First, flash seedlings
The leaves initially appeared as water-stained, then wilted, and eventually faded to white and dry. The cause is a sharp drop in the temperature within the nursery for a short period of time or the cold wind directly blows to the leaves. Prevention methods are: cold insulation, if necessary, add a small plastic shed; if the temperature is low, do not quickly increase the temperature inside the greenhouse when artificial warming, it should be warm slowly. In addition, the newly germinated seeds (crops) are subjected to low-temperature treatment (5 to 7 days at a low temperature of -1°C to 1°C) and low-temperature training during the seedling raising process, which is helpful for reducing the occurrence of flash seedlings.
Second, cold root
Affected by the low temperature of the ground, the roots stopped growing, water absorption was difficult, the leaves of the ground gradually turned yellow, and wilting occurred severely. The cause is the physiological drought caused by the difficulty of water absorption in the root hairs at temperatures below 12°C in the nursery pot or in the nutrition bowl. The prevention method is: Try to raise the temperature.
Third, roots
The main manifestations are the wilting of the aerial parts and the yellowing of the underground roots. The reason is that the soil temperature is too low (usually lower than 12°C) while the soil moisture in the nursery bowl or the nutrition bowl is too high. The prevention method is to strictly control watering while trying to increase the temperature of the ground.
Fourth, burning root
Seedlings above the roots of the seedlings and roots are yellow, wilt, shrinkage. The reason is that the soil moisture in the nursery pot or the nutrient bowl is too small. At the same time, the fertilizer in the nutrient soil is too much and the fertilizer concentration in the soil is not high without adequate decomposing and crushing. The prevention method is: when preparing the nutritious soil, master the amount of fertilizer used, and use organic fertilizer to fully decompose and crush. If burned roots occur, some water may be poured in time to reduce the degree of damage caused by burning roots.
Five, long seedlings
The main performance is that the seedling leaves are large and thin, light in color, the included angle between the petiole and the stem vine is less than 45 degrees, the slender internodes (tall shoots), the tissues are soft and tender, the cuticle is underdeveloped, the disease resistance is reduced, and the roots of the seedlings are lower. Weak and small, poor absorption capacity, above-ground leaf transpiration is greater than underground root absorption, nighttime respiratory consumption is greater than the daytime nutrient synthesis, flower bud differentiation at the growing point is blocked, female flowers are difficult to see, posing a threat to the increase of previous production and total production. The reason is that the nighttime temperature during nursery is too high, or partial application of nitrogen fertilizer, soil moisture is too large, lack of light. The prevention method is: seedlings Qi Qi or strictly control the night temperature after transplanting to keep it at 16 °C ~ 18 °C, keep the temperature difference between day and night at about 10 °C; nutrient soil preparation when controlling the amount of nitrogen fertilizer; strict control of watering, do May increase lighting more
Six, old and young seedlings (flower topping)
Seedling performance is exactly the opposite of leggy seedlings. Plant growth is weak, leaves are thin, and the color is dark green, especially the internodes of the stems are shortened. In severe cases, they are clustered, and there are a large number of male and female flowers. The cause is that the soil moisture is too small during the nursery period and it is in a drought state for a long time; the indoor day and night temperatures are generally low; or the nutrient soil nitrogen fertilizer is seriously deficient, resulting in excessive reproductive growth. The prevention method is: when carrying out nursery transplanting, the nursery bed should be filled with transplanting water in advance; after the watering, the indoor and outdoor temperatures should be appropriately raised to keep it at 25°C~28°C during the day, preferably no more than 30°C, kept at night. 18 °C ~ 22 °C; nutrient soil preparation should be done in a balanced and reasonable nitrogen, phosphorus, potassium; daytime should increase light. In addition, plant growth regulators are sprayed appropriately, such as foliar sprays of gibberellin.
Seven, roasted seedlings
The main manifestations are the leaves of plants in local areas (close to the front of the greenhouse and near the east and west gables). There are patches of chlorosis and chlorosis. The macula can start from the leaf margins and reach the middle part of the leaflet to approach the upper young leaf. In the main, all the affected leaves exhibit a certain regularity, that is, the same time and location, and no development is not contagious. The cause is that when the nursery is raised, the local lighting is too strong and the temperature is too high, causing the local cells of the leaves to drip. The prevention method is: pay attention to the change of indoor temperature in sunny days after nursery and planting, strongly illuminate before and after noon, increase the ventilation and ventilation volume at high room temperature, and keep indoors at 25°C～28°C during the daytime, do not exceed 30°C, and properly water Replenish water lost due to transpiration.
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