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Overwintering lettuce is easy to crack and prevent water and water
When harvesting wintering lettuce, it's common to notice cracks in the stem, which significantly affects its market value. Severe damage can lead to soft rot and sclerotinia, causing the affected areas to turn dark brown. This issue not only reduces the appearance of the lettuce but also makes it more susceptible to disease.
During the stalk hypertrophy stage, lettuce requires adequate nitrogen and water to support rapid stem growth. However, in the late phase of this period—especially close to harvest—overwatering or heavy rainfall can cause the base of the stem to split vertically. This is a common problem that farmers often encounter.
The primary causes of these splits are environmental and management-related. As the harvest time approaches, the outer layer of the tender stem hardens. If there is excessive rain or watering at this point, the internal tissues grow quickly, creating swelling pressure. The hardened skin, on the other hand, exerts an inward wall pressure. Since the swelling pressure exceeds the wall pressure, the stem splits along its length. Additionally, high humidity creates ideal conditions for the spread of harmful bacteria, increasing the risk of disease.
This issue is particularly prevalent in spring lettuce cultivation, where frequent rain is common. In autumn, if the plants have poor early growth, sudden heavy rains or excessive irrigation later on can trigger similar problems.
Once the stems have cracked, it's very difficult to reverse the damage. Therefore, prevention is key. During the early stages of wintering lettuce, fertilizer and water should be carefully managed to promote leaf development and nutrient accumulation for stem growth. When the plant enters the "lotus sitting" phase, the number of leaves increases significantly. At this point, when the heart leaf and lotus leaf are flat, the stem begins to grow rapidly. Fertilization should be done regularly, with extra attention given to nitrogen and potassium. For example, applying 15 kg of urea or ammonium sulfate per acre, and 20 kg of potassium sulfate. In some cases, 1–2 applications of large dung water (1000–1500 kg each) can also be beneficial.
However, over-fertilizing too late can be harmful. At this stage, proper watering is also crucial. The soil should not be allowed to dry out, but excessive watering must be avoided. Too much water early on can cause the stem to swell too quickly, leading to cracking. Additionally, overwatering may result in long, weak leaves that are less sturdy.
To prevent cracking, watering should be limited and evenly distributed as the harvest date approaches. Farmers should also ensure that any rainwater is drained promptly to avoid unnecessary moisture buildup. By managing both nutrients and water carefully, the risk of stem splitting can be greatly reduced, ensuring better quality and higher yield.