This can prove tricky, but when mastered can be extremely rewarding. More specifically, pH is the decimal logarithm of the reciprocal of hydrogen ion activity this sounds more complicated than it is! It is by looking at the detail and understanding this equation a bit more that we realise why controlling the pH in your hydroponic system is so important.
First thing is the log 10 part of the equation. This means that each time you go up or down by one whole pH point e. So pH 4 is ten times more acidic than pH 5, and a hundred times more acidic than pH 6! This explains why precise control down to 0. Basically this means that pH is the inverse of the hydrogen activity. So as the activity of the Hydrogen increases, the pH decreases. This is why all acids have a Hydrogen in them they can release into the solution to increase activity and lower pH e.
The pH scale runs from 0 — 14, with 0 being very acidic and 14 being very alkaline. As you can see in the blog on foliar feeding , the pH of the soil, or hydroponic solution controls the availability of the nutrients to the plant. The elements themselves are still there, what changes is the form they are in. A change in the pH can change the form and therefore reduce or increase the availability. What makes things complicated is different nutrients are available at different pH ranges.
In hydroponics the ideal pH range is between 5. By achieving this positive spiral of EC build-up in the plant, the plant also becomes more capable of absorbing and retaining water. This means that water does not evaporate from the plant too easily and it will not dehydrate too quickly.
The table below shows an example of a plant that has lost its water reserves too soon. When plants become too soft, the intensity of the light must be reduced or the number of hours of lighting shortened to prevent them drying out at the end of the day. Even though EC plays an important role in this story, it is not the only factor that has an influence.
The overall climate around the plant influences the processes of which EC is a part. This demand is controlled by assimilation. The bigger a plant grows, the more nutrition it will need. These nutrients are partly locked up in the plant and converted into amino acids, oils, fats etc. Potassium is one of the most important nutritional elements for this. Once the plant has finished the vegetative growth phase, it can still absorb a lot of potassium for its internal osmotic value and the ovaries.
The ovaries are not the fertilised 'seed'. However, this increasing rate of uptake comes to an end. The game of nutrient stock versus applied EC now starts for growers. While the water in the substrate will evaporate, the salts will not. This means that the bucket contains 20 grams of nutritional salts nutritional stock. In reality, such an extreme example would not occur and when cultivating in soil there is a further buffering process that binds the nutritional salts to organic substrate particles to some extent, but the principle is still valid.
If there is a plant in the bucket and it has absorbed 5 grams of salts from the solution, we can top this up when adding the water in order to maintain 2. If a top-up of 5 litres of water is required, for example, we should add 5 grams of salts, or to put it briefly: a water dose of 5 litres with an EC of 1. The goal here, and in cultivation, is to maintain the EC in the bucket constant.
This is the basic premise of fertilising. We try to maintain a certain level of fertility in the container which ensures that an adequate supply of nutritional elements is available to the plant.
Generally speaking we should lower the EC in the final period. With a system that can be drained we can reduce the nutritional stock ourselves by rinsing out with a solution with a lower EC. The substrate in drainable systems can be corrected much more easily. In non-drainable systems, the nutritional stock can only be increased, and it is constantly added to with successive feed applications.
As well as being a unit for measuring the fertiliser given to plants, EC is also a climate control mechanism that relates to water absorption. Because the water that is used as a means of transport has evaporated, the nutritional salts will remain in the plant and this will raise the internal EC osmotic value.
Since this has been raised the grower can give the roots a higher EC again. By achieving this positive spiral of EC build-up in the plant, the plant also becomes more capable of absorbing water and retaining it. With plants that are too soft the intensity of the light will have to be reduced or the number of hours of lighting will have to be shortened to prevent a shortage at the end of the day. The total climate control around the plant influences the processes that EC is a part of.
This demand is controlled by assimilation. The bigger a plant you grow the more nutrition it will need. These nutrients are partly locked in the plant and converted into usable amino acids, oils, fats etc.
Potassium is one of the most important nutritional elements in this process. Once the plant has finished vegetative growth it can still absorb a lot of potassium for the internal osmotic value and the ovaries. However, this increasing intake also comes to an end. After approx. The game of nutrient stock verses applied EC now starts for growers.
While the water in the substrate will evaporate, the salts will not. So in the last weeks of growth, you should - in most cases - stop feeding the plant and only add water. We have a bucket that contains 10 liters of fertilizer solution with an EC of 2. This means that the bucket contains 20 grams of nutritional salts nutritional stock. In reality it will never be as extreme as this and when cultivating with soil there is a further buffering process that binds the nutritional salts to organic substrate particles to some extent, but the principle is still valid.
Adding back 9 liters brings the EC to 2. If there is a plant in the bucket that has absorbed 5 grams from the solution, we can top this up when giving water if we need to maintain 2. If the water dose is 5 liters for example, we should then give 5 grams, or to put it briefly; a water dose of 5 liters with an EC of 1.
The goal here, and in cultivation, is to maintain the EC in the bucket. This is the basic premise of fertilizing. We try to hold a certain level of fertility in the container which ensures an adequate supply of nutritive elements is available to the plant. Generally speaking we should lower the EC in the final period. With a system that can be drained we can reduce the nutritional stock ourselves by rinsing out with a low EC.
The substrate in drainable systems can be corrected a lot better.
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