Feeding and nutrition

Why does garlic need nitrogen?

The main task of nitrogen is to ensure rapid leaf growth in the first half of the growing season. The quantity and quality of green mass built up in spring directly determines the future size of the bulb (Engeland, 1991). The more healthy leaves, the more sugars and other nutrients they synthesize and send to the bulb during its formation.

When is nitrogen needed?

Nitrogen application is the most critical moment in garlic fertilizing. Its uptake changes greatly during the season.

1. Early spring (from emergence to the start of bulb formation): This is a critical period. The plant is actively growing leaves, and its need for nitrogen is maximal. Approximately 70% of all nitrogen is absorbed during this period (Brewster, 2008). Any delay in fertilizing at this time will result in reduced yield.

2. Late spring and early summer: As soon as garlic enters the phase of clove and bulb formation, the need for nitrogen drops sharply. At this time, the plant switches to carbohydrate accumulation. If you continue to actively apply nitrogen during this period, it will delay maturation, cause “fatty” leaves at the expense of the bulb, and consequently worsen the quality and storage life of the heads (Autko et al., 2012).

How to recognize nitrogen deficiency and excess?

• Deficiency: Plants look pale, turn yellow, especially older leaves. Growth slows, leaves become small and narrow. This is a common problem on poor soils or with insufficient moisture, as nitrogen is easily leached.
• Excess: Leaves become dark green and succulent, and there is vigorous top growth. Bulbs form small, loose, store poorly, and their flavor becomes less pronounced (Autko et al., 2012).

How to apply nitrogen?

Because garlic has a weak root system and high sensitivity to salt burn, especially in the germination phase, a split nitrogen application strategy is very important (Brewster, 2008).

1. Starter fertilizer at planting (optional): Applying a small amount of readily available phosphorus-nitrogen fertilizer directly into the furrow under the clove stimulates root development and early growth. This is especially effective on soils with medium or low nutrient content. Important: the fertilizer should not contact the clove itself.

2. Main fertilizing (early spring): About 3-4 weeks after emergence or when plants reach a height of 15-20 cm, the first and most important fertilizing is done. You can use ammonium nitrate, ammonium sulfate, or organic analogues. Depending on soil condition, apply 40-60% of the total planned nitrogen rate at this stage.

3. Second fertilizing (3-4 weeks after the first): The fertilizing is repeated when the plant is actively growing leaves. In total, it is recommended to apply 70-90 kg/ha of active nitrogen (N) over the season for high yields (Autko et al., 2012; UMass Extension, 2013). For small plots, this roughly corresponds to applying 1-2 tablespoons of urea or ammonium nitrate per square meter, dissolved in water.

Important nuances

• Form of nitrogen: Research shows that in early stages, garlic better absorbs the ammonium form of nitrogen. Ammonium nitrate and ammonium sulfate are good choices for starter and early spring fertilizing (Brewster, 2008). Organic sources (compost, manure, blood meal) work more slowly but improve soil structure and provide longer-lasting nutrition.
• Relation to irrigation: Nitrogen is very mobile in the soil. To prevent it from leaching into deep layers inaccessible to garlic roots, fertilizing is best done before irrigation or applied in dissolved form, combined with drip irrigation.
• Organic farming: As an alternative to mineral fertilizers, you can use well-rotted compost (applied in autumn or 2-3 weeks before planting), blood or bone meal, and herbal infusions.

Conclusion on nitrogen: Nitrogen is the main element for leaf growth, and it must be applied wisely: enough, but strictly before the bulb begins to form. Early spring fertilizing is your key to a high yield of large garlic heads.

Why does garlic need phosphorus?

1. Root and shoot development: Phosphorus stimulates root growth, especially immediately after planting and early spring when the soil is still cold. A strong root system is the key to a quick start and high stress resistance.

2. Energy metabolism: Phosphorus is part of ATP (adenosine triphosphate) — the universal “energy currency” of plants. It powers all energy-consuming processes, from photosynthesis to protein synthesis and sugar accumulation in the bulb.

3. Quality and storage life: Adequate phosphorus supply contributes to the formation of denser, well-storing bulbs. It also positively affects sugar content, which is especially important for garlic flavor.

When is phosphorus needed?

The need for phosphorus in garlic, as in other crops, is highest at the initial stages of growth. An interesting feature of garlic is that the rate of phosphorus uptake per unit root length in young seedlings is almost three times higher than in adult plants (Brewster, 2008). This means that ensuring available phosphorus in the “emergence – 2-3 true leaves” phase is critical for setting yield potential.

Later, during the season, garlic absorbs phosphorus fairly evenly, but its total amount removed with the harvest is not as large compared to nitrogen and potassium.

How to recognize phosphorus deficiency and excess?

• Deficiency: The main sign is the appearance of a purple or reddish-purple tint on the leaves, especially on older ones. Plants become stunted, growth slows, leaves are small and narrow. On acidic soils with low organic matter, phosphorus deficiency is more common.
• Excess: Phosphorus excess is rare but can lead to iron and zinc deficiency, as phosphorus binds these micronutrients into unavailable compounds.

How to apply phosphorus?

Phosphorus is a low-mobility element in the soil. It does not leach into deep layers like nitrogen, but it also does not move to the roots on its own (Brewster, 2008). The plant must “find” phosphorus with its roots. Therefore, the method of phosphorus fertilizer application is crucial.

