Watering Eggplants

1.1. Water as Building Material and Transport System

First of all, water is the main component of all plant tissues. Water makes up 80–90 % of the mass of young, actively growing organs of the eggplant (Rubatzky & Yamaguchi, 1997). It provides turgor (rigidity) to cells, thanks to which leaves and stems keep their shape and can efficiently capture sunlight for photosynthesis.

Moreover, water acts as a universal solvent and transport medium. With the flow of water (transpiration), mineral substances dissolved in the soil rise from the roots to all above‑ground parts – leaves, flowers and fruits (Autko et al., 2012). Without sufficient water, this vital process stops, and the plant begins to starve even when all necessary fertilisers are present in the soil.

1.2. The Role of Water in Thermoregulation

Evaporating from the leaf surface, water protects the plant from overheating. This process, called transpiration, helps maintain an optimal tissue temperature even on hot days. For the eggplant, which is very sensitive to extreme temperatures, this function is critical. Overheating can lead to pollen sterility and the dropping of flowers and ovaries (Rubatzky & Yamaguchi, 1997).

1.3. Root System and Sensitivity to Moisture

The eggplant has a taproot system that is branched but has poor regenerative capacity (Autko et al., 2012). This means that after transplanting or root damage, the plant recovers slowly, making it especially vulnerable in the first weeks after seedling planting. Most of the absorbing roots are concentrated in the topsoil, so the eggplant demands not only good soil moisture but also good soil aeration.

1.4. Effect of Water Stress on Yield

Disruption of the water balance negatively affects the future harvest in the most severe way.

• Lack of moisture (drought): When water is scarce, plant growth slows down, leaves lose turgor and droop. This reduces the photosynthetic area and decreases the amount of nutrients sent to the fruits. Critical periods are flowering and fruit set. At these times, moisture deficiency can cause mass shedding of flowers and young ovaries, directly reducing yield (Swiader, 1992). Drying of the soil also makes the fruit skin rough and the flesh bitter.
• Excess moisture (waterlogging): The eggplant reacts extremely negatively to stagnant water around the roots (Swiader, 1992). Flooding the soil displaces the air needed for root respiration. Under such conditions, roots suffocate and die, disrupting plant nutrition, making it vulnerable to root rots, and possibly leading to death. Moreover, sharp fluctuations in moisture (from dryness to waterlogging) often cause fruit cracking.

Thus, skilful watering of eggplants is the art of maintaining a fine balance – supplying the plant with enough water without the risk of water stagnation in the root zone. This balance is the key to obtaining a high‑quality and abundant harvest. In the following chapters, we will examine in detail how to achieve this at different stages of plant growth.

2.1. Pre‑Sowing Period and Seedlings

At this stage, the main task is to ensure uniform and rapid germination of seeds. For swelling and the start of growth, the embryo needs a large amount of moisture. The soil must be evenly moistened to the full seeding depth (about 1.5–2 cm).

• Requirements: The topsoil layer must be constantly moist but not waterlogged, to avoid seed rotting. To stimulate germination and control infections, pre‑sowing soaking of seeds is recommended, e.g., in a 1 % potassium permanganate solution, followed by rinsing and soaking in clean water for 12–16 hours (Autko et al., 2012). This accelerates emergence.

2.2. Seedling Stage

Growing healthy seedlings is the foundation of the future harvest. At this stage, the root system is still weak and superficial, so drying out of the topsoil is fatal for young plants. However, excess moisture is also dangerous, as it creates favourable conditions for root rots (“damping‑off”).

• Requirements: The soil in pots or trays should be kept moist and loose. Watering should be regular but moderate. Good drainage is essential to prevent waterlogging.
• Importance for the future: Seedlings grown under the correct water regime have a strong, well‑developed root system. Optimal soil moisture (about 70‑80 % of field capacity) and aeration help harden the plants and improve their survival after transplanting (Autko et al., 2012).

2.3. Period after Transplanting to Open Ground

In the first days after transplanting (first 7‑10 days), the root system is damaged. At this time, the plant is extremely vulnerable and its ability to absorb water is limited.

• Requirements: During this period, watering directly into the planting hole is very important (0.5‑3 litres per plant) (Autko et al., 2012). The soil around the seedling should be kept constantly moist to help the plant restore its root system and establish in the new location. In dry weather, additional pre‑planting watering may be needed (Autko et al., 2012).

2.4. Active Vegetative Growth Phase

After the seedlings have established and begun actively growing green mass, the water demand gradually increases. The formation of a strong leaf apparatus and stem requires large volumes of water for transpiration and photosynthesis.

• Requirements: During this period, stable soil moisture should be maintained. The plant develops a powerful root system capable of extracting moisture from deeper layers. Optimal soil moisture at this stage is 70‑80 % of field capacity (Autko et al., 2012). This creates conditions for rapid growth and preparation for flowering.

2.5. Flowering and Fruiting Phase (Critical Period)

This is the most important and moisture‑demanding stage. During flowering and fruit set, water deficiency leads to catastrophic consequences: flowers and small ovaries drop en masse, and yield drops sharply (Swiader, 1992). This occurs because under water stress, the plant stops supplying water to reproductive organs to ensure its own survival.

