The different chemical elements and compounds found in your plants' water and soil are very important to optimise their growth. Among the figures that you must track there are two basic ones: acidity, measured in terms of pH, and the concentration of mineral salts. Both parameters affect the capacity of all plants to absorb nutrients and to nourish themselves. Do you know how?
The first lesson that must be learned by anyone willing to take care of, pamper and watch their cannabis plants grow is that the key factor throughout this process is water. Regardless of the varieties one chooses, the type of cultivation best suited to him, or the irrigation system and accessories he has, water will always be key. Hence, it is essential to know how to determine if the level being employed is correct.
About two thirds of a plant are made out of water, a component that cannot be lacking if it is to survive. Just as our body needs a major amount of water, especially during periods of heat, your plants cannot live without it either. In their case it is even more important, as it allows them to absorb all the nutrients, allowing them to grow healthy and strong.
Of course, not all water is equally beneficial for them. In order to explain this we turn again to a comparison with people: not all the foods we eat are equally good for us, or provide us with the same proportions of vitamins. In the same way, water can feature different characteristics that make it more or less suitable to irrigate your marijuana plants.
One of these properties to keep a close eye on is pH, a measurement of the water's acidity or alkalinity. This indicator expresses the proportion of hydrogen ions (represented by "H+") that deliver acidity, as compared to hydroxyl ions (represented by "OH-"), responsible for alkalinity. The easiest way to get a precise measurement of this is through the use of an electronic pH metre.
A substance's pH value can range from 1 to 14, low numbers indicating greater acidity, and middle numbers expressing the greatest neutrality. This might remind you of the figures appearing on soaps and body creams, often pH neutral because your skin needs a lotion that is not harsh, but when we talk about plants the conditions are different. Neither extreme is good for plants, although the midpoint is not necessarily the best one either, or the most advisable; it depends on the plant's current phase.
This is so because the different pH values alter the plant's capacity to absorb nutrients. In order for them to function normally, the ideal range is around 5.5 to 6.2, although their effect depends on the growing system one is using.
If you have chosen soil, the ground actually acts like a kind of shock absorber, able to balance acidity and mitigate possible damage to your plants. In order to verify their pH, mix a small sample with distilled water and then use a metre, which you can find in gardening stores. Your pH level should, in this case, be around 5.8 to 6.2.
When employing hydroponic growing systems - that is, those lacking soil as a substrate, instead using a solution of nutrients - you cannot count on that cushioning effect of the ground. If you are using coconut fibre or rockwool, these elements do provide some cushioning effect, but not as much as soil does. Thus, you'll have to balance their levels with those of the solution of nutrients that you are using. A pH level of between 5.5 and 6.3 is recommended.
When growing using aeroponics (without any substrate, the plants' roots in the air), those roots need to receive the watery solution with the nutrients directly. Thus, it is necessary to monitor the pH level even more closely, so that it does not surpass the advisable limits.
If you really want to dive into the world of cannabis culture you will have to familiarise yourself with another two terms constituting the two ways to express the concentration of salts in water, another important factor for plant nutrition. This can be measured by total dissolved solids (TDS), expressed in parts per million (PPM), or with electrical conductivity (EC) values.
Roots absorb nutrients by osmosis, a physicochemical process based on the balance between the compounds and elements existing inside and outside the plant. If the concentration is too great in the water (and, therefore, the EC and TDS values are very high), the plant will be unable to absorb them, and may even expel some, which is harmful. If, on the other hand, it is very low, it will absorb too many, which is also damaging.
In short, the EC is used to measure the fertiliser contributed to the plants, but it also acts as a control mechanism of the plant's surroundings, directly related to water absorption. Thus, plants should begin their growth with low EC levels, which should later be increased as quickly as possible, to cover their nutritional needs, with vigorous growth and to elevate their internal osmotic values, yielding a more robust plant.
Cannabis requires almost no additional nutrition during the final weeks of its cultivation. This generally results in reduced EC levels, or can also lead to the need for a weekly filtration of the roots, to clean the accumulated salts and obtain a higher-quality final product in terms of taste and aroma.
These factors are also very important if you are planting in soil. Thus, there are metres to monitor the amount of nutrients in the liquid, thereby preventing your plants from spoiling, above all if you have cultivated directly in a watery medium, or with the roots exposed, in which case one must be more careful.
We are not going to deny that all this tracking of these important parameters requires a little effort and consistency, but once you learn to master them, it will show in your plants. A lot.