Experience Sharing on Root Cutting to Promote Root Growth in Shatang Mandarin

Applying staged root cutting to promote root growth in Shatang mandarin trees can promote root expansion and guide roots to grow downward, improve the root ecological environment, help restore tree vigor, expand the canopy, increase the number of effective branches and total leaves, thereby increasing citrus yield and improving quality. This is a technical measure for maintaining high quality, high yield and stable production in citrus.

Experience in Root Cutting to Promote Root Growth in Shatang Mandarin

Every year from mid-July to early-to-mid August, using the tree canopy drip line as the boundary, dig a strip-shaped root-cutting trench on each of two opposite sides of the canopy. The trench is 80-100 cm long, 25-40 cm deep, and wide enough to cut the roots. In each root-cutting trench, apply per tree 20 kg of green manure or residue mud fertilizer, 0.3-0.5 kg of urea, 0.8 kg of superphosphate, and 30-50 kg of human and livestock manure, applied into the trench with water, then backfill with soil and level it. Roots with a diameter of less than 2 cm are cut; for thicker larger roots, cut the wound smooth with a knife and apply burnt soil to the wound.

From mid-July to mid-August, external conditions are relatively suitable for root growth and development, and the roots are at their peak growth period, so wounds heal quickly and a batch of new roots emerges soon. The following year, use the same method to dig root-cutting trenches once on the other two opposite sides of the canopy. Practice has proven that adopting root-cutting to promote root growth is an effective measure to ensure high quality, high yield and stable production of Shatang mandarin.

Growth Habits of Shatang Mandarin  

The growth, development, flowering and fruiting of Shatang mandarin trees are closely related to environmental conditions such as temperature, sunlight, moisture (humidity), soil, as well as wind, altitude, terrain and slope aspect. Among these conditions, temperature has the greatest influence; even a temperature difference of 0.5°C can sometimes produce completely different results. High temperatures are also unfavorable to the growth and development of Shatang mandarin; when air temperature and soil temperature are above 37°C, fruit and roots stop growing.  

Shatang mandarin is a tree species with relatively strong shade tolerance, but good sunlight is still required for high quality and high yield. Generally, areas with an annual sunshine duration of 1200-2200 hours can support normal growth. Shatang mandarin has a wide adaptability range to soil; it can grow in purple soil, red-yellow soil, sandy beach and coastal mudflat, with a pH value of 4.5-8, and pH 5.5-6.5 is most suitable. 

Fertilizer and Water Management of Shatang Mandarin  

1. Fertilization principles: The needs of blood orange for various nutrient elements should be fully met. It is advocated to apply more organic fertilizer, and to rationally apply inorganic fertilizer and formula fertilizer. Fertilization should also be guided by leaf analysis results, orchard soil analysis results, and the phenological period of blood orange.  

2. Fertilization methods: Soil fertilization is the main method, combined with foliar fertilization. Methods such as ring trench application, strip trench application, hole application and spreading fertilizer on the soil surface are used.  

3. Fertilization for young trees: Apply frequently and lightly, mainly nitrogen fertilizer, combined with phosphorus and potassium fertilizer. Apply fertilizer 5-6 times during the spring, summer and autumn shoot emergence periods. In March, May, June, July, September and December, apply 0.4 jin of ammonium bicarbonate or 0.2 jin of urea per tree each time. For 1-3 year old young trees, apply 100-400 grams of pure nitrogen per tree per year, and the ratio of nitrogen, phosphorus and potassium is preferably 1.0:(0.4-0.5):1.0.  

4. Fertilization for mature trees: Apply four good fertilizer applications to adult trees, namely sprouting fertilizer, fruit-preserving fertilizer, fruit-strengthening fertilizer and fruit-harvesting fertilizer. The application amounts are generally 2-3 jin of chemical fertilizer plus one load of manure water for sprouting fertilizer. Fruit-preserving fertilizer: 1-2 jin of phosphorus and potassium fertilizer + 1 jin of chemical fertilizer. Fruit-strengthening fertilizer: 1-2 jin of chemical fertilizer + 1-2 jin of phosphorus and potassium fertilizer. Fruit-harvesting fertilizer (base fertilizer) is mainly organic fertilizer, with 50-100 jin of organic fertilizer plus 1-2 jin of chemical fertilizer applied per tree.  

5. Water management: Irrigate when the soil is dry, and drain when there is standing water.   

Shaping and Pruning of Shatang Mandarin  

1. Shaping principles: Adjust measures to local conditions, prune according to the tree, promote and suppress appropriately, ensure ventilation and light penetration, and achieve three-dimensional fruiting. The trunk height is 20-40 cm. The main branches (3-4 branches) are distributed on the trunk in a well-arranged manner. The branching angle of the main trunk is 30-50°. Each main branch retains 2-3 secondary main branches. Generally, after the third main branch is formed, the central leader-like trunk is cut off and twisted to one side as a fruiting branch group.  

2. Pruning of young trees: Mainly light pruning. After selecting the central leader-like extension branch and the extension branches of each main branch and secondary main branch, carry out moderate or even heavy heading back, and use the degree of heading back and the direction of the pruning cut bud to regulate the growth balance among the main branches. Apart from appropriately thinning overly dense branch clusters, the inner canopy branches and relatively weak shoots in the middle and lower parts of the canopy should generally be retained.  

3. Initial fruiting period: Continue to select and head back the extension branches at all levels of the framework, remove summer shoots, and promote the emergence of robust autumn shoots. In autumn, adopt flower-promoting measures such as ringing, root cutting and water control for vigorously growing trees.  

4. Trees in full fruiting period: Timely retract fruiting branch groups, flower-dropping fruiting branch groups and declining branch groups, and prune shading branches, dead branches and diseased and pest-damaged branches.

Shatang mandarin is one of the fruits we eat most often. It tastes sweet and sour, with a particularly good flavor. Therefore, the cultivation of Shatang mandarin is also very common in China, but to obtain high yields of Shatang mandarin, in addition to mastering its growth habits, mastering certain cultivation techniques is also very important.