 27, 2020 #12

    Japanfreak

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    Good info already posted. I would just add that you may want to increase your temps considering that you are using LEDs.

    edit: I would go to 83 for LED.
     
    Last edited: Jan 27, 2020
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  13. Jan 27, 2020 #13

    buzzkillz

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    im running cyco coco not in a brick this time. i fed 150 ppm of cal-mag on 700 scale. then did 13ml sensi grow coco a+b, 4ml b-52 for a total of 510 ppm on 700 scale. they looked better today from just watering at 5.8 and adding photosynthisis plus. new growth was twisting but seems to be better today, and i hope they look even better after the added cal-mag.
     

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  14. Jan 28, 2020 #14

    zem

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    I have used compressed coco slabs and they definitely needed treatment when they arrived. I soaked them with Calcium Nitrate to precipitate the sea salt and then I flush and soak with H2O2 then flush again. After this treatment plants grew nicely in it but it seems like it is a magnet to pests and they loved to stay in the coco so I stuck with my growrocks hydro system
     
  15. Jan 28, 2020 #15

    buzzkillz

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    today i put 4 1/2 gallons 5.8 ro water in a 5 gal bucket. put in 10 ml calmag by botanicare, 13 ml sensi grow coco a+b, 4 ml bud ignitor. new growth is still twisting, should i give it a day or 2? to much N? should i back off my base down to like 12 or 11 mls?
     

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  16. Jan 28, 2020 #16

    zem

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    On a 500 scale (NaCl) I would normally have plants at least 1000ppm when they are this big. I also notice that they love the Magnesium and since I am not using Ro water they don't need so much calcium, so I add more magnesium sulfate and magnesium nitrate than I add calcium nitrate. Also it sounds too much water to add 4 1/2 gallons to 5 gal pot, is the runoff draining well? coco holds a lot of water and is better when mixed with perlite...
     
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  17. Jan 29, 2020 #17

    buzzkillz

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    I mix my mutes in a 5 gal bucket. The pot is 3 gal
     
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  18. Jan 29, 2020 #18

    Japanfreak

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    Obviously so many people have great results with coco, but pro-mix is just so much easier.
     
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  19. Jan 29, 2020 #19

    umbra

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    totally agree
     
  20. Jan 29, 2020 #20

    St_Nick

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    I just repotted all my plants into fox farms 'cause coco was driving me crazy. in 10 days they quadrupled in size. I suspect that a feeding regimen that automatically stabilizes the ph would be the way to go with coco
     

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