• Requirements: Soil moisture must be maintained at a consistently high level, but without waterlogging. At this stage, even short‑term drying of the topsoil can cause significant yield losses. Watering should be more frequent and abundant than in previous stages.
• Fruit quality: During fruit growth, water is necessary for fruit filling. Moisture deficit makes fruits bitter, coarse and deformed. Sharp moisture fluctuations are the main cause of fruit cracking in many varieties (Rubatzky & Yamaguchi, 1997).

2.6. Fruit Ripening Phase

When the bulk of the fruit begins to ripen, watering can be somewhat reduced.

• Requirements: At this stage, excess moisture can impair fruit taste, making them more watery and less sweet. Watering should be less frequent, keeping the soil moderately moist. This also improves fruit storage and transportability.
• End of vegetation: As plants age and fruiting ends, irrigation intensity is gradually reduced until complete cessation before the last harvest.

Therefore, the most critical periods for water supply are flowering, fruit set and active fruit growth. At these times, watering mistakes are most damaging and can nullify all previous efforts.

3.1. Visual Assessment of Plant Condition (by Leaves)

The quickest and most intuitive method. The plant itself signals its needs:

1. Lack of moisture:

• Loss of turgor: Leaves and stems become limp and lose firmness. On a hot afternoon, this may be a normal reaction to strong sun, but if turgor does not recover by evening, it is a clear sign that the plant needs urgent watering (Rubatzky & Yamaguchi, 1997).
• Change in colour: Leaves may take on a darker, duller shade, and in some varieties a slightly bluish tint.
• Drop: Under severe and prolonged drought, mass shedding of flowers, buds and even young ovaries begins. This is the most critical signal, indicating that the plant has switched to survival mode and is sacrificing the crop (Swiader, 1992).
• Growth retardation: Formation of new shoots and leaves stops.

2. Excess moisture:

• Yellowing and wilting: Contrary to common belief, with overwatering leaves can also wilt and turn yellow, especially lower ones. This happens because roots suffocate and stop supplying the plant with water and nutrients.
• Rotting: In wet weather, signs of stem base rot or fruit rot may appear.

3.2. Soil Moisture Assessment (Manual Method)

This is the most reliable method for the gardener. Do not rely only on the appearance of the topsoil, as it can dry out quickly.

• “Ball test” (for loamy soils): Take a handful of soil from a depth of 10‑15 cm (about a spade’s depth) and squeeze it in your fist. If the soil crumbles in your hand – watering is urgently needed. If it forms a ball but crumbles when lightly pressed with a finger – moisture is near optimum. If moisture is released from the ball when squeezed, or it becomes plastic and does not crumble – watering is not yet needed (Marshall, 1996).
• “Depth test” (for light sandy soils): Take a small trowel or just your finger and go 5‑8 cm deep into the soil between rows. If the soil at that depth is dry and crumbly – it is time to water. If it is moist and cool – watering can be postponed.

This method is especially important during fruiting, when roots actively work at depths of 20‑30 cm. The top layer may be dry, but there may be enough moisture at depth.

3.3. Using Instruments (for More Precise Control)

For those who prefer precision, simple and affordable instruments exist.

• Tensiometer: This device measures the “suction” force of the soil, i.e., the effort the plant must exert to obtain water. The tensiometer is installed in the main root zone (at a depth of 20‑30 cm). Its readings (in atmospheres or centibars) serve as an accurate indicator of moisture availability. For most vegetable crops, including eggplant, watering is recommended when readings are in the range of 50‑70 centibars (Marshall, 1996). This method is popular on farms.
• Soil moisture meter (soil probe): A simpler and more budget‑friendly option. This is a rod with a tip that is inserted into the soil and measures moisture by electrical resistance or other parameters. Readings may be less accurate, but they allow quick comparison of moisture in different parts of the field or bed.

3.4. Observing Growth and Weather

In addition to visual and tactile methods, consider weather conditions and growth stages:

• Weather: In hot, sunny and windy weather, the soil dries faster, so watering should be more frequent. In cool, rainy or overcast weather, intervals between waterings should be increased.
• Growth stage: As discussed in the previous chapter, during flowering and fruit set, watering should be most frequent and abundant, avoiding even short‑term moisture deficiency. During fruit ripening, watering can be less frequent.
• Soil type: Sandy and sandy‑loam soils hold little moisture and require more frequent watering. Clay and loamy soils, as well as soils high in organic matter (e.g., peat), retain moisture much better and can be watered less often but more abundantly (Marshall, 1996).

Important advice: Never rely on a single indicator alone. Use a systematic approach: inspect the plants, check the soil moisture at depth, and evaluate the weather. Only the combination of these data will allow you to make the right decision and avoid both drought and waterlogging of eggplants.

4.1. Surface Irrigation (by Furrows or Flooding)

This is the traditional, oldest and most common method, especially on large areas. Water is supplied through furrows between rows, or by flooding the entire bed surface.

How it works: Water moves over the soil surface and percolates downwards, wetting the root zone. For eggplants, which do not like excess moisture around the stem, furrow irrigation is preferable to full‑bed flooding.

Advantages:

• Simplicity and availability. No complex equipment required.
• Suitable for large areas and flat terrain.

