Nutrition (fertilizers and dressings)

Major Nutrients: From Macro to Micro

Like all plants, pepper obtains nutrition from the air (carbon and oxygen) and water (hydrogen), but the basis of its diet consists of elements extracted from the soil. These are conventionally divided into two groups:

Macronutrients: consumed in large quantities. These are the “three pillars” of fertility:

• Nitrogen (N): the main building material for leaves and stems. It is responsible for the growth of green mass.
• Phosphorus (P): the energy element. It is essential for developing a strong root system, setting flower buds, and ripening fruits.
• Potassium (K): the “quality element.” It influences the movement of nutrients, disease resistance, fruit size, colour, flavour, and shelf life.

Micronutrients: consumed in minute amounts, but their absence can nullify all efforts. For pepper, the following are particularly important:

• Calcium (Ca) and Magnesium (Mg): responsible for cell wall structure and photosynthesis. Calcium deficiency is a leading cause of blossom‑end rot in fruits.
• Boron (B): critically important for pollination, fruit set, and sugar transport.

Consumption Dynamics: The Pepper’s “Feeding Regime”

The uptake of these elements does not occur uniformly. To avoid overfeeding and to supply what is needed at the right time, you must know three key stages of its “menu” (Bosland & Votava, 2012; Hartz et al., 1993).

1. Youth (from emergence to transplanting): During this period, the plant forms its taproot and programs its future growth. Pepper is extremely sensitive to phosphorus deficiency. It is phosphorus that stimulates active root system development. Additionally, moderate nitrogen helps produce compact, not leggy, seedlings.

2. Rapid growth (from transplanting to the onset of flowering): After being transplanted into the ground, pepper begins to actively build green mass. At this point, nitrogen takes centre stage. The amount of nitrogen determines how powerful a “skeleton” of leaves and stems the plant will build. This green factory will later supply the fruits with nutrients.

3. Flowering and fruiting (setting and filling of fruits): As soon as the first buds appear, the “diet” changes dramatically. The pepper’s task shifts from growing foliage to producing offspring – the fruits. During this stage, the proportion of nitrogen in fertilisers is reduced, and potassium and calcium take the lead. Potassium increases fruit size and sugar content, while calcium ensures their firmness and prevents blossom‑end rot (Miller et al., 1979).

The secret to success is to switch the pepper’s focus from growth to fruiting at the right time. Excess nitrogen during flowering will cause the plant to “fatten” – it will continue to push out greenery at the expense of fruit set and quality (Sundstrom et al., 1984).

Conditions for Availability: pH and Environment

Even if you apply all the necessary fertilisers, pepper cannot absorb them if they are in a form inaccessible to the roots. This depends on soil acidity (pH) (Hochmuth & Sideman, 2023).

The ideal pH range for pepper is between 6.0 and 6.8 (neutral or slightly acidic). In this range, all major nutrients are available to the roots. In acidic conditions (pH below 5.5) or alkaline conditions (above 7.5), many micronutrients (e.g., phosphorus, iron, boron) become “bound” and unavailable, even if they are present in the soil. Therefore, always check your soil pH before applying fertilisers – this is the key to making your feeding work.

Brief summary of Chapter 1:

• Pepper requires a strict balance of macro‑ (N, P, K) and micronutrients (Ca, Mg, B).
• Its nutritional needs change: phosphorus is crucial at the start, nitrogen during growth, and potassium and calcium during flowering and fruiting.
• Fertiliser effectiveness directly depends on soil pH (6.0–6.8), at which all elements are available to the roots.

Now that we know the pepper’s “feeding regime,” let’s move on to specific actions. In the next chapter, we will discuss how to properly organise nutrition immediately after transplanting to give the plants a strong start.

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Why Is Phosphorus So Important for Rooting?

Phosphorus is the “energy element” (Hochmuth & Sideman, 2023). It is part of ATP – the universal energy carrier in all living cells. Young roots, which are actively dividing and growing, consume enormous amounts of energy.

