How to Grow Sugar Mandarin Oranges for High Yield? The Latest Cultivation Technique Guide
Sugar mandarin oranges have the characteristics of early fruiting and high yield, with fruit that is purely sweet and melts in the mouth, suiting Chinese consumer habits, and their market price is 1-2 times higher than other citrus fruits. The main cultivation and management techniques for sugar mandarin oranges are described below.
Select pure-variety, disease-free and pest-free strong seedlings
For the strain, early-maturing varieties have good quality and high yield. Seedlings using trifoliate orange as rootstock are dwarfed, early-fruiting and high-yielding; seedlings using sour orange as rootstock grow upright and vigorously, and come into production late. Seedling height should exceed 40 cm, thickness above 0.5 cm, free of quarantine pests and diseases (canker disease, huanglongbing), with well-developed fibrous roots and good compatibility between scion and rootstock.
Choose the right land, plant at reasonable density
Sugar mandarin oranges can grow and bear fruit normally on ordinary soil, but to grow fast, fruit early, and yield high and steadily, a moist and fertile soil environment is required. Therefore, to develop sugar mandarin cultivation, choose paddy fields, dry land, riverside alluvial land, and gully land that have convenient transportation, sufficient water sources, can be both irrigated and drained, and have deep, loose, fertile soil. To achieve early-stage high yield, when planting on fertile paddy fields and dry land, adopt a dwarfed high-density planting method, planting 200-300 trees per mu, with a spacing of 2 m × 1.5 m or 2 m × 1 m. On hilly land, plant about 100 trees per mu, with a spacing of 3 × 2 m. Production practice has proven that dwarfed high-density planting is an important technical measure for achieving early fruiting and high yield in sugar mandarin oranges. After many years of high yield, the dense planting orchard becomes cross-shaded, and thinning is then carried out.
Planting method
Sugar mandarin oranges are generally planted in spring, in February to March. When developing sugar mandarin oranges on fertile soil, deep soil layers of paddy fields, or riverside alluvial soil, shallow pits can be dug for planting; for paddy fields, arrange by row and plant on raised beds. On poor dry land and sloping soil, dig deep pits 1 m square, prepare sufficient base fertilizer, applying per pit 3 jin of phosphate fertilizer, 5 jin of lime, 100 jin of garbage mud or pond mud, and 30-50 jin of pig, cattle or chicken manure. When filling the pit, mix the fertilizer thoroughly with the soil and then fill it back into the pit, building the tree disc about 20 cm above the ground. Before planting, cut off part of the branches and leaves of the seedling to reduce water evaporation, cut off the main root, and retain as many fibrous roots as possible. When planting, dig a shallow pit, let the fibrous roots spread naturally, then backfill soil, compact the soil, and the buried soil height must not cover the graft union. After planting, cover the tree disc with rice straw or other weeds, and water thoroughly to settle the roots. Within one month after planting, keep the soil near the roots moist. When the temperature is high, there has been a long clear spell without rain, and the soil is dry, water every day; on rainy days, when the soil is moist, no watering is needed.
Management of young trees
1. Fertilizer and water management
Young tree management centers on fertilizer and water management, promoting root growth and early, rapid shoot development, so as to form a canopy as early as possible. Forty days after planting, new roots begin to grow, and decomposed manure water diluted 2-3 times can be applied, once every 10-15 days, 5-10 jin per tree. As the young trees grow, gradually increase the concentration and amount of manure water, and appropriately add urea dissolved in the manure water and apply it. Starting from the second year of planting, the number of fertilizer applications can be reduced and the amount of manure water
and chemical fertilizer per application increased, applying 30 jin of manure water and about 3 liang of urea each time. By September, stop applying nitrogen fertilizer and manure water, and apply a potash fertilizer once, applying half a jin of potassium chloride per tree, to promote flower bud differentiation. At the same time, pay attention to soil moisture management.
