Core Tip: In spring, with the rise in temperature, greenhouses entered a new management period. However, some of the harm in this period also gradually manifested with the advancement of management. Farmers need to focus on preventing "salt damage, drug damage and fertilizer damage". In response to this "three harm", if farmers do not pay attention to it, it will often cause vegetable diseases and even dead trees. Therefore, comprehensive control should be carried out according to the principle of prevention first and combination of prevention and control.

Do not underestimate "salt damage"

In greenhouse cultivation, "salt damage" is an important factor affecting yield. Therefore, it is imperative to solve the "salt damage" in melon and vegetable greenhouses. Blind excessive fertilization, relying solely on chemical fertilizers for yield, will inevitably lead to a rapid increase in salt accumulation in the soil, which is bound to cause the occurrence of fertilizer damage (salt damage). How to solve and avoid the harm caused by blind fertilization?

First, adjust the application ratio of organic fertilizers, chemical fertilizers and microbial fertilizers in melon and vegetable greenhouses. Organic fertilizers account for 65% of the demand for crops in the growth period of melon and vegetable greenhouses, chemical fertilizers account for 30% of the growth period, and microbial fertilizers account for 5% of the total growth period; chemical fertilizers should be based on the physiological needs of different crops, changing the components containing chlorine, nitrate, potassium, and sodium. Microbial fertilizers must always participate in the whole process of base fertilizer, top dressing, and flushing fertilization.

Second, apply 100-150 kg/mu of soil improvement fertilizer to melon and vegetable greenhouses with severe salt damage, and the effect is extremely significant. The application of soil improvement fertilizers can control the occurrence and spread of soil "salt damage", and low-yield sheds have gradually become medium and high-yield sheds, which are very popular with vegetable farmers.

The third is the rational selection of fertilizer types. The order of salinity of commonly used fertilizers from high to low is; ammonium chloride > potassium chloride > ammonium nitrate > potassium sulfate > urea > ternary compound fertilizer and binary compound fertilizer. It can be seen that chlorinated fertilizers have strong salinity. When applying in greenhouse soil, pay attention to the use of chloride, nitrate and sulfate fertilizers.

Do not ignore the "phytotoxicity"

The most common injuries caused by plant growth regulators are seedling shrinkage deformity and leaves showing fern leaf virus symptoms. In better weather conditions, the "phytotoxicity" symptoms are not easy to detect or the symptoms are mild, but after encountering continuous rainy weather, the plants cannot perform normal photosynthesis, and root absorption will have problems. Therefore, the symptoms of plant poisoning will be prominent at this time. The prevention and control measures are as follows:

First of all, do a good job of prevention. Master the correct concentration, method of use, and location of use of plant growth regulators, such as bottle gourd. The use of ethephon can promote the early blooming of female flowers in the main vines, but it must be used in the true leaf stage of 4 to 6 pieces. Early use is prone to phytotoxicity.

Secondly, determine the applicable concentration. If the concentration is too low, it cannot produce the desired effect; if the concentration is too high, it will destroy the normal physiological activities of plants and even harm plants. The concentration effect of plant growth regulators is far more complicated than that of general pesticides. The concentration of the same plant growth regulator used by different crops varies greatly, and it is related to the growth of crops.

Again, pay attention to the climatic conditions. If the temperature is too low, the leaf surface absorbs slowly; if the temperature is too high, the water of the liquid medicine will easily evaporate, which is easy to cause the unabsorbed agent to settle on the leaf surface, which is harmful to the tissue. When applied in arid climate conditions, the concentration of the liquid medicine should be reduced; when applied in the season of sufficient rain, the concentration should be appropriately increased.

don't let go of "fertilizer damage"

greenhouse vegetables "fertilizer damage" can be roughly divided into three kinds, one is that the amount of fertilizer is too large or too close to the plant, and the crop is burned by high-concentration fertilizer; the second is that a certain nutrient element is applied too much, resulting in the lack of other elements; the third is under closed management conditions, excessive application of nitrogen fertilizer, no soil or timely ventilation after application, ammonia or nitrous acid gas poisoning occurs. These three "fertilizer damage" should be prevented and controlled, and the prevention and control of ammonia and other harmful gases on crops should be the focus.

First, scientific fertilization, to prevent one fertilization amount from being too large, cover the soil or fully mix with the soil after application of the base fertilizer; for topdressing, deep soil application should be advocated, and water should be poured in time after application, and fertilizer should not be sprinkled on the ground.

the second is to balance fertilization, the potassium fertilizer should be applied in an appropriate amount, in batches or layers; do not directly mix zinc, iron and other trace element fertilizers with phosphorus fertilizers, it is best to mix with decomposed organic fertilizers and humic acid fertilizers.

Third, excessive application of nitrogen fertilizers will cause ammonia and nitrite gas to accumulate in the soil, so the nitrogen fertilizer should be applied in an appropriate amount and cooperated with phosphorus, potassium and other fertilizers. After application, cover the soil in time or fully mix the fertilizer with the soil, so that the nitrogen fertilizer can be fully absorbed and utilized by crops.

Fourth, the application of organic fertilizers, slow and controlled release fertilizers and other nutrients can reduce the production of harmful gases and inhibit nitrous acid gases. In addition to rational application of nitrogen fertilizers, nitrification inhibitors can also be used in moderation. (Comprehensive)