Moreover, phosphorus stimulates the formation of lateral roots and root hairs, which increase the area for water and nutrient uptake. A strong root system is the foundation for the plant to obtain enough moisture and nutrients during the hot summer months and to be less prone to lodging (Bosland & Votava, 2012).

Key nuance: phosphorus is one of the least mobile elements in the soil. It does not move with water towards the roots. The root itself must “find” it and “pull” it in. Therefore, simply scattering superphosphate over the bed surface is not enough – it will remain in the top layer, inaccessible to the bulk of the roots.

How to Properly Supply Phosphorus at the Start?

1. Pre‑planting application (starter fertiliser): The most effective method is to place phosphorus fertiliser directly into the planting hole or in a furrow before planting. This creates a “hot spot” of high phosphorus concentration right in the future root zone.

• Superphosphate (double or single): incorporate 10–15 g of double superphosphate into the hole, mixing thoroughly with soil to avoid burning tender roots.
• Liquid phosphorus fertiliser: it can be added to the water for watering seedlings just before planting or in the first watering after transplanting.

2. Starter watering: If you did not apply fertiliser in the hole, give a “phosphorus watering” 5–7 days after transplanting, when the plants have slightly acclimatised. Dissolve the fertiliser in water and water the plants strictly at the root.

When Is This Especially Important?

• In cold soil: pepper roots absorb phosphorus poorly when soil temperature is below +15 °C (Autko et al., 2012). Under such conditions, even applied phosphorus may remain “unused.” Therefore, early warming of the beds (black mulch, raised beds) is particularly important. If the soil is cold, it may be useful to apply foliar feeding with monopotassium phosphate – phosphorus will be absorbed through the leaves more quickly.
• On acidic soils (pH < 5.5): phosphorus binds with aluminium and iron into insoluble compounds. Hence, Chapter 2 ties back to Chapter 1: before planting, be sure to check pH and, if necessary, add dolomite flour or ash to deacidify.

Signs of Phosphorus Deficiency

If the plant does not get enough phosphorus, you will see it:

• Stunted growth: the bush looks dwarfed and weak.
• Purple or bluish tint: the undersides of leaves, stems, and petioles develop a characteristic purple or magenta colour (especially noticeable on young plants) (Kasyankina & Kudin, 2018).
• Delayed flowering and fruiting: even if the plant blooms, it will set few fruits.

Brief summary of Chapter 2:

• The main goal after transplanting is strong rooting.
• The key element for this is phosphorus (P).
• Apply phosphorus locally, right in the root zone (in the hole or as a root drench), because it is immobile in the soil.
• Remember that phosphorus is poorly absorbed in cold and acidic soil – this must be corrected before or immediately after planting.
• A sign of deficiency is a purple hue on leaves and stems.

In the next chapter, we will shift our focus from roots to leaves and discuss the main “green building” element – nitrogen – and learn how to balance NPK for active bush growth.

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Nitrogen – the Engine of Growth

Nitrogen is a component of chlorophyll (the green pigment), amino acids (which build proteins), and DNA. Simply put, without nitrogen there is no growth. During the vegetative growth phase (from transplanting to the start of budding), pepper consumes nitrogen most intensively.

Nitrogen sources: at this stage, both root and foliar applications can be used.

• Root feeding: urea, ammonium nitrate, complex fertilisers with a predominance of nitrogen. At this stage, pepper responds particularly well to nitrogen in the nitrate form \mathrm{NO_3} , which is more easily absorbed in cool weather (Hochmuth & Sideman, 2023).
• Foliar feeding (on leaves): a good way to quickly replenish nitrogen deficiency, especially during active leaf growth. Use a weak solution of urea (no more than 1%) or complex fertilisers.

The Golden Rule: NPK Balance

Many gardeners make the mistake of feeding pepper only with nitrogen, forgetting about phosphorus and potassium. But each of these elements performs its own unique role (Bosland & Votava, 2012):

• Phosphorus (P), although we emphasised it at the start, continues to participate in energy metabolism and the formation of flower buds. Its deficiency during growth will result in weak, thin shoots.
• Potassium (K) is the “water balance” element. It regulates the opening and closing of stomata, helping the plant tolerate heat and drought. In addition, potassium participates in enzyme and sugar synthesis, improving the taste and quality of future fruits.

