Soil Grow Guide.1
by, 01-13-2012 at 11:01 AM (367 Views)
So you have decided to grow some 'marijuana'. Good choice my friend but what soil are you going to use and how do you know wether it will do the job or leave you with a dead plant? There is no easy way to explain the intricate nature of soil, it is a complex mix of many additives, minerals, semi composted and composted material, microbes, bacteria and normally peat. Most soil companies like to give you a few weeks of nutrients to allow for strong growth but after this you are on your own. There is also a big difference between seedling soil and flowering soil. Allow me to pick up on a few of these points for you-
Seedling soil This is a fine grade soil which allows roots to penetrate it easily. It should be light and airy as well as being weak in nutes so as not to burn those tender newly formed roots. Seedling soil is normally labled 'Seedling soil' or 'Light mix', this symbolises that it is suitable for seedlings and has a low/light amount of nutrients present. Only start your seedlings in this type of soil, a small pot is essential as it will only need to be in the soil for the first two weeks or so and then need to be potted up to a slightly stronger soil/compost.
Potting/all-mix/flowering soil/pro-mix This is slightly heavier in nutrients so is suitable for on growing of plants from the seedling stage. It supports healthy strong growth but as with the seedling soil it normally only has enough nutrients for the first few weeks. It is not as fine grade as seedling soil and generally consists of more peat and larger peices of composted material. Both seedling and flowering soil may come premixed with perlite or vermiculite saving you the job.
Topsoil This is just the soil on its own, a mixture of organic matter and things like clay, minerals etc. Although it is rich in organic matter it is also too heavy for indoor plant pots and has not been amended with peat or other drainage properties. Steer clear of this as its not good on its own for growing plants and outdoors is added to the top of soils or mixed in with existing soils to amend them. Leave this soil alone if you are inexperienced with it and stick to the already prepared soils available.
Perlite Perlite is a volcanic mineral that is expanded under pressure. It is sterile with a neutral pH and contains many tiny, closed cells or bubbles. The surface of each particle is covered with tiny cavities which provide an extremely large surface area. These surfaces hold moisture and nutrients and make them available to plant roots. In addition, because of the physical shape of each particle, air passages are formed which provide optimum aeration and drainage. Add anywhere between ten and fifty percent to your soil dependidng on needs but to start off with add only twenty to thirty percent as any more will cause you to struggle.
Vermiculite This is pretty much the same as perlite but with a better water and nutrient holding capability. It also contains small amounts of magnesium and iron so is an added benifit to any soil.
Both perlite and vermiculite dust is dangerous to breath in and acts as a lung irritant in similar ways to asbestos so either wet it before use to stop dust particles becoming airborn or wear a mask.
Hydroton Expanded clay pebbles, they provide drainage properties when mixed in the soil and again are similar to perlite and vermiculite by being able to store water and nutes but these capabilities are limited. They are bigger in size then perlite and vermiculite so not really suitable to small plant pots.
Now we have a quick run down of the types of soil and what you may mix with them to increase drainage and nutrient holding abilities but there is a lot more to consider. Firstly most soils as we know are for the large part peat based with anywhere from twentyfive to sixty percent total volume. Lets deal with the peat issue as it is the main reason for crop failure when soil growing.
Peat Most indoor garden soils seem to contain peat, peat moss is a type of sphagnum moss, used in potting soil mixes. It provides drainage and acidity to the mix. Peat moss helps retain water, yet allows oxygen to be available to the root systems of the potted plant. Because the peat moss produces acid conditions in soil a buffer is often needed to raise the pH back up. Sphagnum peat moss has a pH of about 3-4. Most peat moss comes from either canada or ireland and is dug out of wetland bogs. The most common pH amendment for peat based soils is dolomite limestone. This is added to the soil to counteract the acidic nature of the peat. So you see most peat based soils will end up too acidic for marijuana growth and hence a major problem.
Why soil companies refuse to add enough lime to pre bagged soil is very strange and quite often leaves the gardener having to add the extra or suffer from acidic growing conditions. marijuana loves the pH of soil to be between 6.4 and 6.8, outside this and nutrient uptake will suffer. Most soil companies pH their soil to between 6.3 and 6.6 so you see that it will not take long for your soil to become acidic and pass below the ideal growing pH. Now dolomite limestone will raise that pH back up to near pH7 and buffer it here so that it counteracts the acid peat with its alkaline properties. About a teaspoon per litre or tablespoon per gallon is a good starting point with any extra needed being topdressed in the soil and watered in. Other forms of lime that are plant friendly are calcium carbonate (dosen't contain magnesium), aglime, sea shells, etc etc, just make sure you never use hydrated lime, quicklime, hydraulic lime or any other building product that contains lime. The lime in these products releases so quickly that it burns plant roots and causes heat reactions with the water. Please stick to garden and plant freindly lime or you will again have killed your plant.
Dolomite/garden limeThis is a