In early spring, watermelons in greenhouses are often cultivated in the form of “three membranes and one bowl†and covered with heat preservation methods, that is, a small arch shed in a large arch shed, a covered mulch in an arch shed, and a grass cover outside a small arch shed, which can be compared with the exposed watermelon in the morning for more than 60 days. Although the economic benefits are considerable, due to the low temperature during the nursery period, the following problems are likely to occur. Therefore, the melon farmers should take precautions so as not to affect the later agricultural arrangements and economic benefits.
Zombie
Symptoms Seedlings grow less, show slower leaves, new leaves are grayish green, leaves thicken, shrink, stiff tissues, yellow cotyledons and true leaves; yellowish roots, browning, and little new white roots. Once the seedlings of the watermelon seedlings are froze, the recovery will be very slow, which will delay the agricultural season and seriously affect the yield and benefits. Stiff seedlings are the main physiological obstacles for watermelon seedlings.
Causes The low temperature of the seedbed, especially the low soil temperature, can not meet the basic requirements for the growth of watermelon roots; soil bed of seedling bed is heavy, soil water content is high, seedlings are difficult to root, roots have poor absorption capacity; fertilizers are applied to seedbeds or planting holes or Burnt roots without ripe organic fertilizers; too much root damage during planting, improper operation during site preparation and planting, root overhang, no close contact between roots and soil, affecting rooting; underground pests harm the roots of seedlings.
Preventive measures Select loose, well-ventilated pastoral soil as a nutrient soil; improve the nursery environment, use geothermal lines or plastic film to cover seedlings, raise the temperature of the soil; apply rotten organic fertilizer on the seedbed, lightly apply the compound fertilizer away from the roots; timely and appropriate watering to avoid Reduce seedbed temperature and ground temperature, affect root growth; planting with high sorghum deep groove, strengthen drainage; attention to hardening seedlings before transplanting; timely planting, to prevent the impact of low temperature after planting, select the cold tail warm head planting; prevention and control of underground pests .
Acting seedlings
Symptoms Watermelon seedlings grow too vigorously and appear to be long, showing internode elongation, petiole and leaf body lengthening, light green leaves, thin leaf tissue, and tender tissue.
The reason of the occurrence of seedbed light is insufficient, the temperature is too high, soil and air humidity is high, prone to seedling seedlings. The leggy seedlings have poor resistance to low temperature and are prone to frost damage.
Preventive measures Reasonably regulate temperature, humidity and light. The temperature of the seedbed shall be divided into sections, timely ventilation, dehumidification, increasing light, avoiding excessive temperature, lowering the night temperature, increasing the temperature difference between day and night, and appropriately lowering the temperature and humidity under insufficient light conditions.
Thin and weak seedlings
Symptoms The seedlings of watermelon seedlings are small, light in color, small in size, shrivelled, and thin in stems.
The reason for the occurrence of poor seedlings, poor root development; lack of fertilizer.
Preventive measures to improve the conditions of nursery, the use of nutrient é’µ warming measures for nursery; seedbed soil or nutritious soil mix appropriate amount of quick-acting fertilizer, add three yuan compound fertilizer 250 grams per cubic meter, 250 grams of superphosphate; timely increase of foliar fertilizer, The foliar was sprayed with 0.2%-0.3% potassium dihydrogen phosphate solution or 0.2% urea solution.
Root seedlings
Symptoms occur mainly in the roots or stems of watermelon seedlings, and are a common physiological disease in watermelon seedlings. When roots occur, the roots do not grow new roots or adventitious roots. The roots turn brown and rot. The cotyledons and new leaves become thin, yellowish-brown or milky yellow, the leaf margins scorch, and the shoots wilting. When the scorch is severe, the dry film becomes dry and lacking in symptoms. The diseased seedlings are easy to pull up and there is no root hair.
The reason for the occurrence of seedlings is poor, the temperature is too low, or the seedbed soil has high humidity. Precautionary measures: Nutrition, temperature and warming measures are used to nurse the seedlings; seedbeds are to be constructed in places with high dryness, sunny leewards, and convenient drainage; seedbeds should be fully sun-dried and full-base fertilizers should be applied before planting; bed soil or nutrient soil should be treated with pesticides; Soak the seeds in warm water at 55°C for 15 minutes. Soak germination after soaking. Strengthen seedbed management. The seedbed temperature should be controlled at 20°C-30°C, and the ground temperature should be kept above 16°C. Insulation of the seedbed should be done to prevent the cold wind from blowing in; , Small water pouring, to prevent the seedbed humidity is too large.
Albino seedlings
Symptoms When the first true leaf appears, the edges of the cotyledons and young leaves become chlorogenic and white, resulting in stagnant seedling growth. The light can restore growth, and the cotyledons and true leaves are dry and only the growth points are retained, resulting in long seedlings or even stiff seedlings. In severe cases, cotyledons, true leaves, and growing points are all frozen to death.
The reason was that the seedlings were frozen, the ventilation during the seedling period was improper, and the bed temperature was drastically reduced.
