Vegetable seedlings are an important part of vegetable growth. It is also the basis of early maturity, high yield, and high quality of vegetables. In the process of raising seedlings, beware of the following situations: First, prevent "top shell" seedlings. Although the seeds can germinate and emerge, but the seed coat does not fall off after exhumation, clamping the cotyledons, the formation of "top shell" seedlings, also known as "dim cap" seedlings, seriously affecting the photosynthesis and growth of seedlings, easy to form weak seedlings. This phenomenon is most common in melon crops. First, the seeds were too shallow, the topsoil was easily dried, the seed coats dried hard, and the second was that the seeds were not mature enough or old; the third was the premature release of the film. Preventive measures: Fully dip the bottom water before sowing and keep the soil moist before emergence. The depth of sowing should be appropriate. When the topsoil has just emerged, it should be sprayed with water. Two anti-"high" seedlings. Also known as the Tu long seedlings, the field showed fine stems, long internodes, less fibrous roots, thin leaves, light color, poor resistance, and it was not easy to survive after colonization. Mainly due to lack of light, the density is too large, the night temperature is too high, too much nitrogen fertilizer, even rainy days or glass, plastic film and other dust caused by too much. Preventive measures: control of fertilizer and water, timely ventilation and light transmission, increase the light intensity and light receiving time as much as possible, and time seedling weeding, in case of rainy days, should be opened as usual insulation cover to prevent leggy. Three anti-rooted roots. Long-term low temperature, excessive humidity, excessive fertilization, and improper fertilization methods can all cause the phenomenon of burning and rooting in seedlings. Roots generally rust, roots rot, no new roots, wilting seedlings; burning roots showed yellowing roots, not long new roots, but not rot, seedlings dwarf, slow growth, easy to aging. Preventive measures: Rational fertilization, proper control of moisture, and creation of suitable temperature and humidity. Fourth, poison gas pollution. Improper selection of membranes, some membranes are toxic, and many kinds of toxic gases are volatilized under high-temperature conditions, causing seedlings to be contaminated and symptoms of poisoning appear. The leaves turn green and yellow, and soon turn white and dry. Cruciferous seedlings are the most sensitive, such as cauliflower, rape, cabbage, etc. Even if there are trace toxic gases, the cotyledons will turn white and even die. In order to prevent the film from producing poisonous gas to contaminate the seedlings, when selecting seedlings, qualified agricultural special film must be used. If abnormal film is found to be toxic due to poisonous film, replace the film in time or increase the ventilation during the day to release toxic gas. The seedbed should be fully cooked. Organic fertilizers, especially nitrogen fertilizers, should not be used in excessive amounts. Poisoning was found. During the day, ventilation was increased and harmful gases were eliminated. Five defense seedlings were frozen. There are many reasons for the occurrence of frost damage. During the nursery period, it has been relatively warm. Suddenly, a cold spell frequently occurs. The seedlings are often prone to freezing. After a cloudy day, rain, and snow, the weather suddenly turns cloudy, the temperature inside the greenhouse rises rapidly, the relative humidity rapidly decreases, and the seedling tissue dehydrates. Dry and dead; continuous cloudy, rain and snow days, the sun is weak, the temperature is low, the cold resistance of the seedlings is weakened, prone to frost damage; the protection of the nursery facilities is not strict closed, rain and snow fall from the gap to the seedlings, the seedlings are partially affected Frozen; water droplets that condense on the membrane in the morning and fall on the seedlings will also freeze the seedlings locally; the young shoots and leaves at the top are vulnerable to freezing when the seedlings are topped to the membrane; When the temperature is low and the air is suddenly released, the seedlings are also susceptible to freezing, commonly known as "flashing seedlings." When the seedlings were frost-damaged, white and pale yellowish brown necrotic spots appeared on the leaves, or the edges of the leaves turned white, appearing as water-soaked, and gradually dried off. Mild cold injury, the symptoms are not obvious, but the decline in plant physiological function, prone to malformation and malformation. Preventive measures: increase the light intensity, cultivate strong seedlings, low-temperature hardening seedlings, control humidity, rational preparation of bed soil, protection facilities should be tight, before the cold flow came, do a good job of cold insulation. Six pest prevention. Seed disinfection and soil treatment before sowing, guard against damping-off disease, blight, early blight, and gray mold, and prevent the invasion of underground pests, aphids, migratory locusts, and spider mites. Agricultural control and biological control, limited use of chemical control, is strictly prohibited the use of highly toxic, high residue pesticides.
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