Nutrition (fertilizers and feeding)

The Two-Year Development Cycle and Its Significance for Nutrition

Raspberry is a crop with a unique biology. Its above-ground part develops over a two-year cycle:

• In the first year, replacement shoots (or root suckers) grow from the rhizome. They accumulate nutrients, form buds, but do not bear fruit.
• In the second year, these shoots become fruiting canes. They bloom, produce a crop, and die after fruiting.

This means that the current year's harvest is formed from the nutrient reserves accumulated by the shoots in the previous season. Therefore, caring for the nutrition of young shoots in the second half of summer is the key to next year's harvest (Yaroslavtsev, 2003).

Root System and Feeding Zone

Raspberry roots are shallow — the bulk of active roots is found in the 8–10 cm topsoil layer (Yaroslavtsev, 2003). This means that:

• Fertilizers should be applied to the surface soil layer
• Deep digging damages the roots
• The soil must be loose to allow air access to the roots

At the same time, some roots can penetrate to depths of 1.5–2 m, especially in varieties with powerful root systems, which helps plants tolerate drought.

Comparison with Other Crops

Compared to fruit trees, raspberries:

• Are more demanding in terms of mineral nutrition — they enter fruiting quickly and produce high yields annually, requiring significant nutrient removal (Krivko et al., 2014).
• Are more sensitive to excess nitrogen — unlike apples or pears, where excess nitrogen can be offset by vigorous growth, in raspberries it provokes excessive shoot growth at the expense of wood maturation and reduces winter hardiness.
• Prefer organic fertilizer — mulching with manure, compost, or humus not only feeds the plant but also protects roots from overheating and drying out, and suppresses weed growth.

Key idea: Raspberry nutrition is not a one-time event but a continuous process of managing growth and fruiting through timely application of balanced fertilizers.

Intensive Nutrient Removal

With annual fruiting, raspberries remove significant amounts of nutrients from the soil. Large quantities of nitrogen, phosphorus, potassium, and micronutrients are removed from the plantation with the harvest, spent canes, and leaves (Yaroslavtsev, 2003). For plants to bear fruit normally year after year, these losses must be compensated. However, this must be done carefully, based on soil analysis and plant condition.

2.1. Nitrogen (N)

Role in the plant. Nitrogen is the basis of all proteins, enzymes, and chlorophyll. It determines the growth rate of shoots, leaf surface area, and overall productivity. It is nitrogen that is "responsible" for the vegetative mass that will feed the future harvest.

Signs of deficiency. With nitrogen deficiency, the raspberry looks weakened:

• Leaves become small, pale green or yellow, starting from the old lower ones;
• Shoots are thin, short, and reduced in number;
• Berries become smaller, and yield decreases (Yaroslavtsev, 2003).

Signs of excess. Overfeeding with nitrogen is no less dangerous:

• Plants "fatten" — produce vigorous but loose growth with long internodes;
• Leaves are dark green, large, but watery and easily damaged by diseases;
• Shoots do not mature by autumn, wood remains loose, and winter hardiness drops sharply;
• Berries become watery, less sweet, and store poorly (Krivko et al., 2014).

When and how much to apply. Nitrogen is applied only in spring, at the beginning of shoot regrowth. The recommended rate for raspberries is 30–60 kg/ha of active ingredient, which translates to approximately 3–6 g/m² of pure nitrogen for a garden plot (Kurennoi et al., 1985). Reduce the rate on humus-rich soils; increase on poor sandy soils. Autumn application of nitrogen is strictly contraindicated.

Which fertilizers to use. From mineral sources — urea (46% N), ammonium nitrate (34% N), ammonium sulfate (21% N + sulfur, acidifies soil). From organic — well-rotted manure, compost, poultry manure (but with caution).

2.2. Phosphorus (P)

Role in the plant. Phosphorus is an energy element. It participates in respiration, photosynthesis, cell division, and the formation of flowers and seeds. It is especially important for root system development and shoot maturation.

Signs of deficiency. With phosphorus starvation:

• Shoots grow weakly, become thin and brittle;
• Leaves acquire a purple or bluish-green hue (especially in the middle part of the shoot);
• Old leaves die prematurely;
• Berry set decreases, yield drops (Yaroslavtsev, 2003).

When and how much to apply. Phosphorus is immobile in the soil, so it is applied in advance — in autumn under digging or in spring in furrows to a depth of 10–15 cm. Recommended rate — 40–60 kg/ha P₂O₅, or 4–6 g/m² (Kurennoi et al., 1985). On soils low in phosphorus, increase the rate to 70–80 kg/ha.

Which fertilizers to use. Single superphosphate (18–20% P₂O₅), double superphosphate (up to 46% P₂O₅). For better absorption, mix phosphorus fertilizers with organic matter (manure, compost) and distribute evenly in the root zone.

2.3. Potassium (K)

Role in the plant. Raspberries are among the crops most demanding of potassium. Potassium regulates water balance, increases drought resistance, improves the movement of sugars from leaves to berries, strengthens tissues, and increases frost resistance. It is potassium that makes berries sweet, firm, and shelf-stable.

Signs of deficiency. Potassium deficiency manifests quite clearly:

• Leaf edges become dark brown, "marginal burn" appears;
• Tissues between veins die (necrosis);
• Leaves become smaller, wrinkled;
• Shoots lose turgor, bend toward the ground (Yaroslavtsev, 2003).