2. Shaping and pruning
The purpose of shaping is to give the sugar mandarin tree a reasonable framework and a good tree shape with evenly distributed branches, so as to facilitate ventilation and light penetration, three-dimensional fruiting, reduce pest and disease damage, and lay the foundation for early fruiting and high yield. Sugar mandarin shaping generally adopts the natural open-center form. The method is: after planting, cut back the trunk at 40 cm, and after it sprouts, select and retain 3 branches in different directions as main branches. The main branches form a 45° angle with the vertical line of the trunk. If a main branch is too upright, use rope to widen the branching angle. After the main branch matures, retain 30 cm and cut back, then select and retain 3 secondary main branches in different directions on the main branch. This method can thereafter be used to extend the tree's skeletal branches. Upright branches growing on the skeletal branches such as main branches and secondary main branches should be cut off, and weak branches should be appropriately retained as auxiliary branches. Sugar mandarin oranges have strong sprouting ability and relatively dense branches; generally retain 3-4 shoots per flush and thin out all the rest. To make summer shoots and autumn shoots emerge neatly, bud wiping and shoot control are needed, that is, when only scattered branches in the whole orchard have sprouted, wipe off the tender buds to stimulate lateral bud germination, and only when 80% of the branches in the whole orchard have sprouted, release the shoots uniformly, which facilitates pest and disease control.
Fruiting young trees
1. Fertilizer and water management. Young fruiting trees are fertilized in three applications: fruit-stabilizing fertilizer. After flowering, the tree body has consumed a large amount of nutrients, which must be replenished in time; apply 50 jin of manure water per tree, or half a jin each of compound fertilizer and urea.
(2) Fruit-strengthening fertilizer. July to August is the period of rapid fruit expansion and also the early stage of autumn shoot emergence; nitrogen, phosphorus and potassium should be applied in combination, using 1 jin of compound fertilizer and half a jin each of urea and potash fertilizer per tree.
(3) Fruit-picking fertilizer. To replenish tree nutrition and restore the canopy, apply 50-100 jin of decomposed manure water per tree. Each year after the autumn shoots mature, begin water and fertilizer control to control winter shoots and promote flower bud differentiation.
2. Reasonable shoot control and pruning
After sugar mandarin oranges begin to bear fruit, vegetative growth is still relatively vigorous, and spring shoots and summer shoots compete with flowers and young fruit for nutrients, causing flower and fruit drop. Autumn shoots are the fruiting mother branches of sugar mandarin oranges; therefore, in production, measures of thinning spring shoots, controlling summer shoots, and promoting autumn shoots are adopted. Thin out part of the spring shoots to reduce nutrient consumption. When summer shoots emerge, use manual methods to wipe off all tender buds, or spray 500-1000 ppm paclobutrazol to control summer shoot emergence. In early to mid-August, uniformly release one autumn shoot flush, and pay attention to pest and disease control to ensure normal growth of autumn shoots. Pruning of young trees is divided into summer pruning and winter pruning. Summer pruning mainly cuts off upright branches that disrupt the tree shape, crossing branches, and pest- and disease-damaged branches. Winter pruning should carry out renewal pruning of fruiting branches and fruit-dropped branches to prevent excessively rapid canopy growth and premature aging of branches. At the same time, cut off pest- and disease-damaged branches, crossing branches, and upright branches. For branches that are too dense at the top of the canopy, appropriately cut off large branches to open skylights and increase ventilation and light penetration.
3. Flower and fruit preservation and flower and fruit thinning. If the amount of fruit drop is excessive or even almost none remain, it is abnormal fruit drop, and comprehensive fruit preservation measures should be taken:
(1) Thin out part of the spring shoots and all summer shoots.
(2) Apply fruit-stabilizing fertilizer in time.
(3) Spray a mixed fruit-preserving agent once each 10 days before the first and second physiological fruit drop, 50 ppm 920 plus 0.3% potassium dihydrogen phosphate, or 920 plus organic foliar fertilizer.
(4) During the flowering period, make a ring cut around the trunk.