The ideal N:P:K ratio during vegetative growth is roughly 2:1:2 or 3:1:3 (Kasyankina & Kudin, 2018). For example, a fertiliser with the formula 20‑10‑20, 20‑20‑20, or 15‑15‑15 would be a good choice for overall support.

The secret of balance: phosphorus and potassium “restrain” excessive rapid growth of green mass, directing nutrients to strengthen cell walls and develop roots. Thus, the plant receives a signal not just to grow tall, but to grow evenly and robustly (Autko et al., 2012).

What Is the Danger of Overfeeding Nitrogen?

Excess nitrogen, especially at the expense of potassium and phosphorus, leads to a phenomenon experienced gardeners call “fattening” (Pantielev, 1986). Externally, the plant looks splendid: it is vigorous, dark green, with large succulent leaves. However, it expends all its energy on producing this greenery, not on fruiting.

Signs of pepper fattening:

• The bush grows excessively at the expense of flowering: few flowers, they drop without setting fruit.
• Leaves become unnaturally large and dark green, sometimes with “blistering.”
• If fruits do set, they are small, deformed, with thin walls.
• The plant becomes loose and more susceptible to diseases and pests (Bosland & Votava, 2012).

How to fix the situation? If you notice signs of fattening, immediately stop nitrogen fertilisation and emphasise potassium and phosphorus. A foliar feeding with monopotassium phosphate can help “switch” the plant to reproductive mode.

Feeding Technique

1. Timing: fertilising is best done in the morning or evening to avoid leaf burn and to give plants time to absorb nutrients before the heat sets in.

2. Frequency: during active growth, feeding pepper once every 10–14 days, combined with watering, is sufficient.

3. The rule “less but more often”: it is better to give plants a weak fertiliser solution more frequently than to apply a high concentration once, which can cause root burn (salt stress) (Hochmuth & Sideman, 2023).

Signs of Nitrogen Deficiency and Excess

• Deficiency: lower leaves become pale green, then yellow and drop. Bush growth slows, shoots become thin and weak.
• Excess: we have already described – fattening, dark green “plump” leaves, lack of flowers.

Brief summary of Chapter 3:

• During active growth, the main element is nitrogen (N). It is needed to build green mass.
• It is important to maintain an NPK balance (roughly 2:1:2 or 3:1:3) to stimulate even growth, not just foliage.
• Nitrogen overfeeding (“fattening”) causes the plant to produce foliage instead of fruit.
• At the first signs of fattening, sharply reduce nitrogen and increase the share of potassium and phosphorus.

Now that we have provided the pepper with strong foliage and a sturdy skeleton, the critical moment arrives – flowering and fruit set. In the next chapter, we will discuss how to correctly “switch” nutrition towards fruit formation using potassium, calcium, and magnesium.

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Potassium – the “King” of Fruiting

Potassium is the key element for pepper fruit formation. It performs several critically important functions (Bosland & Votava, 2012; Hochmuth & Sideman, 2023):

1. Improves fruit quality: potassium increases fruit size, makes walls thicker and fleshier, raises sugar and vitamin content, and enhances taste and aroma.

2. Strengthens cell walls: this increases fruit resistance to mechanical damage and extends storage life.

3. Regulates water balance: potassium helps the plant use moisture efficiently, especially important in hot weather during fruit filling.

4. Boosts immunity: potassium fertilisation makes plants more resistant to fungal diseases and stress.

When and how to apply potassium:

• Start potassium fertilisation from the moment the first buds appear and continue throughout the fruiting period, until the last harvest.
• Frequency – every 10–14 days, combined with watering.
• Best potassium sources: potassium sulphate (also contains sulphur, which improves flavour), kalimagnesia (contains magnesium), monopotassium phosphate (contains both potassium and phosphorus), wood ash (a good organic source of potassium and micronutrients).
• Potassium, like phosphorus, is best applied by the root method, into the active root zone.