1. Application during pre-sowing tillage (basic fertilization): This is the most important step. The main dose of phosphorus is applied in autumn or early spring under digging or plowing. Phosphorus should be evenly distributed in the upper 15-20 cm soil layer, where the bulk of the roots will develop. At planting, apply 80-100% of the recommended phosphorus rate (Autko et al., 2012; UMass Extension, 2013).

2. Starter fertilizer at planting: Applying a small amount of water-soluble phosphorus fertilizer (e.g., monopotassium phosphate or a starter solution of ammonium phosphate) directly into the furrow next to the clove significantly improves root development in cold soil early in spring (Brewster, 2008). This is especially effective on soils with high phosphorus content, where it is in a difficult-to-access form.

3. Soil application: Superphosphate, ammonium phosphate, and other phosphorus fertilizers are applied and incorporated into the soil. On acidic soils, phosphorus binds into compounds unavailable to plants, so before applying phosphorus fertilizers, it is important to check and, if necessary, adjust the soil pH (optimal pH for garlic is 6.0-7.0).

Important nuances

• Interaction with zinc and iron: Excessive phosphorus application can cause zinc and iron deficiency (Engeland, 1991). Therefore, at high doses of phosphorus fertilizers, it is recommended to monitor the supply of these micronutrients.
• Do not apply large amounts of phosphorus in top dressings: The most effective is to apply phosphorus to the soil before planting. Liquid phosphorus foliar or soil applications can be useful, but they do not replace the basic application.
• Organic farming: Bone meal is an excellent organic source of phosphorus, but its availability to plants increases only in acidic soils and with active soil microflora. For faster action, fish meal or well-rotted manure can be used.

Conclusion on phosphorus: Phosphorus is the foundation for a strong start. Its proper application to the soil before planting and as a starter fertilizer guarantees rapid root system development and high yield potential. Phosphorus deficiency in the early stages is difficult to compensate for later.

Why does garlic need potassium?

1. Bulb formation and growth: Potassium uptake increases sharply during the phase of bulb initiation and reaches a peak during active clove growth (Brewster, 2008). It is potassium that ensures the outflow of plastic substances (sugars, amino acids) from the leaves into the bulb, making it large and dense.

2. Stress resistance: Potassium increases cell turgor, helping the plant better tolerate drought, frost, and temperature fluctuations. This is especially important for winter garlic, which overwinters in the soil and must survive spring frosts.

3. Quality and storage life: Potassium directly affects the synthesis of sugars, which determine garlic flavor. In addition, it strengthens the covering tissues of the bulb, making it more resistant to mechanical damage and diseases during storage. Well-supplied garlic stays dormant longer and is less affected by rots.

When is potassium needed?

Potassium uptake by garlic, unlike nitrogen, increases gradually. The critical period for potassium is the phase from the start of bulb formation to full maturation. Research shows that it is during this period that the plant consumes the most potassium (Brewster, 2008). In early vegetation, its uptake is low, allowing the main part of potash fertilizers to be applied in autumn or early spring.

How to recognize potassium deficiency and excess?

• Deficiency: A characteristic sign is yellowing and dying of the edges of old leaves (“marginal scorch”). Leaves become brittle, wrinkled, internodes shorten. Bulbs form small, loose, with thin, weak covering scales.
• Excess: Potassium excess is rarer but can lead to magnesium and calcium deficiency, as potassium is their antagonist. This manifests as chlorosis (yellowing) between leaf veins.

How to apply potassium?

1. Application during pre-sowing tillage: It is recommended to apply a significant part of potash fertilizers (50-70% of the total rate) in autumn or spring under digging. Potassium, unlike nitrogen, is not leached as much, but in light, sandy soils it can migrate deeper, so it is better to incorporate it into the root zone (Autko et al., 2012; UMass Extension, 2013).

2. Early spring fertilizing: The remaining part of potassium can be applied as a top dressing during the active leaf growth phase (together with nitrogen). This will provide the plant with available potassium by the start of bulb formation.

3. Liquid fertilizing (fertigation): When using drip irrigation, it is very effective to apply potassium with irrigation water (fertigation) during the bulb formation and growth phase. This allows precise dosing and delivery directly to the roots. It is recommended to use potassium fertilizers that are highly water-soluble, such as monopotassium phosphate or potassium sulfate (Brewster, 2008).

4. Organic farming: Wood ash is an excellent natural source of potassium. It can be applied to the soil in autumn or used to prepare ash infusions for root and foliar feeding. Potassium is also found in well-rotted manure, compost, and green manures.

Important nuances

• Relation to nitrogen and water: Potassium enhances the effect of nitrogen and increases water use efficiency. Good potassium supply helps the plant better tolerate drought. However, under dry conditions, potassium deficiency can become more pronounced.
• Choice of fertilizers: Potassium chloride and potassium salt are cheaper but contain chlorine, which garlic tolerates less well than chloride-free potash fertilizers. Preference should be given to potassium sulfate. It not only supplies potassium but also provides an additional source of sulfur, which is critically important for garlic.

Conclusion on potassium: Potassium is the main element for “filling” the bulb. Its uptake is maximal during bulb growth. Proper and timely application of potash fertilizers is the key to forming large, dense, and storable bulbs with rich flavor.

