Growing cucumbers and tomatoes in a greenhouse, the main problems and solutions that arise during the growing process

When using substrates to grow vegetables in a greenhouse, problems that may arise if you violate planting regulations and how to solve them
Growing cucumbers and tomatoes in a greenhouse, the main problems and solutions that arise during the growing process

Situation 1. Chemical burn of seedlings, this problem occurs. The same symptoms occur in different seasons and in different greenhouses and different growers. This is a chemical burn of the plant. The problem arises at the stage of preparing seedlings. Cause: Residues from drugs used for disinfection, usually formalin, can cause chemical burns to seedlings.
This chemical can sit on the structure of the greenhouse for a long time and then condense and drip onto the plants causing burns. The same situation can also occur with manual irrigation via a sprayer. If the sprayer was previously used for disinfection, formalin will still have a residual effect, especially at the beginning of the irrigation, even though the equipment has been cleaned several times.

Situation 2. The main reason why the lower part of the cotyledons of cucumber seedlings is excessively elongated is that the light radiation and microclimate parameters in the greenhouse do not match. This problem is the result of a combination of higher temperatures and low light exposure when growing seedlings. The following rule needs to be followed here: the less light radiation, the lower the air temperature. Don't be afraid to maintain lower temperatures during the cucumber seedling stage.
There will also be another situation: in order to limit the elongation of the lower part of the cotyledons, agronomists use an all-day uninterrupted lighting system in the first 3 days after germination. However, excessive lighting can inhibit plant growth. After this stage, the plant needs time to recover. Seedlings don't need a lot of light. At the same time, this does not take into account economic factors.
Situation 3. Sunburn of cucumber seedlings usually occurs in spring and autumn. Cause: High-intensity light, shining directly on young plants, is often accompanied by insufficient water supply and high air temperatures.
What happens at this time: plant transpiration is strong; water shortage (insufficient irrigation); shading system is missing or not used in time.
In complex environments, plants begin to sacrifice lower leaves in order to survive, resulting in necrosis of lower leaves and loss of part of leaf mass. In this case, experts often believe that it is due to poor quality of the substrate, an imbalance in plant growth due to formaldehyde in the rockwool growing blocks. However, this occurs by the time the plant has grown up, and the effects of surfactants on the plant only appear in the initial stages of the plant.
All substrate quality problems arise in the early stages of the plant: when the seedlings germinate and are just established on the substrate strips. Seedling burn occurs at the end of the seedling stage, when high-quality seedlings have grown on the rockwool growth block. If something happens suddenly, according to normal rules, it has nothing to do with the substrate. It is necessary to understand the nuances of agronomy.

Situation 4. The root system of the plant in the seedling stage is weak. In the seedling stage, problems arise due to incorrect irrigation strategies. It is very important to irrigate according to the weight of the rockwool growth block losing water between irrigations. This is an important condition for the formation of a healthy root system. Under the correct irrigation strategy, the roots continue to grow in search of water, and the weight changes of the rockwool growth blocks are not accurately controlled, and irrigation is just based on feeling, which results in a very weak root system of the plant. This will not yield ideal planting results. For any substrate, if you want to obtain a strong plant root system, you need to master special planting techniques, planting knowledge and skills.

