How Nutrients are made
An in depth look at the components used in hydroponic nutrient formulations.
How Nutrients are made
We are all familiar with the nutrients and additives we purchase from our local hydro-store that contains all of the key elements required for healthy and productive growth of your plants. The shelves are full of different bottles filled with varying liquids of differing viscosity, colour, odour and transparency. So why are all these solutions so different?
At first the answer seems obvious… because they stimulate different things in your plants. Well, yes, but it is not that simple, let’s first take a look at the types of solution that are out there on the shelves.
Hydroponic nutrients and additives can be split into two basic categories, Nutrients and Bio-stimulants. Nutrients are all of those products with a nutritional content to the plant. This includes all base nutrients, but also covers some additive products such as PK products. There are plenty of products out there that are a combination of both nutrient and biostimulant, but for the purposes of this article we’re going to broadly split them along these lines.
Base nutrients contain the key elements needed for growth – nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), sulphur (S), iron (Fe), copper (Cu), zinc (Zn) and all the other microelements. Deficiencies in the availability of these key growth elements will lead your plant performance to suffer, so it’s essential that you’re chosen choice of products covers the plants basic requirements across all of these elements. The availability and ratio’s between these elements can have a significant steering effect on your plants – this is why we have grow and bloom formulations to feed the plants requirements at certain stages of growth and why we have nutrient additives such as PK products that are often used very precisely at certain key stages of growth to both feed and steer the plants growth.
Base nutrients and nutrient based additives will often just contain mineral salts such as potassium nitrate, mono potassium phosphate and magnesium sulphate. These types of salts contain no carbon and are referred to as inorganic compounds. These are usually derived from rocks mined from the ground, which were deposited hundreds and thousands of years ago. This raw rock is often laced with organic matter and other elements which can be toxic, so before these can be used they need to go through a purification process.
After extraction from the earth, the rock is often treated with heat, acids or alkaline solution to purify the rock to the elements of interests. How far this process is taken dictates to the purity of the chemical. This is also referred to as the grade of the chemical and allows it to be categorised for purposes. Low purity chemicals are often used for industrial purposes, such as lubricants, cleaners and building material.
One of the lowest grades, funny enough is fertilizer grade. This grade of salt is usually the what is used in the agriculture sector and applied to fields in huge quantities. For farmers there isn’t really much requirement for high purity chemicals, so the level of refinement for this grade is relatively low – mainly focussing on removing/reducing heavy metal content which can end up in our food chain if supplied to food crops. This grade can be further split into two sub-grades, agricultural and horticultural grade. Agricultural grade is usually coarser and the particles larger in size. Horticultural grade is usually smaller in particle size and dissolves more readily in water, often containing micro-elements (Fe, Zn, Cu etc) as oppose to just macro-elements (K, N and P). The term fertilizer grade is an actually more of a legal guarantee in reference to the available plant nutrients, the NPK ratio’s stated on the products.
The next grade up is known as technical grade. This grade tends to be used for industrial application, where higher quality chemicals will improve performance. In industry this tends to apply to chemicals that are toxic to humans, but have a high purity, and are not intended to be consumed by humans. Some of the higher grades are fit for human consumption if correctly certified and can be used in food, pharmaceuticals and cosmetics. In the hydro world, the majority of higher quality nutrient products use this grade of minerals as it’s relatively high purity of 80-99% results in a quality end product.
The next purity step up would be Lab grade. Lab grade chemicals are 90-99% pure and are designed for use in schools, universities and laboratories. These are higher cost than technical grade and are unlikely to be used in any Hydro industry products.
Right at the top of the tree are analytical grade chemicals which are 99.9999% (nothing can be 100% pure!). These are used in very small quantities for analysis of samples with very tiny amounts of the chemical of interest. The cost of these chemicals is astronomical due to the levels of purification required and these are simply not in use in the hydroponic nutrient world due to the cost.
Hang on – what about pharmaceutical grade!
This falls into the food grade categories and means that it is fit for human consumption. In the US, chemicals which are called food grade split into 3 categories: Feed grade, Human grade and pharmaceutical. These types of products must be a minimum of 90% pure and produced in sanitary conditions ensuring they are not going to cause illness in humans. The microbial content must fall below a strict level be classed and certified as food grade.