Why does garlic need sulfur?

1. Flavor and aroma formation: Sulfur is a key element in the synthesis of allicin and other thiosulfinates. These compounds are not only responsible for the “garlic” character but also possess powerful antibacterial and antifungal activity, which increases plant resistance to diseases and improves storage life (Brewster, 2008).

2. Protein and enzyme synthesis: Sulfur is part of some amino acids (cysteine, methionine), which are building blocks for proteins and enzymes. It participates in photosynthesis and respiration.

3. Increased stress resistance: Sulfur promotes the synthesis of glucosinolates and other protective compounds that help garlic resist not only diseases but also adverse weather conditions (drought, frost).

When is sulfur needed?

The need for sulfur in garlic persists throughout the growing season, but it is especially important during the active leaf growth phase and at the start of bulb formation. At this time, the “flavor” potential of future bulbs is established. Sulfur deficiency, like nitrogen deficiency, is most pronounced on light, sandy soils low in organic matter, as sulfur is easily leached (Brewster, 2008).

How to recognize sulfur deficiency?

Symptoms of sulfur deficiency are very similar to those of nitrogen starvation: leaves become pale green or yellowish, growth slows. However, there is an important difference:

• With nitrogen deficiency, older (lower) leaves turn yellow and die first, because nitrogen is redistributed to young tissues.
• With sulfur deficiency, yellowing begins on young (upper) leaves, because sulfur does not move from old tissues to new ones (Engeland, 1991; Autko et al., 2012).

This is the main diagnostic sign to distinguish sulfur deficiency from nitrogen deficiency.

How to apply sulfur?

Sulfur is available to plants in the form of sulfate ion (SO₄^2-). The main ways to supply garlic with sulfur are:

1. Application of sulfur-containing mineral fertilizers: This is the simplest and most reliable method. Use ammonium sulfate ((NH₄)₂SO₄), which is simultaneously a source of nitrogen and sulfur. This is an excellent choice for early spring fertilizing. You can also use potassium sulfate (K₂SO₄) as a potassium-sulfur fertilizer, especially during bulb formation.

2. Use of organic fertilizers: Well-rotted manure, compost, blood meal — all contain sulfur in organic form, which gradually mineralizes and becomes available to plants.

3. Application of elemental sulfur (powdered): This method is mainly used for soil acidification and as a long-term sulfur source, because elemental sulfur must be oxidized by soil bacteria to the sulfate form. This process is slow and effective only in warm, moist, and aerated soil. As a rule, elemental sulfur is applied in autumn or a few weeks before planting.

Important nuances

• Interaction with molybdenum: Excess sulfates in the soil can compete with molybdenum (Mo) for root uptake. This can lead to molybdenum deficiency on very acidic soils, but in practice this is rare.
• Optimal dose: To supply garlic with sulfur, it is enough to apply 20-30 kg/ha of active sulfur (S) as part of complex fertilizers (Autko et al., 2012). For small plots, this is about 1-2 tablespoons of ammonium sulfate per 10 liters of water for watering or dry under digging.
• Soil testing: If you suspect sulfur deficiency, it is worth testing the soil for available sulfate content. This is especially relevant for light sandy soils in regions with high rainfall.

Conclusion on sulfur: Sulfur is the element that turns an ordinary onion into garlic. Its deficiency leads to loss of flavor and aroma. Use sulfur-containing fertilizers and carefully monitor the condition of young leaves — this is the best way to detect and correct sulfur deficiency in time.

Why does garlic need calcium?

1. Strength of cell walls: Calcium is a key component of pectic substances that bind cells together. The better plants are supplied with calcium, the stronger their tissues. This makes leaves more resistant to lodging and bulbs more resistant to mechanical damage and pathogen entry.

2. Root formation and growth: Calcium stimulates root and root hair growth. For garlic, with its weak root system, this is especially important, because good root development is the key to efficient uptake of all other nutrients (Brewster, 2008).

3. Enzyme activation: Calcium participates in activating many enzymes that regulate metabolism. It also affects stomatal function and water balance.

4. Disease resistance: Calcium increases plant resistance to bacterial and fungal diseases, because dense cell walls are a mechanical barrier to pathogens. This is especially important for protection against rots during storage.

How to recognize calcium deficiency?

Symptoms of calcium deficiency appear on young, actively growing tissues, because calcium does not move from old leaves to new ones (it is an immobile element).

• Young leaves: They become small, deformed, with curled or twisted edges. Chlorotic spots (yellowing) may appear, followed by necrosis (dieback) as brown dots or streaks.
• Root tips: Root growth slows, root tips may die, weakening the plant overall (Engeland, 1991).
• Bulbs: In severe cases, so-called “tip rot” may develop — dark sunken spots at the base of the bulb, although this is rarer in garlic than, for example, in tomatoes.

How to apply calcium?

Calcium is taken up by plants as Ca²⁺ ion from the soil solution. Main application methods:

1. Liming (main method): This is the most important and effective method. Applying lime (dolomite flour, chalk, slaked lime) not only supplies the plant with calcium but also corrects soil acidity (pH). The optimal pH for garlic is 6.0-7.0 (Autko et al., 2012; UMass Extension, 2013). On acidic soils (pH < 5.5), calcium is in an unavailable form. Liming is carried out well before garlic planting — in autumn or, at the latest, spring, but 2-3 months before planting.

