From the middle of April to the end of May, it is the key period from citrus after flowering to fruit stabilization. It is generally called the young fruit period. In citrus production, this period is usually called the fruit preservation period-the fruit stabilization period. The first and second physiological fruit drop stages after citrus flowering after citrus flowering, especially the cultivation management of the second physiological fruit drop period to the stable fruit period, often directly affect the fruit tree's current year Yield and fruit appearance quality. Therefore, it is of great significance to strengthen the management of citrus young fruit period, reduce physiological fruit drop and unnecessary objective factor fruit drop, and increase fruit setting rate.
Key points for management of citrus orchards in April
To this end, the author recommends that all fruit farmers friends implement the following management points and precautions:
1. Timely Shi Xiehua-Wenguo fertilizer
Citrus falling buds, falling flowers and other trees consume the most nitrogen, so nitrogen fertilizers should be applied topically during the flowering period, such as high nitrogen type fertilization, 1-2 kg / mu; for plants with few fruit branches and general tree vigor, Need to apply water-soluble organic fertilizer in the rhizosphere plus NPK balanced type fertilization 2-3 kg / mu to promote root maintenance. From April to June, after flowering-young fruit enlargement period, potassium fertilizer should be applied, such as potassium sulfate 1-2 per plant.
Second, timely application of fruit-protecting fertilizer
The second physiological fruit drop (ie, fruit drop without a stalk) is mainly fruit malnutrition. The embryo lacks essential nutrients during the development process and stops developing to cause fruit drop. The elements required in different stages of fruit development are different, so what needs to be done to ensure the normal development of the fruit and reduce physiological drop.
Essential organic compounds (sugar) and mineral elements in the young fruit stage of citrus flowering: flower buds ~ organic compounds, nitrogen, boron, zinc, magnesium, etc. are needed during the spring shoots; Xiehua ~ young fruit formation stage requires organic compounds, phosphorus, boron, Calcium, etc., need to consume 32% of the total annual phosphorus requirement during the flowering period; young fruit development and expansion period require more organic compounds, potassium, calcium, etc.
3. The right amount of hormone supplement
For trees with sufficient nutrition, spraying cytokinin before the first physiological fruit drop is helpful to reduce the fruit drop; spraying gibberellin GA3 (920) or 2-4 before the second physiological fruit drop is beneficial to inhibit the formation of abscisic acid Thereby reducing the peeling of the fruit stem from the layer. Late-ripening citruses are mostly seedless and less-core citrus varieties, which can be used early. Spray 920 at a concentration of 20ppm (ie 4% water agent 100ml with water 400 kg) on ​​Xiehua 2/3, and spray 25ppm at 15-day intervals 920 (that is, 4% liquid agent 100 mixed with water is about 300 kg). Multi-core varieties or pomelo, less or no use 920. The use of natural regulators such as algin, brassinolide, sodium nitrophenolate, etc. during the fruit preservation period can enhance the stress resistance of fruit trees, regulate the transfer and transportation of plant nutrients from branches and leaves to flowers and fruits, and avoid the excessive growth of branches and leaves caused by fruits. Growth is blocked.
4. Appropriate ring cut to stabilize fruit
Ring cutting is generally aimed at plants with vigorous trees and vegetative growth, such as sugar oranges on tangerine rootstocks. Especially for the plants that bear fruit in the first two years, it is best to cut and preserve the fruit by looping, because the tree has poor nutritional regulation ability, the nutrient growth is too strong, and it is difficult to preserve the flower and preserve the fruit.
Ring cut method: half-turn dislocation method and full-turn ring cut method can be used. The safety factor of the half-circle dislocation method is better than that of the full-circle ring cutting method, and it is not easy to cause the death of the whole plant.
Ring cutting time: According to the amount of flowers, nutrient consumption. For plants with few flowers and fruits, the nutrient growth is relatively dominant due to the low nutrient consumption of the tree. The first knife should be carried out during the full flowering period, and the second knife should be carried out at the end of the first physiological fruit drop. Conversely, plants with many flowers and many fruits should be carried out from the time of flowering to the first physiological fruit drop (about 5 days after flowering). It is usually treated once, if there is much rain, 2-3 times depending on the fruit drop. In mid to late May, if the cut tissue has healed and the tree is still strong, there is a tendency to take the summer shoots, you can cut again. If the small fruits have turned green and there are more fruits in this period, it is generally not advisable to perform ring cutting. Because after the small fruits turn green normally, they should get the support of fertilizer and water through the rhizosphere. Otherwise, after ring cutting again, the growth of young fruit may be affected.
