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Growing Healthy Plants Starts With Your Medium
As a trusted Australian hydroponics retailer, we know from experience how important it is to nail your nutrient mix.
If you're growing using hydroponic methods, making sure you're dialling in the exact proportions of nutrients into your medium at any given time is vital to the success of your specimens.
This is because precise amounts of specific minerals are demanded by your plants at different stages throughout their life cycle. This is true regardless of whether you're using living soil, inert coco coir, or some other substrate.
As complex living organisms, the success of plant life is deeply interwoven with the medium they are embedded in. Plant root systems are literally designed to be connected to the mineral composition of the earth. Their development is subject to the combination and concentration of mineral nutrients present in their medium.
Plant Nutrients 101: A Guide to the Basics
For your plants to thrive in their environment, you'll need to pay attention to their complex nutrient requirements. There are up to 17 types of nutrients that are indispensable to plant development, with varying proportions required from species to species. Each of these nutrients can be sorted into two classes: macronutrients and micronutrients.
Macronutrients are required in large quantities for the formation of proteins and nucleic acids. They function as the building blocks for crucial cellular components. Nitrogen (N), phosphorus (P), magnesium (Mg), and potassium (K) are some of the most important mineralised macronutrients for plants.
Micronutrients are generally required in very small amounts as cofactors for catalysing enzyme activity. Plant micronutrients include iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu).
How to Check For Nutrient Deficiencies in Plants
When it comes to obtaining an adequate supply of nutrients to meet the demands of basic cellular processes, plants often face significant challenges. A nutrient deficiency typically results in decreased productivity and fertility.
Common symptoms of nutrient deficiency include stunted growth, death of plant tissue, and the yellowing of leaves caused by a reduced production of chlorophyll; a pigment necessary for photosynthesis.
Let's cover some of the most common forms of nutrient deficiency and toxicity:
Nitrogen Deficiency and Toxicity
Nitrogen increases leaf size and quality and hastens plant maturity. It's needed by plants to promote rapid growth, especially for fruit and seed development. Plants absorb nitrogen in the form of ammonium or nitrate, which can be readily dissolved in water and leached away from soil.
Symptoms of nitrogen deficiency include general chlorosis of the entire plant to a light green colour, followed by the yellowing of older leaves proceeding towards younger leaves. If initial symptoms are not corrected, plants become spindly and stunted, with secondary shoots developing poorly.
An over-abundance of nitrogen impairs plant growth and maturation, along with affecting a plant's ability to produce flowers and fruits.
Phosphorous Deficiency and Toxicity
Phosphorus is needed by plants to hasten maturity while promoting photosynthesis, protein formation, seed germination, bloom stimulation and budding. Plants absorb phosphorus in the form of phosphate.
A common visible symptom of phosphorous deficiency is the purple or bronze colouration on the underside of older leaves due to the accumulation of pigment. Affected plants tend to develop very slowly, and are stunted compared to healthy organisms.
A high phosphorus content in soil prevents plants from absorbing other nutrients, such as nitrogen, iron, manganese and zinc. This causes malnutrition, watery tissues on the edge of leaves, and necrosis.
Toxicity from too much phosphorous is often difficult to diagnose, since symptoms are similar to manganese and iron deficiency.
Potassium Deficiency and Toxicity
Potassium is required by plants to promote the formation of sugars for protein synthesis. It also increases the plant’s resistance to diseases, and is essential for cell division and root development. Plants absorb potassium as an ion, which can be readily leached and lost through run-off from the soil.
Symptoms of potassium deficiency include leaf edge chlorosis on newly matured leaves, followed by inter-veinal scorching and necrosis from leaf edge to the midrib as deficiency increases. The chlorosis in potassium deficiency is irreversible.
Research indicates that excess potassium can induce nutrient deficiencies, as plants are unable to absorb nitrogen, iron, zinc, manganese, and magnesium.
Magnesium Deficiency and Toxicity
Magnesium is a structural component of the chlorophyll molecule. It's required by plants to regulate nutrient absorption and promote the function of plant enzymes, which produce carbohydrates, sugars and fats.
The most obvious symptom of magnesium deficiency is the chlorosis of older leaves in between veins. This is known as inter-veinal chlorosis. In severe cases of deficiency, plant growth slows, leaf size reduces, and lower leaves are shed.