2. Application of gypsum: Gypsum (calcium sulfate) is a neutral salt that does not change soil pH but is an excellent source of calcium and sulfur. It can be used on soils with neutral or alkaline reaction where liming is not required. Gypsum is applied to the soil before planting or used for liquid feeds.

3. Calcium fertilizers: In specialized stores, you can find calcium nitrate (calcium nitrate) — a fast-acting nitrogen-calcium fertilizer for top dressing. It can be used for watering or foliar spraying, but only if there are signs of acute deficiency.

Important nuances

• Interaction with magnesium and potassium: Calcium, magnesium, and potassium are antagonists. If there is too much of one of these elements in the soil, it can hinder the uptake of the other two. Therefore, it is important to maintain their balance. Dolomite flour (containing both calcium and magnesium) is a good choice for most soils.
• Timing of application: Liming is carried out several months before planting, as lime dissolves slowly and will not have time to act if applied immediately before planting. For top dressing, use fast-soluble forms.
• Do not forget about organics: Humus and compost improve soil structure and promote the accumulation of calcium in available form.

Conclusion on calcium: Calcium is the foundation of strength and health for garlic. Its deficiency is often related to acidic soil reaction. Timely liming is the best way to supply the plant with this element and obtain dense, disease-resistant bulbs.

Why does garlic need magnesium?

1. Photosynthesis: Magnesium is a key component of chlorophyll. Adequate magnesium supply ensures bright green leaf color and high photosynthesis intensity, which directly affects carbohydrate accumulation in the bulb (Autko et al., 2012).

2. Enzyme activation: Magnesium participates in activating many enzymes responsible for respiration, protein synthesis, and nutrient transport. It is also necessary for phosphorus uptake and transport.

3. Carbohydrate formation and transport: Magnesium plays an important role in the synthesis and transport of sugars from leaves to the bulb. This directly affects the size, density, and flavor of the heads.

4. Uptake of other elements: Magnesium helps the plant efficiently use phosphorus and participates in regulating cell water balance.

When is magnesium needed?

The need for magnesium in garlic is fairly uniform throughout the growing season, but it is especially important during the active leaf growth period (spring) and during bulb filling. In early stages, magnesium ensures a powerful photosynthetic apparatus, and in the second half of the season, it ensures carbohydrate outflow to the bulb.

How to recognize magnesium deficiency and excess?

• Deficiency: This is one of the most common nutritional disorders. A characteristic symptom is interveinal chlorosis on older (lower) leaves. The tissue between the veins turns yellow, while the veins themselves remain green. This occurs because magnesium, like nitrogen, is a mobile element and, when deficient, the plant redistributes it from old leaves to young ones and to the bulb. With severe deficiency, leaves may acquire a reddish-brown tint and die (Engeland, 1991).
• Excess: Rare, mostly on very light acidic soils. It can hinder calcium and potassium uptake due to antagonism between these elements.

How to apply magnesium?

1. Using dolomite flour: This is the best way to prevent magnesium and calcium deficiency simultaneously. Dolomite flour (containing calcium and magnesium carbonates) is applied for soil deacidification. If the soil is acidic and requires liming, use dolomite flour rather than chalk or lime, so as to simultaneously enrich the soil with magnesium (Autko et al., 2012; UMass Extension, 2013).

2. Applying magnesium sulfate: If the soil has a neutral or alkaline reaction and does not require liming, but there are signs of magnesium deficiency, you can use magnesium sulfate (MgSO₄·7H₂O) — also known as Epsom salt. This is a fast-acting water-soluble fertilizer. It can be applied to the soil (under digging or as a root feed) or used for foliar (leaf) feeding.

3. Applying as part of complex fertilizers: Many complex fertilizers contain magnesium in their composition. Pay attention to the labeling, especially if you are working with light sandy soils.

Important nuances

• Interaction with potassium and calcium: Magnesium, potassium, and calcium are antagonists. Excess of one can cause deficiency of another. For example, excessive application of potash fertilizers (especially potassium chloride) disrupts magnesium uptake. Therefore, it is important to maintain a balance. The K:Mg ratio in soil should be approximately 3-5:1.
• Soil acidity: Magnesium is best absorbed at pH 6.0-7.0. On acidic soils (pH < 5.5), it becomes less available. Therefore, liming with dolomite flour solves two problems at once: raises pH and enriches the soil with magnesium.
• Foliar feeding: In case of acute deficiency, the most effective are foliar applications with a 1-2% solution of magnesium sulfate (10-20 g per 10 L of water). This is a quick fix.

Conclusion on magnesium: Magnesium is the “engine” of photosynthesis. Its deficiency is easily recognized by yellowing lower leaves with green veins. Dolomite flour during liming and magnesium sulfate in feeds will help supply garlic with this crucial element, laying the foundation for a large and healthy harvest.

Boron (B)

Boron is a critically important micronutrient for garlic and other alliums.

