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Thread: Soils

  1. #1
    Join Date
    Jan 2011
    mazarxnl is offline
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    Maximizing Root Growth in Soil Containers

    Contributed by FarmTheGanja
    Submitted: 03-23-2004

    Root growth/mass(all other factors being equal).

    Space is also one of the major concerns for indoor growers, who generally cannot move to bigger and bigger pots to allow for bigger root masses.

    However, a lot of container space often goes unused, because roots will not grow into the top inches of soil that are often dried out from powerful lights and low humidity. In addition, since MJ soils are typically very airy and light, when watering the top inches of soil are easily disturbed as the dirt is pushed and moved around by the water. This also inhibits roots from growing into the top inches of soil.

    In a 1 foot tall pot the top 3 inches of soil will not allow root growth, you are wasting 25% of your soil mass that could be used for roots. In pots that are wider at the top than the bottom, this wasted soil could be even greater!

    How then to use this soil? We need to prevent the soil from being disturbed and keep it moist, and hydro growers have been using an ideal product for this for a long time - Hydroton clay balls!

    1. Hydroton clay balls are LIGHT.
    They won't compact your soil the way putting pebbles on top would.

    2. A layer of hydroton clay balls on top of the soil will help the soil underneath it lose moisture through evaporation and low humidity.

    By adding a layer of hydroton on top of the soil, soil disturbance is prevented since the water does not directly touch the soil until it has filtered through the layer of hydroton balls. Soil moisture is then trapped underneath the hydroton and less likely to evaporate due to heat and/or low humidity.

    This way it is possible to grow plants with roots stretching up all the way to the top of the soil. Those roots will rapidly provide nutrition to the plant when it is watered. It also will help the plant be able to go a longer time without watering since moisture that would have been lost to evaporation is now available to the plant.

    Use a root stimulator during veg growth to help accelerate the root growth process and make sure there is a strong root mass in flowering. The last things you want in flower are wimpy roots (unless you want wimpy yields).

    Treating old soil

    How do I treat old soil?

    How to properly clean your dirty old soil!

    Disclaimer: I'd like to say that none of the information provided has been discovered by myself. I just did a lot of research on the subject because of a number of complaints from fellow soil growers about fungus gnat infested soil, moldy soil, problems recycling soil, etc.


    Occasionally everyone gets a bad batch of all know what I'm talking about. You're finally ready for your transplant so you open up your bag of rich, organic soil only to find it's filled with fungus gnats or some other unwelcome pest. Soil-borne fungi and nematodes can be very destructive to your crops, causing seed rot, seedling diseases, and vascular wilts.


    There are various ways to treat soil that is infested. The safest and most popular method is Heat Treatment. Various soil fumigants exist which create a toxic environment in the soil and will remain toxic for a few weeks or more depending on what kind of fumigant is used.

    ?Sterilizing? is actually a misnomer, since complete sterilization would completely eliminate every living thing in the soil, creating a ?biological vacuum?. This ?vacuum? would then give an accidentally reintroduced disease-causing organisms the opportunity to multiply and spread rapidly, causing a severe disease situation.

    Instead, treatments can be used that will eliminate the undesirable organisms, but leave many of the harmless or beneficial soil organisms (called pasteurization). This remaining microbial population will compete with any introduced troublemaker and help prevent it from becoming established and spreading rapidly in the treated soil.

    Heat Treatment

    Temperature control is CRITICAL when heat treating soils. Overheating or under heating can lead undesirable results. Most disease-causing fungi are killed by a 30-minute treatment at 140?F.

    Plant parasitic bacteria, most plant viruses, and soil insects are killed at 160?F for 30 minutes, and most weed seeds between 160? and 180?F for 30 minutes.

    Remember: the higher the treatment temperature, the greater the number of beneficial organisms that will also be killed.

    DO NOT OVERHEAT! Chemicals toxic to plant growth can be produced in soils when temperatures reach around 212?F (boiling point of water and temperature of steam). This more commonly occurs with soils having high organic matter content. A maximum treatment of 160?F for 30 minutes is suggested.

