What are the control measures for fertilizer damage and high-temperature damage in greenhouse vegetables

In the technical aspects of vegetable greenhouse planting, fertilizer damage and high-temperature damage are important factors affecting vegetable yield, quality and profitability. The following are essential control methods.

1. How to prevent and control fertilizer damage

1. Apply fertilizer deeply. Chemical fertilizers should be applied deeply or dissolved in water for irrigation.

2. Apply fertilizer in appropriate amounts. Because fertilizer loss inside a greenhouse is small, the application rate should be lower than for open-field vegetables.

3. Apply organic fertilizer after it is thoroughly decomposed. In particular, barn manure and human and livestock manure must be fully decomposed and fermented before application.

4. Ventilate in a timely manner. After application, ventilation and air exchange should be strengthened, and a certain amount of ventilation should also be maintained at night, to prevent harmful gases produced during fertilizer decomposition from accumulating in the greenhouse and poisoning the vegetables.

5. The fertilization distance should be appropriate. When topdressing quick-acting fertilizers such as urea, do not place them close to the roots, to prevent root burn. When applying foliar fertilizer, the concentration should preferably be 0.5%-1%.

6. The application amount should not be too large. Whether topdressing or foliar spraying chemical fertilizers, the amount must be appropriate.

2. How to prevent and control high-temperature damage

1. Strengthen ventilation. Regulate the air inside the greenhouse to keep the air fresh and remove all harmful gases from the greenhouse. When the outside temperature rises to about 18°C, gradually begin ventilation.

2. Control the optimum temperature. Keep the daytime temperature inside the greenhouse at 20-25°C and the nighttime temperature at 15-18°C. Temperature control can be carried out in combination with measures such as ventilation and air exchange and water spraying.

3. Replenish water in a timely manner. When the greenhouse soil is short of water, water should be replenished in time to regulate temperature with water and reduce high-temperature damage.

3. How to prevent and control freezing damage

1. Irrigate to preserve heat. Irrigation can increase the soil heat capacity, prevent ground temperature from dropping, stabilize the air temperature near the surface, and help the air temperature rise steadily, allowing frozen vegetable tissues to recover their functions.

2. Ventilate to lower the temperature. After greenhouse vegetables are frozen, do not immediately close the greenhouse to raise the temperature; only ventilate to lower the temperature, so that the temperature inside the greenhouse rises slowly, avoiding a sudden temperature rise that causes frozen tissues to necrose.

3. Spray water manually. Spraying water can increase the air temperature inside the greenhouse, stabilize the greenhouse temperature, and inhibit evaporation of water exuded from frozen tissues, prompting the tissues to absorb water.

4. Prune withered branches. Promptly prune frozen stems and leaves, to prevent the tissues from becoming moldy and diseased and inducing disease.

5. Set up shade in the greenhouse. Building shade inside the greenhouse can prevent frozen vegetables from direct sunlight and keep frozen tissues from losing water.

6. Apply supplementary fertilizer. After frozen plants recover from transplanting shock, topdress with quick-acting fertilizers. A 2% urea solution or 0.2% monopotassium phosphate solution can be sprayed on the leaves.

7. Prevent and control pests and diseases. After plants are frozen, pests and diseases can easily take advantage of the weakness, so some protective agents and pesticides for disease and pest control should be applied in a timely manner.

4. How to prevent and control climate disasters

Disastrous weather in energy-saving solar greenhouse vegetable production includes: continuous cloudy snow (rain, fog) days, low temperature with little sunlight, blizzards, sandstorms, etc. Although the probability of such weather is very low, once encountered, it will be extremely unfavorable to production. The following measures can be taken in production to respond.

1. Optimize the structure and improve the heat preservation effect.

2. Focus on “protection” and improve the plants' tolerance to damage. In winter management, maintain a relatively low temperature and adopt conservative measures to ensure the plants safely overwinter. Keep 25-28°C during the day and 10-14°C at night. While applying pesticides to prevent disease, spray a 1:200 sugar and nitrogen solution, or add 0.5% glucose and 0.3% monopotassium phosphate. This can not only improve resistance, but also improve the plants' ability to resist downy mildew.

3. During continuous rainy and snowy weather, on the basis of heat preservation, expose the plants to more light and receive scattered light on cloudy days, while keeping the temperature of the solar greenhouse unchanged. Heat should be added before the temperature drops to the point where growth is about to be damaged, to ensure the plants are not damaged by freezing. Raise the temperature to the biological minimum of 13-15°C, not too high, to prevent increased respiratory consumption.

4. After cloudy, rainy and snowy days, the straw mats should be put back. When the weather clears after cloudy and snowy days, after the mats are uncovered, the plants' water balance is disrupted, causing wilting. In mild cases, the growing points are damaged; in severe cases, all greenhouse vegetables die. At this time, attention should be paid to putting the mats back. The method is: after it clears that day, uncover the mats early so the plants see light in the early morning sun and gradually adapt. If the plants are found to be wilting, promptly cover them with the straw mats again, and uncover them again after the plants recover. If wilting occurs again, cover them with the straw mats again. Repeat this several times. Alternatively, after putting the mats back, combine with foliar water spraying to regulate the water balance.