Understanding Soil Nutrients: Key Elements for Optimal Plant Growth

Like any other living creature, plants need the right food to develop and thrive. They need 16 essential components, including carbon, hydrogen, and oxygen. Soil water and the atmosphere provide carbon, hydrogen, and oxygen. The remaining 13 elements, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, manganese, copper, boron, molybdenum, and chlorine, are obtained from organic or inorganic fertilizers, soil nutrients, and organic materials.

Plants get all these nutrients from the soil to perform vital functions like photosynthesis and roots, fruits, and vegetable production. With the proper supply of soil nutrients, plants become strong and resistant to diseases and pests. Soil fertility plays a vital role in supplying essential nutrients to plants. The greater the soil fertility, the greater the ability of plants to absorb these nutrients. Thus, maintaining soil fertility is the key to robust plant growth and optimal health.

From soil microbial food to soil acidifier, Growcycle offers various soil nutrients to ensure lush green and vibrant plants. This blog will highlight all the essential details of soil nutrients and how to use them effectively for thriving plants. By understanding all these elements, gardeners or homeowners can ensure maximum plant growth and development.

What are Soil Nutrients?

Soil nutrients are essential and non-essential nutrients that plants need to complete their growth and reproduction. Plants need essential nutrients to complete their lifecycle, while non-essential nutrients ensure efficient growth and development. Plants get all nutrients from the soil except carbon, hydrogen, and nitrogen, which are supplied through carbon dioxide, water, and nitrogen fixation.

According to the Law of the Minimum, a plant cannot absorb other nutrients at its best rate if the accessible form of a nutrient is not present in sufficient amounts in the soil solution. Thus, a specific nutrient ratio of the soil solution is required to maximize plant growth.

Types of Soil Nutrients

Plants need both macro and micronutrients for proper growth and thriving. These elements are necessary for plant growth due to their involvement in critical physiological processes. Below are some vital nutrients that plants need to grow:

1. Primary Macronutrients

Plants need three primary macronutrients to complete photosynthesis, enzyme activity, and various metabolic functions. These include:

i. Nitrogen (N)

Nitrogen is the backbone of various plant functions. It is present in all plant cells, proteins, hormones, and chlorophyll. Nitrogen is the growth factor that encourages lush, green development. It is a primary protein component found in all living cells. Therefore, compared to other nutrients, nitrogen is typically more responsible for enhancing plant development. Nitrogen is transformed within the plant into amino acids to make proteins.

Since all enzymes are proteins, nitrogen is required for plant enzymatic processes. Additionally, it is a part of the chlorophyll molecule and directly contributes to photosynthesis. It supports the plant's ability to make and use carbohydrates. The first figure displayed on a fertilizer bag or box is the nitrogen percentage concentration.

Low nitrogen levels can cause slower, stunted growth, the falling of older leaves, and light green or yellowish foliage in certain plants. Nitrogen fertilizers are an easy way to make up for a shortfall. However, overfertilization can harm plants, so be cautious.

ii. Phosphorous (P)

Phosphorus helps plants absorb sun energy, accelerates maturity, and encourages early root and plant growth. A lack of sufficient phosphorus prevents the transportation of carbohydrates produced in the leaves to the flower or growing fruit and their storage in the roots or bulbs. Typically, it is linked to fruiting, flowers, and the storage of carbohydrates in roots, tubers, and bulbs.

Phosphorus is not as mobile in soil as nitrogen. Because of this, it is a nutrient that is simple to examine in a lab. Don't add extra if it's already accumulated in the soil; add some if it's low. Diagnosing phosphorus deficiency in most plants is challenging because it results in reduced growth that can mimic other health issues. The leaves, fruit, and stems may show dead spots when a severe nutrient deficiency occurs. Gardeners can use phosphate-based fertilizers to cover up such symptoms.

iii. Potassium (K)

Potassium is required for photosynthesis and regulates cell turgidity, respiration, and plant water flow. It also regulates stomatal opening and closure. Potassium is absorbed as a cation and stored by the soil's cation exchange capacity. Higher clay or organic matter soils are better able to exchange cations and hold onto more potassium. 

Among the most typical symptoms of a potassium deficit is yellowing of the elder leaves' margins. Plants lacking in potassium grow slowly, have weak stalks, and have underdeveloped root systems. Sufficient potassium-based fertilization promotes winter hardiness, disease resistance, crop quality, and the ability of plants to withstand drought stress. Potassium fertilizer is soluble in water and will be absorbed by the plant in proportion to the amount in the soil.