Signs of potassium deficiency:

• A yellow‑brown margin appears on the edges of older leaves (marginal burn).
• Leaves may curl downward and become wrinkled.
• Fruits grow small, with thin walls, unevenly coloured.
• The bush looks weakened and is easily affected by diseases.

Calcium – the “Builder” of Cells

Calcium is responsible for cell wall strength and normal root growth. For pepper, calcium deficiency is disastrous because it directly leads to blossom‑end rot – one of the most common problems (Autko et al., 2012; Pantielev, 1986).

What is blossom‑end rot? It is not an infectious disease but a physiological disorder caused by a lack of calcium in developing fruits. It appears as a dark, sunken, water‑soaked spot on the blossom end (tip) of the fruit. Affected fruits become inedible and quickly rot.

Causes of calcium deficiency:

• Lack of calcium in the soil.
• Overwatering or drought, which disrupts calcium uptake by roots.
• Excess potassium, magnesium, or ammonium nitrogen, which compete with calcium for root uptake (antagonism).
• Sharp fluctuations in soil moisture.

How to prevent and treat calcium deficiency:

1. Regular watering: keep the soil evenly moist but not waterlogged. Calcium enters the plant only with water.

2. Calcium application: in autumn or spring, add dolomite flour or limestone to the soil (especially on acidic soils). During the growing season, use calcium nitrate (which contains both nitrogen and calcium) – it can be applied by both root and foliar methods.

3. Foliar feeding: for quick relief at the first signs of blossom‑end rot, spray the plants with a 0.5‑1% solution of calcium nitrate or calcium chloride (Autko et al., 2012).

4. Nutritional balance: avoid excess potassium and magnesium fertilisers, as they reduce calcium uptake.

Signs of calcium deficiency:

• Blossom‑end rot of fruits (the main and most dangerous symptom).
• Death of growing points (young leaves and shoot tips may yellow and die).
• Roots become weak and grow poorly.

Magnesium – the “Heart” of Chlorophyll

Magnesium is a component of chlorophyll – the pigment responsible for photosynthesis and giving leaves their green colour. Without magnesium, the plant cannot efficiently capture solar energy and produce organic substances for growth and fruiting. Maintaining magnesium balance is especially important during fruit filling, as fruits are a sink for assimilates.

When and how to apply magnesium:

• If you use dolomite flour to deacidify the soil, you are already applying magnesium. On light sandy soils, magnesium can leach out quickly, and deficiency appears more often.
• During the growing season, a good magnesium source is magnesium sulphate (Epsom salt). It can be applied by root (20–30 g per 10 L of water) or foliar (10–15 g per 10 L of water) (Hochmuth & Sideman, 2023).
• Magnesium is also present in complex fertilisers (e.g., kalimagnesia).

Signs of magnesium deficiency:

• Chlorosis between veins on older leaves: the leaf blade turns yellow while the veins remain green (interveinal chlorosis). This starts on lower, older leaves.
• Leaves may become reddish or purplish at the edges.
• Growth slows, yield decreases.

How to Implement This “Fruiting Regime” in Practice?

Important note: during this period, try to use fertilisers with minimal or no nitrogen \mathrm{(N)} . The ideal N:P:K ratio at the fruiting stage is about 1:2:3 or 1:3:4 (Kasyankina & Kudin, 2018). This will switch the plant from foliage growth to fruit filling.

Brief summary of Chapter 4:

• During flowering and fruiting, the main elements are potassium (K) (fruit size, flavour, shelf life), calcium (Ca) (cell strength, protection against blossom‑end rot), and magnesium (Mg) (photosynthesis).
• Nitrogen should be sharply reduced at this stage to avoid fattening and crop loss.
• Calcium deficiency leads to blossom‑end rot – prevent it with even watering and calcium application.
• Magnesium deficiency manifests as interveinal chlorosis on older leaves – apply magnesium sulphate.
• Use fertilisers with low nitrogen content and high potassium and calcium content.