Situation 5. Violation of the soaking requirements of the rock wool matrix. There is a rule: the soaked rock wool matrix must reach a mirror surface. Mirror surface: This is the visual plane of the nutrient solution, which can 100% soak the rock wool matrix. This is also the ultimate goal of soaking the rockwool matrix. Only when we see a mirror surface appear on the surface of rock wool can the injection of nutrient solution stop
There may be situations where the rockwool matrix strip cannot be completely soaked because the membrane of the matrix is ​​damaged or the drip arrow does not work properly, which requires manual addition of nutrient solution. Additional nutrient solution is added to each substrate strip through a valve, usually using a sprayer or hose. If you don't do this, the plant will have trouble taking root. The dry portion of the substrate will last throughout the planting cycle, and plant roots cannot use the substrate in a dry state. Plants grown on these substrates will grow slowly and have weaker root systems. The result is that you purchase a volume of rockwool matrix, but you don't fully use the material (some of the matrix is ​​wasted).
Scenario 6. Violation of soaking requirements for coconut bran substrate
The use of coconut peat substrate requires particularly strict compliance with technical requirements. When arranging the coconut bran substrate in the greenhouse, it must be understood that the coconut bran strips will significantly increase in volume during the soaking process and completely fill the film outer packaging of the substrate. Therefore, it is recommended to arrange coconut bran strips and connect the films at both ends of the substrate, not tightly together. The coco peat strips are packed closely together, resulting in insufficient space after soaking, and as a result, some coco peat strips fall off the bracket.
At the same time, if the substrate is not placed in the middle of the bracket when the coconut bran strips are placed, and the nutrient solution is added to exceed the absorption rate of the coconut bran (which also violates the technical requirements), in the absence of drainage holes, there is a high possibility that the coconut bran strips will be overweight and fall from the bracket due to excessive addition of nutrient solution and uneven distribution of the nutrient solution. This is caused by adding large amounts of nutrient solution at individual locations. The result is that the coconut bran strips cannot absorb these nutrient solutions quickly. Don't rush in the process of soaking the coconut bran strips. You must determine the time to prepare the coconut bran strips and work in an orderly manner.
Situation 7. The root system of tomato seedlings is underdeveloped due to irrigation strategies and repair measures. When planting tomato seedlings, the seedlings are usually grown on rockwool growing blocks before planting. Purpose: To form a strong root system for plants on rockwool growing blocks before planting. This requires strict compliance with the irrigation strategy of the seedlings: irrigate according to the weight loss during 2 irrigations and maintain the required EC level.
Poor root development caused by incorrect irrigation strategies: a. Too much irrigation in the growing block/too high moisture content in the substrate for a long time b. Failure to consider the weight change of the growing block during the two irrigations.
Substrates that are too moist often occur during high temperatures in the summer. Agronomists will increase the frequency of irrigation in order to lower the temperature of the growing patch due to concerns about excessive substrate temperatures, which results in a loss of control over root quality. Consideration must be given to the amount of weight loss of the growing mass during the night, the amount of nutrient solution consumed by plant transpiration during the day, and the amount of drainage. Never over-irrigate at any time!
High concentrations of salt in the growing mass can also affect root growth. High salinity will inevitably damage plant roots, especially under conditions of high temperature and high light radiation. In summer, all processes of the plant are accelerated, including the degradation of the root system. In winter, plants are more tolerant of high salinity.
In the technical specifications, it is clearly stated: the higher the light intensity and temperature, the lower the concentration and EC value of the nutrient solution in the substrate should be.
When salt concentrations increase, the matrix should be flushed quickly to avoid adverse consequences. There is a technical superstition that when irrigating rockwool growing blocks, drainage cannot occur. Many experts fear the appearance of drainage because of the possibility of growth from the root system, but in practice this situation does not become uncontrollable. For rock wool growing blocks, matrix strips and seedling plugs, drainage is necessary during use.
Drainage occurs, which means that the plants received a sufficient amount of nutrient solution, salt renewal occurred in the substrate, and all ballast elements (salt accumulation and high EC) were washed away. Calculating drainage can be determined by the volume of the growing block. It takes several irrigations before drainage occurs. The volume and EC value of the drainage, it is also very important to determine at which stage the seedling is. Rockwool growing blocks should not have much drainage, depending on the growing conditions of the seedlings. This also depends on the growth state of the seedling: the larger the seedling, the greater the amount of drainage allowed.
Situation 8. The problem of nutrient leaching is usually related to the quality of the substrate, since it occurs after the seedlings have been planted on the substrate strips. The seedlings were healthy and of good quality before planting, but problems developed after planting.
Causes of spots: Insufficient water supply in active climatic conditions. The plant begins to absorb water from the bottom leaves due to lack of water (this situation is similar to the situation described previously, but it has nothing to do with light radiation, but is related to the activity of the heating tube. This situation mostly occurs in winter.
After the growing blocks are placed on the substrate strips, irrigation is required to help the plant's roots enter the substrate strips. The "dry period" cannot be started immediately to develop the root system, because at this time the root system is mainly in the growth mass, and the root system must be preserved and increased. At the same time, the required EC levels must be maintained. If the EC in the growing block is higher than in the matrix strip (which is also a requirement of the technical specifications), the roots will quickly move from the unfavorable high-salt environment into the lower EC area.
When growing cucumbers in winter, the EC in the growing blocks can reach 3 – 3.5 mS/cm, in the matrix strips EC = 2.4 – 2.6 mS/cm. In order to speed up the seedling's root system from the growth block to the matrix strip, it is recommended that in the first 3 days, the amount of irrigation water drains out of the matrix strip. The roots of the plant should penetrate the substrate so that the growing block and substrate strip cannot be easily separated later. Only when the roots of the seedlings have completely entered the substrate strips can drying of the substrate begin.
Therefore, in the first 3 days, it is recommended to irrigate with large amounts of water and allow drainage to occur. The growing block should be heavy, completely soaked, with the surface firmly attached to the substrate strips. During this period, it is recommended to use a higher nutrient solution EC, which is beneficial to promote the root system from the growth block into the matrix strip with lower salt concentration. After 3 days, it can be clearly seen that the growth block and the matrix strip are closely connected, and the penetrating roots in the matrix strip can already be seen. The drying period that follows into the substrate is used to develop the root system in the substrate.

