Technical Key Points and Implementation Methods for the Improvement of Abandoned Jujube Orchards
1 Breaking the Hardpan, Deep Plowing, Clearing Weeds and Removing Suckers
Deep plowing can clear weeds, remove excess root suckers, and increase the soil's permeability and capacity to retain water and dissolve fertilizers. It can also turn pest eggs and larvae up to the surface to be dried out by the sun or picked out and killed.
Deep plowing should be carried out when the soil is suitable for cultivation; if too dry or too wet, clods easily form and the structure is destroyed. Deep plowing should also be adjusted in depth according to position: the area far from the canopy should be deeper, reaching about 20 cm; the area near the canopy should be shallower, about 10 cm. This avoids excessive root damage that would affect tree vigor. Deep plowing creates favorable conditions for root regrowth; because the jujube tree has well-developed horizontal roots with strong outward extension and regeneration capacity, damaging part of the root system will also stimulate the sprouting of more horizontal roots.
2 Comprehensive Fertilization and Irrigation According to Soil Moisture
Because abandoned jujube orchards have been left uncultivated for years, the jujube trees grow together with weeds and root suckers, nutrients are severely lost, and the trees are weakened. Therefore, timely topdressing after clearing weeds and removing suckers is the key to building up tree vigor.
Fertilization should follow the principle of being early and complete. Because the jujube tree is a species with an advanced fertilizer absorption period, topdressing in autumn of the current year, after decomposition, uses the functional period of the leaves to manufacture nutrients stored in the tree body for use in flowering and fruit setting the following year. Research shows that the effect of using autumn fertilizer in spring is often better than topdressing in the spring of the same year.
Because various weeds and root suckers grow densely in abandoned jujube orchards, various latent nutrients in the soil are lost in large amounts, resulting in poor soil. Therefore, fertilization should ensure comprehensive supplementation of nitrogen, phosphorus and potassium, use both organic and inorganic fertilizers, and mix in an appropriate amount of micronutrients. The fertilization method should be radial trench application, which gives a large fertilizer coverage area and good results.
After fertilization, irrigate according to soil moisture to dissolve the fertilizer with water, so as to avoid the physiological drought phenomenon of fertilizer damaging the trees caused by insufficient soil moisture, which makes the soil solution too concentrated and causes reverse flow of water from the roots.
3 Thinning and Pruning the Interior to Build Up Tree Vigor
Because abandoned jujube orchards have been left uncultivated for years, the tree shape is disordered. Inferior branches in the interior consume nutrients for nothing due to improper positions, such as rampant water sprouts and whorled branches; useless diseased, pest-damaged and dead branches; thin and weak slanting branches and overlapping branches; overly dense inner branches and crossing branches; as well as drooping branches and senescent branches. These branches not only affect ventilation and light penetration but also have no economic yield; keeping them is harmful and without benefit. They should be thinned out or trained by pruning, so that the effective bearing branches of the whole jujube tree increase, the auxiliary branches are kept at an appropriate amount, thereby strengthening tree vigor and improving fruiting capacity.
4 Timely Prevention and Control of Pests and Diseases
Because pests and diseases in abandoned jujube orchards are out of control, multiplying and spreading at will and reproducing generation after generation, there are more species and more severe damage than in ordinary jujube orchards, making control difficult to a certain extent. Therefore, pest and disease control in abandoned jujube orchards should adopt a method combining key control with integrated control. While controlling one main pest or disease, other pests and diseases should also be controlled at the same time, striving not to miss any control stage, so as to achieve timely and thorough control. As long as pests and diseases are kept under control during the fruiting period, more than half of the harvest is secured.
5 Girdling to Promote Fruiting
After 1 to 2 years of cultivation, under the combined effect of various measures, the tree vigor of the abandoned jujube orchard will be strengthened. Once it has the capacity to bear fruit, girdling at this time becomes the key to how much the jujube trees flower and fruit. The correct method should be adopted and girdling carried out at the right time, which will make empty trees that formerly bore no jujubes hang with fruit all over their branches and achieve an ideal yield.