Kiwifruit Cultivation Techniques: How to Prune and Train Plants to Ensure Fruit Quality

AbstractOrchard site selection: deep soil layer, high soil humus content, loose and fertile, adequate water source with good drainage and irrigation facilities. Planting: sturdy planting stock, reasonable planting distance and male-female ratio. Root pruning: prune the damaged or moldy parts of the root system. Branch pruning: prune the aboveground part of young seedlings; for grafted seedlings the grafting film should be removed. Planting seedlings: dig the planting hole with the planting point as the center. Training: determine the number of retained branches and buds, handle the trunk, prune branches and tips while retaining buds, pull branches and tie vines. Management: thin buds and flowers.

Kiwifruit is a delicious and nutritious fruit. It has a layer of fuzz on the outside and looks hard, yet it tastes especially fragrant, soft and palatable, suitably sweet and tart, and its nutritional value is very high, which has captured the hearts of many food lovers. Because market demand for kiwifruit is large, many people are preparing to enter the kiwifruit growing industry. Let us take a look below at how to grow kiwifruit.

Key Points of Kiwifruit Cultivation Techniques

I. Orchard Establishment

1. The orchard soil layer should preferably be deep, the soil humus content should be high, and the soil should be loose and fertile.

2. The orchard should have an adequate water source, and drainage and irrigation facilities should be well built.

3. The orchard location should have convenient transportation, and the altitude should preferably be 300-1200 m, with 400-800 m being best;

4. The orchard must not be built in a wind gap; it should be built on the leeward side. If building the orchard on mountainous land, the slope aspect should be chosen; for example, an early sunny slope and a late sunny slope are better, but note that the slope must not exceed 30 degrees.

5. Make beds about 3 m wide, plant in double rows at 3×2 m, dig channels 0.8 m deep and about 1 m wide, and ensure drainage and irrigation are convenient.

II. Planting

1. The planting stock should be sturdy, and the male-female pairing should be reasonable. The ratio of female to male plants is generally 8:1, or it can be 6:1. If the female variety is different, then the matching male variety must also be different. The principle for matching male varieties is that they must not only have the same flowering period as the female variety, but also a long flowering period, a large amount of pollen, and strong pollen viability.

2. Planting distance: in the early stage, to increase kiwifruit yield, a row spacing of 2 m and a plant spacing of 1.5 m can be used; after fruiting in the later stage, gradually thin them out year by year according to growth vigor to a row spacing of 2 m and a plant spacing of 3 m.

3. Digging holes: choose the season before planting to do this; the diameter and depth of the holes are both 1 m.

4. Planting time: generally plant from December to January of the following year.

III. Root Pruning

Before planting, reasonably prune the damaged or moldy parts of the root system. Be sure to cut back to healthy tissue, and the cut surface should be smooth. Roots longer than 30 cm should be appropriately shortened, and the roots should be soaked in rooting powder and fungicide, then placed beside a field ditch to keep moist for later use.

IV. Branch Pruning

Before planting, prune the aboveground part of the kiwifruit seedlings. In particular, above the graft union (or root crown), leave 3-4 plump buds and cut short, while all other branches should be completely removed. For grafted seedlings, the grafting film should be removed.

V. Planting Seedlings

With the planting point as the center, dig a planting hole 30-40 cm in diameter and 30-50 cm deep. Place the prepared seedling in the center of the planting hole, then use your hands to comb the roots so they are evenly distributed with the root tips pointing downward. Then fill fine soil around the roots. While filling soil, gently lift the roots upward, press appropriately, and water thoroughly once so the roots spread out and closely combine with the soil. Never tread heavily on it.

VI. Training

Proceed according to the principle of a trunk up on the trellis, one trunk with two canes, four branches and eight laterals. The specific steps are as follows:

1. Determine the number of retained branches and buds

If the yield per mu is 2000 kg, with a plant spacing of 2×3 m and calculated at 100 plants, then the average yield per plant is 20 kg. At 10 fruits per kg, each plant needs to retain about 200 fruits. Adding 20% accidental loss, at least about 240 fruits should be retained. At 3 fruits per fruiting branch, 60-80 flower buds are needed. During winter pruning, prune according to the technique of retaining fewer branches and more buds. If each mother branch is pruned to retain 6-8 flower buds, then 12-18 mother branches are needed. In other words, 2-3 fruiting mother branches can be retained per square meter.