2. Secondary Macronutrients

Like primary macronutrients, secondary macronutrients are necessary for plants to grow and develop to their full potential. Below are the three secondary macronutrients that plants require to thrive.

i. Magnesium (Mg)

Magnesium actively participates in photosynthesis since it is a component of the chlorophyll molecule. It also acts as an activator for various plant enzymes necessary for growth, sugar metabolism, and mobility. Plants absorb magnesium as ions (Mg+2). Since magnesium is translocated inside the plant, deficiencies typically start on the lower, older leaves.

Due to magnesium deficiency, older leaves can turn yellow, copper, or reddish, while leaf veins stay green. Soil tests are one way to assess magnesium demands. Magnesium sulfate is the best source of magnesium for plants to ward off such deficiencies.

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ii. Calcium (Ca)

Calcium promotes the growth of roots and leaves. It fortifies plant structure and creates substances that are a component of cell walls. It lowers plant nitrates by activating multiple enzyme systems that counteract the plant's organic acids. Moreover, calcium facilitates the intake of other nutrients, root development, and molybdenum availability. It indirectly increases plant yields by lessening the toxicity of manganese and aluminum in the soil.

Poor root growth is one of the most prevalent symptoms of a calcium deficit. Occasionally, the developing point dies. A shortage of calcium frequently causes roots to decay and turn black. Calcium generates unique symptoms in young leaves and the growing points of shoots because it is not translocated inside the plant like nitrogen, phosphorus, and potassium. Organic calcium fertilizers are the best source to cover up these symptoms.

iii. Sulfur (S)

Soil sulfur plays an essential role in protein synthesis. It is found in three amino acids (cystine, methionine, and cysteine), all required for protein synthesis. Furthermore, sulfur is included in the oil molecules that give plants scents like garlic and onion. Additionally, sulfur is necessary for nodule production in legumes.

Plants take sulfur from the air through leaves, specifically in industrial areas where sulfur is readily available.  Because sulfur is prone to leaching, sandy soils with little organic matter may have sulfur shortages. Only a soil test can establish the amount of sulfur required.

3. Micronutrients

Micronutrients are equally as essential as primary and secondary macronutrients, yet they are required in smaller quantities. The majority of micronutrients are necessary for specific enzymatic processes in plants. The following soil micronutrients are essential for thriving plants.

i. Boron (B)

Boron controls the metabolism of carbohydrates in plants. It is necessary to differentiate meristem cells, or dividing cells, into particular tissues. Plant cells can continue to divide when boron levels are low, but structural components don’t distinguish. Plants absorb boron as the borate ion (BO3-). Plants require different amounts of boron. Cauliflower, broccoli, turnip, Brussels sprouts, apples, celery, and alfalfa are plants that require a lot of boron.

Too much boron can be harmful to plants. Therefore, boron should be handled according to the recommendations of specific crop soil tests.

ii. Zinc (Zn)

Several plant enzymes require zinc as a necessary component. It is involved in synthesizing protein and chlorophyll and regulates the synthesis of indoleacetic acid, a crucial regulator of plant growth. Plants take up zinc as the zinc ion (Zn+2). 

Zinc deficiency is more likely to occur in sandy soils with low quantities of organic matter.  Zinc becomes less accessible and soluble in high-pH soils, such as high-lime soils. Zinc and phosphorous act differently in soil. Consequently, soils with a high phosphorus content also make zinc available. Zinc shortage can result from damp and cold soil conditions since these factors slow down the growth of roots and the release of zinc from organic matter.

iii. Manganese (Mn)

Manganese acts as an enzyme activator in plant growth processes and helps iron formation. Manganous ions (Mn+2) are the form of this nutrient that plants take up from the soil. Although uncommon, sandy soils with a pH of 8 may have manganese deficiency. The pH of the soil is a valuable predictor of manganese availability, which in severely acidic soils (pH <4.5) can rise to lethal levels. Onions, beans, potatoes, spinach, tomatoes, peas, raspberries, strawberries, apples, and grapes are the crops that react to manganese the best.

iv. Copper (Cu)

Copper stimulates several plant enzymes. It might be involved in the synthesis of vitamin A. Deficiency disrupts Protein synthesis. Soils rarely lack copper. Plants get copper from the soil as cuprous (Cu+) or cupric (Cu+2) ions. The crops that react most to copper are spinach, carrots, lettuce, and onions.

v. Molybdenum (Mo)

