Testing and evaluating your soils PH and texture

BACKCOUNTRY

Self-providing Guerrilla
So you have found a great spot, the sunshine is great, the security is good, now how about the soil? Along with sunshine and security, soil quality is high on the minds of outdoor growers, and it should be, it can make or break a grow.

On the first page we will explore soil texture, basicly evaluating your soils capacity for holding moisture and nutrients, and also its freindliness to your plants roots expansion.

On the second page we will cover soil PH, and dealing with soils that are too high or low in PH.
 
Evaluating your soil texture

Soil texture is important, you can put all the best fertilisers in your soil, but if the texture is too far off your plants will not be able to use it, soil that is too "hard" will impead root growth, soil that is too sandy may not hold moisture or nutrients long enough to benefit your plants. So lets get started!

Taking a soil sample
The first thing you need is a soil sample to work with, tests run on this sample will tell the tale of your soils potential.

To collect an sample, scrape away the first two inches of soil and dig a hole 6 inches down. Try to take a sample at this depth that contains as little topsoil or litter(leaves, twigs) as possible, take about a quart or so of soil. Be sure to label it, so you know which plot it came from. Now head home to run some tests.

Soil texture
Evaluating soil texture means you are basicly trying to figure out how dense your soil is, how "soft" or "hard" it is. Various ammounts of different soil components makes the difference.

Most soils are comprised of combonations of Sand, Clay, and Silt. Other components may be Gravel, rocks and Organic materials(Decaying particles of plant matter).

This is a Soil texture triangle-
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Each corner of the triangle represents soils entirely consisting of (or mostly) either Clay, Sand, or Silt. In the middle part are the different soils that result from different mixtures of the three.

Here is a different version of the same triangle-
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This triangle shows the ideal soils for most cultivated plants(including Cannabis) in purple and blue/green. These soils are known as Loams, they are of the perfect texture for maximum use by your plants roots.
The pink lines show the results of a test done to evaluate a sample of soil.

The soil sample was found to contain: A-58% Sand, B-15% Clay, C-27% Silt.
A dot was put on each side of the scale for each component at the percentage the sample contained for that component. When lines are drawn as shown, the point where they cross reveals what soil type the sample was, in this case, Sandy loam, a very desirable soil for growing.

How to evaluate your soils texture

When you get home, spread the soil sample on a cookie sheet or plate, and allow it to dry if it is moist. When it is dry, pick out any visable pebbles or large pieces of plant matter(roots, twigs), break up any clods.

Now take a straight sided glass jar(a mason jar or Peanut butter jar will do), and place 1 cup of the soil sample in the jar. Also add 1 tablespoon of powdered dishwashing detergent. The detergent is a surfactant, which keeps the soil particles separate, resulting in a more accurate test.

Now fill the jar to the top with water, screw the lid on, and shake the jar for three minutes to thoroughly combine the soap, soil, and water, and to make sure no soil is stuck to the bottom or sides of the jar. Then set the jar on a flat surface to let the sediment settle.

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As the sedimentation progresses, check the sample periodically to watch the layers form and note the size of the particles settling out. Sand particles are the heaviest of the three and settle out of the solution after about a minute. The sand layer is coarser in texture than the silt and clay. Silt is the next heaviest particle and will settle out after about an hour. The silt layer is darker than the sand. Clay, the lightest particle in the mix, can take from one to two days to settle out of the solution. The clay layer that settles on top is fine textured and light in color.

To figure out the percentages of sand, silt, and clay in the sample, measure the total amount of sediment with a ruler, once it has all settled. This number represents 100 percent of the soil sample. To derive the percentages of sand, silt, and clay in the sample, measure the amount of each layer and divide by the amount of total sample. For example, if the total sample measures 1-3/4 inches and the sand layer measures 1 inch, I divide 1 by 1.75 and get 0.57, which translates into 57 percent sand. If the silt layer measures 1/2 inch, I divide 0.5 by 1.75 and get 0.29, which translates into 29 percent silt. If the clay layer measures 1/4 inch, divide 0.25 by 1.75 and get 0.14, which translates into 14 percent clay.

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Now refer to the soil texture triagles above to find your samples soil type.

For general Cannabis growing, soils that fall into any segment of the triangle labeled "loam" are good. If you are lucky enough to have soil like this, you should be good to go as far as soil texture goes, you can move on to testing your PH and planning how you will feed your plants, for the rest of us with less than perfect soil, please read on.

Clay soils-
Clay is very dense, the more clay that is in your soil the harder it wil be to grow good crops in it. Clay soils drain poorly, and don't absorb Oxygen well, plus thay can be very hard for your plants to spread roots in.

If your soil consists of 40% or more Clay, I would advise replacing one quarter of each holes soil with Peat moss, Coco coir, weak compost, potting soil, or Perlite, a combo of Perlite and Peat or Coco coir would be perfect!

If your soil contains 50-60% Clay, I would advise replacing half of each holes soil with Peat moss, Coco coir, weak compost, potting soil, or Perlite, a combo of Perlite and Peat or Coco coir would be perfect!

If your soil contains 70% or more clay, I would advise completely replacing each hole's soil with Potting soil.