• Role in nutrition: Boron is responsible for carbohydrate metabolism, cell wall synthesis, root and pollen growth. It participates in sugar transport from leaves to the bulb and promotes the formation of dense, well-structured heads (Engeland, 1991).
• Signs of deficiency: Young leaves become pale, deformed, may curl. Plant growth slows, bulbs form small and loose. With severe deficiency, cracks may appear on leaves, and brown spots (“black heart”) in bulbs.
• When and how to apply: Boron is applied in spring, during active leaf growth. You can use boric acid (H₃BO₃) or borax (Na₂B₄O₇·10H₂O). It is recommended to carry out one foliar feed (spraying on leaves) at a concentration of 0.05-0.1% (5-10 g per 10 L of water) or apply to the soil together with the main fertilizer at a dose of 1-2 kg/ha of boric acid (Autko et al., 2012). It is important not to exceed doses, as boron is toxic to plants at high concentrations.

Manganese (Mn)

Manganese participates in photosynthesis and respiration, and is a cofactor of many enzymes.

• Role in nutrition: Manganese is necessary for chlorophyll synthesis and activation of enzymes responsible for redox reactions. It also increases plant resistance to drought and frost.
• Signs of deficiency: Interveinal chlorosis appears on young leaves, with only the finest veins remaining green, and the tissue between them turns yellow. With severe deficiency — necrosis (tissue death) between veins. Manganese deficiency often occurs on soils with high pH (alkaline) and with excess iron.
• When and how to apply: Manganese is applied both to the soil (manganese sulfate, MnSO₄·H₂O) and to the leaves (foliar feeding). Soil application is effective on acidic soils, while on neutral and alkaline soils it is better to use foliar feeding at a concentration of 0.05-0.1% (Engeland, 1991).

Zinc (Zn)

Zinc is a crucial micronutrient for the synthesis of growth substances (auxins) and proteins.

• Role in nutrition: Zinc participates in protein synthesis, growth regulation, and reproductive organ development. It also increases plant resistance to stress and diseases.
• Signs of deficiency: Plants become dwarfed, internodes shorten. Leaves are small, narrow, with chlorotic spots (mottling) or yellow-white stripes. Brown necrotic spots appear on old leaves.
• When and how to apply: Zinc is applied both to the soil (zinc sulfate, ZnSO₄·7H₂O) and to the leaves. On soils with high pH, zinc becomes less available, so foliar feeding at a concentration of 0.05-0.1% is preferred.

Copper (Cu)

Copper participates in photosynthesis and respiration, and increases resistance to fungal diseases.

• Role in nutrition: Copper is a component of many enzymes involved in redox reactions. It is also necessary for protein synthesis and iron uptake.
• Signs of deficiency: Young leaves become pale, chlorotic, roll into a tube. White or light yellow dieback appears on leaf tips. With severe deficiency, the plant slows growth and may die.
• When and how to apply: Copper is applied both to the soil (copper sulfate, CuSO₄·5H₂O) and to the leaves. On peat and sandy soils, copper deficiency is more common.

Molybdenum (Mo)

Molybdenum participates in nitrogen metabolism (particularly nitrate reduction) and vitamin synthesis.

• Role in nutrition: Molybdenum is a cofactor of the enzyme nitrate reductase, which converts nitrates (NO₃^-) into ammonium (NH₄⁺) — a form of nitrogen the plant can use for amino acid synthesis. It also participates in molecular nitrogen fixation (although garlic is not a legume and does not fix nitrogen from the air, this process is important for soil microorganisms).
• Signs of deficiency: Symptoms are very similar to nitrogen starvation: leaf yellowing, slow growth. In garlic and other alliums, molybdenum deficiency is rare, more often on acidic soils.
• When and how to apply: Molybdenum is applied in very small amounts — at a dose of 0.1-0.2 g per hundred square meters (or 0.5-1 g/ha). Usually ammonium molybdate ((NH₄)₆Mo₇O₂₄·4H₂O) is used.

Iron (Fe)

Iron is necessary for chlorophyll synthesis, although it is not a component of chlorophyll.

• Role in nutrition: Iron is a cofactor of enzymes involved in chlorophyll synthesis and redox reactions.
• Signs of deficiency: A characteristic symptom is interveinal chlorosis on young leaves, with larger veins remaining green. With severe deficiency, leaves become completely yellow or white. Iron deficiency often occurs on carbonate (alkaline) and overlimed soils.
• When and how to apply: Iron is best absorbed in chelated form. Use iron chelate (Fe-EDTA or Fe-DTPA) for foliar feeding at a concentration of 0.05-0.1%. On alkaline soils, ordinary iron salts (iron sulfate) are of low effectiveness.

How to apply micronutrients?

1. Soil application: Micronutrients can be applied as part of complex fertilizers (especially “micro” blends), as well as individual salts. Soil application is effective when long-term supply is needed, but on neutral and alkaline soils many micronutrients (especially iron, zinc, copper) become poorly available.

2. Foliar feeding (on leaves): This is the most effective method in case of acute deficiency or on soils with high pH. Micronutrients in chelated form quickly penetrate leaves and are absorbed by the plant. Spraying is carried out during active leaf growth (spring) or at the beginning of bulb formation.

