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Production and Prevention of Cracking Fruits in Nutrient Liquid Cultivation
In the facility greenhouse, cultivated tomato varieties are generally of unlimited growth type, from the mid-August of each year to the mid-July of the following year. The growth period of the whole tomato is as long as 11 months. From the late spring and early summer to the summer high temperature stage, the yield of tomato is quite high, accounting for about 60% of the total tomato production. Therefore, the outside temperature is increasing day by day, and the sunshine intensity is increasing day by day. The suitable climate for the outside world is more suitable for the growth of tomatoes. At this time, if it is not properly managed, there will be slight errors in the control of the greenhouse environment, and a large number of cracked tomatoes can easily be produced. As a result, the commerciality of the tomato products will be reduced, which will cause great economic losses. First, the symptoms. According to the size of tomato cracking fruit, we divide tomato split fruit into two kinds: 1. Slight epidermal dehiscence This kind of cracking generally shows slight dry cracking of the epidermis. The size of the fissure is usually about 1 mm wide and 5-10 mm long. Frequently, cracks occur around the pedicel, which is characterized by many small dry cracks around the pedicel on the skin surface. As a result, the commercial quality of this type of fruit is significantly reduced, the preservation time is shortened, and if it is placed in a high-humidity place after harvest, it is easily rotted. The cause of this type of cracking is mainly in the young fruit period, the peel loses its elasticity and causes the fruit to grow and crack. The reasons for the loss of elasticity of young fruit are mainly the following three: (1) The planting density is too low (less than 2/m2), when the direct sunlight is too strong for more than 80,000 lx, and the sunshade net is not opened in time, In addition, the plant's reproductive growth is too prosperous or the nutrition is weak. The plant leaves are too small. The leaves cannot cover most of the surface of the fruit and cause the surface of the peel to lose its elasticity and cause fruit cracking. (2) Since the night temperature was too low (below 16°C) the night before the next day, when the temperature in the greenhouse rose rapidly the following morning, the temperature of the skin increased slowly, and condensation was likely to occur on the skin surface. If this phenomenon occurs for a long time, it will easily cause the tomato peel to harden, lose its elasticity, and cause cracking. (3) The imbalance between vegetative growth and reproductive growth. When the vegetative growth is excessive, the reproductive growth is weak, which easily leads to a very slow growth of the whole plant from flowering to fruit discoloration. It also causes the peel to harden and cause cracking. 2, large skin cracking (1) Another dry crack often encountered in production, cracks about 2-5 mm wide, cracks longer, along the fruit stem around the ring-shaped, deep white crack-like. The causes of its damage are usually the reasons mentioned above (1) and reasons (2). (2) There is also a large skin cracking, crack width is also 2-5 mm, but it is a wet crack, the crack from the stalk to the bottom of the fruit. Different from dry cracks, the flesh will flow out automatically along the cracks. This kind of fruit is very poor in commodity and is generally treated as the worst product. The reason for this wet cracking is mainly due to the severe changes in the outside weather. Due to the lack of timely measures, the high humidity in the greenhouse is accompanied by a high root pressure of the plant, causing the fruit to expand and crack inside. Second, prevention measures. In order to minimize the production of cracked fruit in production, we mainly adopt the following measures: 1. Choose a good variety. The study found that the frequency and severity of cracking were significantly different among different varieties. Under the same cultivation conditions, in general, cracking is more likely to occur in varieties with high sugar content. In actual production, we should choose varieties with moderate sugar content. 2, a reasonable nutrition solution irrigation. Reasonable nutrition solution irrigation not only means establishing a good root system at the early stage of plant growth, but also has a reasonable EC value in the matrix, and it can accurately control the opening and closing of nutrient solution supply in one day according to the needs of plant growth. Time and quantity. On sunny days, the first irrigation time is generally 1.5-2 hours after sunrise, and the last irrigation time in the afternoon is 1.5-2 hours before sunset. In the rainy morning, irrigation is started 0.5-1 hour later, and the last irrigation in the afternoon is ended 0.5-1 hours earlier. Early irrigation in the morning or late irrigation in the evening can cause the root pressure of the plant to increase, which will prevent water supply to the fruit and cause fruit cracking. The frequency of irrigation should be controlled on sunny days. Usually, irrigation should be performed once every 30-40 minutes in the morning and at night, and once in 20-25 minutes at noon, and on rainy days, irrigation should be performed once every 2.5 hours and 120 milliliters per irrigation. In addition, the time, frequency, and irrigation volume of daily nutrient solution irrigation are determined based on the matrix moisture content, ambient temperature and humidity, lighting, plant size, and the amount of waste recovered the previous day. The water content of the matrix is ​​generally controlled at 65-75% at this stage. If the water content is too high for a long time, the plants will develop toward the vegetative growth direction, and vice versa, it will develop toward the reproductive direction. The difference in water content between day and night is controlled at 6-8%. If the difference is too small, the plant will develop in the direction of vegetative growth, and vice versa, it will develop in the direction of reproductive growth. The amount of liquid waste recovered is generally controlled at 25-30% of the amount of irrigation in sunny days and between 20-25% in rainy days. 3, the control of the greenhouse environment. It is very important to prevent the cracking of tomato fruit by maintaining the elasticity of the peel, which requires us to maintain a balance between the vegetative and reproductive growth of the plant. During the day, when the temperature in the greenhouse exceeds 35°C for a long time, the temperature in the greenhouse can be reduced by ventilation and spray on the roof. The night temperature should not be too low at night and cannot be lower than 16°C for a long time. When the ambient light is too strong, especially When the outside world changes from cloudy to sunny for a long time, the shade net should be properly opened according to the growth of the plants. Generally, the shade net is turned on when the direct light intensity reaches 60,000 lx, because all the aspects of the plant, including root growth Weak, can't immediately adapt to the severe weather changes outside. For a few days of continuous sunny days, the opening time is gradually pushed back until 3-4 days later, if the direct light intensity of the outside world is not higher than 80,000 lx, we do not open the shade net so that the plants get as much light as possible. When the weather changes from sunny to cloudy, corresponding measures should be followed in time to change the irrigation method. If the humidity in the greenhouse is too high, appropriate heating methods can be used to reduce the humidity and promote the transpiration of the plants, thereby reducing the root pressure. . 4, the correct method of pruning. At the end of February to early March of each year, the planting density is increased by leaving lateral branches. In general, the measures we take are one lateral branch per four plants, and the planting density is increased from 2.5 to 3 per plant. /m2, Prevents cracking of tomato fruits caused by high light exposure due to prolonged irradiation of peels. 5, the control of plant growth potential. Maintain the balance between vegetative and reproductive growth. Under normal conditions, it is normal for each plant to maintain 7-8 bunches of fruit. 6, the appropriate amount of fruit. For string tomatoes, the reason for the easy cracking of fruits is not only the above, but also an important reason is the amount of fruit left. If the first fruit of the bunch has completely changed color, and the last fruit is still green, the string If the first fruit is easy to crack the fruit. Therefore, it is generally advisable to leave 5-6 at this stage. In addition, since the string of tomatoes adopts the whole bunch of harvesting, the flowering orderliness of a string of flowers is very demanding, so the powder should be given once a day. (Source: vegetables)