When and how much to apply. Potassium is applied in autumn (for shoot maturation) and during berry filling (to improve taste and shelf life). Recommended rates — 40–80 kg/ha K₂O, or 4–8 g/m² (Kurennoi et al., 1985). On light soils, increase the rate to 100–120 kg/ha.

Important caution. Raspberries are very sensitive to chlorine. Do not use potassium chloride or potassium salt — they cause leaf burn. Preferred are potassium sulfate (45–50% K₂O) and potassium magnesium sulfate (contains magnesium). Wood ash also gives a good effect (it contains up to 10% potassium in available form but alkalizes the soil).

2.4. Calcium (Ca) and Magnesium (Mg)

These elements are often underestimated, but they play an important role.

Calcium strengthens cell walls, ensures normal root and shoot growth, and participates in the transport of other elements. Its deficiency manifests as dieback of shoot tips and deterioration of berry quality. Calcium application usually solves the problem of acidic soils — it is enough to apply dolomite lime (which also provides magnesium).

Magnesium — the central atom of the chlorophyll molecule. With its deficiency, old leaves turn yellow from the center to the edges, then brown and fall off. This often occurs on light sandy soils, as well as with excessive potassium application (potassium competes with magnesium for uptake). Use dolomite lime (in autumn under digging), magnesium sulfate, or potassium magnesium sulfate to replenish.

2.5. Micronutrients

Micronutrients are required in small doses (grams per hundred square meters), but their deficiency can nullify all efforts with macronutrient fertilization.

2.6. How to Assess Nutrient Supply

The gardener does not necessarily need to conduct complex laboratory analyses, but it is useful to know the signs of the "golden mean":

• Healthy leaves have an even green color, medium size, characteristic of the variety.
• Shoots reach the typical height for the variety (usually 1.5–2 m), have firm wood and well-developed internodes.
• Yield is stable, berries are large, sweet, with good shelf life.

If in doubt — conduct an agrochemical soil analysis (once every 3–4 years). This will help precisely adjust rates and avoid overfeeding.

Summary of Nutrients

Remember: Excess of even a useful element is more dangerous than a moderate deficiency. This is especially true for nitrogen and boron. It is better to underfeed than to overfeed — plants will tell you what they lack, but excess is much harder to correct.

3.1. Manure and Humus

Manure is a traditional and most complete organic fertilizer. It contains all major macronutrients (nitrogen, phosphorus, potassium) in plant-available form, as well as a full range of micronutrients and organic substances that improve soil structure.

Types of manure and their characteristics.

• Cattle manure — the most common. Contains on average 0.5% N, 0.2% P₂O₅, and 0.6% K₂O (Funt et al., 2013). Moderately nutritious, structures the soil well.
• Horse manure — richer in nitrogen and phosphorus, decomposes faster, produces more heat during decomposition. Considered the best for mulching and biological heating.
• Sheep and goat manure — more concentrated than cattle manure, requires careful dosing (Kurennoi et al., 1985).
• Pig manure — contains little calcium, often acidic, with high ammonia nitrogen content. Rarely used for raspberries and only in rotted form.
• Poultry manure — the most concentrated (up to 1–1.5% N, 0.8–1.2% P₂O₅, 0.4–0.6% K₂O). Requires mandatory dilution with water or composting, otherwise causes root burn.

Degree of readiness. Fresh manure contains many weed seeds, pathogens, and ammonia that can burn roots. For raspberries, use mainly semi-rotted (aged 3–6 months) or well-rotted manure (humus) — a uniform dark crumbly mass with a humus content of up to 15–20% (Krivko et al., 2014). Humus can be applied safely even to planting holes.

Rates and methods of application.

• Under digging (autumn or spring). Apply 10–12 kg/m² (approximately 1 bucket per 1 m²) once every 3–4 years. On poor soils, increase the rate to 15 kg/m².
• As mulch. A layer of semi-rotted manure 5–10 cm thick is spread around the bushes in spring (after loosening) or autumn. Decomposing, it gradually feeds the plants during the season (Yaroslavtsev, 2003).
• In planting holes. When planting, add 8–10 kg of humus to each hole, thoroughly mixing with soil.

Precautions. Do not apply manure annually in large doses. Excess organic matter, especially on rich soils, provokes "fattening" — vigorous growth at the expense of fruiting and reduced winter hardiness (Kurennoi et al., 1985). The optimal frequency is once every 2–3 years, in combination with mineral supplements.

3.2. Compost

Compost is an organic fertilizer obtained through the aerobic decomposition of plant and animal residues. Its nutritional value is close to humus, but it is safer regarding weed seeds and diseases.

What can be composted.

• Grass, leaves, vegetable plant residues
• Mown green manures (clover, lupine, vetch)
• Vegetable peelings, eggshells
• Manure, poultry manure (mixed with plant materials)
• Straw, sawdust (in small quantities)

What to avoid. Diseased plants, rhizomes of couch grass, sow thistle and other noxious weeds, meat and fatty waste — they attract rodents and pathogens.

Methods of applying compost.

• In autumn under digging — 8–10 kg/m².
• In spring as mulch — a layer of 5–7 cm.
• In planting holes — 5–8 kg per plant.

Compost not only feeds raspberries but also improves the moisture-holding capacity of light sandy soils and drains heavy clay soils. On acidic soils, compost with added dolomite lime helps regulate pH.

