When harvesting wintering lettuce, it is often found that there are many cracks in the stem, which affects the commerciality. The severe wounds cause soft rot and sclerotinia to become dark brown.
Lettuce enters the stalk hypertrophy period, and needs sufficient nitrogen fertilizer and water to promote the rapid growth of the tender stem, but in the late stage of the stem hypertrophy, especially near the harvesting period, due to excessive watering, or even heavy rain, the base of the stem often A longitudinal split appears.
This phenomenon is mainly caused by weather or administrative reasons. Near the harvesting period, the epidermis of the base of the tender stem has hardened. At this time, there is too much rain or watering, the inside of the tender stem grows fast, and swell pressure occurs. The externally hardened skin produces wall pressure inward, because the swell pressure is greater than the wall pressure. And causing a crack in the longitudinal direction of the base of the tender stem. At the same time, it is in the condition of high humidity, suitable for the reproduction and spread of pathogenic bacteria, so it is easy to develop. This phenomenon is more common in the cultivation of spring lettuce with more rain. If the autumn lettuce grows badly in the early stage, it may easily lead to the occurrence of sudden precipitation or artificially large amount of water in the later stage.
After the stems of lettuce are cracked, the measures for radical treatment are more difficult, mainly by taking preventive measures. The wintering lettuce is in the early stage of rejuvenation, and the management of fertilizer and water should be controlled mainly, so that the leaf area is enlarged and enriched, and the nutrient is accumulated for the stem hypertrophy. When entering the lotus sitting period, the number of leaves increased significantly. When the heart leaf and the lotus leaf were flat, the stem of the lettuce was accelerated. The fertilizer should be applied frequently. Pay special attention to increase the available nitrogen fertilizer and potassium fertilizer. Apply 15 kg of urea per acre or ammonium sulfate. 20 kg, 20 kg of potassium sulfate, conditional can be applied 1 to 2 times of large dung water, 1000-1500 kg each time. But fertilization should be less, and it must be done too late. At this time, it is also a critical period for water supply. It can neither make the soil dry. Otherwise, it will be watered, and the stem of the lettuce will be cracked due to rapid water swelling. It is not too much watering too early. If it is too much too early, it is easy. The leaves are long and the young leaves are not strong. Therefore, the water should be poured less, and the water should be evenly distributed to prevent the lettuce from cracking. The watering is controlled in the near harvesting period, and the rain is harvested in time.
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