Disadvantages:

• Uneven wetting: The soil is wetted unevenly, especially on slopes or heavy soils.
• High water consumption: A significant part of the water is lost to evaporation from the soil surface and deep percolation below the root zone.
• Soil compaction: Water destroys the structure of the top layer, forming a crust that needs to be loosened.
• Disease risk: Water can splash onto stems and leaves, promoting fungal diseases (late blight, alternaria) (Autko et al., 2012).
• Weed growth: The entire surface is wetted, stimulating vigorous weed growth.

Suitability for eggplants: This method can be used but requires considerable experience and attention. It is important to avoid water contact with the root collar and ensure rapid drying of inter‑rows. It is most justified on heavy clay soils with a high water table.

4.2. Sprinkler Irrigation (using sprinkler systems)

This method mimics natural rain. Water is sprayed over the plants using various sprinklers (circular, sector, impulse).

How it works: Water is delivered through a system of pipes and nozzles and falls on plants and soil as droplets.

Advantages:

• Automation of the process.
• Ability to cover large areas.
• Effective in hot weather for lowering air temperature (Rubatzky & Yamaguchi, 1997).

Disadvantages:

• High risk of fungal diseases: Wetting leaves and stems creates an ideal environment for pathogens such as late blight and alternaria (Autko et al., 2012).
• Inefficiency in windy weather: A significant portion of water is blown away by wind.
• Water loss through evaporation: Part of the water evaporates without reaching the root system.
• Sunburn: When sprinkling on a sunny day, water droplets left on leaves can act as lenses and cause burns.

Suitability for eggplants: This method is not recommended for regular watering of eggplants, especially during flowering and fruiting. Excess moisture on leaves and fruits leads to massive diseases. It can be used occasionally in very hot weather for refreshing, but only in the morning so that leaves dry before evening.

4.3. Drip Irrigation (Micro‑Irrigation)

This is the most efficient and economical method, especially popular in modern vegetable growing and among home gardeners growing eggplants. Water is delivered directly to the root zone of each plant through a system of drippers (tapes or tubing).

How it works: A drip tape with emitters is laid along each row or between plants, and water is supplied at low pressure.

Advantages:

• Maximum efficiency: Water is applied point‑wise, exactly to the root zone; losses to evaporation and deep percolation are minimal.
• Water savings: Water consumption is reduced by 30‑50 % compared to sprinkler and surface irrigation.
• Maintaining optimal moisture: The soil in the root zone is kept constantly moist, while leaves and stems remain dry, preventing disease development.
• Fertigation capability: Fertiliser solutions can be supplied through the drip system directly to the roots, increasing nutrient uptake efficiency (Autko et al., 2012).
• Reduced labour: Watering and fertilising are automated.
• Fewer weeds: Water is applied only to the plant zone; inter‑rows remain dry, suppressing weed growth.

Disadvantages:

• Higher initial cost: Requires purchase of tape, fittings, filters, water tanks.
• Dependence on water quality: Water must be clean, free of suspended solids and high salts, to avoid clogging emitters.
• Regular maintenance: The system must be flushed and filters kept clean.

Suitability for eggplants: This is the best method for growing eggplants, especially in hot and arid regions, on light sandy soils. Drip irrigation allows precise water dosing and ensures plants have moisture during the most critical periods – flowering and fruiting (Rubatzky & Yamaguchi, 1997). It also works perfectly with mulching film.

4.4. Watering and Mulching

Regardless of the chosen watering method, using mulch significantly increases its efficiency. Organic (straw, mown grass, compost) or inorganic (black or reflective film) mulch performs several functions:

1. Retains soil moisture, preventing evaporation from the surface.

2. Suppresses weed growth, which compete with eggplants for water and nutrients.

3. Prevents soil crust formation, improving root aeration.

4. Regulates soil temperature: black mulch warms the soil in spring, while reflective mulch protects roots from overheating in summer.

When using drip irrigation, mulch is almost an obligatory element of the technology.

Conclusion for the gardener: For growing eggplants in a home garden or small farm, drip irrigation is the most recommended method. It provides the plants with the necessary moisture, reduces disease risk, saves water and time. If drip irrigation is not possible, furrow surface irrigation is better than sprinkling, but you must be prepared for more frequent hoeing and weed control.

5.1. General Principles of Norming

The watering norm is the amount of water to be applied per unit area (litres per square metre or cubic metres per hectare) or per plant. The frequency is the intervals between waterings.

For eggplants, the principle is: water less often but more abundantly rather than frequently and superficially. This is because the bulk of absorbing roots lies at a depth of 15‑30 cm. Surface watering wets only the top layer, not reaching the roots, and promotes weed growth.

Recommended approximate watering norms:

• For open ground: On average, eggplants require from 25 to 50 litres of water per 1 m² per week, depending on growth stage and weather. This is equivalent to 3‑5 waterings of 10‑12 litres per m².
• Per plant: During active fruiting, one eggplant plant may consume up to 3‑5 litres of water per day (Swiader, 1992).

For a more precise calculation, you can use the simple rule: in one watering, the soil should be moistened to a depth of at least 30 cm. To check this, you can dig a small hole or use a probe.

