Fertilizers are a huge topic in itself, for anyone who has been in a garden center or hydroponics retail store can attest to the massive quantity of different fertilizers offered to you the end user.
What makes these products different? the differences are subtle to say the least, most good quality fertilizers have the same basic ingredients the differences lie in the quality and quantity of these ingredients.
Most fertilizers have an NPK value indicated on the container, NPK stands for Nitrogen, Potassium and Phosphors. there should also be micro nutrients.
The type of fertilizer you will require will depend the type of plant you are growing and the medium you are growing in for instance a person growing in hydroponics will require a complete fertilizer mix with micro nutrients as hydroponic growing mediums as almost void of micro nutrients. the same person depending on the type of crop being cultivated may require different nutrients at different stages of growth.
It is important to understand what is going on with regards to fertilizer, your plant will use different components of the fertilizer at different times. those of you with a continuous read out PPM (TDS) meter probably have seen your PPM drop not long after mixing up a fresh reservoir, this is largely to do with how the plants adsorb the nutrients. This does not mean that the plant has just chowed a whack of food this means that the plant just used the ammonia nitrogen out of the mix, this form of nitrogen being the first and fastest used. Which is exactly why it is often used to help yellow clones generally as a foliar.
Now if you top up this reservoir too soon you are just adding more of this form of nitrogen back into the mix and in essence giving your plants a double shot whether they require it or not.
Another component of the fertilizer solution will be Phosphorus this is the portion of the food that the plant will use to initially build a good root structure and later on in allot of plants will utilize for flower and fruit production.
Potassium is also a key component plays a huge part in how the other nutrients are moved through the plant, think of this component as the nutrient transit system within the plant
The micro nutrients are available in any good complete fertilizer, although this component are only needed in minute amounts and in some rare cases are not needed at all. In a large portion of the world the water itself supplies all the calcium, iron, etc that you will need.
Take a look at your kettle, shower, taps, toilet, etc and see if you have “hard water” deposits if you have the standard off white deposits then in all probability you have all the calcium needed for normal plant growth. Now if the same deposits are brown or rust color then you most likely have a high Iron content. a PPM meter is another great way to find out the mineral content of your tap water. Now in most cases this wont affect plant growth but there are exceptions, that is exactly why a few of fertilizer companies have now started to make a “hard water” version of their micro nutrient component to there product line.
On the flip side if you are using a reverse osmosis machine, then you might need to boost up your micro nutrient content as an RO machine tends to bring your tap water down to a 0 TDS reading making it void of all micronutrients along with everything else.
If you are looking at a Reverse osmosis machine, I would get one that is self cleaning you will apreciate this feature after a month or two.
Something else to keep in mind is that there have been great advances in organic fertilizers in the past few years and it is now possible to by a complete organic fertilizer that is usable in most aeroponic and hydroponic systems, which is better for you and the environment. There are also lines of fertilizers that start with food grade components rather than your run of the mill chemical components. I’ve seen and heard allot about these fertilizers and believe that because the components are cleaner it makes them easer for the plant to digest thus cutting down on time and energy used by the plant, not to mention better for everyone involved.