3.3. Green Manures (Cover Crops)

Green manuring — growing plants followed by incorporation of their green mass into the soil. This technique is especially valuable for raspberries as it allows improving the soil without importing large volumes of organic matter.

Best green manures for raspberries.

Technology. Sow green manures in the row middles after harvest (August–September) or early spring. 1–2 months before planting raspberries (or before the start of active shoot growth), mow the green mass, chop it, and incorporate it into the soil to a depth of 10–15 cm. In the south, with sufficient moisture, green manures can be sown in summer in the row middles and incorporated in autumn (Kurennoi et al., 1985).

Important. Green manures with high fiber content (oats, rye) should be chopped and slightly wilted before incorporation to speed up decomposition. For better effect, they can be watered with nitrogen or organic solutions.

3.4. Mulching with Organic Materials

Mulching is not only a way to conserve moisture and suppress weeds but also a continuous source of nutrition for raspberries. Decomposing, organic mulch gradually releases nitrogen, potassium, phosphorus, and micronutrients into the soil (Yaroslavtsev, 2003).

Which materials to use.

• Well-rotted manure or compost — the best option, both feeds and improves structure.
• Straw (oat, wheat, rye). Layer 10–15 cm. It consumes nitrogen during decomposition, so additional nitrogen fertilizers are desirable (8–10 g/m² urea).
• Sawdust and wood chips. Require mandatory composting or nitrogen application (approximately 15–20 g urea per 1 kg sawdust). Fresh sawdust acidifies the soil, which is useful on carbonate soils but harmful on acidic ones.
• Mown grass, leaves. Decompose quickly, provide much nitrogen. Use only dry (or dried) to avoid rotting.
• Pine needles, bark. Suitable for acidic soils (blueberries, cranberries), for raspberries — only in mixture with compost and lime.

Mulching rules.

• Mulch layer — at least 5–8 cm, to effectively suppress weeds and retain moisture.
• Renew mulch annually, adding a new layer on top of the old one.
• When mulching with manure or compost, additional mineral fertilizer application can be reduced by 30–50%.

Special technique. In some regions (Non-Black Earth region, Siberia), mulching with black film or non-woven material is practiced. This accelerates soil warming, suppresses weeds and suckers, but does not provide organic nutrition. Combine: on top of the film — a layer of organic mulch, or use film only in row middles and organic matter in the rows.

3.5. Organic Liquid Feeds (Infusions)

Root and foliar feedings with organic infusions are a quick way to replenish nutrient deficiencies in critical periods.

Cattle manure infusion. Fresh cattle manure is filled with water in a ratio of 1:3, infused for 3–5 days, stirring periodically. Before use, dilute with water 1:5–1:10 (depending on plant age) and water at the root (1–2 L per bush). Apply in spring, during active shoot growth.

Poultry manure infusion. Dilute 1:20–1:30, infuse for 3–5 days. Water strictly at the root, avoiding contact with leaves. Use only in the first half of the growing season.

Herbal infusion (green fertilizer). A 100–200 L barrel is filled with mown grass (nettle, dandelion, comfrey, ground elder) to 1/2–2/3, filled with water, covered, and infused for 10–15 days until fermentation stops. The ready infusion is diluted with water 1:10 and watered over raspberries 2–3 times per season — in spring and early summer (Krivko et al., 2014). Such an infusion is rich in nitrogen, potassium, and micronutrients.

3.6. Soil Fatigue and Crop Rotation

Organic fertilizers help combat the so-called "soil fatigue" — a phenomenon where pathogens, pests, and toxic root decomposition products accumulate in one place. In intensive fruit growing, it is recommended not to return raspberries to the same place earlier than after 3–4 years, and ideally — after 6–8 years (Kurennoi et al., 1985).

Organic matter, especially compost and green manures, helps renew soil microflora and reduce the negative effects of soil fatigue. However, this does not eliminate the need for periodic plantation relocation.

3.7. Comparative Characteristics of Organic Fertilizers

Summary

Organic fertilizers for raspberries are not a luxury but a necessity. They:

• supply nutrients in available, gradually released form;
• improve soil structure, moisture capacity, and aeration;
• support beneficial microflora;
• promote humus accumulation and combat soil fatigue.

The optimal system for raspberries includes:

• Annual mulching with humus or compost in a 5–8 cm layer.
• Periodic (once every 2–3 years) application of well-rotted manure under digging (10–12 kg/m²).
• Growing green manures in row middles to enrich the soil with organic matter and suppress weeds.
• Liquid organic feedings in critical periods (start of growth, budding).

It is important to remember: fresh, unrotted organic fertilizers (especially poultry and pig manure) can burn roots and introduce infection. Always use only rotted or diluted forms.

4.1. Nitrogen Fertilizers

Nitrogen fertilizers are the most "risky" for raspberries but also the most necessary in spring.

Main types of nitrogen fertilizers and their characteristics.

How to choose. On neutral and slightly acidic soils (pH 5.5–6.5), all forms are equivalent — choose the most economical (usually urea, as the most concentrated). On acidic soils, use calcium nitrate (does not acidify), on alkaline — ammonium sulfate (provides sulfur and lowers pH).

Rates. For raspberries, 30–60 kg/ha of active nitrogen is recommended, or approximately 3–6 g/m² (Kurennoi et al., 1985). For example: urea (46% N) will need 6.5–13 g/m². On poor sandy soils, increase the rate to 8–9 g/m²; on humus-rich soils, reduce to 2–3 g/m².

