We all know that plants need nutrients to survive, just the same as you, me, and all other living things. If our diets are limited and without all the right proteins, vitamins, and minerals, we’ll eventually feel unwell, tired, grumpy (heaven forbid!), lacklustre, and generally not at our best. Ensuring that your garden has the right balance of plant nutrients is just as important as eating a balanced diet yourself.
With a continued lack of the right foods, we will become susceptible to all manner of health issues. Viruses, diseases, and brittle bones are just a few issues we may suffer, affecting long-term health and quality of life. Read on to learn how to spare your plants a similar fate by ensuring they have the balanced nutrition they need.
Knowledge is Power
This unfortunate predicament has exactly the same results in the plant kingdom. Without the correct nutrients and H20, (water), plants will become weak and nutrient deficient. They’ll start to perform poorly and eventually die off.
I’m a firm believer that knowledge is power, especially in the garden! Whether you’re a fair weather gardener, an enthusiastic wannabe, or a fully fledged member of the green-fingered club, I think it’s essential for each of us to have a clear understanding of soil structure and plant nutrients. Once we understand the basics, we know what plants need, how to look after them, and what tell-tale signs we need to look out for that may point to a nutritional deficiency.
Here’s a common example: I’m sure that many of us buy plant fertilizers and feeds, but have no real understanding of what they contain or how these are processed by our plants. Well, today I hope to change that by giving a simple explanation of all you need to know about plant nutrients. This will help you to have a productive, colorful, healthy, and glorious garden. My motto is: “Happy Garden—Happy You!”
Firstly, we must start with the most important factor: the soil. After all, we can help to create a good growing base well before we get around to planting anything. This takes me back to my college days when all I had to think about was the Principles of Plant and Soil Science. Happy Days!
Soil’s Three Different Elements: Sand, Clay, and Silt.
Some soils will be more sandy and free-draining, whilst others will be more clay-y and less free-draining.
This all comes down to particle size. Sand has the largest-sized particles in soil makeup, and is coarsely textured. This allows water to enter and pass through it quite quickly. Since they’re larger, there will be fewer sand particles per spadefuls than clay.
Clay soils tend to be more fertile. The clay particles are much smaller in size than the sand—they stick together more and hold more water and nutrients within them. These soils are more prone to swelling in wet conditions and cracking in dry conditions.
Silt sits in the middle. Its particles hold more water then sand, but less than clay. Silt feels smooth and silky to the touch, (not tacky like clay), but it has little structure. A pure silt soil will be susceptible to erosion and weathering. You see a lot of eroded river banks near to where I live— these are all nearly pure silt.
Poor soil structure can affect plant growth in many ways. When the soil is too compact it contains very little oxygen, which can cause the plant to suffocate. Furthermore, rain water will sit on its surface and not penetrate into the ground. Not only does this cause puddling and eventual rotting of plants above the soil, it can cause drought underneath and dehydration to the plant root system.
On the other hand, soils that are too free-draining have both a lack of stability and lack of essential water and nutrients. All the goodness is washed out of the soil, which results in nutritional deficiencies.
Ideal soil contains equal parts sand, silt and clay—this is known as medium-textured soil. That which has a balance of all three elements will be fertile, (so contain more nutrients for planting), and have adequate water holding properties (so it won’t dry out so quickly). It contains adequate oxygen levels when cultivated, (to give the roots a chance to breathe), and gives sufficient structure and stability, enabling plant roots to take hold and grow.
Do you know what “organic matter” actually means? We assume it’s compost or a soil improver, and that is partially right. Organic matter is something that was once alive but is now dead—such as compost (made from plants, vegetables, and grass cuttings), leaf mold, well-rotted farmyard manure, and fauna.
Fauna is present in all soils and organic matter, and includes all of the decaying bugs, worms, lice, yeasts and bacteria. This fauna plays an important role by adding even more good nutrients to the soil.
The Three Major Nutrients in Soil, and How These Affect Plant Life
Below I have listed the major plant nutrients along with their chemical symbols. You’ll recognize these from feed or fertilizer packets, which commonly have N,P, and K values listed on their sides to show their chemical makeup.
This is crucial for any life on Earth, and is used in greater quantities than any other of the major nutrients. It’s incorporated into proteins, is in all amino acids, and plants use it within chlorophyll molecules, which are essential for photosynthesis. In other words, it encourages green vegetative growth, so it’s good for foliage. Nitrogen deficiency leads to stunted plant growth and leaf yellowing (chlorosis).
