Analysis of common physiological diseases of over-summer vegetables

Affected by high temperature, oversummer vegetables often produce physiological diseases due to improper management such as watering, fertilization and medication, such as curly leaves, leaflets, yellow leaves of tomato, yellow cucumber, premature senescence of plants and so on.

For these physiological diseases, many vegetable farmers will mistakenly think that infectious diseases, can not be symptomatic control, resulting in reduced yield and low efficiency of summer vegetables.

In this period, we will focus on the typical physiological diseases of summer vegetables for vegetable farmers' reference. One of the manifestations of physiological diseases: curling leaves of tomato

Symptoms: the leaf rolls up, rolls into a tube when it is severe, and develops from the bottom up.

The physiological curling of tomato leaves is caused by lack of water intuitively. In the case of lack of water, the leaves regulate themselves, closing the stomata to reduce water transpiration and causing the leaves to roll up.

Perhaps some vegetable farmers will ask: when we plant over-summer tomatoes, we water them once every three or five days. How can we be short of water? Don't worry, this is exactly what we are going to analyze.

In addition to the problem of insufficient watering (that is, the amount of watering can not meet the evaporation of soil water and transpiration of plants), poor root development or root injury is the key to plant water shortage. In particular, it should be pointed out that improper watering is likely to be the culprit for root stunting or root damage.

Therefore, summer tomatoes must be watered reasonably and scientifically.

First, it must be watered according to the characteristics of different growth periods.

In general, tomato seedlings should be watered slowly 3-5 days after planting water, and then properly maintain soil drought, promote deep root system, and cultivate strong trees. Results in the early stage, the plant was small and the ground transpiration was large, so it could be watered once every 7 days, and ploughed and hoed after watering. Later, with the growth and development of the plant, the water demand of the plant increases, so it should be watered in time to prevent the occurrence of sudden dry and wet, affecting the normal growth of vegetables.

Second, watering according to the growth.

The plant is dark green, the leaves are glossy, green and flat, and the heart leaves are extended, which is the performance of uniform and suitable moisture. If the heart leaf wrinkles, the leaf color is dark green, the sunny day has the mild leaf prolapse for the lack of water performance, should replenish the water in time. If the heart leaf is over-spread, the leaf is large and thin, and the leaf surface spits too much water, which is the performance of too much water, so the water should be controlled to prevent the growth.

Third, the one-day watering time in the greenhouse.

In summer, do not water when the temperature is higher at noon, you should generally choose before 10:00 and after 4pm.

Some vegetable farmers don't understand why they can't be watered at noon, but the reason is very simple. Because the ground temperature is already high in summer, if the ground absorbs more heat after a few hours of strong light in the morning, the ground will absorb more heat, making the ground warmer, while the water used to irrigate the land is pumped from the ground, and the temperature is much lower. Watering vegetables with such well water will cause a sharp drop in soil temperature, weaken the metabolic activity of roots and affect water absorption. At the same time, the transpiration of the branches and leaves on the ground is still strong because of the high temperature, so the water absorption rate of the root system can not compensate the water loss rate of the aboveground, which makes the vegetables lose a lot of water in a short time, resulting in wilting of the plant. dry edge and tip of leaves. The second manifestation of physiological diseases: plant premature senescence

Symptoms: the plant has thin stems, small leaves, yellow leaves, weak growth, less fruit setting, poor fruit development, low yield, and weakening disease resistance and stress resistance.

There are many reasons for plant premature senescence, such as aggravation of diseases and insect pests, lack of light, root injury and so on, but for over-summer vegetables, improper fertilization is the main cause of plant premature senescence.

Some vegetable farmers may say: for over-summer vegetables, we generally do not use organic fertilizer before planting, just sprinkle some chemical fertilizer before planting, and then wash some fertilizer with water each time. How can there be root damage?

In fact, it is these practices that cause root damage to vegetables.