This is followed by a drying period of the substrate, when plant growth is active, and the irrigation strategy does not need to take into account sunrise and sunset times. During this period, priority is given to the conditions in the greenhouse: when the heating tubes and growth tubes are at the best temperature, when there is the most light, all of which lead to the most active plant metabolism and transpiration. For example, in winter the heating track at the bottom is very active, which has a direct impact on the plants, which require water and constant heating, but during the day with the arrival of solar radiation, the bottom area of ​​the greenhouse becomes hotter.

The nutrient solution must be supplied in small doses, without drainage, only moistening the growing block, and the roots are mainly distributed in the lower and upper parts of the matrix strips. When using this irrigation strategy, the plant roots quickly pass through the substrate strips and enter the underside of the substrate to form a "root gathering area", but there may be few roots in other areas of the substrate, so there is no need to worry about this situation.

A small-dose irrigation strategy will promote downward root growth during the rooting stage. The plant roots will gradually fill the entire matrix strip. This avoids possible growth deviations: lack of water and nutrients in the lower leaves
Situation 9. During the rooting period, the root development of the plant in the substrate is destroyed. The reason for this situation: after the rooting period begins, use a large dose of nutrient solution for irrigation. After the plants are fixed on the substrate strips, if the irrigation strategy is not adjusted during the rooting period, the roots will quickly pass through the substrate strips with drainage and form a 2-3 cm high root system at the bottom of the substrate strips. In this case, the substrate is not fully utilized by the plant.
At the beginning, the correct irrigation strategy was not selected and a large amount of water was used for irrigation, which caused the roots to penetrate the matrix strips and form a "root gathering area" at the bottom. Throughout the planting season, the life activities of the roots will be in this area, which is not conducive to plant growth. This can also happen when the substrate is not fully soaked to a mirror-like state. Plants feel discomfort from the initial stages and struggle to get from the dry layer of the matrix strip into the aquifer.
Situation 10. Weak plant root systems. Weak root systems mainly occur in winter due to insufficient solar radiation. Because of the lower light radiation, plants produce fewer assimilates, so it becomes very important to strictly observe the relationship between temperature and light, in order to avoid undesirable consequences: stem stretching and excessive reproductive growth of the plant.
It is necessary to ensure that all resources are used to promote vegetative growth of the plant, resulting in a stronger root system. Timely quantitative management of fruits and strict irrigation according to changes in substrate weight are important measures to avoid the formation of weak root systems.
Repairing the Weak Root System of Plants During the stage of cultivating the root system, irrigation must be carried out according to the decrease in the weight of the substrate between irrigations. Gradually drying out the substrate will stimulate plant root growth in search of available moisture. In the early stages of planting, the ovaries must be removed to create conditions conducive to vegetative growth of the plant.
Situation 11. During the vegetative growth stage of the plant, the root system of the plant is poorly developed. Root death occurs frequently and in most cases is the result of incorrect irrigation strategies and unreasonable management. In order to avoid this situation, basic requirements need to be followed: control the weight loss of the substrate at night; ensure that the plants have enough water when the light and temperature are the highest; control the salt concentration (rock wool or coconut bran) inside the substrate strips and in the drainage,
During vegetative growth, plants undergo changes. At the beginning of planting, the plant has a strong root system and sufficient nutrients. Naturally, plants actively absorb nutrients and require large amounts of water, and the entire process: absorption-transpiration-becomes more intensive, just like young people, whose growth capacity is at its peak. This physiological period must be taken into account.
When growing cucumbers and tomatoes, the plants absorb large amounts of nutrients from the nutrient solution at the beginning. Experts often set high concentrations in drip irrigation to ensure the plant's growth needs by maintaining the necessary EC value in the substrate, and the plant absorbs a large amount of nutrients. After a certain period of time, the situation changes, the nutritional needs of the plants decrease, and under the maximum nutritional load they begin to "fatigue". When the growing conditions of the plant become poor (light, plant growth balance, climatic conditions), the need to absorb nutrients from the substrate also changes. At this time, it is necessary to control the plant's nutrient absorption by adjusting the irrigation strategy and EC value in a timely manner.
The strategy should be adjusted and changed in time according to the growth status of the plant: a. When the actual situation changes, adjust the concentration of the nutrient solution. b. Reconsider irrigation strategies based on drainage results. If the plant absorbs little water but drains more, the amount and frequency of irrigation must be changed.
The effects of irrigation strategy and nutrient solution concentration on plants are shown in the previous photo. High concentrations of nutrient solutions that remain uncontrolled for long periods of time can cause root death. To keep the root system in working condition at all times requires continuous agronomic work and control of plant growth, taking into account all external factors.
Nighttime substrate drying is a continuous process and the concentration of substrate extracts (controlling plant growth and maintaining healthy root systems by controlling irrigation water volume and drainage)
If the planting strategy is followed, there are usually no situations where it is necessary to stimulate root growth. The exception occurs during the difficult period of the plants, before the beginning of fruiting, when the plants are under maximum load and they need help. At this stage, plant reproduction and growth are vigorous, and this is the only period when plants need help to gain growth assistance. An exception may be viral damage to plant roots, in which case adjustments to the irrigation strategy and treatment should be performed as a whole.