Instances of magnesium toxicity are rare; in most cases, calcium or potassium deficiency precedes it. Symptoms of magnesium toxicity are very similar to those of calcium deficiency.
Calcium Deficiency and Toxicity
Calcium is a constituent of plant cell walls that provides structural support. It is needed by plants to produce new growing points and root tips.
Calcium is immobile within plants, remaining in the older tissue throughout the growing season. This is why the first symptoms of deficiency occur on the younger leaves and leaf tips.
A calcium deficiency will lead to stunted growth in new foliage, buds and roots, with roots becoming shorter and stubbier. Younger leaves curl downwards, with leaf edges and tips burning brown. Some plants may show abnormally green foliage.
One indication of calcium toxicity is pH imbalance in the soil, which tends to cause blossom-end rot in plants. An imbalance in pH often inhibits the uptake and absorption of other nutrients in your medium.
Iron Deficiency and Toxicity
Iron is essential for the synthesis of chloroplast proteins and various other plant enzymes.
Iron deficiency is visually very similar to magnesium deficiency... except it appears on young leaves and shoots instead of older leaves. It is common to see shoots dying from the tip inwards. In severe cases, newly emerged leaves may reduce in size and turn white with necrotic spotting.
Iron toxicity in soil is not common. However, some plants do secrete acids from the roots, which can lower soil pH and lead to excess iron absorption. The bronzing and stippling of leaves is a typical symptom of iron toxicity.
Manganese Deficiency and Toxicity
Manganese acts as an enzyme activator for nitrogen assimilation. It's necessary for photosynthesis, respiration and enzyme reactions.
If newly emerging leaves are exhibiting a diffused inter-veinal chlorosis with poorly defined green areas around the veins, your specimen probably has a manganese deficiency. Necrotic spotting is another common symptom. In severe deficiency, new leaves become smaller and tip dieback can occur.
Plants suffering from manganese toxicity usually show a chlorosis of leaves and stunted growth. In certain plants, there is a marked yellowing of the oldest leaves. Dark brown, necrotic spots may occur in these yellow areas.
Bioavailability and Mineral Absorption
A wide range of variables affect the absorption of minerals in plants. Changes in the climate and atmosphere are known to have a significant impact on nutrient absorption.
The availability of specific nutrients also plays a major role. The chemistry and composition of soil can make it harder for plants to absorb nutrients. If certain nutrients are not available, are available in excess, or are only present in forms that the plant cannot use, a cascade effect can occur that inhibits the uptake of other nutrients.
Soil properties such as water content, pH levels, and soil compaction may exacerbate these problems. The below chart from Penn State shows the relationship between pH and nutrient availability:
To complicate things further, most plants have developed unique evolutionary advantages for growing in certain types of nutrient limited soils. Indeed, the vast majority of plants have evolved nutrient uptake mechanisms that are adapted to their native soils.
In Australia, for instance, the pH of soils is typically quite low; with less phosphorous and nitrogen, and higher proportions of calcium. Many plant organisms native to this continent have evolved to endure these conditions.
This is why there is no 'one-size fits all' nutrient schedule for plants. Plants are known to show different responses to different specific nutrient deficiencies, with responses varying between species.
You will need to experiment with your own hydroponic setup. We recommend looking up various guides to gather more information on the nutrient requirements for plant you wish to grow. Be prepared to fine-tune and adjust.
Choosing Your Plant Fertiliser
Your choice of plant nutrients should keep your end goal in mind. What crops are you growing? How much of which specific nutrients will you require over the course of the growth cycle? Do you want them in wet or dry form?
If you’re growing leafy greens, you may want to consider using something different than if you are growing flowering plants like tomatoes. This can maximise plant health and help you get the best possible production out of your system.
How Do I Maximise the Quality and Quantity of My Yield?
When we speak to our customers, we're often told that nutrient scheduling is one of the most intimidating aspects of getting started with hydroponics.
That's why our helpful team members are here - we want to help you out! As hydroponic specialists, we're proud of the value we bring to Australian hydroponic community. We love consulting enthusiasts about their problems, and would be more than happy to assist you on your hydroponic journey.
If you have any other questions or enquiries, we're here for those, too :)
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