First, do not pay attention to the use of organic fertilizer before planting. Organic fertilizer is a slow-acting fertilizer and long-acting fertilizer, which can not only improve the soil and enhance soil fertility, but also play a balanced and long-term role in supplying nutrients for vegetable growth. If the use of organic fertilizer is insufficient, it often leads to the phenomenon of de-fertilization and premature senescence in the middle and later stage of plant growth and development, even if no matter how much fertilizer is used, it can not save the situation of premature senescence.

At the same time, if we do not pay attention to the use of organic fertilizer and unilaterally increase the application of chemical fertilizer, it will often cause soil consolidation, reduce soil permeability, and easily lead to poor root growth and premature senescence.

Second, excessive use of nitrogen fertilizer. Some vegetable farmers in order to promote crop growth, excessive use of nitrogen fertilizer, resulting in root damage, making plants thin, stunted, and premature senescence. In addition, excessive use of nitrogen fertilizer can easily lead to overgrowth of plants and premature senescence of crops.

Third, excessive fertilizer at one time. One-time application of excessive fertilizer will increase the concentration of soil solution, form salt damage, affect root growth, and then lead to insufficient supply of water and nutrients for plant growth, resulting in premature senescence.

In order to prevent root injury of vegetables, it is necessary to put an end to the above fertilization methods and apply fertilizer scientifically.

The scientific method of fertilization is: on the basis of fully applying organic fertilizer (generally, it is suitable to use more than 5000 kg of organic fertilizer per mu per year), use appropriate amount of chemical fertilizer according to the growth needs of crops, not partial application of nitrogen fertilizer. For example, the most suitable ratio of nitrogen to potassium in tomato fruiting period is 1:2, and 60 jin of compound fertilizer per mu can be applied.

After the occurrence of premature senility of crops, the combination of upper and lower irrigation should be used to remedy it. Upper spraying, that is, foliar spraying foliar fertilizer. Nitrogen, phosphorus and potassium nutritious leaf fertilizer mixed with cytokinin 400 times can be used for foliar spray to quickly supplement the nutrients needed for crop growth and delay plant senescence. Under irrigation, that is, the application of rooting agent or microbial fertilizer to promote the growth of roots and enhance the ability of roots to absorb water and fertilizer. After the plant returned to normal, topdressing was carried out in time according to the growth needs of the crop. The third manifestation of physiological disease: tomato gluten rot

Symptoms: uneven coloring of fruit and blackening of flesh on the inside and outside. In the lightly diseased fruits, part of the vascular bundles turned brown and necrotic, and the shape of the fruits did not change, but the browned parts of the vascular bundles did not turn red. In the seriously diseased fruit, the vascular bundles of the pulp were all dark brown, the placental tissue of the diseased fruit was dysplastic, some of them were accompanied by hollow fruit, the fruit surface was obviously uneven red and green, and in severe cases, the diseased part was light green and the surface hardened.

The main manifestation of tomato gluten rot is poor fruit coloring. Poor fruit coloring can be caused by lack of light, imbalance of nitrogen, phosphorus and potassium, and root injury. To sum up, it is caused by unsuitable cultivation conditions.

Perhaps some vegetable farmers will say: growing over-summer vegetables is like waiting on a child, covering it with a sunshade net for fear that it is hot, giving it a good fertilizer for fear of insufficient nutrition, and watering it every three or five days for fear of insufficient moisture. How can there be inappropriate cultivation?

Although vegetable farmers have done a lot of things, not all of them have done it right.

First, the sunshade net is covered all day, resulting in lack of light. The purpose of setting up the sunshade net is to create a suitable growth environment for vegetables when the light is strong at noon, but many vegetable farmers are no longer managed after being covered with the sunshade net, resulting in insufficient light for vegetables. However, the incidence of muscle rot was higher when the light hours were insufficient, especially when the light hours were less than 7 hours. Light is the power source of photosynthesis. Vegetable farmers are advised to cover the sunshade net only at noon on sunny days and remove it in time in the evening and rainy days to ensure the light exposure time and light intensity of tomatoes.