Plants use potassium to regulate the stoma’s opening and closing on the leaves’ undersides. This reduces water loss, increases drought tolerance, and is essential for the fruiting and flowering of all plants. It’s mainly present in soil and is derived from clay particles. Soils that have a low clay content, such as sand, may be low in this nutrient.
Deficiency leads to blue-green leaves with browning around the edges, which is more noticeable on semi-mature leaves.
This is required in smaller quantities than nitrogen, and needed for the conversion of light energy to chemical energy (ATP) during photosynthesis. It’s also used for cell signalling and the formation of flowers and seeds. Phosphorus quantities are usually adequate in most soils apart from those with no or little organic matter.
Phosphorus deficiency shows through the plant’s leaves and stems, which become very dark green with purple veins. Prolonged deficiency can also cause stunted plant growth.
Carbon (C), Hydrogen (H) and Oxygen (O) are also essential for plant growth, but are obtained from the air and water. These are generally in plentiful supply, since normal soil has approximately 25% water content.
Minor Plant Nutrients
Boron (B) is a trace element (or micronutrient ) that is essential for reproductive growth, and creating new plant cells. It also helps with pollination, as well as fruit and seed development.
Magnesium (Mn) is a secondary nutrient here, which is used by the plant during photosynthesis. Without magnesium, plants wouldn’t have their green color, nor could they capture essential energy from the sun.
Calcium (Ca) plays an important role in plant growth and nutrition It helps maintain a chemical balance in the soil and improves water penetration.
Sulphur (S) is a necessary component in forming chlorophyll. It also aids in the plants’ resistance to disease, and helps growth and seed formation.
Why add Organic Matter to Soils, and How Does it Benefit Plant Nutrition?
Fertilizers, (such as liquid or granule feeds), don’t provide any bulk to the soil—only nutrients and minerals. Decaying organic matter adds bulk, acting as a glue to hold the soil particles together. This bulky mass is high in both water and essential plant nutrients, and therefor is much better for the soil’s structure than a straight fertilizer.
Now that we have got to grips with soil structure and essential nutrients, it’s time to talk about a soil’s pH values.
A soil’s pH value is very important. It’s a means of expressing the acidity or alkalinity of soil using a scale. Knowing the pH value of a soil will determine which nutrients are available for plant use. It also helps to influence the soil fauna present.
The scale runs from 0 to 14 pH. Anything from 0 to 7 is on the acidic side, so the soil contains more hydrogen ions than hydroxide ions. Anything from 7 – 14 is on the alkaline side: this soil contains more hydroxide ions than hydrogen ions.
When the two are balanced, the soil will be neutral, with a pH value of around 7. You’ll find that most soils are within the 5 to about 9.5 pH range.
You can measure your soil’s pH levels by using indicator solutions or specialist indicator papers. Both are widely available in kit form from most garden centers. These have really clear instructions and are easy to use.
Right Plant, Right Place
There are certain plants that prefer acidic soil, and others that prefer alkaline soil. By using pH soil indicators you can be sure to make the right planting selection for each soil type.
Plants that prefer an acidic soil are known as calcifuges, which in latin translates to “calcium haters”!
Known calcifuges include heathers (Erica), acer, hydrangea, pieris, and rhododendrons. These calcifuges are likely to have nutritional deficiencies when planted in neutral or alkaline soils, as they can’t the nutrients they need to prosper. Examples of this include leaf yellowing through chlorosis, or “lime-induced chlorosis”.
At the other end of the scale, there are plants that prefer an alkaline soil, and these are known as calcicoles. Derived from Latin, this means to “dwell on chalk”.
Getting the Best From Your Plants
There are few plants that must have an alkaline soil, but many that can tolerate them. These varieties include native trees such as the Field maple, (Acer campestre), the hornbeam, (Carpinus betulus), the common beech, (Fagus sylvatica), and the ash, (Fraxinus excelsior). All of these are suitable for growing on this type of soil.
Now that we’ve talked about soils, organic matter, and essential plant nutrients, I hope you have all the know-how to get the best from your plants and understand the basics on nutrition.
The best, most productive soils that I’ve worked on have taken many years to perfect. I use a generous dose of organic matter in the form of rotted compost and well-seasoned horse manure at least once a year, and dig this into my empty beds. I’ve found that this works well for me and incorporates all of the goodness back into the soil for the next season.
If I could give one Top Tip, it would be much like a life mantra: the more goodness you put in, the more goodness you get out!
Happy gardening, everyone!