    Oven Method:

    Place the soil in containers so that the soil is level, not more than 4 inches deep. A glass or metal baking pan will work fine. Cover each container tightly with aluminum foil. Place a meat or candy thermometer through the foil and into the center of the soil. Set the oven to 160-180?F and heat for 30 minutes after the soil temperature reaches 160?F. After the treatment, allow the soil to cool.

    Note: For large amounts of soil it may not be possible to use an oven. Instead you can use the heat of the sun. First break up the soil and make sure it?s moist. If not, water it and cover with a piece of plastic. Add more soil around the edges of the plastic to keep it from coming loose and letting the moisture and heat out. Leave the soil undisturbed under the sun for a few weeks before planting.

    [Editor's note: greenhouses commonly use electric soil sterilizers, able to process larger amounts of topsoil.]

    Soil Fumigants
    There are various products available for use in outdoor plots that can be used when heat treatment is not an option. These products are VERY hazardous and should not be used under any circumstances where you're plants are already in the plots!

    They are for treating unplanted soil and once applied, the area must be covered with a tarp and left. Aeration times vary. Read the label.

    I just put a post in the grow faq about Cation Exchange Capacity. Read the short little part about Sodium buildup. 15% total saturation is considered borderline toxicity. From what I?ve read Clearex is awesome.

    I have seen research suggesting a high beneficial bacteria and micro-organism content helps prevent outbreaks from undesired critters.

    The technique your talking about to sterilize compost piles is called solarizing. You can get more information but I've heard of just putting clear plastic sheeting over the pile.

    DO NOT OVERHEAT! Chemicals toxic to plant growth can be produced in soils when temperatures reach around 212?F (boiling point of water and temperature of steam). This more commonly occurs with soils having high organic matter content. A maximum treatment of 160?F for 30 minutes is suggested.

    Organic matter such as humus or clay have high Cation Exchange Capacity. If you?ve ever taken chem 100 you know heat accelerates the release of bonds between ionized metal salts and the medium.

    What is a fortified medium?

    A fortified medium is one that has been amended with nutrients. Vic's Super Soil is an example of a complete fortified medium, that is, the grower does not feed the plants during the time they are in this medium. Just add water.

    A partially fortified medium contains some of the nutrients the plant will need, but the grower must also feed the plants during their growth cycle. casting/perlite/vermiculite mix may be partially fortified with guano and kelp meal. The grower will still need to feed the plants, but on a reduced schedule.

  2. #2
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    Jan 2011
    mazarxnl is offline
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    How can I measure the pH of soil/soilless runoff?

    How to test the pH of your soil mix

    Measuring the pH of soil is just as important as with hydro applications, but few people know how to test soil pH to see if it is within the optimum range for growing robust healthy plants. Here I will try to explain my method of testing any soil / soilless mix, enabling me to spot any problems and correct them if necessary.

    Firstly, wait till your soil has dried out and is due for its next watering schedule. Then take some plain water that you usually water your garden with, and adjust the pH to 7.0. You must make sure that you know the exact pH of the water going into your soil, and the neutral 7.0 is best, but anywhere from 6.5 ? 7.0 will suffice.

    Then place your pot into a bowl of some sort to catch the runoff water, and then start to water your soil slowly (with your pH- corrected plain water) till the water starts to drip from the bottom.
    It?s the first drops of water that will give you the best reading of your soil, so make sure to water slowly till you see the first droplets. Then remove the pot from the bowl to eliminate excess water entering the bowl. Then perform the pH test on the runoff and compare it too your initial test.
    The results of the runoff test will likely be lower than your starting value of 7.0. If this is the case, a small drop of 0.5 pH to 6.5 pH (example) would be ok and your soil needs no further alterations at the moment. But that?s not to say that it won?t need any future tests at all, just not at this time.