Molybdenum is a micronutrient that is necessary for plants to utilize nitrogen. In plants, molybdenum is soaked as molybdate ions (MoO4-). Legumes cannot fix air nitrogen, and plants cannot convert nitrate to amino acids without molybdenum. Molybdenum deficiency can arise in sandy, acidic soils. The solution is to lime the soil to a pH of 6. The applications of molybdenum in the soil, on leaves, or in seeds also work well. Among vegetable crops, cauliflower is the most susceptible to low soil molybdenum levels.

ix. Chlorine (Cl)

Chlorine is essential for plants to complete photosynthesis. Since chlorine is found in all parts of nature, soil deficiencies are uncommon. Plants absorb chlorine as the chloride ion (Cl-).

vii. Nickel (Ni)

Nickel is a component of the enzyme urease, which stops dangerous urea buildups (a byproduct of nitrogen metabolism in plants). Plants absorb it as Ni+2. It is believed that nickel has a role in the nitrogen metabolism of legumes throughout their reproductive stage of development. Nickel is also necessary for the growth of seeds. Due to competition between these elements in plant absorption, high soil nickel levels might cause deficiencies in zinc or iron.

viii. Iron (Fe)

Iron is necessary for chlorophyll formation in plants. Plants absorb iron as the ferrous ion (Fe+2).  It acts as an activator for symbiotic nitrogen fixation, respiration, and photosynthesis, among other metabolic processes. Although a lack of iron in the soil is generally not an issue, turf, ornamentals, and some trees are particularly vulnerable to iron deficiency. Iron deficiency symptoms might appear in soils with a pH above 7.0. Visual symptoms and soil and tissue tests can be used to identify specific iron requirements.

Symptoms of Soil Nutrient Deficiencies

A deficiency of soil nutrients can significantly impact plant growth and development. Early detection of symptoms prevents several consequences. Below are the common symptoms of nutrient deficiencies in plants.

• Nitrogen: Slow and stunted growth, yellowing of leaves (commonly seen in mature parts), turning of leaves margin
• Phosphorous: Growth retardation, purplish color foliage, dark green tips of leaves, delayed maturity, poor fruit formation.
• Potassium: Burning of leaves tips and margins, weakening stalks, slow growth and fruit production.
• Calcium: Burning of tips, death of growing stems, premature shedding of leaves and flowers, stunted root development.
• Magnesium: Yellowing and curling of older leaves, turning midrib into green surrounded by yellow areas.
• Sulfur: Turning of young leaves from light green to yellow, slow growth and maturity, small plants.
• Zinc: Shorter stem length, decreased fruit bud production, molted leaves.
• Iron: Chlorosis of young leaves, death of limbs and twigs.
• Manganese: No proper discrimination between veins and inter-veins, pale green areas surrounded by darker green areas, yellowing of the interveinal regions. 
• Copper: Slow and retarded growth, death of shoots, decreased pigmentation, wilting of leaf tips.
• Boron: Yellow, thick, curled leaves, terminal buds death, necrotic spots on fruits, decreased flowering.
• Molybdenum: Reduced vigor, scorching, and cupping of leaf tips.
• Chlorine: Yellowing and bronzing of leaves, extreme branching of roots.
• Nickel: Urea accumulation in leaf tips, necrosis of leaf tips.

Maintain Soil Fertility for Thriving Plants

Soil nutrients play an essential role in soil fertility for thriving plants. Below are some that a gardener or homeowner must follow to ensure excellent soil fertility.

Use of Fertilizers

Fertilizers play a magic role in ensuring an efficient supply of nutrients to plants. They can be inorganic or organic fertilizers, each formulated to meet the specific soil nutrient requirement.

Organic plant nutrients or fertilizers gradually release nutrients and improve soil structure over time, but inorganic or artificial fertilizers are usually more concentrated and offer instant nutrient availability.

Regular Mulching and Soil Amendments

Mulching is another efficient technique for improving soil fertility and encouraging robust plant growth. Straw, wood chips, or grass clippings are examples of mulch that help control soil temperature, suppress weeds, and maintain soil moisture.

Mulch adds organic matter to the soil as it decomposes, improving its structure and nutrient content. Furthermore, soil amendments like sulfur or lime can change the soil's pH to increase nutrient uptake.

Crop Covers and Rotation

Crop or soil covers prevent soil and plants from erosion. Rye or clover are examples of crop covers that can be sown and then tilled into the soil to provide nutrients and organic materials. Additionally, crop rotation lowers the danger of soil nutrient depletion since various crops use different nutrients and help prevent the accumulation of pests and illnesses.