2. Handling the trunk

First, for trees with multiple trunks on the trellis, remove year by year the curved, bark-damaged, diseased or pest-damaged trunks and poorly growing trunks, but do not remove too many at one time, so as not to affect yield; second, heavily rejuvenate and cut back main branches and main canes that have severely shifted outward, aged, or become diseased and weak; third, for trunks with unsatisfactory growth, cultivate and use vigorous shoots from the middle and lower parts for replacement, and after the new trunk bears fruit, remove the old trunk. Trunk and large branches that need to be removed should be sawed off immediately after fruit harvest, so as to avoid bleeding from the wounds in spring.

3. Pruning branches

That is, select and retain the fruiting mother branches for the next year. When selecting and retaining mother branches, follow the principle of removing five and retaining five:

① Remove distant and retain near (bare-legged branches far from the trunk);

② Remove upper and retain lower (when there are several mother branches at the same time, retain the lower-position branch)

③ Remove outer (that is, peripheral branches, outward-shifted branches beyond the second trellis wire) and retain inner

④ Remove curved (curled and twisted growing branches) and retain straight;

⑤ Remove weak (thin and weak branches, extremely short branches) and retain strong, while also pruning off withered branches, overlapping branches, dry stubs and overly dense branches, etc.

4. Pruning tips and retaining buds

After pruning is finished, handle the selected and retained fruiting mother branches. Generally, regardless of spring or summer shoots, as long as they are plump buds, all should be retained on the cane; remove all non-plump buds, sprouting buds, necrotic buds or autumn shoots. Autumn shoots should be cut off from the blind node (that is, the pinching point). The buds below the blind node are generally of the best quality and should be retained. Then, according to the pruning method of retaining fewer branches and more buds and the yield calculation, strong long fruiting mother branches can retain 12-15 plump buds, medium branches retain 8-12 buds, and weaker mother branches should preferably retain 6-8 buds.

5. Supplementary pruning

The selected and retained fruiting mother branches should be carefully compared. After retaining enough good fruiting mother branches, again prune off inappropriate, unsatisfactory and missed weak branches.

6. Pulling branches and tying canes

After pruning is finished, the work of pulling branches and tying canes should be carried out. This task is generally completed by the end of January of the following year. Tying canes too late will cause damaged branches to bleed easily. So we must first pull the branches flat on the trellis surface, use double-curved cloth strips to loop over the branches, pull them to the outer wire and tie them tightly. For trees whose branches have shifted outward and become hollow in the center, the branches can be crossed and tied. Tie each branch with 1-2 ties, and the branch distribution should be even and reasonable.

7. Six-step pruning method

First, highlight the role and characteristics of the “T” trellis. From young trees to the early fruiting stage, use multiple branches on the trellis to facilitate crown expansion and increase early yield, while in the full fruiting stage gradually improve it to a single main trunk with multiple branches on the trellis.

Second, prune according to the kiwifruit variety and handle it flexibly. Do not apply a one-size-fits-all approach; the practice of mechanically copying is wrong;

Third, control apical dominance and prevent the fruiting position from shifting outward;

Fourth, cultivate and renew branch groups and rejuvenate tree vigor;

Fifth, take improving the commercial fruit of kiwifruit as the premise, rather than simply pursuing higher yield.

VII. Management

1. Pay attention to thinning buds, thinning flowers and thinning fruit, supplemented by artificial pollination.

2. Soil improvement mainly adopts the ridge-bed type.

Environmental Requirements for Kiwifruit Cultivation

1. Temperature: Temperature is one of the important factors affecting the growth and development of kiwifruit. It can grow normally in areas with an annual average temperature above 11°C. The sprouting of kiwifruit is very sensitive to temperature requirements. Its average temperature requirement for sprouting is relatively stable. Its biological zero point is 8°C. If the daily average temperature is above 8°C, it begins to sprout and grow; if the daily average temperature is below 8°C, its growth will be affected. Long periods of clear, hot weather and drought in summer will also affect the growth and development of kiwifruit, causing leaf drop, fruit drop or withered shoot tips.

