QUOTE (Zappa @ Jun 21 2009, 11:11 AM)
..any thoughts, anyone?
hi ya zappa
your right about bat-mix its a fecking really strong planting medium, I used it for one grow only, not using it now because of the peat content and peat for me is not sustainable long term, just my point of view on the subject...
The cation exchange capacity (CEC) it is a value given on a soil analysis report to indicate its capacity to hold cation nutrients. The CEC, however, is not something that is easily adjusted. It is a value that indicates a condition or possibly a restriction that must be considered when working with that particular soil or planting medium. Unfortunately CEC is not a packaged product. The two main colloidal particles in the soil are clay and humus and neither are practical to apply in large quantities.
The CEC of the soil is determined by the amount of clay and/or humus that is present. These two colloidal substances are essentially the cation warehouse or reservoir of the soil and are very important because they improve the nutrient and water holding capacity of the soil. Sandy soils with very little organic matter (OM) have a low CEC, but heavy clay soils with high levels of OM would have a much greater capacity to hold cations.
The disadvantages of a low CEC obviously include the limited availability of mineral nutrients to the plant and the soil’s inefficient ability to hold applied nutrients. Plants can exhaust a fair amount of energy (that might otherwise have been used for growth, flowering, seed production or root development) scrounging the soil for mineral nutrients. Soluble mineral salts (e.g. Potassium sulphate) applied in large doses to soil with a low CEC cannot be held efficiently because the cation warehouse or reservoir is too small.
Water also has a strong attraction to colloidal particles. All functions that are dependent on soil moisture are also limited in soils with low CEC. Organisms such as plants and micro-organisms that depend upon each other’s biological functions for survival are inhibited by the lack of water. Where there is little water in the soil, there is often times an abundance of air which can limit the accumulation of organic matter (by accelerating decomposition) and further perpetuate the low level of soil colloids.
High levels of clay with low levels of OM would have an opposite effect (i.e. a deficiency of air), causing problems associated with anaerobic conditions. The CEC in such a soil may be very high, but the lack of atmosphere in the soil would limit the amount and type of organisms living and/or growing in the area, causing dramatic changes to that immediate environment.
If a soil has a very low CEC, adjustments can and should be made but not solely because of the CEC. A soil with a very low CEC has little or no clay or humus content. Its description may be closer to sand and/or gravel than to soil. It cannot hold very much water or cation nutrients and plants cannot grow well. The reason for the necessary adjustment is not for the need of a higher CEC but because the soil needs conditioning. A result of this treatment is higher CEC.
The more organic matter the better for your planting medium
The difference between organic and synthetic, also called chemical, fertilizers is the origin.
Organic fertilizers comes from plants, or from previously living animals, or their excrements.
For example, manure, blood meal, bone meal, etc are also considered organic fertilizers.
Organic fertilizers have in common that they can not be taken up by plants directly. First the complex organic molecules must be broken down by soil microbes before the fertilizer nutrients can be taken up by plant roots.
Chemical fertilizers are so-called because they - often - dissolve into their chemical elements (such as nitrogen, phosphorous, potassium, etc) as soon as they come in contact with water. They typically do not need microbes to break down the bonds between the molecules before they can be taken up by the plant roots. As you may have guessed, most chemical fertilizer compounds are salts. Examples are potassium nitrate, calcium phosphate, ammonium sulphate, etc.
Plants can only take up very basic elements in simple form (small molecules). Examples are nitrogen (as ammonium NH4+ or Nitrate NO3-). The nitrogen in large complex molecules must first be released by microbes in the soil to be available to plants, whereas water will typically release nitrogen in chemical fertilizers.