Important nuances

• What not to do: Do not apply micronutrients “just in case” in large amounts. Many of them (especially boron, zinc, copper) are toxic to plants even in low concentrations. It is better to diagnose via leaf or soil analysis.
• Interactions: Micronutrients can compete with each other. For example, excess phosphorus causes zinc and iron deficiency, excess potassium causes magnesium deficiency, excess copper causes iron deficiency. Also remember that on acidic soils (pH < 5.5), many micronutrients (especially manganese, aluminum) become too available and can cause toxicity.
• Chelates: For effective foliar feeding, use chelated forms of micronutrients. Chelates are organic compounds that protect micronutrients from binding and make them available to plants.

Conclusion on micronutrients: Micronutrients are the “last 20% of success.” Even with ideal supply of major elements, a deficiency of one micronutrient can negate all efforts. Use micronutrients purposefully, based on diagnosis or prophylactically — as balanced mixtures in chelated form.

Phase 1: Planting and Rooting (Autumn)

Goal: Ensure rapid and powerful root system development, help the plant overwinter well, and lay the foundation for future growth.

Key elements: Phosphorus (P), Calcium (Ca), and Potassium (K).

• Phosphorus is critical for root development and the initiation of generative organs. The main portion of phosphorus fertilizers is applied (Brewster, 2008).
• Potassium increases winter hardiness and disease resistance. A significant portion is also applied in autumn.
• Calcium is applied in the form of liming materials (dolomite flour, chalk) to optimize soil pH 2-3 months before planting (Autko et al., 2012; UMass Extension, 2013).
• Organics: Applying well-rotted compost or humus (4-5 kg/m²) not only enriches the soil with nutrients but also improves its structure, water permeability, and aeration.

Practical recommendations:

1. Conduct a soil test to determine pH and the content of major elements (especially phosphorus and potassium).

2. Apply lime (dolomite flour) 2-3 months before planting if pH is below 6.0. For most soils, 300-500 g/m² is sufficient, but the exact rate is given only by soil analysis.

3. Apply basic fertilizer: Phosphorus (superphosphate, ammonium phosphate) and potassium (potassium sulfate) fertilizers are applied under digging 2-3 weeks before planting. Approximate rates: 30-40 g/m² superphosphate and 20-25 g/m² potassium sulfate.

4. Starter fertilizer (optional): At planting, a small amount of water-soluble phosphorus fertilizer (e.g., 5-10 g/m² monopotassium phosphate) can be applied to the furrow to stimulate root growth in cold soil.

Phase 2: Active Leaf Growth (Early Spring)

Goal: Build a powerful leaf apparatus capable of producing maximum carbohydrates for the future bulb.

Key elements: Nitrogen (N) — the main element of this phase. Also important are Magnesium (Mg), Calcium (Ca), and Micronutrients (B, Mn, Fe, Zn).

• Nitrogen ensures intensive green mass growth. This is the most critical period for nitrogen fertilizer application (Brewster, 2008).
• Magnesium — the basis of chlorophyll, ensures powerful photosynthesis.
• Calcium strengthens cell walls, making leaves more robust and resistant to lodging.
• Micronutrients (boron, manganese, iron, zinc) are important for photosynthesis, respiration, and protein synthesis.

Practical recommendations:

1. First fertilizing: As soon as shoots appear (usually 3-4 weeks after snowmelt or when plants reach a height of 10-15 cm). Apply 40-50% of the total annual nitrogen rate. Nitrogen is best applied in the form of ammonium sulfate (contains nitrogen and sulfur) or ammonium nitrate. Approximate rate: 20-25 g/m² (Autko et al., 2012).

2. Second fertilizing: 3-4 weeks after the first. Apply the remaining nitrogen (20-25 g/m²) to maintain intensive growth.

3. Foliar feeding: For rapid supply of micronutrients, carry out 1-2 leaf sprays with a complex fertilizer containing micronutrients (e.g., 5-10 g/10 L water) or individual elements (boron, manganese) when deficiency signs appear.

Phase 3: Bulb Formation and Growth (Late Spring – Early Summer)

Goal: Ensure intensive bulb growth, formation of dense and large cloves.

Key elements: Potassium (K), Sulfur (S), Calcium (Ca), and Phosphorus (P) to a lesser extent.

• Potassium — the main element of this phase. It ensures the outflow of carbohydrates from leaves to the bulb, making it large and dense (Brewster, 2008).
• Sulfur — a key element for flavor and aroma formation, as well as for improving storage life.
• Calcium strengthens the covering tissues of the bulb, increasing its resistance to diseases during storage.
• Phosphorus is also important but in smaller amounts. Its main portion has already been applied in autumn.

Practical recommendations:

1. Third fertilizing: When the bulb begins to form (usually in late May – early June, when leaf growth slows). Main focus — potassium. Use potassium sulfate, which is simultaneously a source of potassium and sulfur. Rate: 25-30 g/m². Nitrogen at this stage is not applied or applied in minimal amounts.

2. Fertigation: With drip irrigation, it is very effective to apply potassium with water (monopotassium phosphate or potassium sulfate) for 3-4 weeks during active bulb growth (Brewster, 2008).

Phase 4: Maturation and Preparation for Harvest (Mid – Late Summer)

Goal: Complete bulb formation, strengthen covering scales, and prepare the plant for harvest and storage.

Key elements: Potassium (K) and Calcium (Ca).

• Potassium continues to play an important role in bulb maturation and strengthening its covering tissues.
• Calcium is necessary for forming dense, strong outer scales, which is critical for long-term storage.