Second, the proportion of nitrogen and potassium is out of proportion when applying fertilizer. Tomato needs a large amount of potassium fertilizer in the fruiting period, which is about 1.8 times that of nitrogen fertilizer. When topdressing, the amount of nitrogen fertilizer is too large, potassium fertilizer is insufficient, and the incidence of muscle rot is high. In addition, the frequent application of unrotten manure will also aggravate the occurrence of the disease. Therefore, the proportion of nitrogen and potassium should be coordinated when topdressing, and Dayuan Merida (17:5:28) or Fangrun (15:15:30) can be used for topdressing.

Third, root injury leads to a decrease in the ability to absorb water and nutrients, and the incidence is high. At present, due to the high temperature and large water evaporation, some vegetable farmers overwatering in order to promote the rapid growth of tomato, resulting in root injury and promoting the occurrence of gluten rot fruit. Therefore, tomato watering should "look three times", looking at the sky, the earth, and the crops.

For the greenhouse tomato which has occurred gluten rot disease, under the condition of enhanced light, the leaves can be sprayed with 200,300times of potassium dihydrogen phosphate, or 1000 times of Lede foliar fertilizer, or 800,800 times of aromatic foliar fertilizer, to quickly supplement nutrients and reduce the probability of diseased fruit in the later stage. The fourth manifestation of physiological diseases: yellowing of cucumber strips

Symptoms: cucumber strips turn yellow, but there are no disease spots on them.

There is no disease spot on the yellowed cucumber strips, which can rule out the possibility of infectious disease and be judged to be a physiological disease. According to the specific analysis, the poor root development of cucumber in summer is the main reason for the yellowing of melon strips, which will affect the growth and development of the whole plant, so that the cucumber can not get sufficient nutrition, thus causing the yellowing of melon strips.

Perhaps some vegetable farmers will say: in order to make cucumbers nutritious, we do not use less fertilizer, ah, how can this happen?

If the cucumber root system is not well developed, it is useless to apply more fertilizer, because the root system is underdeveloped and cannot fully absorb fertilizer to supply melon strip growth, resulting in the phenomenon of melon strips yellowing.

In fact, root dysplasia is mostly caused by improper subjective management of vegetable farmers. In this regard, root maintenance should be the main way to manage cucumber in summer.

First, change the planting method of watering after planting.

Many vegetable farmers tend to dry and then water when planting. The disadvantage of this is that there is sufficient water and fertilizer in the surface layer, and the root system develops horizontally in the shallow surface layer, which plays a limited role in the expansion of the root system in the future; in addition, it is easy to produce excessive luxuriant phenomenon because of the high fertilizer efficiency of topsoil.

If watering thoroughly before planting, the root system can be induced to develop in depth, there is less fertilizer in the deep soil, and the vegetable absorbs less fertilizer before flowering, which makes the shoot not easy to grow too much, and at the same time, watering first can also reduce the soil temperature. it is more conducive to root growth and slow seedling growth.

Second, protect the leaves and promote rooting.

Most of the nutrients needed by the root system are provided by the middle and lower leaves, so the lower leaves should not be removed prematurely, and leaf diseases should be strictly controlled.

Third, rational fertilization, root cultivation and root protection.

A large amount of fertilizer is easy to cause capillary root aging or injury. Excessive application of base fertilizer or insufficient maturity of organic fertilizer can directly cause root burning and death; excessive application of chemical fertilizer, especially nitrogen fertilizer, can also cause root burning in the fruiting period of vegetables.

The suitable fertilization method is as follows: after applying proper amount of base fertilizer in the shallow layer, and then applying biological fertilizer deeply in the planting site, such as rooting in large sources, it can improve the soil, prevent diseases, promote the growth of new roots and promote the root system to develop in depth to form a strong root system. After entering the fruiting period, the vegetative growth and reproductive growth of vegetables are synchronized. When applying fertilizer, we should not only consider attacking the plant, but also pay attention to attacking the fruit, so we should not apply too much nitrogen fertilizer, but should apply appropriate amount of high-quality compound fertilizer. In addition, if the temperature is too high, the amount of chemical fertilizer should be reduced and biological fertilizer should be applied to ensure the normal growth and development of the root system.