What Do Minerals and Trace Elements Do? Part 1

The aim of all gardeners is to grow healthy plants and vegetables, often it is a mis-construed idea that you have to feed the plant in order to make it healthy.

This, however is not the case, it is the soil that needs the nutrients, in conjunction with, the correct pH so the roots of the plants and vegetables can feed themselves and their plant at the correct time.

Understanding what you are aiming for, when you are conscientiously putting compost, organic matter and mulch on your soil, will give you a better understanding of how things work underground.

So, just what nutrients should be in your soil?

Lets take each element separately:
P = Phosphorus
An important element, and one of the ‘big’ three most gardening books recommend and talk about. It is necessary for cell division, especially at the roots and tips of shoots.

So, when the seedlings are starting off their life and growing rampantly, their phosphorus requirements will be quite high.

A plant with a deficiency in phosphorus will have a bluish green tinge, especially noticeable on the leaves. Also a soil pH lower than 6 and higher than 8, makes phosphorus unavailable for the roots to take up.

Phosphorus is found in most manures, especially, manures from grain fed animals as these contain high sources of phosphorus. Organic compost is another good source of phosphorus, especially the compost that has re-cycled vegetable matter in it.

Excess phosphorus can make some of the other elements unavailable, like magnesium, sulphur and other trace elements. This is the problem with ‘super phosphates’ being liberally put onto farmer’s land indiscriminately.

N = Nitrogen
Perhaps, the most commonly known element and certainly the most talked about of the ‘big three’. Nitrogen, is essential for new growth and is a pivotal part of chlorophyll, the green pigment present in all plants, which is responsible for the absorption of light to provide energy for photosynthesis.

Also important, is the ability of nitrogen to help the plant use water efficiently. This vital element is found in all animal and vegetable matter, it make up 80% of air and rain also contains some.

Bacteria in the soil and bacteria on legume roots help assist ‘fixing’ nitrogen in the air so the soil can make it available to plant roots. You can assist this particular process by growing a ‘green manure’ crop of broad beans, also known as ‘faba beans’ in the winter.

Nitrogen becomes unavailable when the soil pH is lower than 5.5 or higher than 8.5. A common cause of nitrogen deficiency is adding too much woody material like wood shavings to the soil as a mulch.

This causes the soil micro-flora to use energy to break down the extra nitrogen and so have less to readily give to the plants.

This is known as ‘Nitrogen robbery’ and is more likely in soils deficient in organic matter, but it can happen is any soil where too much nitrogen is added.

This can also be an effect in simply using chicken manure too early before it has matured, as ‘fresh’ chicken manure contains high levels of nitrogen.

One lesser known fact, is that nitrogen fixation in the soil is lower when copious amounts of nitrogen are put into the soil, so a little is better than more, in this case.

Plants that are deficient in nitrogen will have poor overall growth, the leaves will loose the vibrant ‘green’ colour and be dull or yellow especially in the Brassica family.

The lower leaves tend to be affected first and this can be mistaken for insect attack or disease as the leaves will turn yellow and die back, falling from the plant. Plants displaying nitrogen deficiency can also be slow to flower and to set fruit.

Short term solutions include adding grass clippings as a mulch, don’t be too heavy handed as grass clippings when wet will form a tough water repellant mat or make a manure tea and spray the affected plant leaves, this is known as folar spraying.

In the following winter grow a winter ‘green manure’ crop this will help in the long term. Also cold wet weather can make nitrogen temporarily unavailable.

K = Potassium
Potassium the third most talked about element and indeed a vital one. Potassium is needed for a whole range of things including: photosynthesis, stem growth, ensures good sap flow, helps with fruit and flower quality, guards against disease and helps with drought tolerance.

Potassium is often referred to a ‘potash’ in gardening books and is found in seaweed, rock dust, animal manures, NATURAL wood ash (this is from wood that is untreated, not painted) and fish fertilisers. Also, once you have your potassium sources in the soil, leaching (the draining away) of this element from your soil after heavy rain is less likely if you have a good amount of humus to help bind it to soil particles.

Plants lacking potassium will show signs of small flowers, stunted growth or general failure to thrive. If you are seeing the signs of deficiency it is always a good idea to check the soil pH first before adding more of an element.

For instance, potassium may be present in the soil but unavailable due to the pH being lower than 5.5 or higher than 7.5. It is easier to correct the pH before overloading the soil with potassium, as too much potassium can prevent other essential nutrients, like magnesium, to be blocked from being taken up by the roots.

C = Calcium
A little talked about element, which is needed by all the cells, especially at the tips of the stems and roots, to help build strong cell walls. It is also important for healthy fruit formation.

Calcium is often deficient in sandy soils as the main source of calcium is found in organic matter, which is lacking is a sandy soil. Calcium becomes unavailable when soil pH is below 6 and an excess of calcium can prevent the element Boron being available for the roots to use.

Sources of calcium include: Eggshells (always best crushed as it takes an incredibly long time for an eggshell to decompose) bones, seashells. Probably the most popular source of calcium that is readily available is garden lime, but do check the magnesium levels before adding lime. As calcium and magnesium will interact and an excess of either will cause a depletion of the other.

Mg = Magnesium
Like calcium, magnesium hardly gets a mention, but this element is important for the activation of enzymes that breakdown humus into usable food for the roots and release rock minerals into the soil so again the roots can use then for the health of the plants. Is it also an essential part of chlorophyll, and has an important role in seed germination and helps prevent some diseases.

Magnesium can be found in green vegetable matter, dolomite which is similar to lime and comes from sedimentary rock dusts that contain magnesium and calcium.

Magnesium availability is restricted when soil pH is below 6 or after extravagant amounts of potassium fertilizers have been used. Humus plays a vital role in magnesium being absorbed by the plants and deficiency is rare in humus rich soils.

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