(5) Control pests and diseases. If fruit set is too heavy, it reduces single fruit weight and flavor, thereby affecting the selling price. Carry out timely flower and fruit thinning; flower thinning should be done at the bud stage. Fruit thinning is done after the first and second physiological fruit drops end. For the first fruit thinning, retain fruit at 3 times the reserved amount; for the second, retain fruit at 1/3 more than the reserved amount. Thin out diseased, pest-damaged, deformed, and poorly developed young fruit. The reserved fruit load of sugar mandarin oranges is mainly determined according to tree vigor and fertilizer and water conditions.
Pest and disease control
Citrus has many types of pests and diseases. The damage symptoms and control methods of several major pests and diseases are introduced below:
1. Scab. It mainly damages tender branches, leaves and young fruit. Leaves initially show water-soaked small spots when infected, then become waxy yellow. After the fruit is damaged, many tumor-like protrusions often grow.
[Control method] When spring buds sprout to 1 cm, spray 50% Tuzet 500 times or 70% thiophanate-methyl 800 times. The second time, at the end of flowering, spray 70% thiophanate-methyl 800 times solution.
2. Anthracnose. The main feature of anthracnose is that under rainy and high-temperature conditions, the lesions show small red dots, and under dry conditions they appear as small black dots in concentric rings.
[Control method] Spray 1-2 times each during the tender shoot stage and young fruit stage, using 0.5% equal-amount Bordeaux mixture, or 50% Tuzet 500 times, or 70% thiophanate-methyl 800 times.
3. Huanglongbing. The main symptom, besides yellow shoots, is that the main feature for identifying the disease is yellowing at the base and edges of leaves, showing irregular mottled leaves with alternating yellow and green.
[Control method] (1) Choose disease-free seedlings and plant in isolated disease-free areas. (2) Strictly control the disease transmission vector, the Asian citrus psyllid, applying insecticides to control the insect and protect shoots during each tender shoot stage, spraying omethoate 1000 times, aphid-psyllid net 2000 times, imidacloprid 2000 times. (3) When diseased trees are found, dig them out promptly to eliminate the source of disease.
4. Mites, mainly red spider mites and rust mites. Red spider mites damage leaves, fruit and tender shoots; damaged leaves lose their luster and turn grayish-white. Rust mites mainly damage fruit, causing black-skinned fruit.
[Control method] In winter, use 1 degree Baumé lime-sulfur mixture to clean the orchard. During the growing season, acaricides such as dicofol, Jinba mite, isocarbophos, and propargite can be sprayed alternately, once every 7-10 days, for 2-3 consecutive times.
5. Rust mite control. Starting each year in June, observe the pest population density; when rust mite damage appears, spray immediately for control, using the same pesticides as for red spider mite control.
6. Scale insects. Mainly cottony cushion scale, armored scales, etc., damaging branches and fruit, weakening tree vigor, inducing sooty mold, and reducing fruit yield and quality.
[Control method] In winter, use 16-20 times rosin compound to clean the orchard, and cut off insect-infested branches. Control should focus on the peak emergence period of the first-generation nymphs from May to June, spraying continuously 2 times. The pesticides used include: 40% omethoate 500-800 times, 40% isocarbophos 800 times; adding 100 times machine oil emulsion to these two pesticides gives better results. Scale-kill Special 1500 times, Supracide 1500 times.
7. Leafminer. Commonly known as the drawing worm or ghost scribble, its larvae tunnel under the leaf epidermis to feed, forming white curved tunnels on the back of leaves, and the leaves curl. Damage is most severe on summer and autumn shoots.
[Control method] Wipe out scattered tender shoots, release shoots uniformly, and spray centrally. Spray the first time when the tender buds of summer and autumn shoots are the length of a grain of rice, then spray again every 7-10 days, spraying 2 times per shoot flush. Ke'e Bao 1500 times, Decis 2000 times; Anlü Bao 1500 times, Banqian E 1500 times can be used for spraying and killing.