How to apply. Nitrogen fertilizers are evenly spread over the soil surface in rows and row middles in early spring, incorporated to a depth of 5–8 cm (no deeper, to avoid damaging roots). When mulching with organic matter, the nitrogen rate can be reduced by 30–40%.

Important. Nitrogen fertilizers are not applied after mid-July. Late application delays shoot maturation and reduces winter hardiness. For raspberries, this is critical — poorly matured shoots freeze even at slight frosts.

4.2. Phosphorus Fertilizers

Phosphorus is immobile in the soil, so it is applied in reserve, in advance, into the root zone.

Main types.

Rates. For raspberries — 40–60 kg/ha P₂O₅, or 4–6 g/m² (Kurennoi et al., 1985). On soils low in phosphorus, increase the rate to 70–80 kg/ha. In home gardens, it is more convenient to use complex fertilizers where phosphorus is already balanced with nitrogen and potassium.

How to apply. Phosphorus is applied in autumn under deep digging (or in furrows to a depth of 10–15 cm) or in spring locally — in rows or holes, always mixing with soil. Phosphorus does not leach, so it can be applied once every 2–3 years at an increased rate.

Compatibility. Superphosphate should not be mixed with lime, ash, and other alkaline materials — phosphorus becomes unavailable. Mix with organic fertilizers only immediately before application.

4.3. Potassium Fertilizers

Potassium is a key element for berry quality and winter hardiness in raspberries. It is important to choose a chlorine-free form.

Main types.

Rates. For raspberries — 40–80 kg/ha K₂O, or 4–8 g/m² (Kurennoi et al., 1985). On light sandy soils, increase the rate to 100–120 kg/ha, as potassium leaches.

How to apply. Potassium fertilizers are applied in autumn (for accumulation in tissues and increased winter hardiness) and during berry formation (to improve taste and shelf life). In spring, potassium is applied only as part of complex fertilizers or with obvious deficiency on light soils.

Alternative — ash. Wood ash contains up to 10% potassium (as potash) and is rich in micronutrients. It can be applied under digging (200–300 g/m²) or as a solution (1 glass per 10 L water). However, ash alkalizes the soil, so use with caution on alkaline soils.

4.4. Complex (Compound) Fertilizers

Complex fertilizers contain two or three macronutrients in one granule. They are convenient for precise dosing and save time.

Main types.

How to choose the ratio.

• In spring (start of growth). Nitrogen is needed — nitrophoska, nitroammophoska (16–16–16) or urea + superphosphate will work.
• During flowering and fruit set. Formulas with increased phosphorus (10–20–20, 13–40–13) are preferred for good pollination and fruit set.
• During berry filling. Potassium and phosphorus are important, nitrogen is excluded — potassium monophosphate or diammophoska will work.
• In autumn. Only phosphorus-potassium (0–20–30, 0–25–25), without nitrogen.

Rates of complex fertilizers. For an adult raspberry bush (4–6 canes), 30–40 g of nitroammophoska in spring and 20–25 g of potassium monophosphate during berry filling are recommended. Check exact rates on the package, based on the percentage of active ingredient.

4.5. Microfertilizers

Micronutrients in mineral form can be applied both to the soil (boron superphosphate, manganese sludge) and foliarly. Foliar micronutrient feedings are more effective, as micronutrients are quickly fixed in the soil and become unavailable (Krivko et al., 2014).

Practical recommendations for application.

Important rule: do not mix micronutrients with alkaline solutions (ash, lime) — they precipitate. Use a separate container and check compatibility on a small volume.

4.6. Mixing Mineral Fertilizers

Not all mineral fertilizers can be mixed with each other and with organic matter. Violation of compatibility leads to nitrogen losses (ammonia), precipitation of phosphorus or potassium, and reduced efficiency.

Basic rules.

• Do not mix superphosphate with lime, ash, chalk, dolomite lime — phosphorus becomes unavailable.
• Do not mix urea with single superphosphate (if humidity is high) — possible nitrogen losses. Better to apply them separately.
• Do not mix ammonium nitrate with potassium sulfate (during long storage) — possible caking and reduced flowability.
• Allowed to mix ammonium sulfate with superphosphate, urea with potassium salt (if chlorine-free) — provided the mixture is used immediately.
• Organic matter and mineral fertilizers are mixed only immediately before application, not stored in mixture (Kurennoi et al., 1985).

Practical advice. For raspberry feedings, it is more convenient to use ready-made complex fertilizers from the factory — they already account for component compatibility and optimal ratios.

4.7. Calculation of Mineral Fertilizer Rates

To avoid dosage errors, use the formula:

Required amount of fertilizer (g/m²) = (Recommended element rate (g/m²) × 100) / Element content in fertilizer (%)

Example. It is recommended to apply 6 g/m² of nitrogen. Use urea (46% N).

Calculation: (6 × 100) / 46 = 13 g/m² of urea.

For complex fertilizers, similarly: if 6 g of nitrogen from nitrophoska (16% N) is needed — (6 × 100)/16 = 37.5 g/m².

4.8. Application Features in Different Regions

• In regions with frequent rains and leaching regime (Non-Black Earth, Northwest). Nitrogen leaches easily, so split application is recommended: half the rate in spring, the second half after 3–4 weeks, and on sandy soils — also in early June (Funt et al., 2013). Potassium also leaches, so it is applied annually.
• In arid regions (south, steppe zone). Nitrogen can be applied all at once in spring, as there is little rain and losses are minimal. Potassium and phosphorus — in autumn, under deep digging, so they end up in the moist soil layer.
• On carbonate (alkaline) soils. Phosphorus and micronutrients (iron, zinc, manganese) are poorly absorbed. Use acidifying fertilizers (ammonium sulfate, potassium sulfate), apply organic matter (acidifies the rhizosphere), and use chelated forms of micronutrients (Kurennoi et al., 1985).