In the next chapter, we will discuss how to quickly and accurately determine what exactly your pepper lacks – that is, how to diagnose deficiencies by visual signs.

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Nitrogen (N)

How to recognise: Nitrogen deficiency starts on the lower, older leaves. This is logical: the plant “moves” nitrogen from old parts to young growing points. Leaves become pale green, then yellow, brown, and drop. The bush looks weak, with thin shoots (Kasyankina & Kudin, 2018).

What to do: Apply nitrogen fertiliser urgently. Nitrate forms (calcium or potassium nitrate) are best, especially in cool weather, when nitrate nitrogen is absorbed better than ammonium nitrogen (Hochmuth & Sideman, 2023). Organic options – cow manure or poultry manure extract – can also be used.

Potassium (K)

How to recognise: Potassium deficiency appears on old leaves as marginal burn – a yellow‑brown border along the leaf edges. Leaves may curl downward and become wrinkled. Fruit flavour deteriorates, walls become thinner (Bosland & Votava, 2012).

What to do: Apply potassium fertiliser. Potassium sulphate is the best choice because it contains no chlorine, which pepper dislikes. Kalimagnesia is an excellent option if magnesium deficiency is also present. Wood ash is a good organic potassium source, but remember it strongly alkalinises the soil.

Calcium (Ca)

How to recognise: The main symptom is blossom‑end rot of fruits (Autko et al., 2012). This is a dark, sunken, water‑soaked spot on the “bottom” of the fruit, which gradually enlarges and rots. It is not an infection, but a physiological disorder caused by calcium shortage in the fruits. Other signs: dieback of growing points, brittle stems.

What to do: The problem is often not the absence of calcium in the soil, but disrupted transport to the fruits due to uneven watering. Calcium enters the plant only with water, so regular and even watering is prevention #1. For quick help – spray fruits and leaves with a 0.5‑1% calcium nitrate solution. Maintain a neutral soil reaction (pH 6.5‑7.0).

Magnesium (Mg)

How to recognise: The typical sign is interveinal chlorosis on older leaves: veins stay green, while the tissue between them turns yellow. In severe deficiency, leaves may take on a reddish or purple tint (Hochmuth & Sideman, 2023).

What to do: Magnesium is a mobile element, so its deficiency often appears on poor sandy soils. Foliar feeding with magnesium sulphate (Epsom salt) – 20 g per 10 L water – gives a rapid effect. If you use dolomite flour for deacidification, you are already addressing magnesium for the future.

Boron (B)

How to recognise: Boron is a micronutrient, but its role is critical. It is responsible for pollination, pollen tube growth, and fruit set. Deficiency symptoms: dieback of growing points (shoot tips), brittle and deformed young leaves, poor fruit set, fruit deformation and dropping (Pantielev, 1986).

What to do: Foliar feeding with boric acid (1 g per 1 L water) during budding and early flowering is one of the most effective ways to boost pepper yield. Do not exceed the concentration – excess boron is toxic.

Important Diagnostic Rules

1. Compare old and young leaves:

• If the problem is on old leaves – it is likely a deficiency of mobile elements: nitrogen, potassium, magnesium (the plant moves them to young organs).
• If the problem is on young leaves – it is a deficiency of immobile elements: calcium, boron, iron (the plant cannot move them to new tissues).
• Consider environmental conditions: Deficiency often appears not because the element is absent from the soil, but because of conditions that hinder uptake (cold, drought, waterlogging, disturbed pH).
• Do not treat blindly: If you are unsure of the diagnosis, it is better to perform a soil or leaf analysis than to add extra fertiliser and cause antagonism with other elements.

Brief summary of Chapter 5:

• Being able to read deficiency symptoms allows you to respond quickly to problems.
• Nitrogen: yellowing of old leaves → urgent nitrogen feeding.
• Potassium: marginal burn on old leaves → feed with potassium sulphate.
• Calcium: blossom‑end rot → regulate watering and apply calcium.
• Magnesium: interveinal chlorosis on old leaves → feed with magnesium sulphate.
• Boron: deformation of growing points and poor fruit set → spray with boric acid at early flowering.