    [Editor?s note: It may be beneficial to obtain an initial sample, as well as a ?full flush? sample in seperate bowls. In addition, test several plants in the garden just to verify your results]

    What if the pH is off?
    If your results prove to have dropped considerably, say to around 5.5 (which can happen in late stages of flowering), you will need to add some lime into your soil to help buffer the pH back up again.

    Remove the first inch or so of soil, taking care not to damage any roots whilst performing this task. Then sprinkle the lime into the pot, nice and evenly at a rate of 1 teaspoon (5 ml) of lime per gallon of soil. Then replace the soil you removed earlier, and saturate the soil good to wash in the lime.

    Do the same test next time your plants need watering just to check that everything is fine, if more lime needs to be added then just repeat the process again till you reach close to 6.5 ? 7.0 with the runoff.

    Ensuring that your pH is correct should be done throughout the life cycle; this will help eliminate any nutrient lockout that may occur. I recommend doing this once a month just to keep the PH in check, and you should never have a problem with deficiencies caused by pH lockout.

    What is nutrient lockout?

    Nutrient lockout happens when your plant can not access specific, or all nutrients in the growing medium, this is due to a chemical reaction within the medium/solution which prevents nutrients from being absorbed by the roots.

    Aged nutrients can precipitate in the bottle, causing some of the ingredients to become solids or even evaporate, the same problem may also occur in the growing medium.

    Lockout will display the same symptoms as nutrient deficiency; to help control this problem dispose of old liquid feed containers as you would old medicine and use fresh nutrients from a bottle that has been recently opened.

    The following points can also be responsible for nutrient lockout.

    [LIST][*]PH is incorrect or fluctuates.

    [*]Single pack hydroponic solutions.

    [*]Salt build up.

    [*]A chemical reaction between 2 or more nutrient
    solutions that are mixed together.

    [/LIST]For acute deficiency symptoms caused by toxicity and nutrient lockout a first Aid program should be immediately administered.

    Step 1)
    Leach the plants roots and growing medium using a professional leaching agent to thoroughly leach away metals, calcium, sodium, chlorides, sulphates and many other compounds, which can build up in the growing media.

    Step 2)
    Feed with 1/4 strength high quality complete plant food mix along with a high quality vitamin B-1 product such as Superthrive (1 drop per gallon).

    Step 3)
    Spray a professional stay green formula on the leaves. After 24hrs, spray the leaves with a quality vitamin B-1 product.
    Feed at 25% of recommended fertilizer dosage until first signs of growth.

    What are Water-Absorbent Polymers and how do I use them

    What are polymers and what are water-absorbent polymers?

    A polymer is a string of repeating molecules that forms a long chain. DNA is a polymer, as are starches, proteins, etc. For example, casein - the protein that makes cow's milk - is a polymer. About 30 years ago the plastics industry was looking to change the negative image people have of the word plastics, and pick up on a friendly sounding name to confound the public so they started calling a wide-range of their plastic products 'polymers'.

    Water-absorbent polymers (also known as hydro-gel, water crystals, super absorbent polymers, etc) - are simply a type of plastic that possesses some unique water absorbing qualities.

    What makes this polymer water absorbent is the presence of sodium or potassium molecules that form bridges between the long hydrocarbon chains. These bridges - known as cross-linking - enable the polymer to form into a huge single super-molecule (desirable for a number of reasons), including its ability to degrade in the environment and break-down into simpler molecules, and hold significant amounts of water. The polymer crystals that you purchase, whether the size is small, medium, or large, will always be a single molecule (making it very difficult for you to chop up large crystals into smaller crystals - try it in a coffee grinder sometime.)

    All water-absorbent polymers are cross-linked, and cannot work if they are not cross-linked. It is often written on labels to make it sound like a "feature" - don't be tricked into paying more for polymers that are labeled as being "cross-linked".

    How are they used?

    Water absorbent polymers (hereafter referred to as just polymers) can be used for two purposes: to store and hold water to add an extra few days between watering; or alternatively, to protect your plants from over-watering - especially if they are planted in an area that tends to pool water.

    Are there different types of super-absorbent polymers?

