1. How to prevent nutrient deficiency
① Phosphorus deficiency. Symptoms are the slow growth of vegetable plants, the leaves become smaller but not chlorosis, or the color of the leaves becomes darker, and the stems become thinner. For remediation, use superphosphate 50-100 kg/mu as basal fertilizer, or spray 0.3%-0.5% potassium dihydrogen phosphate solution on foliage during the growth process.
② Nitrogen deficiency. Symptoms are vegetable plants are short, the leaf color becomes pale or red, and some leaves turn yellow; the stem color often changes, and the change is rapid, brown after drying, and the stem is short and thin. Quick-acting nitrogen fertilizers, such as urea, can be topdressed in time, and ammonium bicarbonate is generally not used in greenhouses.
③ lack of potassium. The symptoms are that the leaves of vegetables are light grayish green, the edges of the leaves turn yellow and dry, and the stems are thin and hard. Topdressing quick-acting fertilizers, such as potassium sulfate, can be applied immediately, or 0.3%-0.5% potassium dihydrogen phosphate solution can be sprayed on the foliage.
④ Lack of manganese. The symptom is mesophyll necrosis of young leaves, but the veins of the leaves remain green, and the leaves are deciduous in the later stage. The best way is to keep the soil neutral, apply 1-4 kg of manganese sulfate per mu as base fertilizer, or topdressing 0.2% manganese sulfate outside the roots.
⑤ lack of copper. Young leaves show shrinkage, plant growth is weak, leaf color changes, and leaf tips turn white. Spraying 0.05% copper sulfate solution on the leaves and applying more organic fertilizers can prevent the occurrence of copper deficiency.
⑥ Iron deficiency. The young leaves show a greenish-yellow-white color between veins. In severe cases, the whole leaves turn yellow-white and dry. 0.1%-0.2% ferrous sulfate solution can be sprayed on the foliar
⑦ Boron deficiency. The growth points are shrinking, browning and withering, the plant type is clumped, and the leaves are curved, showing symptoms of leaf burn. Apply 0.5 kg of borax per mu as base fertilizer, or spray 0.1%-0.2% boric acid on the foliar surface.
⑧ Magnesium deficiency. Old leaves become green and yellow, but the veins are still green, the leaves become brittle, the edges of the leaves are rolled up, and sometimes the leaves appear purple-red. 0.5% magnesium sulfate solution can be sprayed on the foliar surface in time.
2. How to dehumidify
Vegetable greenhouses are often in a humid state. Therefore, dehumidification is the main content of its humidity management, and it is also an important link in the operation of greenhouse vegetable planting technology.
① Maintain ventilation. Ventilation must be carried out at high temperatures, otherwise it will easily cause the indoor temperature to drop. When ventilating, close the vents in time to prevent the temperature from dropping and freezing the vegetables.
②Temperature increase and decrease humidity. This method can not only meet the temperature requirements of vegetables, but also reduce humidity. When the plant grows to a certain degree of resistance, water and close the shed to heat up to about 30 ℃ for 1 hour, and then ventilate to remove moisture. It can be repeated once when the shed temperature is lower than 25℃ after 3-4 hours.
③ Water reasonably. Watering increases the humidity. For winter and spring production, you can choose ditch watering on sunny days or branch watering, and mulch mulch can use under-film dark irrigation. Strictly control the amount of watering to prevent excessive humidity. Properly ventilate after each watering, and hoe and loosen the soil in time to reduce soil and air humidity.
④Increase the amount of light transmitted. The increase in light transmittance can increase the room temperature. After the room temperature is increased, ventilation is performed to achieve the purpose of dehumidification.
⑤ Use insulation curtain material with good moisture absorption. For example, the non-woven fabric can prevent condensation on the inner surface and prevent dew from falling on the plants to achieve the purpose of reducing air humidity.
⑥ Natural moisture absorption. Use rice straw, wheat straw, quicklime, etc. to absorb water vapor or fog between rows to achieve the purpose of dehumidification.
⑦ Plastic film covering. Film mulching in the greenhouse can reduce the evaporation of soil moisture in the greenhouse. The ridges of different sizes are alternately spaced and the mulching film covers the double ridges. When watering, the water flows in the small ridges under the mulching film. As the mulching film prevents the water from evaporating, it avoids the large increase in air humidity in the solar greenhouse after watering.
⑧ Cultivation and dehumidification. Cut off the soil capillary tube to prevent the soil capillary water from rising to the surface and prevent the large amount of soil moisture from evaporating.