Ring cutting position: ring cutting is close to the top, and the branch is cut on the branch extending 1.5 meters from the top.
Ring cutting strength: It is advisable to use No. 0-1 knife (No. 0 knife / straight hook; No. 1 knife / 1 mm), and the depth should be just up to the xylem.
Fifth, pay close attention to pest control
Disease and insect hazards: red and yellow spiders, yellow spiders, aphids, flower bud maggots, malignant leaf insects, anthracnose, scab, scab, brown spot disease and other hazards in the flower and fruit stage cause deciduous flowers and fruits.
Effective agents: red spider yellow acetoconazole, spirotetramat, avermectin, etc .; aphids, thrips imidacloprid, acetamiprid, thiacloprid, etc .; flower bud maggot, malignant leaf insect chlorpyrifos, pyrethroids, etc. ; Anthracnose, scab, scab, brown spot can be used alternately with mancozeb, procarbazine, thiophanate-methyl, azoxystrobin, pyraclostrobin, etc.
6. Prevent abnormal weather
1. In case of drought weather, timely irrigation and moisturizing are required; clear the internal and external drains of the orchard in rainy and rainy weather to avoid water accumulation after rain affecting root growth and causing fruit drop.
2. Abnormally high temperature weather. When the temperature in the young fruit stage of citrus exceeds 34 ℃, it will affect the growth of the fruit, especially the photosynthesis and antioxidant defense system, which will cause fruit drop. Precautions: Before the onset of high temperature, spraying alginin high phosphorus foliar fertilizer can improve stress resistance.
3. Strong typhoons, hail and other extreme weather should be done in time for wind and air defense work, and measures such as the establishment of windproof walls, film covering, and reasonable thinning of spring branches should be taken to prevent young fruits from being damaged by wind and falling fruit.
Seven, early control of summer shoots
1. Controlling time: before the spring shoots are mature and mature-the early germination of summer shoots (early May)
2. Technical requirements: Nutrition control shoots: after flowering-before spring shoots mature, high-potassium low-nitrogen flushing fertilization 3-5 kg ​​/ mu, 1-2 times. Foliar spray: 0.3% -0.5% potassium dihydrogen phosphate 2-3 times; under rain conditions, 500-750ppm paclobutrazol can be added and sprayed once. Suppressing shoots with shoots, suppressing shoots with fruits: For orchards that cannot control summer shoots with excessive growth and no artificial smearing, it is recommended to use the method of promoting the rapid ripening of summer shoots to reduce the fruit drop caused by the competition for shoots. Ring cutting is beneficial to control the summer shoots. Manual wipe. When there is a small amount of summer shoots, do not remove them immediately, otherwise it will only induce more summer shoots. When the amount of summer shoots in the tree is within 5% of the total branches, let it grow and consume some growth hormone through the growth of summer shoots. On the one hand, it promotes the roots to absorb nutrients in the soil, on the other hand, it makes the vegetative and reproductive growth of the tree body in a balanced state, so as to achieve the effect of suppressing a large number of summer shoots with a small amount of summer shoots.
8. Matters needing attention
1. Precautions for ring cutting
The weather during ring cutting is preferably sunny, which is helpful for wound healing; if it is rainy and rainy after ring cutting, the wound should be smeared with a fungicide to avoid infection. Ring cutting is suitable for the third and fourth grade branches. Try to avoid the first and second grade branches. Never cut the trunk on the trunk to avoid the death of the whole plant. For the sake of insurance, the branches with less fruit and more branches can be kept without ring cutting. As an auxiliary measure, ring cutting should not be used year after year, otherwise it will easily cause premature decay. After the ring cutting, we should strengthen the foliar nutrient spray to promote the vigorous tree. Those with excessive ring cuts should disinfect the wounds with disinfectant in time and wrap them with electrical tape.
2. Be wary of drug damage
Spraying pesticides at the flowering stage and the young fruiting period, keep safety first. Be careful to use emulsifiable concentrates, organophosphorus, triazoles, acarin / triazole tin and other pesticides, or drugs containing hidden ingredients to avoid unnecessary fruit drop due to abuse, chaotic mix or excessive concentration; it is recommended to spend During the fruiting period, especially sunny and hot weather, little or no such agents are used.
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