    There are about 800 to 1000 different recipes for these polymers - but they are divided into two big categories: polyarcylamide and polyacrylate.

    Polyacrylate (called in the industry PAC) are used in disposable diapers, sanitary napkins, etc. and are capable of holding a huge amount of water - between 600 and 800 times its weight (purity of the water determines this range - the more dissolved solids in the water, the less liquid the polymers can hold).

    Polyacrylates are usually made with sodium and are more environmentally friendly, breaking down first into ammonia salts and then nitrogen and CO2 in about 4 to 6 months. They are often sold with an environmentally friendly green label and retail for around $10 to $12 per pound.

    In contrast, polyacrylamides (often known as PAM) absorb only about 300 - 400 times its own weight in water, use a variety of potassium molecules for cross-linking, and take between 5 and 7 years to completely breakdown. Because of the lower absorbency and longer time to breakdown, polyacrylamides usually sell for around $6 to $8 per pound.

  3. #3
    Join Date
    Jan 2011
    mazarxnl is offline
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    Do polymers affect the taste?

    Do water absorbing polymers affect the taste of finished marijuana?
    I experimented with the use of polymers on my canola farm over a period of years, and have grown cannabis in extreme drought conditions using these crystals.

    Growers have reported that these polymers adversely affect the taste of the finished product. Many others have reported no impact on the taste of the quality of the smoke. This debate and the difference of opinion is due to the type of polymer used.

    Polyacrylates will negatively impact the taste of cannabis. As noted, polyacrylates take approximately 4 to 6 months to completely break down - with intermediary chemicals including ammonia salts, nitrogen (nitrites), and CO2. This breakdown usually happens when most growers are flushing their plants - and it is the plant absorbing this residue that negatively impacts the taste, including a variety of sodium by-products.

    In contrast users of polyacrylamides - which take 5 to 7 years to break down - will not be introducing intermediary residual chemicals to their plants, and will not notice any impact on taste or quality of the smoke.

    Given a choice between the two - it is strongly recommended that growers use the less absorbent polyacrylamide.

    How do I tell if the polymer is polyacrylate or polyacrylamide? (if there is no label)

    If you cannot buy from a recommended online supplier, and are buying locally, look for these four clues to distinguish products: absorbency, price, "environmental friendly", and a "safe for food crops" label.

    Polyacrylates (the one you want to avoid), report absorbency of 600 to 800 times its weight, cost around $12 Cdn per pound, and almost always have on the label "Environmentally friendly".

    In contrast, polyacrylamides are labeled as absorbing 300 - 400 times its own weight, are priced at $6 - $8 Cdn per pound, and may have a note on its label that reads "Safe for Agriculture and Food Crops". Only certain polyacrylamides (and very few polyacrylates) can be labeled as safe for food crops.

    Can you recommend a reliable source for polyacrylamides?

    This is a non-profit - native American run business. Their customer service is absolutely great. This is a statement taken from their web page: " is an American Indian owned and operated corporation dedicated to restoring and improving the environment through technology, and meets all qualifications as a SBA 8 (a) minority owned corporation."

    Their prices are the best you will find too - $12 for 2 pounds; $26 for 5 lbs - delivered anywhere in the USA. They are very good people to deal with and understand your needs.

    An international package - 4 lbs delivered to Canada or anywhere in the world is available for $24.50 US from the same website - in the international section.

    {Edit - changed international price to reflect recent shipping price increase. The FAQ author has purchased from this company for several years and service is excellent. They also have a very informative web site that will provide additional information on polymers.}

    What size do I buy?

    Avoid the powder, it is difficult to mix thoroughly. Likewise, the large size is also difficult to work with and to mix thoroughly with the soil. Both tend to cause the roots to clump up and bind around the polymers rather than grow outwards and search for water in the natural soil environment. Improper use of either of these sizes actually diminishes performance characteristics.

    If you are growing indoor with a soil mix (perlite, etc), in fine sandy soil, or where water pooling is a problem, use the small grade as an amendment.