Now that we know how to diagnose and treat deficiencies, let’s move to the next chapter to decide what is better for feeding: organic or mineral fertilisers.

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Organic Fertilisers: The Natural Approach

Organics are products of animal and plant metabolism: manure, compost, humus, green manures, bone meal, ash, various extracts (cow manure, poultry manure, herbal teas). Their main advantage is complex action on soil and plant.

Advantages of organics:

1. Improves soil structure: Organic matter feeds soil microorganisms and earthworms. It binds soil particles into aggregates, making the soil loose, air‑ and water‑permeable. On sandy soils, organics increase water‑holding capacity; on clay soils, they improve drainage (Hochmuth & Sideman, 2023).

2. Nutrients released gradually: Plants receive nutrients not immediately, but as organic matter decomposes by microorganisms. This reduces the risk of “overfeeding” and provides long‑lasting nutrition.

3. Contains micronutrients: Organics provide a full spectrum of micronutrients (boron, zinc, copper, manganese, molybdenum) in balanced proportions, often lacking in complex mineral fertilisers.

4. Increases soil buffering: Organics moderate sharp pH fluctuations, making the soil more resistant to acidification or alkalinisation.

5. Eco‑friendliness: It is a renewable resource, and its use recycles waste.

Disadvantages of organics:

1. Inaccurate composition: The content of nitrogen, phosphorus, potassium, and other elements in manure or compost varies greatly depending on the raw material, age, and storage conditions. You never know the exact dosage you apply (Hochmuth & Sideman, 2023).

2. Slow action: In cold weather or poor soils, decomposition is slow, and plants may not get the nutrients they need during critical periods (e.g., early vegetation).

3. Risk of diseases and weeds: Fresh manure may contain weed seeds, helminth eggs, and pathogens. Composting solves this but requires time and proper technique.

4. Inconvenient application: Requires large volumes and physical effort to spread.

Mineral Fertilisers: Precision and Speed

Mineral fertilisers are chemical compounds containing nutrients in concentrated form. They are manufactured industrially and have guaranteed composition and active ingredient content.

Advantages of mineral fertilisers:

1. Precise dosage: You know exactly how much nitrogen, phosphorus, or potassium you apply per square metre. This allows you to fine‑tune nutrition at different growth stages.

2. Fast action: Most mineral fertilisers are water‑soluble and available to roots within hours after application. This is ideal for “emergency” acute deficiencies.

3. Convenience: Available as granules, powders, or liquids, easy to dose and apply (broadcast, watering, spraying).

4. Cleanliness: They contain no weed seeds, pathogens, or parasite eggs.

Disadvantages of mineral fertilisers:

1. Risk of “overfeeding”: Excess minerals, especially nitrogen, can cause root burn, fattening, nitrate accumulation, and nutrient antagonism (Hochmuth & Sideman, 2023).

2. Soil salinisation: Accumulation of salts (especially chlorides, nitrates, sulphates) with systematic overfeeding can degrade soil structure and inhibit root systems.

3. Do not improve soil: Mineral fertilisers do not add organic matter, do not feed microorganisms, and do not improve soil structure. With exclusive use, soil gradually degrades.

4. High energy consumption: Manufacturing mineral fertilisers requires large energy inputs, making them less environmentally sustainable.

Where and When Does What Work Better?

Now let’s see which type is better to apply in practice, based on pepper’s characteristics.

• Organics are mainly used at the soil preparation stage (before planting). Adding well‑rotted manure, compost, or humus in autumn or spring builds the foundation of fertility. It improves soil structure and creates a long‑term reserve of nutrients (Autko et al., 2012).
• Mineral fertilisers are best for quick feeding during the growing season. They allow precise adjustment of nutrition according to the growth stage: nitrogen for growth, phosphorus for roots, potassium and calcium for fruits.
• Liquid organic feeds (extracts of cow manure, poultry manure, herbal teas) can be a good compromise. They act faster than dry organics and contain many micronutrients. However, one must be cautious with nitrogen, as their concentration is often unpredictable.

