Why do tomatoes in a greenhouse turn yellow and what to do?

The reasons for the appearance of yellowness on the leaves of crops grown in greenhouses are manifold. The process of yellowing of plants itself occurs in a different sequence and depends on the specifics of diseases, lesions, soil conditions and the characteristics of the microclimate in greenhouses.

There is no doubt that greenhouse crops are to a greater extent protected from the vagaries of nature; neither unexpected light frosts, nor heavy rainfall, nor heat are dangerous for them. The main task of gardeners is to maintain an optimal microclimate within greenhouses and other relevant conditions for the successful cultivation of tomatoes.

The optimal temperature regime in greenhouses is 23-30 degrees, the humidity level is 60-70% and the required amount of sunlight. In such conditions, the culture feels quite comfortable. In addition, the condition of the bushes should be regularly monitored, in a timely manner identifying signs of possible problem situations. For example, if the lower or upper leaves of tomatoes in polycarbonate greenhouses begin to turn yellow and dry, then these are signs of possible diseases, which always have specific causes. It is important to qualify such reasons in a timely manner, taking urgent appropriate action.

This directly applies to the yellowness that appears on the plants. It can be caused by disturbances in the temperature and humidity state in greenhouses, improper irrigation, damage to the roots, disturbances in the balance of trace elements in the soil, viral or fungal infections, etc. In each individual case, if the leaves of tomatoes in greenhouses turn yellow either at the top, or at the bottom, or after planting, such yellowness looks different, but this process is specific.

For example, if yellow spots began to appear on the leaves in the center of the plate, then this suggests that there is a deficiency of potassium in the culture - potash feeding is needed (a glass of wood ash, dissolved in 10 liters of water, 500 g per bush). If the leaves of the plants are covered with yellow spots all over the plate, then a nitrogen deficiency is quite possible here. But pale yellow shades on the leaves appear when plants are cultivated in soils with rich organic matter, but in copper-depleted peaty soils.

Light yellow shades of young leaves indicates a deficiency of iron in the soil, and if such a process occurs with old leaves, then the reason lies in the deficiency of manganese. The leaves are also covered with yellowness during phosphorus starvation, and with its excess, only the tips of the leaves change color. It is also important to remember that plants can turn yellow from old age, such leaves are simply removed. They often turn yellow and dry out due to unsatisfactory functioning of plant roots. (damage, hypothermia, etc.). Sharp temperature fluctuations can lead to disruption of nutritional functions - the leaves, for the most part, get bluish tints.

Root functions also deteriorate after receiving mechanical damage during soil cultivation procedures (the lower deciduous layer of plants is covered with yellowness). When the roots are restored, the plants come to life. Culture ovaries often turn yellow. There are also many reasons for this: sharp temperature shifts, degree of humidity, lack of lighting, thickened planting line. It is unpleasant when the yellowed ovaries die off, depriving you of hopes for good yields.

Competent care of a particular crop consists of a set of agrotechnical techniques, which, when properly executed, give the results desired by the gardener.

• Compliance with the norms of crop rotation. We recommend growing nightshades in one place after 3-4 years. If you cultivate tomatoes on the same garden bed all the time, then this is fraught with significant yield losses (up to 40%). This is due to the monotonously applied mineral fertilizers, residual accumulation of various pathogenic elements in the soil. The best predecessors in this sense are traditionally: various varieties of cucumbers, onions, winter wheat and varieties of perennial grasses.
• The cultivation of high-quality tomatoes at a considerable distance from other solanaceous species remains an actual agrotechnical rule, especially from potatoes.
• The quality of pre-sowing soil cultivation is also of great importance for the cultivation of healthy bushes.... In the fall, it is important to dig the beds to a depth of at least 25-30 cm. This procedure favors the incorporation and quick elimination of weeds, unnecessary plant surpluses and pathogenic flora remaining for the winter.
• Excessively acidified soils should be calcified with freshly slaked lime (0.5-1 kg per 1 m²). On alkaline soils, during autumn digging, gypsum is carried out, adding 100-300 g of gypsum per 1 m².
• Increases the resistance of tomatoes to diseases, the timely use of the right fertilizers and dressings. Mistakes made in this area sometimes lead to serious consequences:
  • nitrogen deficiency leads to the fact that the aged leaves of the lower layer of plants are covered with yellowness - the negative process develops throughout the entire leaf blade, the veins get a bluish color, and the young leaves - pale shades;
  • with a lack of potassium yellowing and drying begins from old leaves, from their periphery (marginal burns);
  • in case of magnesium deficiency the yellowing process starts from medium and old leaves, without touching the veins, and the affected leaves slowly but surely begin to turn brown and curl;
  • with manganese deficiency yellowing begins with young leaves, without touching the veins, and the disease ends with necrosis of greenery;
  • lack of sulfur affects plants similarly to nitrogen deficiency, but affects the upper leaves;
  • manganese poisoning leads to yellowing of old leaves, with the appearance of brown necrotic spots and manifestations of interveinal chlorosis in young leaves;
  • in case of copper poisoning the yellowing process spreads over all leaves without affecting the veins, and then irreparable dying off occurs.

