Which are limiting nutrients for plant growth?

Nutrients are essential for the life and growth of plants whether they develop in conventional outdoor fields or a modern indoor planting system. These are the indispensable chemical elements and substances derived from the air, water and the soil that are also indispensable for plant growth, reproduction and metabolism. It is essential to know the needs and functions of each nutrient to maximise growth and increase the yield, but to promote the sustainability of agriculture.

There are three main categories of plant nutrients including macronutrients, secondary nutrients, and micronutrients, all of which play vital roles in the health and productivity of plants.

Macronutrients

These are nutrients that plants require in large amounts. The three main macronutrients are N, P, and K.

1. Nitrogen (N)

Role and Importance

Nitrogen is an essential macronutrient that markedly affects plant growth and productivity. It is an important nutrient in the formation of strong, green growth and lush leaves. N in proteins, amino acids, and chlorophyll is essential for photosynthesis and energy metabolism in plants.

As the basic unit of proteins, amino acids are essential for plant growth and development. They take part in the synthesis of enzymes and hormones and assist in the building of cell structures. These amino acids are vital to the overall health and function of plants, capable of regulating responses to stress and uptake of nutrients.

Proteins – made of long chains of amino acids – are a crucial component of almost every function in plants, ranging from growth to repair to defense. Enzymatic catalyst for biochemical reactions, structural support for cells, and a transporter of nutrients and other compounds throughout the plant.

Chlorophyll is a green pigment found in the chloroplasts of plant cells that captures the light needed for photosynthesis, allowing plants to then use it to convert it into food for growth. Blue and red wavelengths of light are absorbed most efficiently by chlorophyll, while green light is poorly absorbed and is thus reflected, producing the green color of the plants. This pigment is crucial in photosynthesis, which is the process that allows plants to generate the energy they require to grow and develop.

Therefore, Nitrogen is essential for developing amino acids, used to create proteins that construct chlorophyll essential for photosynthesis. In sheltered cultivation, plants receive their light energy in the form of artificial light from local light sources such as LED lamps.

Outdoor Agriculture

In conventional (outdoor) farming, Nitrogen is commonly introduced in the form of synthetic fertilizers, organic (worm)compost, or animal faeces. Nonetheless, adequate Nitrogen management is also needed to avoid negative environmental issues, such as leaching and runoff, which are responsible for water pollution and the release of greenhouse gases.

Indoor Agriculture

In indoor systems such as hydroponics and vertical farms, Nitrogen is supplied in precise nutrient solutions. With a controlled atmosphere, your nitrogen levels can be managed in a much better way, which can then help reduce waste while also improving nutrient uptake efficiency.

2. Phosphorus (P) 

Plants rely on it being moved and stored where it is needed in the form of energy, and this is where phosphorus comes in. It is a basic component of adenosine triphosphate or ATP, the carrier of chemical energy, which is required for the biological processes in the body, such as photosynthesis, respiration, and the movement of nutrients. Phosphorus also aids in root and flower growth.

Phosphorus is commonly applied as phosphate fertilizers in outdoor agriculture. Proper P-application management is essential for reducing soil loss and P runoff-induced water pollution. In various controlled environment system such as indoor farming, phosphorus is applied through the various stages of plant growth in nutrient solutions. Using this managed feeding technique will also increase root production and flowering resulting in a higher yield!

3. Potassium (K) 

Role and Importance

Potassium is vital for a wide range of physiological processes, from enzyme activation to protein synthesis to osmoregulation. It can stimulate water regulation, improve drought and waterlogging resistance, and improve the fruit and vegetable yield and quality.

Outdoor Agriculture

In outdoor farming, potassium is often added through potash fertilizers. Adequate potassium levels may contribute to increased plant resistance to stress and disease, and maximized crop yield and quality.

Indoor Agriculture

Potassium is vital and plays an important role in the life system of the plant. It is involved in osmotic balance, regulation of water uptake and retention and efficient stomatal action, which is fundamental for maximising water use efficiency. Potassium also aids in the carrying and use of nutrients, maintains the balance of ions and also helps in moving sugars and carbohydrates. Potassium deficiency can be especially dangerous under high-density hydroponics, as potassium is important to moderate stress response and disease suppression in addition to overall plant health and yield.

Secondary Nutrients

Plants need relatively smaller quantities of micronutrients than macronutrients, but more micronutrients than macronutrients. The other secondary nutrients are Calcium, Magnesium, and Sulfur.