Combined approach – the best strategy:

Practical Recommendations for the Gardener

1. Do not use fresh manure under pepper. It contains a lot of nitrogen and can burn roots. Use only well‑rotted manure (at least 1 year old) or mature compost.

2. Wood ash is an excellent organic source of potassium and micronutrients. But it strongly alkalinises the soil (raises pH). Therefore, it is better to apply it on acidic soils, and moderately on neutral and alkaline soils (Kasyankina & Kudin, 2018).

3. Combine organics and “minerals.” Apply the main organics in autumn or spring, and use mineral fertilisers during the season for quick and precise feeding.

4. Alternate root and foliar feeding. Mineral fertilisers can be applied both under the root (solution) and on the leaves. Foliar feeding is particularly effective for micronutrients and for quick correction of deficiencies (Pantielev, 1986).

5. Monitor soil pH. Organics (especially acidic peat) can acidify soil, while ash can alkalinise. Mineral fertilisers also affect pH (ammoniacal – acidify, nitrate – alkalinise). Keep pH in the range of 6.0‑6.8 – the optimal range for uptake of all elements.

Brief summary of Chapter 6:

• Organics – for long‑term soil improvement and slow, balanced nutrition. Best at the soil preparation stage.
• Mineral fertilisers – for fast and precise corrective feeding during the season. Essential for managing growth and fruiting.
• Best strategy – a combined approach: organics as a base + mineral feeds at key vegetative stages.
• Remember: both organic and mineral fertilisers can be harmful if misused. The key is moderation and understanding the plant’s needs at each stage.

Now that we have covered the basic principles of choosing fertilisers, in the final Chapter 7 we will summarise and discuss the most common mistakes to avoid when feeding peppers.

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1. Nitrogen Overfeeding and “Fattening”

This is perhaps the most common mistake, especially among beginners. Seeing that pepper responds well to nitrogen fertilisation with vigorous growth, many start applying it with doubled strength – and get the opposite effect.

What is “fattening”? The plant channels all its resources into building vegetative mass: leaves become huge, dark green, succulent, stems thick. The bush looks magnificent, but there are few or no flowers and fruit sets (Autko et al., 2012). This is the classic signal of imbalance: the pepper is “fattening.”

Why is it bad? A fattening plant wastes energy on building a green “factory” rather than producing “product” – fruits. It becomes loose, more susceptible to diseases and pests. If fruits do set, they are small and deformed.

How to avoid and what to do?

• Do not apply nitrogen fertilisers during flowering and fruiting. All the nitrogen the pepper needs should be applied before budding starts.
• Use balanced fertilisers with an NPK formula where nitrogen does not exceed phosphorus and potassium (e.g., 10‑20‑20 or 15‑15‑15) (Kasyankina & Kudin, 2018).
• If fattening has already started, immediately stop all nitrogen feeding and give the plant potassium and phosphorus. Root or foliar feeding with monopotassium phosphate (10‑15 g per 10 L water) helps “switch” metabolism towards fruiting (Bosland & Votava, 2012).

2. Salt Stress (Overfeeding with Mineral Fertilisers)

Mineral fertilisers are salts. At low concentrations they are necessary, but excess in the soil solution causes the opposite effect: roots stop absorbing water (osmotic shock). This is called salt stress.

How to recognise?

• The plant looks wilted, even though the soil is moist.
• Leaves may yellow and die from the edges.
• A white crust (salt crystals) may appear on the soil surface.
• Growth slows, fruits become small and bitter (capsaicin content increases in hot varieties as a stress response) (Bosland & Votava, 2012).

Causes:

• Applying too high doses of mineral fertilisers at one time.
• Using fertilisers with a high salt index (e.g., potassium chloride, ammonium nitrate) without sufficient watering.
• Watering with hard water high in salts.

How to avoid and what to do?