What are the advantages of coco peat matrix in this case? Coco coir is easier to control. Because of its buffering, coconut coir can maintain high concentrations for long periods of time. Rockwool matrix does not have this property because it is chemically inert. If small errors in irrigation occur over a long period of time and changes in salt content in the nutrient solution are not detected in time, the coconut bran substrate provides the possibility to preserve the root system. For rockwool substrates, this mistake is unforgivable. If the high concentration is not adjusted in time, the plants will react quickly and the roots will die quickly.
The reaction of the rockwool substrate takes an average of 5 – 7 days, then the high concentration of salt begins to take effect and the plant roots begin to die, but for the coconut bran substrate, the time to start the reaction is 10 – 12 days.
Flushing the substrate in the morning avoids excessive humidity in the substrate at the end of the day and also avoids high pressure in the plant's root zone at the end of the night. Flushing the substrate at noon, especially in summer, is very difficult because the substrate first gets moisture from the nutrient solution and then leaves behind ballast salts. Irrigating with large amounts of water in the morning will not harm the plants and fruits, but only if the specified weight loss indicators of the substrate strips at night are achieved. The amount of irrigation water in the morning can be increased 1-2 times, depending on what substrate flushing requirements need to be achieved. If the technique required for nighttime substrate drying is followed consistently (depending on the plant), the plants will become accustomed to restoring the weight of the substrate each morning with a large dose of nutrient solution. At this time, rinsing the substrate in the morning will not stress the plants.
Therefore, it can be summarized as follows: a. Continuously control the salt concentration in the root zone, because as time changes, the plant's demand for salt changes, and excess salt will destroy the root system, so large doses of irrigation need to be used in the morning to flush the substrate. b. In order to restore the root system, the plant roots must be stimulated by controlling the changes in substrate weight at night. Sometimes it is necessary to increase the change in substrate weight at night.
The situation analyzed above often occurs during the work process of using substrate planting. In the examples given, these are specific production experiences and the influence of all factors needs to be taken into account and all situations analyzed before making a decision to avoid possible errors.