Raising and Lowering pH Values Based on a Soil Test
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- Опубликовано: 2 авг 2024
- Raising and Lowering pH Values Based on a Soil Test
Professor DeBacco
Know What Your Plant Prefers
The optimum pH is based on the plant species you are growing.
Most garden plants prefer a soil pH between 6.0 and 6.8.
This includes cannabis, however hydroponic growers tend to favor 5.5-6.5
Notable exceptions…
Acid-loving blueberries prefer a pH of 4.5 to 5.3.
Potatoes varieties without scab resistance are also grown at a lower pH (5.2 to 5.4) to inhibit the growth of this disease organism.
Region Impacts pH
Geographic area can also influence native soil pH
General soil pH by region…
East Coast: 4.8 - 5.5
Midwest: 6-6.5
SW: 7.5-8.5
Getting to Your Plants Optimum pH
You will likely need to raise or lower your soils pH to reach the optimum levels for your plants.
Raising Soil pH (lime)
Ground limestone is commonly used to raise a soils pH
Soil testing labs will offer recommendations that is based on the actual pH, plants being grown and the buffering capacity of the soil
Typically the lower the pH and the more clay and organic matter in the soil the greater the amount of limestone required to raise the soil pH to the targe level.
Limestone Applications
Limestone recommendations by the soil lab are made in tons/acre or pounds/100 or pounds/1000 square feet, so know the square foot area of your growing space.
Limestone needs to react with the soil so it is highly recommended to be tilled into the soil.
If you are not going to incorporate the lime than apply no more than 50 - 75 lbs/1000 square feet (5 -7.5 lbs/100 sq. ft.) to the soil surface at one time.
Reapply at one- to six-month intervals until the total recommended amount is administered.
Limestone Options Powdered vs Pelletized
It will take several months to a year for the soil pH to increase.
However, it is possible to move soil pH a full point even over winter months is powdered lime is applied and tilled into the soil.
Powdered vs Pelletized
Powdered lime will be quicker acting, but is more difficult to apply
Pelletized lime is easier to apply, but may take longer to adjust pH
This is essentially the same lime, but is inside a small coating to make application much easier, so there is a slight delay as this coating dissolves.
Limestone Options Dolomitic vs Calcitic vs Hydrated
Many growers think there is just lime, but there are three types…
Dolomitic limestone: (Calcium carbonate + Magnesium carbonate)
Most commonly found
Contains elevated levels Mg
Which can be an added bonus
Calcitic limestone: (Calcium carbonate)
Often called “hi-cal lime”
Lacks high levels of Mg
Used if Mg levels are determined to be optimum
Hydrated Lime: (Calcium hydroxide)
Quick acting lime
May change pH quickly, but does not have a long residual change as the other lime options
Mucus membrane irritant, so be careful if you are applying it
Lowering Soil pH
Sulfur or Ferrous sulfate is often recommended is used to lower pH
The recommendations by the soil lab are made in tons/acre or pounds/100 or pounds/1000 square feet, so know the square foot area of your growing space.
Typically the higher the pH and the more clay and organic matter in the soil the greater the amount of material is required to lower the soil pH to the target level.
Both of these compounds need to react with the soil so it is highly recommended to be tilled into the soil.
If you are not going to incorporate the sulfur than apply no more than 400lbs/acre to the soil surface at one time to established plants per year.
Sulfur vs Ferrous sulfate
Elemental Sulfur (S)
Spring application and incorporation work best since the acidification process is based on soil biology and not a chemical reaction.
Soil temperature should be above 55F and have good aeration so the bacteria are active.
If soil is anaerobic (water logged) the sulfur gets converted to hydrogen sulfide and can damage plants.
Ferrous sulfate
More costly to use than sulfur
Eight times more ferrous sulfate is needed than elemental sulfur.
It is quicker acting than sulfur
Avoid Aluminum Sulfate and Sulfuric Acid
Aluminum sulfate can be toxic to certain plants (ex. Blueberries) if high rates are applied.
Irrigating with dilute sulfuric acid can lower the soil pH, but it can damage plants and also corrode metal pipes and fittings in irrigation systems.
Follow Lab Recommendations
The soil lab you select will know not only the pH of your sample but the buffer capacity (resistance to ph change) and soil type.
Utilizing all of these factors will help produce a good starting point for correcting your soils pH.
Remember the lab is only as good as the sample you provide them so make sure it is representative of the entire growing area and not just a single site to ensure the pH adjustment will maximize plant performance.
Link to Lecture Slides:
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Matt..thanks for coming down to my level in understanding the diff nutrients. Happy New Year!
Thanks for coming up to my level of understanding;-)
this channel is so underrated.... im so grateful for the information i get here, thank u so much ! im european english is not my language but this is easy to listen to .
Thanks for posting this and great to hear! Please share the channel with others!
Straight information, straight to the point.
Glad you went straight to the comments after watching.
Happy frog soil tested at 6.9 i have fast-actin gypsum, has sulfur and sulfate in it will adding that to the top of the soil drop the PH to 6.2 to 6.5 (cannabis) great knowledge in this video.ive been watering at 6.0 with PH down my water PH around 7.00 to 7.2 tap water
Hope this plan works well for you.
would like to see a video on pH fluctuation damage to cannabis leaves
This can have a variety of visual symptoms, but pH is easy to check.
👍👍
Thanks!
How about adding Calcium betonite? Are earthworms not affectd by adding the chemicals you mentioned?
How about sap analysis vs soil analysis?
So many questions...
Calcium betonite = clay based and would not impact pH nearly as effective as limestone
Earthworms = not impacted at the levels recommended, infect with improved plant health their populations may benefit
Sap vs Soil testing... ruclips.net/video/BLBnk2Kmr2c/видео.html and ruclips.net/video/rp3QnypfIAU/видео.html
Thanks man .just got my run off back at 7.5 pH and was worrying to hell my plants going to start showing defiencys soon.i know exactly where I mucked up I just hope I can level the pH out to a more balanced pH level for my baby....help lool 😂
Once you know the problem you know what to fix;-)
Question: Would adding a product called CAL - MAG to the watering do the same thing?
In short, no it does not have a great impact on the long term pH values of the soil.
What about lowering the pH for indoor (potted) plants? I need something to drop the pH from 7.5 to 6 quickly. I don't think sulfur (which I have from another project) is going to acidify the soil fast enough. Should I buy an expensive pH down bottle or can I use vinegar?
pH down is "best" but vinegar would work.
Lemon juice is the one ..
Aluminum sulfate
Question: I use a soil mix with a Ph of 5.5. Could someone advise me on the amount of Dolomite Lime I should add to make it around 6.8 Ph ? (per litre).
This DeBacco University video may help you out... ruclips.net/video/qTJcXS78HQg/видео.html
That shouldn't affect your ph. And what are you growing that you need Lime?? I only heard of that for like bugs or rodents in the garden, or if you have a dog that loves digging up things in your yard
If you use ph up and it goes too far up is it safe to use ph down in the same solution I've heard conflicting reports on this it seems if it's safe to use both products on your plant it shouldn't be a problem but what are your thoughts? Thanks
Yes, you can use both, but your ppm will likely increase.
Hydrogen to drop soil ph?
Hydrogen ion concentrations is the definition of pH... pH = -log [H+]
Aluminum sulfate