5.2. Norms and Frequency by Growth Phase

As we have discussed, water needs change with development stage. Here are specific recommendations:

First 7‑10 days after transplanting seedlings:

• Norm: Abundant watering directly into the planting hole at transplanting (0.5‑3 litres per plant) (Autko et al., 2012).
• Frequency: Watering should be regular to keep the soil moist while the root system recovers. In hot weather – water every 2‑3 days.

Active growth period (before flowering):

• Norm: 2‑3 buckets (10‑15 litres) per 1 m².
• Frequency: About once every 5‑7 days, depending on weather. The soil should dry out between waterings but not completely dry. The main goal is to support the growth of a strong leaf apparatus.

Flowering and fruiting period (critical):

• Norm: Increase the norm to 20‑25 litres per 1 m².
• Frequency: At this time, watering should be more frequent – every 3‑4 days, and in extreme heat – every other day. Avoid even short‑term soil drying, otherwise flowers and ovaries may drop (Rubatzky & Yamaguchi, 1997). Water at this stage is the main factor in yield formation.

Fruit ripening period:

• Norm: Reduce to 10‑15 litres per 1 m².
• Frequency: Intervals between waterings increase to 5‑7 days. Excess moisture at this stage can lead to fruit cracking and deterioration of taste. The soil should be kept moderately moist.

5.3. Factors Affecting Watering Frequency

There is no universal watering calendar. It must be adjusted considering:

• Weather conditions: In hot, sunny and windy weather, moisture evaporates faster, so water more often. In cool and overcast weather – reduce frequency.
• Soil type: Sandy and sandy‑loam soils need more frequent watering but with smaller amounts. Clay and loamy soils retain moisture longer, so water them less often but more abundantly (Marshall, 1996).
• Mulch presence: As discussed, mulch significantly reduces evaporation from the soil surface. On mulched beds, watering frequency can be reduced by 1.5‑2 times.
• Plant age: Young plants with a small root system are watered more often but with smaller volumes. Mature bushes with strong roots require infrequent but very abundant watering.

5.4. Optimal Time for Watering

Choosing the time for watering is not just a matter of convenience; it is an important factor affecting plant health and water use efficiency.

The best time to water eggplants is early morning (before 10 a.m.).

Why morning?

1. Moisture has time to soak in: The soil is cool, and water can deeply penetrate the root zone before the intense heat.

2. Plants are ready for the day: By the time the sun becomes strong, the plants have already received sufficient moisture, helping them withstand daytime heat.

3. Dry leaves: Leaves and stems dry before evening, significantly reducing the risk of fungal diseases (late blight, alternaria) (Autko et al., 2012). Wet leaves overnight are an ideal environment for pathogens.

If morning watering is not possible:

• Evening watering (after sunset) is also acceptable. In this case, moisture also soaks in well. However, it is important that leaves dry before nightfall. Therefore, watering late in the evening is not recommended.
• Watering at hot noon is strictly forbidden! Water on leaves under the scorching sun acts as a lens, causing burns. Moreover, most water evaporates without reaching the roots, and a sharp temperature contrast can shock plants.

Important advice: Use warm water that has been warmed in the sun for watering. Watering with cold water from a well or borehole causes stress to the heat‑loving eggplant, slows its growth and can trigger ovary drop.

Practical takeaway: Get into the habit of regularly observing the weather and soil condition. On hot days, water eggplants abundantly (20‑25 L/m²) and frequently (every 3‑4 days), preferably early in the morning. Use mulch to reduce evaporation. Always remember that during flowering and fruiting, watering mistakes are the most costly.

6.1. Water Temperature

This is one of the most important yet simple‑to‑control parameters. The eggplant is a heat‑loving plant from the tropics, and its root system is very sensitive to low temperatures.

Optimal temperature: Water for irrigation should be warm, about 22‑25 °C. This temperature is recommended for watering seedlings and adult plants in protected cultivation (Autko et al., 2012).

Danger of cold water: Watering with cold water from a well, borehole or directly from the tap causes severe stress to the eggplant. Sudden cooling of the root zone:

• Slows growth: At soil temperatures below 14‑16 °C, roots lose the ability to absorb phosphorus (by 50‑75 %) and other nutrients, manifesting as anthocyanin (purple) colouring of leaves (Autko et al., 2012).
• Lowers immunity: Stress makes the plant more vulnerable to root rots and other diseases.
• Causes drop: During flowering and fruiting, cold watering can trigger flower and ovary drop.

Practical advice: Always collect water for irrigation in advance in large containers (barrels, buckets) so that it warms up in the sun. If you use a drip system from a borehole, try to water in the morning so that water in the hoses warms up a bit, or use longer supply lines running on the soil surface.

6.2. Chemical Composition of Water (Salinity)

Water is a solvent, and dissolved salts are always present. Their concentration directly affects the plants’ ability to absorb water and nutrients.

Electrical Conductivity (EC): The main indicator of water salinity is its electrical conductivity (ECe), measured in deciSiemens per metre (dS/m) or millimhos per centimetre (mmho/cm). The higher this value, the more salts are dissolved.