Sandy soils-
Sandy soils aren't too bad too grow in, but nearly pure sand soils don't hold moisture and nutrients so well.

If the soil contains 90% or more sand, I would advise replacing one quarter of each holes soil with organic materials like Peat, Coco coir, or weak compost, too improve moisture and nutrient holding qualities.

Silt soils-
Like clay soils, pure Silt soils can be dense, and need help loosening up.

If the soil contains 80% or more silt, I would advise replacing one quarter of it with organic materials like Peat, Coco coir, or weak compost.

If you who think all of this is a bunch of complicted knitpicking, read here!!
If this seems like alot of trouble, but you are not sure of your soils texture potential, don't fret! There is a easy way out!
When you dig your holes, simply fill them with your favorite potting soil, add 2 tablespoons of Dolomite lime per gallon of soil, and add your fertilisers, simple as that.
 
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Testing your soil PH

Evaluating soil PH
Soil PH is important, you can have all the best fertilisers in the soil but if the PH is far enough off the ideal, the nutrients may not be available to your plants, this is called "Nutrient lockout". Too high or low a PH changes the properties of the nutrients, and makes them unusable by your plants. A good PH helps keep your plants healthy and growing strong, because the nutrients they need are available to them.

The scale for measuring pH runs from 0 to 14, with 7 assigned as neutral. A pH below 7 is acid; a pH above 7 is alkaline.

Here is a link explaining soil PH- Link to Wikpedia explaining soil PH

Cannabis grows in soils with a pH range from 5 to 8.5, but it thrives in nearly neutral soils. A PH of 6.5 to 7.5 is ideal.

Taking a soil sample
The first thing you need is a soil sample to work with, tests run on this sample will tell the tale of your soils potential.

To collect an sample, scrape away the first two inches of soil and dig a hole 6 inches down. Try to take a sample at this depth that contains as little topsoil or litter(leaves, twigs) as possible, take about 2 gallons or so of soil. Be sure to label it, so you know which plot it came from. Now head home to run some tests.

If you will be adding organic materials like peat or compost to loosen or otherwise improve your soil texture, you will need to prepare a soil sample for PH testing that has the same ratios of native soils and the organic materials.

A example: You have clay soil that needs texture improvement, you have decided you will be replacing 25% of the soil with Peat moss. Take a 1 cup measure, fill it to 3/4 cup with the native soil sample, now add peat moss until you have 1 cup. Now moisten it, and mix it very well. This will now serve as your soil sample for PH testing.


How to test your soils PH

Litmus paper-
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To test your soils PH using Litmus paper you need to make a water sample with the plots soil. Fill a glass jar about 1/3 full with your soil sample, fill the rest with distilled water. Shake the jar vigorously and then allow it to settle out for 24 hours. The clear (or semi-clear) water on top contains your sample.

When a strip of Litmus paper is dipped in your sample, its color will change in shade, in reaction to the PH of your sample. Comparing the color of the PH paper with a chart supplied with it will show your PH.
Litmus paper can be hard to find, places to look: Beer and wine making stores, Drugstores, Healthfood stores, Medical supply, Lab supply, or online.
You need two sets of Litmus, one that reads Acid(4-7), and one that reads alkiline (7-9).

Rapid test soil test kit-
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This another good way to test your soil PH, it also comes with tests for the big 3 plant nutrients, Nitrogen, Phosphorus, and Potassium(NPK), which may also come in handy. With this test, you make a sample similar to how I described for the Litmus paper, a chemical dye is added to the water sample in a vial, the dye causes the water to change a certain shade of color, which indicates its PH, the tests for NPK are similar. A chart showing the PH scale with their representitive shades are convenently built into each vile for comparison.
This is the method I personally use. There are other brands available, your local growshop should have them.

Hand held PH meter
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These are PH meters like indoor hydro growers use, if you can afford one they are the easiest way to test PH. You use them to test soil the same way you use Litmus paper, by making a sample with your soil and distilled water. Your local grow shop should have them.

Rapidtest PH meter
These meters are frequently found to be inaccurate, and I don't advise using one. Here is alink to a test comparing it to other methods- A comparison of soil PH test kits

As stated above, Cannabis will grow in soils from PH 5 to 8.5, many growers feel that 6.5 to 7.5 is ideal. If your soil falls into this range, you should be in good shape! If not, move on to the next step, ajusting your soil PH.

Acid soils(Below PH 6.5)
If you soil is below PH 6.5, raising your PH is advised, this is most commonly done with either Dolomite lime or Hydrated lime.
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Dolomite lime is the one most used because it also ammends your soil with Calcium and Magnesium, micro-nutrients that Cannabis needs. Also it is gentler than Hydrated lime, and it is harder to hurt your soil with over application.

Rather than haul all your supplies to the plot, fill you holes and test them, we will make a test batch of the soil at home. With this test batch we will find out how much Lime will be needed to treat each hole.

If you are going to be mixing organic ammendments like Peat moss or Compost into your holes to improve texture, you will need to make a soil sample with the same ratios of native soil and introduced materials(If you will be using Perlite, it has neutral PH, and doesn't need to included in this test).