• Apply fertilisers fractionally, in small doses. It is better to feed pepper with a weak solution more often (every 7‑10 days) than to apply a high dose at once (Hochmuth & Sideman, 2023).
• Always water abundantly after applying dry granular fertilisers. This helps dissolve salts and distribute them through the soil profile.
• At the first signs of salt stress, flush the soil generously with clean water (2‑3 times the normal watering volume) to leach excess salts from the root zone.
• Use fertilisers with low salt index: potassium sulphate, magnesium sulphate, calcium nitrate. Potassium chloride is not a good choice for pepper.

3. Ignoring Soil pH

As mentioned in Chapter 1, pH is the key to nutrient availability. If pH goes beyond 6.0‑6.8, even the most expensive and high‑quality fertilisers will lie useless in the soil.

How does it manifest?

• The plant experiences a combined deficiency of several elements (phosphorus, iron, manganese, boron) even though you apply them regularly.
• Leaves become pale with chlorosis that ordinary feeding does not correct.

How to avoid:

• Regularly (once a year) test soil pH using test strips or a pH meter.
• On acidic soils (pH < 5.5), apply dolomite flour or ash (in autumn or spring). Dolomite flour is preferable because it enriches the soil with both calcium and magnesium.
• On alkaline soils (pH > 7.5), use acidifying fertilisers (e.g., ammonium sulphate) or add peat.

4. Incorrect NPK Ratio at Different Stages

Many use the same complex fertiliser from start to finish. This is a serious mistake, as different stages require different proportions of elements.

Balance errors:

• Using nitrogen fertilisers during fruiting → fattening.
• Lack of phosphorus at planting → weak root system and stunted growth.
• Insufficient potassium and calcium during fruit filling → blossom‑end rot, small and tasteless fruits.

How to avoid:

• Use three different feeding approaches depending on the growth stage (see table at the end of the chapter).
• Keep records: what, when, and in what doses you applied. This will help track dynamics and correct mistakes in the next season.

5. Ignoring Foliar Feeding

Root feeding is the foundation, but sometimes it does not work – for example, in cold weather or when roots are damaged. In such situations, foliar (leaf) feeding is the only way to quickly deliver nutrients to the plant.

When is it especially effective?

• For micronutrients (boron, iron, manganese) – they are absorbed by leaves 5‑10 times faster than by roots.
• In acute deficiency (e.g., emergency treatment of blossom‑end rot with calcium nitrate).
• In cool weather, when root nutrition is weakened.

How to avoid mistakes?

• Use foliar feeding as a supplement to root feeding, not as a replacement.
• Spray leaves in the evening or early morning so the solution has time to be absorbed before drying.
• Use the concentration indicated on the package (usually 2‑3 times weaker than for root application) to avoid burns.

6. Violating Timing and Frequency of Feeding

“More is better” – this principle does not work for fertilisers. Pepper is a crop that requires regular but moderate nutrition. Long gaps between feedings or overfeeding are equally harmful.

Mistakes:

• Infrequent feeding (once a month) → pepper experiences “starvation” during critical growth phases.
• Too frequent feeding (every watering) → risk of salt stress and nitrogen excess.

How to avoid:

• During active growth and fruiting, feed pepper once every 10‑14 days.
• Combine feeding with watering so that salts do not accumulate in the topsoil.
• In hot weather, reduce fertiliser concentration but increase watering frequency (to avoid salt stress).

Summary: Mistake Checklist and Solutions

Table: Ideal N:P:K Ratio at Different Life Stages of Pepper

Brief summary of Chapter 7:

• Nitrogen overfeeding is the main mistake leading to fattening. Fix by sharply reducing nitrogen and boosting potassium‑phosphorus nutrition.
• Salt stress results from too high a concentration of mineral salts. Treated with fractional fertilisation and heavy watering.
• Soil pH is the fundamental basis. Without optimal pH (6.0‑6.8), any feeding is ineffective.
• NPK imbalance at different growth stages leads to yield loss. Change element ratios according to development phase.
• Foliar feeding is an important supplement, especially for micronutrients.
• Regularity is the key to success. Feed pepper once every 10‑14 days, combined with watering.
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