The process of photosynthesis provides the energy for growth (and metabolic processes. Plants use water (H2O), carbon dioxide (CO2) and light-energy to produce glucose - an energy-containing sugar. This glucose can then be shuttled to the parts of the plant where it is needed to power plant growth.
While photosynthesis provides the energy for growth, it is generally the roots that are responsible for absorbing the elements which are used as the building blocks. These elements can be absorbed by a plant through its leaves by means of a foliar spray, but the most usual route is through the roots.
One of the things that new growers need to get their head around is that of nutrient strength. The art of growing the best produce depends (among many things) on feeding plants at the correct level right the way through their life. Many growers take a while to realise that where feeding is concerned, there is an optimum level. If the nutrient solution is too weak then plant growth speed is usually compromised. If the nutrient strength is too strong then this will usually lead to an overfed and sick looking plant with burned leaf tips. As a result, plant growth is slowed. Also, if a plant gets overfed, particularly near to cropping time, the plant may be unable to use up it's stores before harvest and the nutrient hangs around inside of it, impairing the final taste and texture. Use a high quality nutrient strength meter such as the excellent Bluelab Truncheon.
Feeding a plant with organic nutrients is a different matter to feeding a plant with the usual dissolved salt type feeds. With organic feeds, the microflora in the soil break down the feed gradually and make nutrients available to the plant in a sustained and gradual manner.
Non-organic nutrients are made of salts and/or minerals in a solution. These nutrients are added to your feed water to turn it into nutrient solution which you can then use to feed your plants. The elements are immediately available to the plant which means that the plant is in the hands of the grower to provide the right amount. As said before - too little and plant growth is slowed due to a lack of available raw materials. Too much and the plant will suffer.
Dosages for nutrient solutions are usually specified by nutrient manufacturers in millilitres per litre. This is all very well and good, but a manufacturer's feeding schedule is usually only meant to be a guide. Getting to know what is really going on by getting to know your particular plant's exact requirements with a nutrient strength meter can help you to take your growing to a whole new level.
Before we delve into how a nutrient strength meter can revolutionise your growing, it is useful to understand how they actually work. Nutrient strength meters work by passing a small current between two probes which are dipped into the nutrient solution. The higher the level of salt in the solution, the more current that flows between the two probes. The nutrient strength meter then displays an indication of how salty the solution is. Pure, unadulterated water (such as from a reverse osmosis unit) is actually a poor conductor of electricity. However, if the water contains salts then it makes a big difference. The conductivity of the water goes up proportionally with the amount of salt in it.
Nutrient strength also needs to be matched with a plant's growth stage and also it's rate of transpiration. During warmer and drier conditions, a plant will suck up more water, but it's physical nutrient requirements will stay more or less the same. With more liquid being drawn up by the plant, but the same amount of nutrient being required, it means we need to reduce down the nutrient strength so that we don't overfeed the plant.
As an example, take 2 identical plants. Let's say they each require 2 millilitres of nutrient per day. One plant is in hot, dry conditions and is transpiring water quickly and needs 2 litres of water to satisfy its needs. The second plant is in cooler, more humid conditions and is transpiring water less quickly and therefore needs only 1 litre of water per day.
So for plant 1, we mix the 2ml of required nutrient into 2 litres of water. For plant number 2 we mix the required 2ml of nutrient but we mix it into only 1 litre of water. Because the nutrient has been mixed into only half the amount of water as for plant 1, the nutrient strength for plant 2 is double the nutrient strength as it is for plant number 1.
With organic feeds, while it possible to overfeed with liquid feeds, those foods that are mixed into the soil break down slowly and to a certain extent, the plant controls the speed of the breakdown.
Also, the nutrient strength requirement of a plant generally increases as it grows into a fully established plant and reaches the peak of the flowering/fruiting stage. When the peak has passed, its nutrient strength requirements begin to go back down again.
Having a nutrient strength meter means that you are not flying blind. You get a clear indication of how strong the feed is that you are giving to your plant. As time goes by, you will get a feel for how strong a feed your plant is going to require. This means taking into consideration the size, the stage of growth, and the health that the plant is in, as well as the environmental factors (temperature and humidity) at the time. Experience helps the will begin to tell the grower
We can think of a plant a little bit like a housing estate that is under construction. Each house can be thought of as a plant cell. (The site will contain different plans and layouts for different types of house. just like there are different types of plant cell). The estate grows as more and more houses are built and completed. The workers on the construction site can be thought of as the "energy" to put various different materials together to create a house.
A huge aspect of growing is learning how to give your plants the right strength of nutrient solution. Most nutrient manufacturers provide a feeding schedule which tells the grower how many ml/litre the grower needs to add to their feed water depending on the week of the grow.
As a plant grows larger in veg and approaches the peak of flowering, it will generally need an increasing nutrient strength and this will be reflected in the manufacturers feeding schedule. However, different types of plant require different feed strengths. Some, like broccoli, are hungry plants. Others types of plant, such as lettuces are light feeders. Even different strains (varieties) of the same type of plant will have different requirements. To put this into perspective,