A example: Your soil contains 50% Clay, you will be replacing half of the native soil with Peat moss. To make a soil sample, fill a gallon container half full with the native soil sample, now fill it to 1 gallon with Peat moss, (dump in a larger container for mixing) moisten the soil and mix it very well. Now you have your soil sample, move on to the next step.


Into a container larger than a gallon, dump 1 gallon of your soil sample. Now add two Tablespoons of Fine Dolomite lime, moisten the soil and mix very well. Let the mixture sit for 1 hour, and do a PH test.

If the test puts your soil at, or above 6.3, this will be good, by the time the Dolomite is done treating the soil months later, its PH should rise to 7, you can move on to the next step. If your test came up short, add one more Table spoon of Dolomite, mix and repeat test, this should fix it.

Now you know how much dolomite you will need to treat each gallon of soil in your plots holes.

If you aren't sure how to estimate your holes size, read this:
First determine how large your holes will be in gallons. Convert the number of gallons into Cubic feet, there are 7.5 gallons in a cubic foot, so number of gallons divided by 7.5 equals needed cubic footage of hole.

A cubic foot is a cube that measures 1 foot on all sides. A hole measuring 1 foot by 1 foot wide, and 2 feet deep would have 2 cubic feet of capacity 1'x1'x2'=2 cubic feet. A hole measuring 1.5 feet by 1.5 feet wide and 2 feet deep would have 4.5 cubic feet of capacity, 1.5'x1.5'x2'=4.5 cubic feet.

Once you know how large your hole will be, multiply the number of Tablespoons of Dolomite it took to treat your 1 gallon soil sample, by the number of gallons each hole will contain.

A example: I want 15 gallon holes, so 15 gallons divided by 7.5 equals 2 cubic feet, I dig my holes 1 foot by 1 foot wide, and 2 feet deep.
My 1 gallon soil sample PH reached 6.5 with 2 tablespoons of Dolomite lime, so I will multiply 2 tablespoons by 15 gallons, for a total of 30 TBS of Dolomite per hole.


Alkaline soils(Above PH 7.5)
Very rarely growers may encounter soils that are too alkaline, the procedure for ajusting is similar to ajusting a low PH, insted of Dolomite use pure Sulfur in 1/2 Table spoon increments to find your needed ammounts.
 
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Thanks guys! A big reason I wrote this thread was to save the huge number of growers who buy excessive ammounts of soil improvers, when their soil may be very good to start with, or may not need much help. No point in spending $$$ if your soil didn't need it in the first place, or if it only needed a little help.
 
Bump

This is exactly how my powerpoint presentation for environmental horticulture soils class looks. This is university level info here everyone. Not just opinion

Good time to get ready for this summer
PEACE
420
 
"Soil" Off The Chart - Any suggestions?

Unfortunately, one of this years' seed patches ended up in the Crappiest medium I've ever encountered. Tucked deep in a thicket of bushy invasive species was a little clear area that only supported low grasses and weeds. The reason soon became obvious. Two inches down, the organic material stopped. Below it were two feet of hard packed gravel, sand, and coal cinders, with a layer of solid gray clay visible at the bottom.

What the heck. It was worth a shot. So far, so good. The equipment and amendments that could be hauled to the spot was severely limited, so each hole received less than a gallon of prepared soil, 1/2 mixed in the hole, the rest mixed near the top. The old-school, seed-in-ground, breeding scheme ( "Darwinian Tough-Love" ), is now well on it's way to fruition.

So far, the weather has cooperated. There's been sufficient rain, and the storage containers near the patch are doing their job. The question is this: How do I compensate for the lack of organic material? The top-dressing of slow release organic nutes and castings seems to have worked, and the dose of molasses they got last week couldn't have hurt, but there's almost nothing below to hold those soluble goodies in place. The "soil" is as porous as hydro medium.

Other than molasses and a dose or two of seaweed extract and epsom salts, is there anything else to be added that can compensate for the lack of organic matter below? Periodic doses of castings should provide bacteria, and there's sufficient slow release organic fertilizer on top to be washed in with rain or stored water. What's missing here?

It could be possible to haul in a few gallons of living, organic, "bubble tea", but would it be worth the hassle? Couldn't do it very often either. These plants aren't expected to get big, just to make it through the worst of the Summer heat healthy enough to reproduce. ( A four foot bush can grow a decent bag of bud, and a Lot of seeds. )

Will this turn into "organic outdoor hydro" whether I like it or not?
 
Thanks for the soil test info. Great help for me.

I have problems knowing the pH of my soil. I have 2 or 3 diff brands of pH meters. None of them read the same in the same sample. Very aggggeeeerrrrrrvvvvating!

Any way, thanks for the info in this thread, very good & very helpful!!

Thanks!!

ZZ
 
Yoooo!!!! Love this information!

This is so important to soil health and improved soil aggregates are linked to many positive results such as better fertility, better water relations in soil, and improved yield. Better than that, aggregates also support microbial life and can effectively sequester and immobilize soil pollutants.

Looking forward to seeing more great soil information you all have here and hopefully being able to contribute to the conversation!!
 
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