Conversation Tillage

Conservation tillage, which includes reduced-till and no-till techniques, reduces soil disturbance and maintains soil structure. These methods improve water retention, lessen erosion, and preserve organic matter levels.

Conservation tillage boosts nitrogen cycling and creates a home for beneficial species, thus improving overall soil fertility by allowing crop residues to remain on the field.

Integrated Pest Management (IPM)

Integrated Pest Management (IPM) is an eco-friendly pest and disease control strategy that employs biological, cultural, physical, and chemical instruments. IPM promotes natural insect predators, uses resistant plant types, and utilizes proper crop management techniques to reduce dependency on chemical pesticides and foster a better soil ecology.

Steps to Manage Soil Nutrients to Support Healthy Plants

Managing soil nutrients is the key to maintaining soil fertility and plant health. Below are some steps that a gardener must follow for optimal and healthy plant growth.

1. Soil Testing

A soil test is a way to check how many nutrients the soil can provide. While plant analysis looks at what nutrients plants have taken up, soil testing shows what nutrients are in the soil. It's recommended to do a soil test every 2-3 months to know exactly what nutrients are in the soil. This is important because it helps identify which nutrients are missing and guides gardeners to fix the soil correctly.

2. Adjusting Soil pH

Soil pH controls the availability of plant nutrients. However, the soil pH should always be adjusted based on the results of soil tests. Gardeners can add some types of organic matter, sulfur, or sulfates to lower the pH of the soil; however, Maine soils rarely require this.

Adding wood ash, lime, or certain types of fertilizer can raise the soil's pH. However, the adverse effects of using large amounts of these compounds are hard to overcome, so examine the soil first.

3. Selection of the Right Fertilizer

After conducting the soil test and pH analysis, the next step is to select the right fertilizer. Fertilizers can be organic or inorganic, so they should always be applied based on soil testing. Gardeners can either use nitrogen or potassium-based fertilizers to increase the better supply of nutrients.

4. Application of Organic Matters

Organic matter such as compost or aged manure improves soil structure, improves water retention, and allows for a slow drip release of nutrients. The best time to add organic matter is during the growing stage. Use organic mulch, such as wood chips or straw, to keep plants moist and minimize nutrient loss.

5. Avoid Overfertilization

Over-fertilization leads to nutrient imbalances and plant toxicity. When nutrients are washed away, the environment becomes polluted. Always read the fertilizer manual to follow the recommended dose and avoid over-fertilization. 

6. Monitor Plant Health

Always monitor plant health to examine signs of nutrient deficiency, such as yellowing leaves, stunted growth, or weak stems. Inspect the plants regularly for signs of nutrient and environmental stress for prompt and instant treatment. This helps ensure long-term support for plants' health.

FAQs

What is the best time to apply soil nutrients?

The best time to apply soil nutrients is early spring. This allows nutrients to integrate into the soil for optimal growth and development. During the growing season, apply nutrients to plants as much as needed to establish plants and encourage root development.

How do we increase NPK in soil naturally?

The natural way to increase soil NPK (nitrogen, phosphorous, potassium) is to use organic matter like compost, manure, or grass clipping for nitrogen. A gardener can also use bone meal for phosphorous and wood ash for potassium. Don’t forget to rotate crops regularly for efficient growth.

How do plants absorb soil nutrients?

A plant's nutrient absorption process is known as mass flow. Nitrogen, calcium, and sulfur are usually given to plants via mass flow, while plants absorb other soil nutrients through their roots after they dissolve in water. This process is called diffusion. 

The Bottom Line

Soil nutrients are essential for optimal plant growth and thriving plants. These nutrients include macro and micronutrients that support photosynthesis, enzymatic activities, root development, and disease resistance. Regular soil health and pH monitoring and treating any nutrient deficiencies with the appropriate fertilizer can help plants maintain balance and an adequate nutrient supply.

Growcycle provides various essential plant nutrients to gardeners and growers, ensuring long-term results. However, regular and appropriate care is required to achieve lush green and abundant yields. 

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, where he covers the latest news, trends, and innovations in sustainable agriculture. He has a deep passion for storytelling that emphasizes ecological balance and responsible farming practices.

Before joining Growcycle, Victor worked for several agricultural and environmental publications, reporting on significant environmental issues and interviewing key figures in the sustainability sector. His work has been featured in various industry journals and online platforms.