Summary of Mineral Fertilizers

• Nitrogen — only in spring, moderately, preferably in complex forms.
• Phosphorus — from autumn, into the root zone, on acidic soils — with organic matter.
• Potassium — chlorine-free, in autumn and during berry filling.
• Complex — convenient for precise dosing and saving time.
• Micronutrients — apply foliarly when deficiency signs appear or on poor soils.
• Mixing — check compatibility, do not store mixtures for long.

The main rule: mineral fertilizers are a "surgical instrument" in raspberry nutrition. Use them purposefully, as needed, not out of habit. Organic fertilizers remain the base, and mineral fertilizers are the fine-tuning.

5.1. Principles of Seasonal Feedings

Before moving to the calendar, remember a few basic rules.

1. Base — base fertilizer, feedings — supplement. The main dose of phosphorus, potassium, and organic matter is applied in autumn or during soil preparation. Feedings during the season are "quick help" that corrects nutrition at critical moments (Kurennoi et al., 1985).

2. Nitrogen — only in spring. This rule is critical for raspberries. Nitrogen feedings are permissible only before flowering begins, at most — until mid-June. Anything applied later provokes late growth, impairs shoot maturation, and sharply reduces winter hardiness.

3. Potassium and phosphorus — throughout the season. They do not cause uncontrolled growth but improve berry quality and winter preparation. Potassium is especially important in the second half of summer.

4. Focus on plant condition, not the calendar. Frosts, drought, excessive rainfall shift development timing. Observe phases: start of shoot growth, budding, flowering, berry filling.

5. Better to underfeed than to overfeed. Excess fertilizers (especially nitrogen) is difficult to correct, and the consequences (reduced winter hardiness, deterioration of berry quality, diseases) affect more than one year.

5.2. Feedings by Development Phases

5.3. Features of Feeding Remontant Raspberries

Remontant varieties (Babie Leto, Sentyabrskaya, Poklonnik, Heritage, Augustina, Abrikosovaya, etc.) have a fundamentally different development rhythm than regular raspberries:

• They bloom and bear fruit on current-year shoots (in autumn).
• Their vegetation is continuous: shoot growth, flowering, and berry ripening occur in parallel.
• The crop is harvested on one-year-old wood, which is cut completely in autumn.

How this affects feedings.

Practical recommendations for remontant varieties.

1. In spring give a complete complex fertilizer (e.g., nitrophoska 30–40 g/m²) for a strong start.

2. From June to August feed raspberries with potassium-phosphorus fertilizers every 10–14 days — this supports continuous flowering and fruiting. Use potassium monophosphate or complex fertilizers with low nitrogen content (e.g., 10–20–20).

3. Do not forget about micronutrients. Foliar feedings with boron and zinc in the budding and flowering phases are especially important for remontant varieties, where fruit set occurs in a more compressed time frame.

4. After fruiting ends (late autumn, after frosts) cut all canes to the ground. Apply phosphorus-potassium fertilizers and organic matter — this will lay the foundation for the growth of next year's shoots.

Important. Remontant varieties consume more nutrients during the season than regular ones because they grow and bear fruit simultaneously. Therefore, the number of feedings is 1.5–2 times higher, and rates can be increased by 20–30% (Yaroslavtsev, 2003).

5.4. How to Properly Conduct Feedings: Practical Tips

For root feedings (dry form).

• Evenly distribute the fertilizer over the soil surface in the rows.
• Incorporate it to a depth of 5–8 cm using a hoe or cultivator.
• After application, be sure to water the raspberries (if no rain) — this will accelerate dissolution and nutrient uptake by roots.

For root feedings (liquid form).

• Water the raspberries with clean water 1–2 hours before application to moisten the soil and avoid root burn.
• Pour the fertilizer solution into grooves along the row (20–30 cm from the stems), then cover with soil.
• Liquid dose — approximately 5–10 L per 1 m² of row (depending on plant age).

For foliar (leaf) feedings.

• Spray in cloudy weather, in the morning or evening, to avoid sunburn.
• Treat the underside of leaves — it absorbs nutrients better.
• Make fresh solutions, do not store leftovers (Krivko et al., 2014).

5.5. Cheat Sheet Table for Seasonal Feedings

Summary

Seasonal feedings of raspberries are a system built on understanding the biology of the crop. Key points:

• Spring — nitrogen for growth, but moderately.
• Flowering and fruit set — phosphorus and potassium, without nitrogen.
• Berry filling — potassium for taste and shelf life.
• Autumn — phosphorus, potassium, organic matter, without nitrogen.

Remontant varieties require more frequent feedings (every 2 weeks) and balanced nutrition throughout the season.

And most importantly: feedings are a supplement to the base fertilizer (organic matter), not its replacement. Without regular organic matter application, even the most precise feedings will not produce stable yields.

6.1. Why Foliar Feedings Are Needed

This technique has several key advantages.

1. Speed. Foliar feeding acts 5–10 times faster than root feeding. This is critical during periods when the plant is experiencing acute deficiency of an element (e.g., chlorosis, weak fruit set) (Krivko et al., 2014).