1. Calcium (Ca)

It helps in the formation of cell walls by maintaining their structure and stability, which in turn affects the structural stability of plants. It also has the benefit of encouraging a healthy root system and nutrient intake. Calcium is also added to soil as lime or gypsum, or is applied to the foliage of plants to mitigate infestations of such diseases as blossom-end rot in tomato and pepper plants.

In the indoor systems, calcium is included in the nutrient solution for the correct cell production and the stiff structure of the plants. This is particularly an issue in hydroponic systems because of the lack of soil-based sources of calcium.

2. Magnesium (Mg)

More than that, magnesium is part of the center of the chlorophyll molecule, of vital importance for photosynthesis. It is also an enzyme cofactor that assists many metabolic processes. Mg-deficiency in the open field is generally corrected by application of dolomitic limestone or magnesium sulfate. A balanced amount of magnesium supply enhances photosynthesis and encourages healthy plants. Supplying enough Mg is also necessary to maintain good growth and strong photosynthetic processes in controlled indoor growing environments.

3. Sulfur (S)

Sulfur is a key element of certain amino acids, proteins, and vitamins, and is necessary in the formation of chlorophyll and in the regulation of plant functions. It is usually applied in outdoor agriculture as sulfate fertilizers or organic amendments, which is important for crop quality and disease resistance as well as crop yield. Sulfur is used in the nutrient solution for indoor cultivation to meet essential metabolic demands and protein production. Optimal controls for sulfate to ensure healthy and nutritious crops.

Micronutrients

These are essential nutrients needed in far smaller amounts, but are essential for the growth and development of plants. The main micronutrients are Iron, Manganese, Zinc, Copper, Boron, and Molybdenum.

1. Iron (Fe)

Iron is an essential element for chlorophyll synthesis and acts as an enzymatic catalyst in many enzymatic reactions, involved in energy transformation and respiration in plants. Iron deficiencies will usually be corrected by applications of foliar sprays or the soil application of iron chelates to avoid the development of chlorosis and encourage healthy green foliage.

2. Manganese (Mn)

Manganese is essential in photosynthesis, nitrogen metabolism, and enzyme synthesis, and in resistance to oxidative burst. Soil drenching or foliar spray applications are the most common forms of application, providing plants with essential nutrients for strong growth and stress tolerance. In soilless culture, manganese is supplied in the nutrient solution to meet the requirements during several metabolic processes and to reinforce plant defenses and avoid the development of nutrient deficiencies that can negatively impact growth.

3. Zinc (Zn)

Zinc is vital for the synthesis of DNA, making proteins, and regulating hormones, and it is involved in the production of growth hormones and activation of many enzymes. Zinc deficiency is conventionally treated by soil or foliar application of additives that ensure crop growth and development, particularly in zinc-sensitive crops such as corn and beans. In indoor agriculture, the element is monitored in a nutrient solution to maintain good health function and growth control of the plant.

4. Copper (Cu)

Copper plays a crucial role in photosynthesis and lignin synthesis, strengthening plant tissues. It serves as a cofactor for a number of enzymes, also. Copper deficiencies are commonly corrected using either soil. Sufficient copper provides plant health and disease resistance. In indoor operations, copper is added to the nutrient solution to promote enzymatic health and structure.

5. Boron (B)

Boron is necessary for pollen germination and seed development. Boron deficiencies are generally treated with soil application or foliar spray. Sufficient boron is necessary for reproduction and general plant health. B is provided in the nutrient solution to the indoor cultures to promote the development of the cell wall and reproductive functions. Good husbandry yields quality crops and successful crop reproduction.

6. Molybdenum (Mo)

Molybdenum plays an important role in nitrogen fixation and nitrate reduction in plants, therefore influencing nitrogen metabolism and enzyme function. Molybdenum drops can be corrected by applying the element in the soil or with a foliar spray. The supply of molybdenum is essential to achieve an efficient nitrogen use by plants and the growth of the plant.

Disclaimer: This material is for informational purposes only and should not be relied on for legal, medical, financial, or any other form of professional advice.

About the Author

Victor Miller

Environmental Journalist Focused on Sustainable Agriculture

Victor Miller is an environmental journalist at Growcycle, specializing in sustainable agriculture. With a passion for storytelling, he highlights the latest trends, innovations, and practices that promote ecological balance and responsible farming.