Just like people, plants need a range of nutrients to keep healthy, grow well and look fabulous. There are the 16 nutrients that plants need. There are nine macro-elements, as shown below:

• Hydrogen, carbon and oxygen-major components of plant tissue, producing sugars and fibres like cellulose and lignin.
• Nitrogen-is a component of all living cells, in the chlorophyll (where photosynthesis takes place, makes plants green) and in every protein (many of which are enzymes). With plenty of nitrogen, there is green, succulent growth. A lack of nitrogen means a loss of colour, reduced protein production and yellowing, stunted growth
• Phosphorous-also a component of every living cell, being really important for root growth and stem strength. A deficiency causes purple colouring at seedling level, later causing yellowing leaves, stunted growth and delayed maturity.
• Potassium-essential for cell metabolic processes. It seems to influence other element uptake, along with having effects on respiration and transpiration. Potassium helps maintain cell pressure and is important for flowering. It also encourages carbohydrate synthesis and translocation of carbohydrates, therefore encourages cell wall thickening and stem strength. A deficiency causes yellowing in leaf tips and margins, mainly due to leaching of the potassium and continuous cultivation.
• Calcium-forms part of the cell wall structure, and is required for shoot/root growth. Deficiency results in malformation of growing parts of the plant.
• Magnesium-active within the the plants enzyme system and forms part of the chlorophyll molecule so has an essential role in photosynthesis. A deficiency results in discolouration of leaves and sometimes premature defoliation.
• Sulphur-present in some amino acids (protein building blocks), and in the oils of some plants (like cabbages). Deficiencies cause stunting and yellowing.

There are seven micro-elements need by plants, as shown below:

• Iron and manganese-both elements have a role in enzyme systems and are required in chlorophyll synthesis. The activity of iron and manganese is interrelated due to the fact that excessive manganese causes iron to be inactivated. Iron deficiency is seen on younger leaves, which is seen as yellowing in inter-veinal parts of the leaf, more common on alkaline soils. Manganese deficiency is similar to iron but the chlorosis in the leaves is more marked, with the whole inter-veinal area loosing the green colour.
• Boron-seems to aid in calcium utilisation and in plant parts in active growth. Essential for nitrogen fixation by bacteria in the root nodules of legumes. A deficiency impedes calcium uptake. Toxicity prevents the production of pigments.
• Copper and Zinc-both form part of the enzyme system and essential for forming growth-promoting substances. Copper deficiency leads to abnormalities in growth like rapid wilting and weak stalks. Zinc deficiency symptoms vary by plant-in citrus, this leads to mottled leaves.
• Molybdenum-essential for reducing nitrates in the plant, which, if it accumulates, will interfere with protein synthesis. It is also required for for nitrogen fixation by legumes. Deficiency causes plant abnormalities.
• Chlorine-regulates osmotic pressure and cation balance in plants. Deficiency causes a wilting appearance and leaves to look bronze in colour.

There are several other things to note here in relation to nutrient uptake by plant roots. The nutrients are taken up by the roots in the water that they absorb. Without water, the plants can’t absorb the nutrients they need, so they starve.

The pH of the soil can affect how much of each individual nutrient is absorbed. This does vary by plant species, and depends on their ideal growing conditions. As a general guide many, but not all, plants are quite happy around pH 6.5. Kits for testing pH readily available and generally not too expensive to buy and are easy to use. The key is to buy plants that are happy in the conditions you have, which includes the soil. Always look at information on the plants you want to buy before you do so, that way you can see if you have the right conditions and aid in ensuring you have a garden that looks great.

• All photos are my own
• Stewart, A., Leake, S., 2017, Grow your own: Hoe to be an Urban Farmer, Allen & Unwin, Crows Nest Australia
• Class notes-Horticultural Soils 2: Plant Nutrition, 2011, J.M. Lauricella & A.M.D. Thomas