2. Micronutrients — "addressed". Many micronutrients (iron, zinc, copper, manganese, boron) when applied to soil quickly bind, especially on carbonate or heavy soils, and become unavailable. When sprayed, they go directly into plant tissues, bypassing soil barriers.

3. In stressful situations. During drought, waterlogging, root damage (e.g., from too deep loosening), root nutrition is impaired. Foliar feedings help "support" the plant during this period.

4. Fertilizer economy. In foliar feeding, micronutrient doses are 5–10 times lower than with soil application, and the effect is comparable or even higher (Kurennoi et al., 1985).

5. Possibility of combining with protection. Foliar feedings can be done together with treatments against diseases and pests (provided the preparations are compatible), saving time and labor.

Limitations. Foliar feedings do not replace root feedings and do not solve the problem of long-term macronutrient deficiency (nitrogen, phosphorus, potassium) in the soil. They are an additional, not the main feeding method. In addition, they do not affect the root system and do not improve the soil.

6.2. When to Conduct Foliar Feedings

For raspberries, there are several key periods when foliar nutrition is especially effective.

For remontant varieties foliar feedings are relevant throughout the growing season, as shoot growth and fruiting occur in parallel. Feedings in the budding phase and at the start of fruiting are especially important to maintain continuous flowering.

6.3. Concentrations of Working Solutions

For raspberries, concentrations must be strictly observed. Exceeding the dose causes leaf burn, while too low a dose results in no effect.

Important. For urea, 1% concentration (100 g per 10 L) is already on the verge of burn for young leaves. For adult plants it is acceptable, but start with 0.5% (50 g per 10 L). Do not use potassium sulfate above 1% — burn is inevitable. For zinc sulfate, the mandatory rule: add 0.15% slaked lime (15 g per 10 L) to neutralize acidity and prevent burns (Kurennoi et al., 1985).

6.4. How to Properly Conduct Foliar Feedings

Rule 1. Time of day. Spray in cloudy weather or in the morning (before 9–10 AM) / evening (after 5–6 PM). In hot sunny weather, solution droplets act like lenses, causing leaf burns. Also, the solution dries quickly, and elements do not have time to be absorbed.

Rule 2. Leaf side. Treat the underside of leaves. Stomata on the underside are more active and absorb nutrients better. In addition, evaporation is lower there, and the solution stays on the surface longer.

Rule 3. Fine spraying. Use fine atomization (mist), not large drops. The finer the drops, the faster absorption and the lower the risk of burns. A hand sprayer should produce a fine "dew".

Rule 4. Liquid consumption. For raspberries, the working solution consumption is approximately 100–150 L per 100 m² (1–1.5 L per 1 m² of row) or until leaves are thoroughly wetted but without dripping. No more is needed.

Rule 5. Repetition. Usually 2–3 foliar feedings per season are sufficient — in critical phases. If necessary (micronutrient deficiency, chlorosis), repeat at intervals of 10–14 days, but not more often.

Rule 6. Compatibility. Foliar feedings are often combined with pesticide treatments, but always check the compatibility of specific preparations. Do not mix:

• Boric acid with calcium-containing preparations (insoluble precipitate forms).
• Micronutrients with alkaline solutions (ash, lime, Bordeaux mixture) — precipitate.
• Urea with chlorine-containing substances.

Always check compatibility on a small volume (e.g., 0.5 L) and see if precipitate forms or the solution color changes.

6.5. Features of Different Preparations for Foliar Feedings

Urea. Ideal for quick nitrogen nutrition in spring. When sprayed on leaves, urea is absorbed within 1–2 hours. Concentration 0.5–1% is safe for adult plants, but for young ones — 0.5% (50 g per 10 L). In the flowering phase, urea is not used.

Boric acid. A classic agent for improving pollination and fruit set. Dissolves in hot water (pre-dissolve in 1 L hot water, then top up to 10 L). Apply in the budding phase and at the start of flowering. Boron also improves sugar transport, increasing berry sweetness.

Potassium monophosphate. The best feeding for the berry filling period. Provides potassium and phosphorus without nitrogen. Improves taste, firmness, and berry color. Apply 1–2 times with an interval of 10–14 days.

Chelated micronutrients (iron, zinc, manganese, copper). These are micronutrients in an organic "wrapper" that do not bind in the soil and easily penetrate through the leaf. Use for chlorosis, rosetting, and other deficiencies. Work faster than sulfate forms.

Sulfate forms (zinc sulfate, manganese sulfate). Cheaper than chelates but more aggressive. Require the addition of lime (for zinc) to prevent burns. Better to use before or after flowering, not during (Krivko et al., 2014).

6.6. Deficiency Signs "Treated" by Foliar Feedings

Foliar feedings are an ideal way to quickly correct visible nutritional disorders.

6.7. Approximate Calendar of Foliar Feedings for Raspberries

For remontant varieties this calendar can be extended until September, repeating potassium-phosphorus feedings every 10–14 days to maintain continuous fruiting.

Summary

Foliar feedings are:

• A quick way to deliver nutrients to plant tissues.
• Indispensable for micronutrients (boron, iron, zinc, manganese, copper).
• Effective in stressful conditions (drought, waterlogging, root damage).
• Do not replace root feedings but only complement them.

Main rules:

• Do not exceed the concentrations indicated in the table.
• Spray only in the morning or evening, in cloudy weather.
• Treat the underside of leaves.
• Observe compatibility of preparations.
• No more than 2–3 treatments per season (except remontant — up to 5–6).