Irrigation mistakes lead to plant health problems, reduced growth rates and reduced yields. In the southern regions of the country, tomatoes are irrigated up to 7-9 times during the growing season, and in the northern regions - up to 5-7 times a season. It should be irrigated in the grooves, keeping the soil moisture level at 60%. It is better to use a drip irrigation method, when water is supplied directly to the roots; it is advisable to do this also from the calculation of saving water resources.

Errors made when mulching are performed are typical - poor-quality mulching leads to known violations of crop growing conditions. Often there are also violations committed in the preparation of seed materials.

Root damage, as practice shows, occurs in a number of cases.

• When the seedlings are in small and cramped containers, when the roots of plants roll into a ball, and therefore they are damaged during transplantation. This worsens the degree of adaptation of plants to a new place, they begin to turn yellow and wilt.
• We get a similar effect by overexposing the seedlings at home. - the roots become overdeveloped, which interferes with the successful adaptation of plants in greenhouses, yellowness and loss of leaves appear.
• Insect pests can also harm plant roots. (bear or wireworm). Therefore, when the seedlings turn yellow, after planting them in the greenhouse, the soil is treated with appropriate insecticides.
• Mechanical damage to the roots often occurs as a result of:
  • unsuccessful planting of seedlings in the soil;
  • careless loosening or weeding of plants.

These conditions include violations of the microclimate, as well as the condition of the soil inside greenhouses. There are a number of rules that must be followed.

• It is recommended to build greenhouses not in places that are open from different sides., but it is better on those where at about lunchtime the place will be somewhat shaded either by trees or outbuildings. With constant sunlight in greenhouses, it will be difficult to maintain a stable temperature regime (no more than 30 C). Otherwise, the plants will begin to turn yellow.
• The greenhouse soil is subject to regular replacement (before the start of each season), since it is in the ground that the larvae of pests hide, for a long time fungal spores and pathogenic pathogens can lurk there. Greenhouses should be disinfected in spring (both walls and wooden pallets). The garden inventory is also subject to such processing.
• For planting material, it is necessary to select seeds obtained from healthy plants.after keeping them in a pink solution of manganese.
• In order to reduce the level of humidity, it is important to slightly open both windows and doors in greenhouses, carrying out beneficial ventilation. If there is not enough moisture in the greenhouses (the leaves turn yellow), then small and open containers with water are placed in them. It should be remembered that heat and humidity are a favorable environment for the progressive development of infectious diseases and fungal manifestations. It is for this reason that the degree of plant disease in greenhouses is higher than in open soils.
• Violations of the soil moisture regime in greenhouses is a significant mistake... You should know that tomatoes are drought-resistant plants, and irregular irrigation is bad for them. Therefore, waterlogging of the soil has a worse effect on plants than undermoistening. Overflows are more often the cause of yellowing of foliage, since waterlogged soil is less aerated, it can sour, and the roots of the bushes will hurt. In these cases, the following symptoms are recorded: the leaves of the lower tier undergo complete yellowing, like the petioles. The yellowed leaves lose their turgor and die off. Pale shades spread throughout the plant.
• With significant changes in day and night temperature regimes, the state of plants deteriorates sharply, which is expressed in the following symptoms:
  • the leaves begin to turn yellow and dry out, starting from the edges (they overheat during the day - they burn out under the rays of the sun);
  • the foliage becomes yellow and loses its turgor, the plant withers before our eyes (from hypothermia at night and poor functioning of the roots).

It is important to monitor the degree of soil acidity in greenhouses. Heavy and acidic soils are difficult for plants to tolerate. The required soil pH for tomatoes is 6.0-6.8. Significant deviations from these parameters inhibit the development of roots, impair the process of assimilation of nutrients, and lead to yellow foliage.

Soils for growing crops should be loose, well aerated. Do not allow moisture stagnation in them, which naturally ends with soil acidification. Remember to periodically check and adjust the pH level in the soil, as a number of agricultural practices change the degree of acidity in it.