Effect of salinity on eggplants: Eggplant is moderately sensitive to salinity. Its roots extract water from the soil solution by osmotic pressure. If the salt concentration in the water is too high, osmotic pressure rises, making it harder for the plant to “suck” water from the soil. This state is called physiological drought: there is plenty of water in the soil, but the plant cannot obtain it (Marshall, 1996).

• Threshold values: Research indicates that yield reduction in eggplants begins when soil salinity exceeds a certain threshold. Although exact numbers may vary, it is important to remember that for most sensitive and moderately sensitive crops, irrigation water with EC above 1.5‑2.5 dS/m can already cause problems (Marshall, 1996). Continuous use of such water leads to salt accumulation in the soil, which over time reduces fertility.

How to check: In a laboratory, you can test water for salt content. At home, you can judge by the water source:

• Rainwater is the softest and best for irrigation.
• River and lake water usually has moderate mineralisation.
• Well and borehole water is often hard and may contain elevated salts, especially in arid regions.

Practical advice: If you suspect your water is too salty, try using rainwater or mix hard water with soft water. Also, periodic abundant watering (leaching) with clean water helps wash salts out of the root zone. This is most effectively done with drip irrigation.

6.3. Water Purity (Suspended Solids and Impurities)

This parameter is especially important when using drip irrigation.

• Suspended particles: Sand, silt, rust, algae fragments can clog drippers and emitters, disabling the system. To prevent this, always install filters at the inlet of the drip system.
• Chemical impurities: High levels of iron, manganese or hydrogen sulphide in water can not only clog the system but also be toxic to plants.
• Biological impurities: Water from open reservoirs may contain fungal spores or pest eggs.
• Practical advice: For drip irrigation, use only clean water. Water from ponds or lakes should be settled or filtered before use.

6.4. Water pH (Acidity)

Although eggplants prefer neutral or slightly acidic soil reaction (pH 5.5‑6.5), the pH of irrigation water also matters. Excessively alkaline water (pH > 7.5) can hinder the uptake of some micronutrients, especially iron, leading to chlorosis (yellowing) of leaves (Rubatzky & Yamaguchi, 1997). When using acidic fertilisers, this issue is usually resolved automatically.

Main takeaway: For watering eggplants, use warm, clean water with low salt content. If you have doubts about water quality, have it analysed at an agrochemical laboratory. This will help you avoid many problems and get the maximum return from your efforts.

7.1. How Mulch Helps Save Water

The main function of mulch in the context of watering is preventing evaporation of moisture from the soil surface. In hot weather, bare soil loses huge amounts of water that could have been used by the plant. The mulch layer creates a barrier between soil and air, significantly reducing these losses.

• Moisture retention: Mulch can reduce watering frequency by 1.5‑2 times. The soil under it stays moist and loose much longer, even during dry periods.
• Lower water demand: Plants on mulched beds spend less energy extracting water, allowing them to channel more resources to growth and fruit formation (Swiader, 1992).

7.2. Other Important Functions of Mulch

Besides moisture conservation, mulch performs several other critical functions:

1. Regulating soil temperature: Black mulch (film, agrotextile) warms up well in the sun, which is especially beneficial in spring to accelerate the growth and development of heat‑loving eggplants. On the other hand, light mulch (straw, mown grass, white film) reflects sunlight and protects roots from overheating in summer heat (Rubatzky & Yamaguchi, 1997).

2. Suppressing weed growth: Weeds are serious competitors for water and nutrients. Mulch suppresses their growth, saving you from frequent weeding. This is especially important when using drip irrigation, as weeds in inter‑rows do not get moisture.

3. Preventing soil crust formation: After watering or rain, a dense crust often forms on the soil surface, hindering air access to roots and reducing water permeability. Under mulch, the soil remains loose and well‑aerated, promoting strong root development.

4. Protecting fruits from soiling and diseases: Mulch prevents fruit contact with wet soil, protecting them from rotting and disease development.

7.3. Types of Mulch

Mulching materials can be divided into two large groups: organic and inorganic. The choice depends on your goals and material availability.

Organic mulch:

Materials: Straw, hay, mown grass, sawdust, bark, compost, leaf litter, peat.

Advantages:

• Improves soil structure: As it decomposes, organic mulch turns into humus, making the soil looser and more fertile.
• Nutrient source: During decomposition, it releases nutrients, serving as an additional fertiliser.
• Eco‑friendly: Natural material that you can obtain on your own plot.

Disadvantages:

• Requires renewal: The mulch layer thins over time and needs replenishing.
• Attracts pests: Slugs, snails and some insects may hide in thick mulch.
• May acidify soil: For example, pine litter and fresh sawdust acidify the soil.

Practical tips for eggplants:

• Use rotted sawdust or straw, as fresh sawdust can tie up nitrogen.
• The organic mulch layer should be at least 5‑8 cm thick.
• Leave a small space (5‑10 cm) around the plant stem to avoid rotting of the root collar.

Inorganic mulch:

Materials: Black and reflective polyethylene film, black and white spunbond (agrotextile), geotextile.

Advantages:

• Durability: Can be used for several seasons (especially agrotextile).
• Reliable weed control: Completely blocks weed growth.
• Effective temperature regulation: Black mulch warms the soil in spring, white protects from overheating in summer.