Preventive measures should be planted in due time and seedbed insulation measures should be taken to ensure that the bed temperature should be above 20°C during the day and not less than 15°C during the night; the emergence period should not be ventilated too early in the morning and ventilation should be gradually increased to avoid sudden changes in seedbed temperature and injury to the seedlings.
Zombie
Symptoms Seedlings grow less, show slower leaves, new leaves are grayish green, leaves thicken, shrink, stiff tissues, yellow cotyledons and true leaves; yellowish roots, browning, and little new white roots. Once the seedlings of the watermelon seedlings are froze, the recovery will be very slow, which will delay the agricultural season and seriously affect the yield and benefits. Stiff seedlings are the main physiological obstacles for watermelon seedlings.
Causes The low temperature of the seedbed, especially the low soil temperature, can not meet the basic requirements for the growth of watermelon roots; soil bed of seedling bed is heavy, soil water content is high, seedlings are difficult to root, roots have poor absorption capacity; fertilizers are applied to seedbeds or planting holes or Burnt roots without ripe organic fertilizers; too much root damage during planting, improper operation during site preparation and planting, root overhang, no close contact between roots and soil, affecting rooting; underground pests harm the roots of seedlings.
Preventive measures Select loose, well-ventilated pastoral soil as a nutrient soil; improve the nursery environment, use geothermal lines or plastic film to cover seedlings, raise the temperature of the soil; apply rotten organic fertilizer on the seedbed, lightly apply the compound fertilizer away from the roots; timely and appropriate watering to avoid Reduce seedbed temperature and ground temperature, affect root growth; planting with high sorghum deep groove, strengthen drainage; attention to hardening seedlings before transplanting; timely planting, to prevent the impact of low temperature after planting, select the cold tail warm head planting; prevention and control of underground pests .
Acting seedlings
Symptoms Watermelon seedlings grow too vigorously and appear to be long, showing internode elongation, petiole and leaf body lengthening, light green leaves, thin leaf tissue, and tender tissue.
The reason of the occurrence of seedbed light is insufficient, the temperature is too high, soil and air humidity is high, prone to seedling seedlings. The leggy seedlings have poor resistance to low temperature and are prone to frost damage.
Preventive measures Reasonably regulate temperature, humidity and light. The temperature of the seedbed shall be divided into sections, timely ventilation, dehumidification, increasing light, avoiding excessive temperature, lowering the night temperature, increasing the temperature difference between day and night, and appropriately lowering the temperature and humidity under insufficient light conditions.
Thin and weak seedlings
Symptoms The seedlings of watermelon seedlings are small, light in color, small in size, shrivelled, and thin in stems.
The reason for the occurrence of poor seedlings, poor root development; lack of fertilizer.
Preventive measures to improve the conditions of nursery, the use of nutrient é’µ warming measures for nursery; seedbed soil or nutritious soil mix appropriate amount of quick-acting fertilizer, add three yuan compound fertilizer 250 grams per cubic meter, 250 grams of superphosphate; timely increase of foliar fertilizer, The foliar was sprayed with 0.2%-0.3% potassium dihydrogen phosphate solution or 0.2% urea solution.
Root seedlings
Symptoms occur mainly in the roots or stems of watermelon seedlings, and are a common physiological disease in watermelon seedlings. When roots occur, the roots do not grow new roots or adventitious roots. The roots turn brown and rot. The cotyledons and new leaves become thin, yellowish-brown or milky yellow, the leaf margins scorch, and the shoots wilting. When the scorch is severe, the dry film becomes dry and lacking in symptoms. The diseased seedlings are easy to pull up and there is no root hair.
The reason for the occurrence of seedlings is poor, the temperature is too low, or the seedbed soil has high humidity. Precautionary measures: Nutrition, temperature and warming measures are used to nurse the seedlings; seedbeds are to be constructed in places with high dryness, sunny leewards, and convenient drainage; seedbeds should be fully sun-dried and full-base fertilizers should be applied before planting; bed soil or nutrient soil should be treated with pesticides; Soak the seeds in warm water at 55°C for 15 minutes. Soak germination after soaking. Strengthen seedbed management. The seedbed temperature should be controlled at 20°C-30°C, and the ground temperature should be kept above 16°C. Insulation of the seedbed should be done to prevent the cold wind from blowing in; , Small water pouring, to prevent the seedbed humidity is too large.
Albino seedlings
Symptoms When the first true leaf appears, the edges of the cotyledons and young leaves become chlorogenic and white, resulting in stagnant seedling growth. The light can restore growth, and the cotyledons and true leaves are dry and only the growth points are retained, resulting in long seedlings or even stiff seedlings. In severe cases, cotyledons, true leaves, and growing points are all frozen to death.
The reason was that the seedlings were frozen, the ventilation during the seedling period was improper, and the bed temperature was drastically reduced.
Preventive measures should be planted in due time and seedbed insulation measures should be taken to ensure that the bed temperature should be above 20°C during the day and not less than 15°C during the night; the emergence period should not be ventilated too early in the morning and ventilation should be gradually increased to avoid sudden changes in seedbed temperature and injury to the seedlings.
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