With proper use, foliar feedings allow you to significantly increase yields, improve berry quality, and promptly correct deficiencies without waiting for the root system to "fix" the situation.

7.1. Mistake #1: Overfeeding with Nitrogen

What the mistake is. Applying nitrogen fertilizers in too high doses, late application (after mid-summer), or using nitrogen feedings "just in case."

What happens to the plant.

• Shoots grow excessively vigorous but loose ("fattening") with long internodes.
• Leaves become dark green, large, but "watery" and easily affected by diseases.
• Shoots do not mature by autumn — wood remains succulent, does not lignify.
• Winter hardiness drops sharply. Even slight frosts can damage shoots.
• Berries become watery, less sweet, and store poorly.
• Flowering and fruit set may be delayed or weak (Krivko et al., 2014; Yaroslavtsev, 2003).

How to avoid.

1. Apply nitrogen only in spring, at the very beginning of the growing season. The optimal time is from soil thawing to the start of active shoot growth (usually April — early May).

2. Strictly adhere to dosage: 3–6 g/m² of pure nitrogen (this is 10–15 g of urea or 8–12 g of ammonium nitrate per 1 m²). On fertile soils — use the minimum dose.

3. Do not apply nitrogen after flowering. If you missed the spring timing, it is better to skip the nitrogen feeding altogether — it will be safer.

4. On soils rich in organic matter (where humus or compost is regularly applied), the nitrogen rate can be reduced by 30–50% — organic matter itself gradually releases nitrogen.

5. When mulching with fresh sawdust, straw, or wood chips, on the contrary, nitrogen fertilizers are mandatory (8–10 g urea per 1 m²), as microorganisms decomposing coarse organic matter bind soil nitrogen, and plants may experience its deficiency (Yaroslavtsev, 2003).

Golden rule: It is better to leave the raspberry slightly hungry for nitrogen than to overfeed. Excess nitrogen in raspberries is practically impossible to correct in the current season, and its consequences (winter kill) will only show in winter.

7.2. Mistake #2: Using Chlorine-Containing Potassium Fertilizers

What the mistake is. Applying potassium chloride, potassium salt, or other chlorine-containing fertilizers to raspberries.

What happens to the plant. Chlorine is toxic to raspberries. It causes:

• marginal leaf burn (darkening and drying of edges);
• interveinal necrosis (tissue death between veins);
• reduced photosynthesis;
• deterioration of taste and shelf life of berries (Yaroslavtsev, 2003).

How to avoid.

• Use only chlorine-free potassium fertilizers:
• potassium sulfate (45–50% K₂O),
• potassium magnesium sulfate (30% K₂O + 10% MgO),
• wood ash (contains up to 10% potassium, chlorine-free, though alkalizes the soil).
• Look for "chlorine-free" or "sulfate" on the package.
• If you are forced to use potassium chloride (e.g., you have it on hand), apply it only in autumn so that chlorine has time to leach from the root zone over winter. However, the risk remains, and for raspberries it is not recommended (Kurennoi et al., 1985).

7.3. Mistake #3: Ignoring Soil Analysis

What the mistake is. Fertilizers are applied "by eye," without knowing the initial content of elements in the soil.

What it threatens. You can apply phosphorus and potassium for years on soils where they are already abundant, or underestimate micronutrient deficiencies. As a result — fertilizer waste, environmental pollution, deterioration of berry quality, and sometimes toxicity to plants (Funt et al., 2013).

How to avoid.

• Once every 3–4 years, conduct an agrochemical soil analysis. In a home garden, it is enough to submit a sample to the nearest agrochemical laboratory (it is inexpensive but saves years of mistakes).
• Focus on indicators: for raspberries, the optimal pH is 5.5–6.5, phosphorus content (P₂O₅) — 10–15 mg/100 g, potassium (K₂O) — 15–25 mg/100 g (for average soils). Micronutrients are assessed according to specific laboratory recommendations.
• Based on the analysis results, adjust fertilizer rates: if potassium content is high, reduce the rate; if low, increase it (Yaroslavtsev, 2003).

Important. Soil analysis will also help determine the need for liming. On acidic soils (pH < 5.5), the effectiveness of phosphorus fertilizers decreases, and molybdenum and calcium become less available.

7.4. Mistake #4: Incorrect Timing of Application

What the mistake is.

• Nitrogen is applied in summer or autumn.
• Phosphorus is applied superficially, without incorporation into the root zone.
• Potassium is applied only in spring, not during berry filling or autumn.

How to avoid. Strictly adhere to the seasonal calendar (see Chapter 5). Basic principles:

• Nitrogen — only early spring, before active growth begins.
• Phosphorus — in autumn (under digging) or spring (in furrows, to a depth of 10–15 cm). Phosphorus is immobile, so it needs to be incorporated into the root zone.
• Potassium — in autumn (for shoot maturation) and during berry filling (for fruit quality). In spring, potassium can be applied only on poor soils or as part of complex fertilizers.
• Organic matter — in autumn or spring. Fresh organic matter is best applied in autumn so that it decomposes by spring.

7.5. Mistake #5: Deep Fertilizer Incorporation and Root Damage

What the mistake is. Deep digging (deeper than 10–15 cm) or fertilizer incorporation to a great depth damages the shallow root system of raspberries. The bulk of active roots is in the 8–10 cm layer (Yaroslavtsev, 2003).