Disadvantages:

• Does not improve soil: Unlike organics, it does not decompose or enrich the soil.
• Disposal required: Film must be collected and disposed of after use.

Practical tips for eggplants:

• Black film or spunbond is ideal for spring planting and early harvests in cooler climates.
• Reflective (white, silver) film is recommended for southern regions with hot summers to protect roots from overheating.
• When using film or agrotextile, drip irrigation is mandatory, as surface watering over mulch is ineffective. Water must be supplied directly under the mulch.

7.4. Timing of Mulching

• Spring: It is best to mulch 1‑2 weeks after transplanting seedlings, when the soil has already warmed up well. Eggplants are planted directly onto black mulch by making cross‑shaped slits for planting.
• Summer: In hot climates, organic mulch (straw, hay) can be added throughout the season, maintaining the layer. If you used black film and the summer is very hot, you can spread a layer of light mulch (straw or mown grass) on top, or use two‑colour film (black‑white).

Practical takeaway: Mulching and proper watering are two complementary techniques that together give excellent results. Mulch saves water, reduces labour for weeding and hoeing, and creates an optimal microclimate for eggplants. The choice of mulch type depends on your climate and goals: organic mulch gradually improves soil, while inorganic (film) ensures faster growth and early harvest.

8.1. Advantages of Fertigation for Eggplants

This method offers several important benefits to the gardener and farmer:

1. Maximum fertiliser efficiency: Nutrients go directly to the active root zone, where they are immediately taken up. Losses to evaporation and leaching into deeper layers are minimal. Fertiliser efficiency increases by 30‑50 %.

2. Precise dosing: You can apply fertilisers at the right concentration and at the right time, strictly according to the plant’s growth stages.

3. Fertiliser savings: Due to high efficiency, total fertiliser consumption with fertigation can be reduced compared to traditional application.

4. Even distribution: With a properly adjusted system, all plants receive the same amount of nutrients, equalising the yield.

5. Reduced plant stress: Fertilisers are applied in liquid form, allowing the plant to take them up without extra effort. This is especially important when the root system is damaged (e.g., after transplanting) or under stress.

6. Automation: The fertilising process can be fully automated by setting the schedule and concentration. This saves your time and energy.

8.2. Basic Principles of Fertigation for Eggplants

To make fertigation beneficial rather than harmful, a few simple rules must be followed:

1. Use only fully soluble fertilisers. This is a key condition. Special fertiliser lines for fertigation contain no insoluble impurities that could clog drippers. Also suitable are well‑soluble mono‑fertilisers: ammonium nitrate, potassium nitrate, monopotassium phosphate, magnesium sulphate, etc.

2. Start with low concentrations. Do not give the plant a full dose immediately. Start with 50 % of the recommended concentration and gradually increase it while observing the plant’s response.

3. Apply fertilisers in the first half of the irrigation. First run water, then the fertiliser solution, and finally clean water again. This flushes the system of salt residues and delivers nutrients to the root zone.

4. Consider the acidity (pH) of the solution. The optimal pH for uptake of most elements is 5.5‑6.5. In alkaline conditions (pH > 7.0), many micronutrients (iron, manganese, zinc) become unavailable to plants. If necessary, pH can be adjusted with acids (e.g., nitric or orthophosphoric).

5. Alternate feedings. Do not apply the same fertiliser continuously. Alternate nitrogen, phosphorus and potassium feeds according to growth stage.

8.3. Fertigation Schedule by Growth Phase

The eggplant’s need for nutrients changes during the season. Here is an approximate scheme that can be adapted to your conditions:

• After transplanting (first 7‑10 days): The main task is to help the plant establish. Water with clean water. If the soil is poor, a weak phosphorus solution (monopotassium phosphate) can be given to stimulate root formation.
• Active growth phase (before flowering): The plant needs nitrogen for green mass. Apply nitrogen fertilisers (ammonium nitrate, calcium nitrate). Approximate dose: 1‑2 grams per litre of water. Apply once every 7‑10 days.
• Flowering and fruit set phase: Reduce nitrogen, increase phosphorus and potassium. Phosphorus (monopotassium phosphate) stimulates flowering and fruit set, while potassium improves fruit quality. Use compound fertilisers with N:P:K = 10:20:30 or 5:15:20. Frequency: once every 5‑7 days.
• Active fruiting phase: The plant consumes maximum nutrients. Continue with potassium and phosphorus, keeping nitrogen at a moderate level. Increase potassium fertilisers (potassium nitrate) to improve fruit taste. Frequency: 1‑2 times per week.
• Fruit ripening phase: 2‑3 weeks before the end of harvest, gradually reduce and stop fertilisation.

8.4. Preparation of Stock Solutions

For fertigation, it is convenient to use concentrated stock solutions that are then diluted in the irrigation system.

• Example of making a stock solution (from Autko et al., 2012 for seedlings): Dissolve the required amount of each fertiliser separately in a small amount of warm water, then make up to the desired volume (e.g., 10 litres). Store stock solutions in a dark place to prevent precipitation.
• For field‑grown eggplants, ready‑made compound fertilisers for fertigation can be used, following the package instructions.