Human grade and Feed grade must meet FDA (Food and Drug Administration) requirements, however the human grade must also pass USDA inspection. Now, pharmaceutical grade in this categorisation means a chemical that is 99% pure, have virtually no microbial content and must have been verified by an independent laboratory which has no link with the manufacturer. The production facility and manufacturing process must also reach a particular standard and be approved by regulatory bodies, such as the United States Pharmacopeia (USP), British Pharmacopeia (BP), European Parmacopoeia (EP) or the Japanese Pharmacopeia (JP). Now as you can imagine, taking a product from 90% purity to 99% purity is very costly, and quite often unnecessary. All of this approval from regulatory bodies also places cost on to the production of the pharmaceutical grade chemical. One kilogram of pharmaceutical grade chemical can therefore cost hundreds of pounds or dollar, where as technical grade can be hundreds of pounds per tonne and still be fit for purpose. In short, it’s not economically possible that only pharmaceutical certified minerals are used in hydro feeds. The cost per litre of nutrient solution would be astronomical.
The production of nutrients is surrounded by a lot of mystery and myths, and most of the time liquid fertilizers start life as a solid in the form of a powder. To produce large volumes of base feed concentrated solutions, up to 500 kg of powdered ingredients are dissolved per 1000 Litres of pure, filtered, sterile water. So ask yourself this question – if you are producing thousands of litres of solution, are 99% pure “pharmaceutical grade” chemicals going to be cost effective to use when they offer no real benefit? For some of the chemicals where minute quantities are used, yes, but for all the chemicals to be officially pharmaceutical grade, the cost of producing the nutrient would be prohibitive.
Bio-stimulants contain compounds known as active ingredients, that stimulate the plant and its metabolic pathways to help improve the productivity of the plant and give better yields. Basically, the nutrients are the plants’ food and the bio-stimulants are the like supplements or drugs which help the plant, but are not essential for growth. In the hydro world there are countless bio-stimulants included in all kinds of products from rooting compounds to bloom boosters. They really are everywhere and it’s important that as growers we all understand a little about what these compounds are and how they work.
Some highly effective active ingredients such as Triacontanol can be naturally derived from plants, other compounds from seaweed extracts. Others can be synthetic and produced in the laboratory via very complicated and costly process. Both natural and synthetic active compounds quite often are not freely soluble in water and do not dissolve readily. This can be due to many reason, from them being hydrophobic (water hating), being a lipid or fatty acid (fatty type compound), low solubility, the pH of the solution, but it is basically down to the properties of the compound. I shall not bore you with the in-depth chemistry lecture on why something is soluble in water, but if you are really interested any A-level chemistry book can assist with your quest for this knowledge!
In order to make some of these compounds dissolve, solvents such as methanol or acetone could be used. These are often referred to as volatile organic compounds (VOC) and can cause the solution to become flammable, which is never a good thing. VOC can also be toxic to plants and damaging to the environment. In recent years there have been a move to more green chemistry and the production of emulsion and suspensions with the aid of substances such as emulsifiers, surfactant and adjuvants. Without giving away all of our secrets, this is how better nutrient brands manage to keep consistent and uniform bio-stimulant products stable in their concentrated form without having to resort to the more harsh chemistry of VOC.
So what’s best to give to my plants?
The million dollar question! The short answer is that there is no right answer to this. Nutrient manufacturers around the world have different research bases and different methodologies. No two nutrients or bio-stimulants are the same and it really does come down to what works best for you.
What I would say is beware of marketing hype! Cynically calling something pharmaceutical grade to appeal to a subset of customers doesn’t sit very well with me. It implies an advantage that simply will not exist. Similarly when it comes to bio-stimulants, beware of what’s actually in the bottle. Naturally derived bio-stimulants are refined compounds from natures own pharmacy and have predictable and safe results. Synthetic compounds can have huge effects on plants but have often been designed in a lab to have a specific effect on certain plants – often not ones that are meant for human consumption such as cut flowers or ornamentals. You need be sure that what you are using on your plant will have no effect on your crop safety, and there are many compounds out there that you wouldn’t want anywhere near your plants. Just be careful, do your research, and buy from reputable manufacturers and you won’t go far wrong!
Dr. Callie Seaman is a plant obsessed Formulation Chemist at AquaLabs – the company behind SHOGUN Fertilisers and the Silver Bullet plant health range. She has been in the hydro industry for 15 years in research development and manufacturing and had previously worked on the VitaLink range. She has a PhD in fertiliser chemistry and a BSc (HONS) in Biomedical sciences and loves nothing more than applying this knowledge to pushing the boundaries of nutrient performance.