Practical recommendations:

1. 3-4 weeks before harvest: Apply potassium (potassium sulfate) at a low dose — 10-15 g/m². This will strengthen the covering scales and improve storage life.

2. Stop fertilizing: 2-3 weeks before the expected harvest, all fertilizing is completely stopped. The plant should “dry off” naturally, and excess nutrition at this time can only harm, delaying maturation and worsening storage quality (Engeland, 1991; Autko et al., 2012).

Summary Table of Fertilizing by Growth Phases

Important note: All the rates given are approximate. Specific doses depend on initial soil fertility, soil type, and region. The best way to determine precise needs is to conduct an agrochemical soil test and follow the recommendations of your regional agronomist.

Why are foliar feeds needed?

1. Rapid correction of deficiencies: If you notice signs of deficiency of any element (e.g., yellowing leaves due to lack of nitrogen or magnesium), foliar feeding is the fastest way to fix the situation. Elements applied to leaves are absorbed within hours, while root feeding can take days or even weeks.

2. Effectiveness on problematic soils: On soils with high pH (alkaline), many micronutrients (iron, zinc, manganese) are in unavailable forms. Foliar feeding with chelated forms bypasses this problem.

3. Support during critical phases: During active leaf growth and at the beginning of bulb formation, when nutrient uptake is maximal, foliar feeds can provide additional “supplementation” without overloading the root system and without the risk of salt burn (Engeland, 1991).

4. Fertilizer economy: With foliar feeding, nutrients are absorbed with very high efficiency (up to 90-95%), while with root application a significant portion may be lost (leached, bound by soil, or unavailable due to competition). This allows using smaller amounts of fertilizer for the same effect.

5. Compatibility with plant protection: Foliar feeds can often be combined with treatments against diseases and pests, saving time and labor.

When to carry out foliar feeding?

Critical periods for foliar feeding of garlic:

1. Early spring (active leaf growth phase): During this period, the plant needs nitrogen, magnesium, and micronutrients. Foliar feeding with nitrogen (urea) and magnesium (magnesium sulfate) can give a powerful growth impulse, especially on poor soils.

2. Before bulb formation begins: 1-2 weeks before bulb initiation (late spring – early summer), you can carry out a foliar feed with potassium, sulfur, and micronutrients. This will prepare the plant for switching to the “bulb” mode.

3. During active bulb growth: During this period, potassium, sulfur, and micronutrients (especially boron) are particularly important. Foliar feeding with potassium sulfate or monopotassium phosphate will help improve bulb quality and size.

4. When deficiency signs appear: If you notice symptoms of any element deficiency (see respective chapters), carry out a targeted foliar feed immediately.

Which elements are best absorbed through leaves?

For foliar feeding of garlic, the following elements are most effective:

• Nitrogen: Urea (carbamide) — the best nitrogen fertilizer for foliar application. It dissolves well and quickly penetrates leaves. A urea solution at 0.5-1% (5-10 g per 1 L of water) is an excellent option for early spring feeding.
• Magnesium: Magnesium sulfate (MgSO₄·7H₂O) — Epsom salt. Use a 1-2% solution (10-20 g per 1 L of water) for spraying when magnesium deficiency is evident.
• Potassium and phosphorus: Monopotassium phosphate (KH₂PO₄) — the ideal fertilizer for foliar feeding during bulb formation. It is highly soluble and provides both potassium and phosphorus in available form. Use a 0.5-1% solution (5-10 g per 1 L of water).
• Sulfur: Potassium sulfate (K₂SO₄) and magnesium sulfate (MgSO₄) are also sources of sulfur. For foliar sulfur feeding, you can use the same fertilizers.
• Micronutrients: Best to use chelated forms of micronutrients (Fe, Zn, Mn, Cu). They are stable in solutions and penetrate leaves well. Use complex chelate fertilizers, following the instructions on the package.

How to properly carry out foliar feeding?

1. Solution concentration: Never exceed recommended concentrations! Too concentrated a solution can cause leaf burn. Typically, solutions of 0.5-1% for macronutrients (N, Mg, K) and 0.05-0.1% for micronutrients (B, Mn, Zn, Fe) are recommended (Engeland, 1991).

2. Temperature and time: Spraying is carried out in the morning (before 10:00) or evening (after 18:00), when the sun is not active. Temperature should be above +10 °C but not above +25 °C. In hot weather and bright sun, the solution can dry quickly, reducing effectiveness and increasing the risk of burn.

3. Solution pH: For better uptake of micronutrients (especially iron), the solution should have a slightly acidic reaction (pH 5.5-6.0). If necessary, acidify it with citric or acetic acid.

4. Wetting agents (surfactants): Adding a small amount of wetting agent (surfactant) to the solution significantly improves droplet distribution on the leaf and penetration into tissue. This increases the effectiveness of feeding (Engeland, 1991).

5. Spraying: Spray plants with a fine mist so that droplets evenly cover the entire leaf surface but do not run off. Pay special attention to the underside of leaves, where stomata are more active.

What not to do?

• Do not replace root feeding with foliar feeding. Foliar feeding is only a supplement, not a replacement for basic root nutrition. It cannot supply the plant with all necessary elements in full (Brewster, 2008).
• Do not spray plants in cloudy or rainy weather. This reduces effectiveness and can lead to fungal diseases.
• Do not apply micronutrients in high concentrations. This can cause toxicity.