8.5. Practical Recommendations

• Water quality: Use only clean water without suspended solids for fertigation. Always install filters at the system inlet.
• Fertiliser compatibility: Do not mix in the same tank fertilisers that may react and form insoluble precipitates (e.g., calcium nitrate with magnesium sulphate or phosphorus fertilisers). Use separate tanks or apply them sequentially.
• Micronutrients: In fertigation, it is especially important to supply micronutrients, as they are often poorly available from the soil. For eggplants, boron, manganese and zinc are particularly important, positively affecting growth and productivity (Autko et al., 2012). They can be added in small doses or using ready‑made complex micronutrient fertilisers (chelated forms).

Conclusion: Fertigation is a powerful tool in the gardener’s hands. It not only saves water and fertilisers but also allows precise management of plant growth and development. For eggplants, which are very demanding in nutrition, especially during fruiting, this method gives a noticeable increase in yield and quality. However, successful fertigation requires care, precision and adherence to all rules for preparing and applying solutions.

9.1. Watering Eggplants in Open Ground

This is the most common growing method. Here, plants depend most on weather conditions, and your task is to compensate for the lack of natural moisture and protect them from overheating.

Basic principles:

• Weather orientation: In hot, dry and windy weather, increase watering frequency and amount. In cloudy and rainy periods, reduce or temporarily stop watering. In open ground, water evaporates quickly from the surface and is used for transpiration, requiring constant monitoring.
• Deep wetting: As noted, eggplant roots go down to 30 cm or more. Watering must be abundant enough to moisten the soil to that depth. Surface watering only harms.
• Mulching: In open ground, mulch (especially organic – straw, mown grass, compost) is essential. It protects the soil from overheating, retains moisture, prevents weeds and crust formation.
• Hoeing: If you do not use mulch, after each watering or rain, when the soil dries, loosen the inter‑rows to a depth of 5‑8 cm to break the crust and provide air to the roots.

Features for different climatic zones:

• Southern regions with hot, dry summers: The main emphasis is on drip irrigation combined with reflective mulch (white film, straw) to avoid root overheating. Watering should be very abundant and frequent, especially during flowering and fruiting (Rubatzky & Yamaguchi, 1997). Use warm water from storage tanks, as cold borehole water causes stress.
• Regions with temperate climates: Watering is also important, but frequency may be slightly lower. However, during dry spells, eggplants still need abundant watering. Black mulch works well for warming the soil in spring.
• Regions with frequent rains: The main task is to drain excess water away from the roots. For this, eggplants are planted on ridges or raised beds to prevent water stagnation around the root collar. During rainy periods, watering is completely stopped, and the soil is only loosened for aeration.

9.2. Watering Eggplants in Protected Cultivation (Greenhouses and Polytunnels)

Growing in a greenhouse gives more control over the microclimate but also requires a more careful approach to watering. Here, plants are protected from wind and rain, but evaporation occurs differently.

Microclimate features:

• High air humidity: In a closed greenhouse, air humidity is often high (especially without ventilation). This can lead to fungal diseases and reduced pollen quality (Autko et al., 2012). Therefore, watering in the greenhouse must be organised so as not to raise air humidity.
• Overheating: On a hot day, greenhouse temperatures can rise to critical levels (above 30‑35 °C), causing pollen sterility and ovary drop. In this case, watering helps lower both soil and air temperatures.

Watering recommendations:

• Drip irrigation is the best choice. It delivers water directly to the roots without wetting leaves or raising air humidity.
• Watering in the first half of the day. This lowers the greenhouse temperature before midday heat and allows leaves to dry by evening, preventing diseases.
• Abundant but infrequent waterings. Intervals between waterings should be slightly longer than in open ground, because evaporation from the soil surface is lower in the greenhouse. However, the watering amount should be sufficient for deep wetting.
• Ventilation: After watering, be sure to ventilate the greenhouse to reduce air humidity. This is critical during flowering and fruit set.
• Mulching: In greenhouses, mulch is also used, but more often inorganic (black film, agrotextile) for cleanliness and weed control.
• Temperature regime: During fruiting, optimal daytime greenhouse temperature is 22‑27 °C, night 16‑18 °C (Autko et al., 2012). Watering helps regulate this regime.

9.3. Watering Eggplants in Containers and Limited Areas

Growing eggplants in pots, boxes or containers is an excellent option for small plots, balconies and terraces. However, the soil volume is limited, which affects the watering regime.

Features:

• Rapid drying: Soil in a container warms up and dries much faster than in open ground. In hot weather, watering may be needed daily, sometimes twice a day.
• Limited root volume: The root system is restricted, so it cannot extract moisture from deeper layers.
• Root overheating: Thin container walls can heat up in the sun, overheating the root system. Light‑coloured containers and mulch help solve this problem.

Recommendations:

• Good drainage: The container bottom must have a layer of expanded clay or drainage holes to prevent waterlogging.
• Water “as needed”: Check the soil with your finger at 3‑5 cm depth. If dry – water, if moist – wait.
• Mulching: In containers, mulch (compost, coconut fibre, mown grass) is especially important, as it prevents rapid drying.
• Protection from overheating: On hot days, shade containers or wrap them with light‑coloured material (e.g., white spunbond).
• Frequency and amount: Water in small portions (1‑2 litres per plant) as the soil dries. Try not to get water on the leaves.

