When you think about human health, what we need to keep us going seems simple in some respects: carbohydrates, proteins, fats, water, vitamins, and minerals. But these can come from varied sources and our diets are a wonderful combination of so many things, so we get what we need. I remember from my school days being taught that if all else fails, a boiled egg with wholemeal toast and a glass of orange juice would give you something of everything you need to start the day. It was one of the few things from that class that stuck.
But if you break it all down – carbohydrates are carbons, hydrogens and oxygens; minerals are naturally occurring chemical compounds like phosphorus, potassium, sulphur and magnesium. So, while a grand buffet at a fancy restaurant may seem like a great way to satisfy all our needs – we aren’t that different from plants and what we actually need is food that is on a molecular level, so our cells can utilise it best. But the beauty of it all is we can eat a wide variety of delicious things, so we can satisfy our tastes as well as our needs.
Plants on the other hand aren’t so lucky and need just a few things on a molecular level. The plants that give us wonderful things to eat are stuck with a very bland diet for themselves. Plants only need a handful of ingredients from the soil.
The ones that get talked about the most are the NPK combo. Nitrogen, Phosphorus and Potassium (we mentioned him earlier in the sciency stuff – he’s the K, just to confuse the already bewildered) These are the ones that get headline billing on bags of fertiliser, in the hope that the keen gardener will be able to work out which product is best for the plant. But then you need to know what your plant needs and what state your soil is in before making an informed choice, otherwise you are just taking a stab in the dark and could be wasting your money and stuffing up your soil. Over fertilisation can be a bigger problem than under fertilisation. This is why we need to know about these things.
Nitrogen (N) generally originates from organic material and is what makes strong shoots and leaves and makes healthy foliage. Although, depending on what you are growing, too much can come at the expense of flowers and fruit.
Phosphorus (P) is mineral from inorganic sources and helps the plant grow strong roots and we have already learnt the importance of strong, healthy roots.
Potassium (K) is also a mineral and plays a big part in plant reproduction – flowers, fruits and seeds. You really don’t want to lack this in the veggie garden or the harvest wouldn’t be all that great.
There are three other important ones that make up a huge part of the plant, Carbon (C), Hydrogen (H) and Oxygen (O) but the plant has no trouble getting hold of these, usually from the atmosphere to use in photosynthesis, that they are hardly even counted as the essential nutrients for plants.
But the plant diet is a little more varied than just these top six. There are others. The secondary elements, the plant needs them, but not in great quantities. However, they are essential for plant function and if they are lacking – for whatever reason, remember it doesn’t necessarily need to be absent from the soil, but just being too cold, or some other excuse, for the plant to take it up, the plant has ways of letting the gardener know. Nutrient deficiencies show up in the leaves like some kind of code – from yellowing leaves with green veins, to purple leaves, to patchy leaves to stunted and munted leaves. Each deficiency represents in different ways. It is a bit like a pregnant woman screaming out “I want ice cream and I want it now!” And if you know what is best, you go and find ice cream straight away!
So, these secondary elements are Calcium (Ca) and this is important for making strong cell walls. Sulphur (S) is involved in making chlorophyll, the thing that makes plants green, so it is kind of important as most plants are green! Magnesium (Mg) has an important job in the photosynthesis process so you really wouldn’t want your plant not to have access to this. But of an interesting note too much chicken manure in your soil can interfere with the availability on Magnesium. Which is another reason it is important to know all of this stuff. It is so easy to take handfuls of ‘good for the soil’ things and lob them about like it is some kind of lolly scramble, without realising you aren’t actually helping.
Then there are the Trace Elements. Plants need them but in minute quantities. The plant will let you know in its leaves if they are lacking, but absolute care must be taken when adding them to soil. You can’t unmake the sea salty.
Boron (B) has a key role in plant growth, so it is pretty important. Without it you can end up with stunted growth. Iron (Fe) and Manganese (Mn), like Sulphur are gainfully employed in the production of chlorophyll. Copper (Cu) and Zinc (Zn) work closely with enzymes to make things happen. Molybdenum (Mo) is a little-known nutrient that helps the plant convert nitrogen into more plant friendly forms and so the smallest nutrient is essential for the use of the largest.
There are a few other teeny tiny ones that are hardly worth mentioning and from what I can understand aren’t all that problematic or they would be higher up the list.
So if you look at it like a high school social structure – you have the popular kids, N, P and K – everyone knows about them and think they are important. They get talked about a lot! Then there are the kids everyone seems to like and get on with, but at the same time they are just average and ordinary and no one notices them. The poor C, H and O’s. Lost in their ease and abundance. The sporty ones – the secondary elements – they make the school look great – or not if they don’t do well and everyone notices them when they win or when they lose. The rest of the time no one really thinks about them, out there in the field, doing their thing and practicing all the time.
The trace elements have to be the geeks and the nerds. Their importance is barely noticed but without them there would be no school newsletters, no librarians, and no one to do all those volunteer jobs everyone else loves to hate. I have to confess back in the heady days of school I was a trace element and found there were certain privileges being in the science club that the more popular kids had completely overlooked – like being inside at lunchtime on a rainy day, for one! And ironically Nitrogen can’t be without Molybdenum doing its homework!
And that is what a plant needs in it’s daily diet to stay healthy. But we are still looking at things in a tiny molecular level and it is still a far cry from shovelling barrow loads of compost onto new season soil. So, the next question is, who chops up the plant food into bite sized chunks?
Come again soon – we’re almost there in this journey and then I can start digging.
Sarah the Gardener : o)
In school, we hydroponically grew tomatoes, each lacking one of the essential nutrients, to see how they reacted and grew. It got ugly.
That would have been fascinating. I’m the kind of person that learns best by seeing and doing. I wouldn’t have forgotten that lesson in a hurry! : o)
That was in the late 1980s, and I still have not forgotten it. Some looked like you can imagine. Others were really creepy and disfigured!
Yet another excellent post! Thanks.
Thanks. I try to make it fun, because it isn’t the easiest topic! : o)