Conclusion on foliar feeding: Foliar feeding is a powerful and flexible tool for managing garlic nutrition. Use them purposefully: for quick correction of deficiencies, in critical growth phases, or to improve crop quality. Properly chosen concentration, timing, and spraying method will make this operation effective and safe.

Mistake 1: Ignoring sulfur

This is perhaps the most frequent and critical mistake. Many gardeners focus only on nitrogen, phosphorus, and potassium, forgetting about sulfur. Yet it is sulfur that is responsible for that characteristic “garlic” flavor and aroma, as well as for the storage quality of the bulbs. Without sufficient sulfur, you will get large but tasteless and poorly storing bulbs (Brewster, 2008; Engeland, 1991).

How to avoid: Use sulfur-containing fertilizers, such as ammonium sulfate (for nitrogen feeding) and potassium sulfate (for potassium feeding). Remember that sulfur deficiency symptoms are very similar to nitrogen starvation, but appear on young (upper) leaves, unlike nitrogen.

Mistake 2: Excess nitrogen in the second half of the growing season

Applying nitrogen in large amounts after the bulb begins to form is one of the most harmful mistakes. Nitrogen stimulates leaf growth, not bulb growth. As a result, the plant “fats”: leaves become dark green and succulent, while the bulb forms small, loose, stores poorly, and loses flavor (Autko et al., 2012).

How to avoid: Apply the bulk of nitrogen in spring, during active leaf growth. After the bulb begins to form (usually in late May – early June), nitrogen fertilizing is either completely stopped or minimized.

Mistake 3: Incorrect phosphorus application

Phosphorus is a low-mobility element in the soil. Surface application or application as top dressing during the growing season is ineffective, as it simply does not reach the roots in time (Brewster, 2008). The main mistake is relying on phosphorus top dressing when the basic fertilizer was not applied to the soil.

How to avoid: Apply the main portion of phosphorus (80-100% of the rate) in autumn or early spring under digging, incorporating it into the root zone. For a quick start, use a starter fertilizer at planting, applying it directly to the furrow.

Mistake 4: Ignoring soil pH

On acidic soils (pH < 5.5), many nutrients, including phosphorus, calcium, magnesium, and most micronutrients, become unavailable to plants. Gardeners may apply fertilizers, but the plant simply cannot absorb them (Autko et al., 2012; UMass Extension, 2013).

How to avoid: Regularly check soil pH. If it is below 6.0, carry out liming with dolomite flour 2-3 months before planting garlic. This will not only raise pH but also enrich the soil with calcium and magnesium.

Mistake 5: Lack of potassium during bulb formation

Potassium is the main element for bulb “filling.” If during this period (late spring – early summer) the plant suffers from potassium deficiency, bulbs form small, loose, with thin covering scales. This directly affects yield and storage life (Brewster, 2008).

How to avoid: Supply the plant with potassium during bulb formation. Use potassium sulfate, which is simultaneously a source of potassium and sulfur. Apply it as a root feed or with irrigation water (fertigation).

Mistake 6: Using fresh manure

Fresh manure is a source of nitrogen in ammonium form, which can “burn” the roots of young garlic. In addition, fresh manure contains many weed seeds and can be a carrier of diseases (Engeland, 1991).

How to avoid: Use only well-rotted manure or compost (at least 1-2 years old). Apply them in autumn under digging or a few weeks before planting, so they have time to decompose and become available to plants.

Mistake 7: Neglecting foliar feeding

Many gardeners underestimate the effectiveness of foliar feeding. Yet it is a fast and reliable way to deliver nutrients directly into plant tissues, especially when deficiency signs appear or during critical growth phases (Engeland, 1991).

How to avoid: Use foliar feeding as an additional tool. They are especially effective for micronutrients (boron, manganese, zinc, iron) and for rapid correction of nitrogen or magnesium deficiency. Carry them out in the morning or evening, using a fine mist sprayer.

Mistake 8: Ignoring deficiency signs

Waiting for the plant to “show” its needs and taking action only when obvious symptoms appear is a strategy that leads to yield losses. By the time visible deficiency signs appear, the plant has already lost potential.

How to avoid: Carry out preventive feeding, especially during critical growth phases. Regularly inspect plants to notice changes in leaf color or shape in time. At the first suspicion of deficiency, carry out a targeted feed.

Mistake 9: Unsystematic fertilizer application

Applying fertilizers “by eye” without considering the plant's development phase and soil type is a guessing game. At best, this leads to inefficient fertilizer use; at worst, to nutrient imbalance and reduced yield.

How to avoid: Develop a clear fertilizing plan based on garlic growth phases (see the “Fertilizing by Growth Phases” chapter). Consider your soil type (sandy, clay, loam), as doses and frequency depend on it. For accurate diagnosis, use soil analysis.

We have covered the basic principles of garlic nutrition, the role of each element, the fertilizing strategy by growth phases, and typical mistakes. By applying this knowledge in practice, you can grow large, healthy, and flavorful garlic that will delight you with its taste and store well. Remember that the key to success is a balanced approach, attention to the plant's needs, and timely response to changes in its condition. Good luck and bountiful harvests!