General conclusion: Regardless of growing conditions, the key principles of eggplant watering remain the same: water must be warm, sufficient for deep wetting of the root zone, and overwatering is unacceptable. However, in greenhouses more attention is given to air humidity control, in open ground to mulching and hoeing, and in containers to watering frequency and overheating protection.

Mistake No. 1: Irregular Watering (from drought to waterlogging)

This is one of the most damaging mistakes. Sharp fluctuations in soil moisture cause severe stress to the eggplant.

Consequences:

• Fruit cracking: When water is suddenly supplied after a long drought, fruits start to fill rapidly, and the skin cannot withstand the pressure, causing cracking (Rubatzky & Yamaguchi, 1997).
• Flower and ovary drop: During flowering and fruiting, stress from water shortage followed by excess leads to massive shedding of reproductive organs (Swiader, 1992).
• Blossom‑end rot: Sharp moisture fluctuations disrupt calcium uptake into fruits, promoting this physiological disorder (Autko et al., 2012).

How to avoid: Try to water eggplants regularly, keeping the soil consistently moist, especially during flowering and fruiting. Use mulch to smooth out moisture fluctuations.

Mistake No. 2: Surface Watering

Many gardeners water eggplants frequently but in small amounts, wetting only the topsoil. This is a serious mistake.

Consequences:

• Weak root development: Eggplant roots tend to go deeper in search of moisture. With surface watering, they develop mainly in the top layer, making the plant less drought‑tolerant.
• Increased weed growth: The topsoil is constantly moist, creating ideal conditions for weed seed germination.
• Reduced yield: The plant does not get enough water, affecting fruit quantity and quality.

How to avoid: Water abundantly but less frequently. Water should penetrate to at least 30 cm depth. Check moisture at that depth with a probe or trowel.

Mistake No. 3: Watering with Cold Water

Watering eggplants with cold water (from a well, borehole or tap) is a direct path to stress and disease.

Consequences:

• Root shock: Sudden soil cooling slows or stops water and nutrient uptake. At soil temperatures below 14‑16 °C, roots lose the ability to absorb phosphorus (Autko et al., 2012).
• Ovary drop: Cold watering during flowering and fruiting can trigger flower and ovary drop.
• Root rot development: Roots weakened by cold stress become easy prey for pathogenic fungi.

How to avoid: Always use warm water for watering. Collect it in containers (barrels, buckets) in advance to warm in the sun. Optimal water temperature is 22‑25 °C.

Mistake No. 4: Overhead Watering (Sprinkling) in Hot Weather

Although some sources recommend sprinkling to lower temperature, for eggplants it often does more harm than good.

Consequences:

• Sunburn: Water droplets on leaves in sunny weather act as lenses, causing burns.
• Fungal diseases: Wet foliage is an ideal environment for late blight, alternaria and other fungal diseases (Autko et al., 2012).
• Reduced pollen quality: High humidity created by sprinkling can make pollen sterile, disrupting pollination and fruit set.

How to avoid: Use drip irrigation or water strictly at the base. If you must use sprinkling (e.g., on large areas), do it only in the early morning so that leaves dry by evening. Sprinkling should not be the primary watering method.

Mistake No. 5: Overwatering and Stagnation

Eggplants do not tolerate standing water around the roots. This often happens on heavy clay soils or when drainage is poor.

Consequences:

• Root rot: Excess water displaces air from the soil; roots suffocate and die.
• Yellowing and wilting of leaves: Paradoxically, the plant wilts even though there is plenty of water.
• Root diseases: Anaerobic conditions favour pathogenic fungi that can kill the plant.

How to avoid: Plant eggplants on raised beds or ridges to drain excess water. On heavy soils, incorporate loosening materials (sand, compost) before planting. Ensure good drainage in containers.

Mistake No. 6: Ignoring Weather Conditions

Watering strictly on a schedule without considering the weather is another common mistake.

Consequences: In rainy or cool weather, excessive watering leads to waterlogging. In hot and windy weather – to drying out.

How to avoid: Adjust your watering schedule according to the weather. In hot, dry and windy weather – water more often and more abundantly. In overcast and rainy – reduce or temporarily stop watering.

Mistake No. 7: Not Using Mulch

Many gardeners underestimate the role of mulch, especially in open ground.

Consequences: Rapid soil drying, weed growth, crust formation, root overheating, splashing mud onto fruits.

How to avoid: Always use mulch (organic or inorganic). This will reduce watering frequency, retain moisture and protect roots from overheating (Swiader, 1992).

Mistake No. 8: Incorrect Fertigation (when combining watering and feeding)

Mistakes in fertigation can not only reduce fertiliser efficiency but also harm the plant.

Consequences:

• Root burns: Overly concentrated fertiliser solution can burn the root system.
• Clogged drippers: Use of insoluble fertilisers or insufficient water filtration leads to system blockage (Autko et al., 2012).
• Nutrient imbalance: Improper element ratios (e.g., excess nitrogen) can cause excessive vegetative growth at the expense of fruiting.

How to avoid: Use only fully soluble fertilisers for fertigation. Strictly follow recommended concentrations (start with low doses). Always install filters at the system inlet.