    If you are growing in heavy soil or in drought conditions use the medium size. Why? In sandy light or fast draining soils you are most likely using the polymer to slow the rate of water drainage and you want to maximize the probability of water contacting the polymer and being absorbed.

    In heavier soils and in drought conditions the medium grade is better for several reasons. One characteristic immediately noticeable when growing in drought affected areas is that the soil tends to harden and compact. There are several reasons for this - earthworms and other insects are not living in the top couple feet of soil and do not work and loosen the soil; plants can't live naturally in drought, and the absence of a good root system causes the soil to compact; and finally, the heat itself causes the soil to expand slightly and fill the gaps that might have once existed.

    Because the medium size polymers expand rapidly when they absorb water and contract when they release the water to the plant or environment - this expansion and contraction helps work and loosen the soil and promotes good root growth in what would otherwise be a very difficult environment.

    How much do I use?

    Consider that one cup of dried polymers (250 ml) will absorb 100 liters of water (about 24 US gallons). This would likely launch your plant out of its hole in a matter of minutes!

    That said, an appropriate amount will be significantly less - between a teaspoon and a quarter cup of crystals. It all depends on your environmental conditions. In drought situations (no rain for more than 28-days), you want a lot of polymer crystals to absorb any water they come in contact with - and it is unlikely that any single polymer will absorb its maximum potential. A couple tablespoons to 1/4 cup of polymers is recommended for this sort of environment. In more "normal" meteorological conditions - a rainfall every seven to ten days - your objective is likely to minimize stress between rainfalls - and one to two teaspoons would be the more than enough.

    How do I use them?

    The optimum use involves some experimentation for your soil and growing conditions. As a general rule of thumb, this method worked well for the FAQ author in extreme drought conditions (no rain for 60-days). First - make a deep hole - at least 3 feet (80 cm). An 8-inch posthole auger is very good for this as it completely eliminates the back-breaking work of shoveling - and if you are lucky enough to use a power auger - it will be very fast too.

    Back fill about 6-inches (15 cm) into the hole and sprinkle a tablespoon of medium-grade polymers over the soil. Continue backfilling another 6-12 inches and gently work the polymers into the soil. Make the soil wet with a couple liters of water and wait a few minutes. This will allow the polymers to absorb the water and expand.

    In the next 12 inches (30 cm) add any amendments plus another tablespoon of polymers - pack the soil hard and when finished add another couple liters of water. With the final soil - add your soil mixes and at most a third application of polymers - about a half teaspoon maximum, moisten with a liter or two of water, and insert your plant. Do not fill your hole to ground level with the soil - you will need to leave at least a couple inches (5 cm) for expansion and heaving. The slight depression also acts as a natural pooling for water in the environment - which is important in drought environments.

    As an added drought protection measure, use a brown grocery store paper bag as a liner for the hole (and mix the third half teaspoon of polymers in the soil in the paper bag). The paper bag slows the drainage rate significantly - and takes about a month or two to dissolve, in time to let the roots reach the deeper levels of polymers.

    How many days will I be able to go between watering if I use polymers?

    There is no real answer to this question because it depends on the environment and the plants themselves. In hot dry environments, the plants will transpire and loose moisture rapidly as compared to more humid dry environments. Dry wind also has an impact on the rate that plants transpire. Evening and night temperatures also impact the length of time that the polymers can hold water.

    It is best to experiment and observe your plants, but as a general rule of thumb, if used correctly, the polymers should buy an extra three to five days between when you would normally water.

    I once went 21 days between heavy watering in a severe drought situation. The plants with polymers, while definitely heat stressed, did not die; whereas plants without polymers did not survive this 21-day period of neglect.

    What is Sandy Soil?

    Sandy soils have an open soil structure. The particle size is large and there is a lot of open space between and around the particles. They take up water readily and are sharp draining. They are often short on nutrients but easy to work. Soils should contain at least 70 percent by volume sand particles to be classified as "sand".

  4. #4
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    mazarxnl is offline
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    What is Clay Soil?