Diseases of the culture in greenhouses that cause yellowness on the leaves are more frequent than in open conditions... Of the most common diseases, we will give an example of tobacco mosaic. The disease manifests itself with chaotic, mosaic manifestations of yellowness in various parts of the leaf blades. Such manifestations are more clearly observed on young leaves. The spotted wilting of the culture in its initial form is manifested by small yellow or orange specks on mature leaves, the edges of which are slowly dying off. The disease proceeds against the background of yellowing of the foliage, its gradual wilting.

Fusarium oppression of plants starts with the appearance of yellowness and wilting of the apical part of the plants, slowly covering all their parts. With this disease, the leaves begin to turn yellow at the bases, and the veins gradually acquire light shades. Alternaria disease is characterized by the fact that yellow spots capture the plants from below, gradually rising up. They are grouped between veins, gradually storming. At high humidity levels, signs of sporulation can be discerned on them. Here, after harvesting the fruits, disinfection is mandatory in the greenhouses. Without it, even if one plant was affected, epiphytoty may well develop.

Attacks by sucking pests on crops are usually characterized by local manifestations of yellowing of leaves in places where these harmful insects live. In addition, some of their species can be carriers of infectious diseases.

The ways of solving the problem of the appearance of yellowness on the leaves of the culture have already been discussed in the course of the presentation of the topic. Let's try to briefly summarize the above, noting the main aspects. It is important to understand that the whole range of measures for caring for plants in a greenhouse or in a greenhouse is interconnected, if you ignore at least one point, then one way or another the disease will manifest itself.

• Correct irrigation of the culture is carried out in the morning or in the evening, because through the droplets of water, the foliage receives severe burns, manifested by their yellowing. During irrigation, only settled and warm liquid is used. Do not allow water to be found on the leaves and stems of plants, this stimulates the appearance of fungi. We use only root type irrigation or drip irrigation system. Watering plants is best done rarely, but abundantly. The ideal irrigation schedule is to water 2 times every 7 days. Young animals need large amounts of water. The degree of irrigation is reduced as the fruit ripens.
• With a deficiency of some elements, in order to avoid the appearance of yellowness on the leaves, you should:
  • with a nitrogen deficiency, the leaves are treated with a solution of humic fertilizer, and from folk remedies - with mullein infusion or "herbal herbal tea";
  • there is not enough potassium - treatment is carried out by spraying plants with potassium humate, infusion of ash or solutions of complex fertilizers ("Kristalon tomato");
  • magnesium deficiency is compensated by a solution of "Kalimagnesia";
  • with a shortage of manganese, one should fight by spraying the plants with a pinkish composition of potassium permanganate or manganese sulfate;
  • with a sulfur deficiency, the bushes should be fed with a composition of manganese sulfate;
  • in the event of manganese poisoning, treatment is futile - we remove the bush, change the topsoil, deeply rinse the soil with water;
  • in the case of copper poisoning, measures are taken similar to the previous case.
• For diseases:
  • in the process of identifying the first signs of a fusarium disease, the bushes are treated with "Trichodermin" or "Previkur" (young bushes, as well as mature plants with ripening fruits, are susceptible to this disease);
  • the appearance of signs of late blight is prevented by the drip irrigation system, and in case of an obvious disease, Bordeaux liquid is used.

Summarizing the above, one should focus on an approximate system of preventive measures to prevent yellowing of leaves in a culture. With a shortage or excess of nutrients, timely fertilizing of the crop is carried out, without exceeding the standard indicators for adding fertilizers.

Anti-infectious preventive measures include:

• autumn disinfection of greenhouses;
• seed dressing;
• strict adherence to landing schemes;
• systematic ventilation of greenhouses;
• preventive measures against pests;
• careful selection of more resistant varieties.

In case of possible damage by pests, perform:

• strengthening the immune defense of plants;
• autumn disinfection of soil in greenhouses;
• microclimate control and maintenance;
• elimination of weeds.

With overheating or hypothermia of plants:

• planting seedlings in greenhouses exclusively when the soil warms up to +15 C;
• regular ventilation;
• installation of heat accumulators (barrels, water bottles, etc.), which reduce the level of daily temperature fluctuations.

To avoid mechanical damage to plant roots:

• planting seeds in separate containers;
• careful transplantation into the soil;
• competent loosening and weeding of beds;
• installation of special traps for bears.

For heavy and acidic soils:

• regular monitoring of PH;
• soil deoxidation with dolomite flour;
• introduction of organic additives and baking powder (sand, straw chaff, brick chips, etc.);
• the device of drainage systems.