2. Water: Water is the most basic component of kiwifruit. All its various life activities must involve water. Insufficient or excessive water will affect the growth and development of kiwifruit. Kiwifruit has a shallow root system and is not drought-tolerant, so during the growing season, in times of high temperature and drought, timely and reasonable irrigation is needed to supplement enough water and lower the tree temperature. Kiwifruit can grow and develop well under conditions of about 1000 mm rainfall and relative air humidity of 70%-80%.

3. Soil: Soil is the foundation of kiwifruit growth and development. The nutrients and water it needs are mainly obtained from the soil. The various physical and chemical properties of the soil directly affect its growth and development. Kiwifruit prefers sandy soil with a deep soil layer, fertility and looseness, good water retention and drainage, and high humus content. Therefore, when cultivating, attention should be paid to selecting and improving the soil. Kiwifruit also has certain requirements for soil pH. Kiwifruit can grow normally in the soil pH range of 5.5-6.5. In alkaline soil above pH 7.5, iron deficiency chlorosis appears, so measures must be taken promptly to improve the conditions needed by kiwifruit in order to achieve good growth and fruiting results.

4. Light: Kiwifruit's light requirements vary with age. During the seedling stage it likes shade, while adult plants like light. Under good sunlight conditions, the tree is robust and flowers and fruits. Yield and quality are affected. In its natural distribution areas, the sunshine hours are mostly between 300-2600 hours, which generally meets its light requirements for growth and development.

Seedling Planting Techniques

Planting time should be from October to the end of February of the following year. Planting is mainly with seedling rootstock plants, supplemented by grafted seedlings. Seedlings should be selected free of disease and pests, new, and growing robustly with a developed and complete root system. Damaged roots, damaged branches, diseased or pest-damaged roots or branches should be cut off with pruning shears. For dryland soil improvement and orchard establishment, the plant spacing is 2-2.2 m and the row spacing is 3-4 m. For orchard establishment in paddy fields, plant at a plant spacing of 2-2.5 m and a row spacing of 4 m. When planting grafted seedlings, remove the binding material at the graft union. Female:male = 10:1 pairing. At the planting point, dig a hole directly and make a soil mound. Make the mound in a steamed bun shape. The size of the mound depends on the seedling root system, but the mound must be 10 cm higher than the bed surface. When planting, separate the roots and spread them evenly on the soil mound, with the roots slanting straight. After the roots are placed, fill with fine soil and firm it. After planting, water thoroughly to settle the roots. When the water has slightly dried, cover with a layer of fine soil and shape a planting dish 1 m in diameter. Finally, pay attention to moisture retention and warming. For autumn and winter planting, use plastic film covering; in spring, use straw or turf covering.

Pollen Collection

2-3 d before pollination, select male plants that have a slightly earlier flowering period than the female tree variety, produce a large amount of pollen, have strong compatibility with the female variety, have a high pollen germination rate, and have a long flowering period. Collect male flowers that are about to open or have just opened but whose anthers have not yet split. Remove the anthers with small tweezers, a toothbrush, scissors, etc., and then use the following methods to release the pollen:

1. Spread the anthers evenly on paper and place them at 25-28°C for 20-24 h to let the flowers release pollen;

2. Spread the anthers on a tabletop, hang a 100 w electric light bulb 100 cm above the tabletop to shine on them, and wait for the anthers to split, then take out the pollen;

3. Cover the anthers with a layer of newspaper and place them in sunlight to release pollen, or release pollen on a hot kang that is not at a high temperature. After the anthers split, sieve out the pollen with a fine sieve, put it into a clean glass bottle, and store it in a low-temperature dry place for later use. Pure pollen can be stored for 1-2 years in a sealed container at -20°C, and for more than 10 d in a household refrigerator at 5°C. Under dry room-temperature conditions, pollen stored for 5 d can achieve a pollination fruit-setting rate of 100%, but as storage time lengthens, the weight of the fruit after pollination gradually decreases. Pollen stored for 24-48 h gives the best pollination effect.

As stated above, kiwifruit is healthy and delicious, has many benefits for the human body when eaten, and is a rare health-preserving fruit. Moreover, there are many ways to eat kiwifruit: eating it raw, juicing it, making wine, and so on. From this point of view, kiwifruit cultivation is also a profitable project with promising prospects.