Consequences. Damaged roots absorb water and nutrients less efficiently, yield decreases, and the plant becomes more susceptible to drought and diseases. Root recovery takes several weeks, which is critical during active growth.

How to avoid.

• Incorporate fertilizers to a depth of 5–8 cm — simple loosening with a rake or flat cutter is sufficient.
• Avoid deep digging in the rows. In row middles (where there are fewer roots), digging to a depth of 10–12 cm is permissible, but it is better to limit to surface loosening.
• Mulching is an ideal way to apply organic matter without damaging roots. Organic mulch decomposes at the surface and gradually feeds the roots.
• For applying mineral fertilizers, you can use furrows along the row to a depth of 5–8 cm, at a distance of 20–30 cm from the stems.

7.6. Mistake #6: Mixing Incompatible Fertilizers

What the mistake is. Gardeners often mix all fertilizers in one container or apply simultaneously those that react with each other, forming insoluble precipitates or losing nutrients (Kurennoi et al., 1985).

Main forbidden combinations.

• Superphosphate + lime, ash, dolomite, chalk. Phosphorus becomes poorly soluble (calcium phosphate), unavailable.
• Urea + single superphosphate (if wet) — possible nitrogen losses as ammonia. Better to apply separately with an interval of several days.
• Ammonium nitrate + potassium sulfate (during long storage) — caking and loss of flowability.
• Micronutrients (boron, zinc, iron) + alkaline fertilizers (lime, ash) — precipitate.

How to avoid.

• Use ready-made complex fertilizers from the factory — they already account for component compatibility.
• If mixing yourself, first check compatibility on a small volume (0.5–1 L). If precipitate forms or the solution becomes cloudy — do not use the mixture.
• Mix organic and mineral fertilizers only immediately before application, do not store mixed.
• For foliar feedings, prepare micronutrient solutions separately and check their compatibility with pesticides.

Practical advice. If in doubt about compatibility, apply fertilizers separately, with an interval of 1–2 weeks — it is safer.

7.7. Mistake #7: Excess of Micronutrients (Especially Boron)

What the mistake is. Gardeners, having heard about the benefits of boron for fruit set, apply it "with a reserve," sometimes repeatedly, exceeding concentrations.

What it threatens. Boron is a micronutrient with a very narrow "window" between normal and toxic levels. With overdose:

• characteristic marginal leaf burn appears (like potassium deficiency but without necrosis);
• leaves may turn yellow-brown and fall off;
• growth slows, internodes shorten;
• berries may be deformed, with hard inclusions;
• with severe overdose, roots die, and the plant dies.

How to avoid.

• In soil, boron is applied only on poor soils (sandy, podzolic) or with confirmed deficiency by leaf analysis. Dose — 0.5–1 g of boron per 1 m² (this is 5–10 g of borax per 10 m²).
• In foliar feedings, strictly observe the concentration: 0.1–0.2% (10–20 g boric acid per 10 L water). No more!
• Apply boron feeding no more than 1–2 times per season: in the budding phase and (if necessary) immediately after flowering.
• If you have already applied boron to the soil, foliar feeding is not needed — excess boron stays in the soil for years.

Remember: It is better to underapply boron once than to overapply once.

7.8. Mistake #8: Uneven Fertilizer Application

What the mistake is. Fertilizers are scattered in "handfuls" near individual bushes or unevenly along the row. As a result, some plants receive excess, others — nutrient deficiency.

Consequences. Uneven growth and fruiting: some plants "fatten," others starve. Yield decreases, berries are of different sizes.

How to avoid.

• For uniform application, use spreaders (for large areas) or measuring containers (for small areas).
• Divide the row into meters and apply the calculated dose for each meter.
• When applying liquid fertilizers — mix the solution well and water evenly.
• Use band application — in furrows along the row, which provides uniform distribution along the length.

7.9. Mistake #9: Ignoring Plant Condition

What the mistake is. Fertilizers are applied strictly by the calendar, not paying attention to plant appearance, weather, and soil moisture.

Consequences. In dry weather, fertilizers are not absorbed and can accumulate in the soil, causing root burn at the first watering. In rainy weather — leach to lower horizons, becoming unavailable.

How to avoid.

• Apply fertilizers only to moist soil (after rain or watering). In dry weather, first water, then apply fertilizers, then water again.
• If plants look depressed (yellowing, chlorosis, weak growth) — first find the cause, only then apply fertilizers. Perhaps the problem is not nutrition but diseases, pests, or waterlogging.
• Watch for signs of deficiency and excess (see Chapters 2 and 6). Adjust feedings based on the condition of the raspberries.

7.10. Summary: Safe Raspberry Fertilization Checklist

Before picking up fertilizers, check yourself against this list:

If you answered "yes" to all questions — your raspberry fertilization system is safe and effective. If in doubt — review rates and timing.

Conclusion

Avoiding mistakes in raspberry fertilization is not difficult if you remember two main principles:

1. Moderation. Raspberries do not like excess, especially of nitrogen and boron. It is better to underfeed than to overfeed — the consequences of excess are much harder to correct.

2. Observation. Plants themselves indicate what they lack or have in excess. Careful observation of leaves, shoots, and berries is the best "laboratory analysis" for the gardener.

Follow the recommendations in this chapter, and your raspberries will reward you with stable yields of large, sweet, and healthy berries without the risk of overfeeding and associated problems.