    Clay soils have a very dense soil structure. The particle size is extremely small and there is very little open space between and around the particles. Water enters and drains from clay slowly. Clay soils can be very fertile but hard to work. Soils should have at least 35 percent by volume clay particles to be classified as "clay".

    What is loam?

    Loam has a mixture of sand, silt, and clay particles. Typically, loam soils contain approximately 40% by volume sand, 40% by volume silt, and 20% by volume clay. Loam is ideal for most plants and is easy to work.

    There are a number of intermediates in the classification of soil texture such as loamy sand or sandy loam but they are still the result of the relative percentages of sand, silt and clay.

    What is Soil?

    While this may appear to be a very basic question it is in actuality a very complex topic.

    Traditional soils have five basic components:

    [LIST][*]Air[*]Water[*]Mineral Particles[*]Organic Matter[*]Biology[/LIST]Air:

    Soil air refers to the gaseous phase of soil which is neither liquid nor solid. It is estimated that 25% of any given soil is composed of air that is a gaseous medium.

    Soil Water or Soil Solution is the liquid phase of the soil. Soil water contains dissolved salts and chemicals (in the form of ions) that are free-floating and not attached to any solid particles (mineral surfaces). Water also comprises an estimated 25% of any given soil sample.
    Mineral Particles:

    The mineral part of soil is composed of varying amounts of sand, silt, and clay. On the whole these particles are not derived from materials that were once living, meaning that the minerals are inorganic. The characteristics of mineral particles greatly influence soil behavior and management needs.

    Sand: The soil component sand is mainly small rock fragments and hard minerals such as quartz. It contains few plant nutrients and soils high in sand can be particularly arid due to high drainage low nutrient ratios.

    Of the three types of soil particles, sand is the largest in size and provides the following benefits if used as a soil component in moderate amounts:

    Improves drainage, aeration, and tilling quality.

    Silt: Silt consists of ground up sand and rock minerals. Silt like sand contains few nutrients, but it can have nutrients clinging to its surface.

    Silt is between sand and clay in terms of size.

    Clay: Clays are aluminum-silicate minerals that also have varying amounts of nutrients important to plants such as potassium, calcium, magnesium, iron, etc. A good part of a soil's native fertility can come from its clay portion.

    Clay particles are the smallest of the three soil mineral components and they have a negative charge which makes them attract all positive charged plant nutrients. This helps trace elements stay in the soil rather than being constantly leached away.

    Too much clay can result in harder tilling, compaction (Lack of air) & poor drainage.
    Organic Matter:

    Organic matter in the soil includes plant and animal residues at various stages of decomposition. There are also the cells and tissues of soil organisms and substances synthesised by plant roots and soil microorganisms. It is estimated that organic matter makes up about 5% of most common soils. Despite this small proportion, organic matter has a remarkable effects on soil behavior and crop yields. Organic matter in the soil is frequently in the form of humus, partially decomposed organic matter that has become dark and crumbly and continues decomposing at a slow rate.

    While not actually a component of soil in the traditional sense, that is, mineral based there is a huge living component of soil. This includes the microorganisms in the soil, the earth worms and the myriad of other living things which help process organic and inorganic matter into soil. If we are to look at soil as a Gestalt then we must include the soil biology.

    I'm a beginner and need a simple and easy soilless mix

    From your local Hydro store get some Promix, vermiculite and Perlite.
    Mix in the portions of 50% promix, 35% perlite and 15% vermiculite. This mix is nice and loose and will promote great and fast root growth. All though it doesn't retain water that well it is good for beginners because it will help safeguard against over watering. Plus if a beginner runs into problems with PH or over fertilization the properties of this soil make it quick and easy to remedy.

  5. #5

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    markuskemy is offline
    United States
    7 times
    Victoria has a wide variety of soil types that reflect differences in soil forming processes indicated by factors such as geology.Harder - soil covers much of the land surface of the planet. This is an important natural resource that is directly or indirectly supports most life on earth.

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