A Detailed Guide to the Nutritional Needs and Fertilization Techniques of Loquat
Loquat anthracnose is a fungal disease that can harm loquat leaves, fruit and seedlings, mainly attacking the fruit. Initially, pale brown water-soaked round spots form on the fruit surface, later turning tea-brown to dark brown round or oval lesions; the affected part becomes sunken and is densely covered with small pale red dots that later turn into small black dots arranged in concentric rings, and the fruit...
(1) Fertilizer amount and number of applications. The fertilizers commonly used in loquat cultivation include human and livestock manure, poultry manure, cake fertilizer, compost, refuse compost, burned soil and chemical fertilizers. According to the mineral nutrient requirements for loquat growth and development, loquat is a plant with a high potassium requirement; the potassium content of loquat fruit is almost 3 times that of nitrogen. With too much nitrogen fertilizer, the fruit is large, but both color and flavor are strong, and the appearance and quality are poor; if there is too much potassium fertilizer, the sugar content of the fruit increases, but the flesh becomes coarse and hard. Therefore, the various fertilizer elements should be properly combined.For young loquat trees, fertilizer should be applied 5-6 times throughout the year, using the method of light fertilizer applied frequently, roughly once every two months. Apply 15-25 kg of decomposed dilute human (pig) manure and urine (at a concentration of 20%-30%) per tree, or 150-250 g of imported compound fertilizer.
For mature fruiting loquat trees, fertilizer is generally applied three times a year, mainly arranged according to the fertilizer requirements and phenological periods of loquat. The fertilizer amounts summarized in different regions vary slightly. In a 15-20-year-old vigorous loquat orchard on mountain land in Putian, Fujian, 10-13 kg of nitrogen, 8-10 kg of phosphorus and 13-15 kg of potassium are applied per 667 sq m per year. This can be roughly divided into the following applications:
① Post-harvest fertilizer is applied in May-June. It mainly replenishes the nutrients consumed by fruiting, restores tree vigor, promotes vigorous summer shoot growth, and promotes good root growth and flower bud differentiation. It is based mainly on quick-acting fertilizers, combined with deep plowing, and a large amount of decomposed organic fertilizer is applied. The ratio of nitrogen, phosphorus and potassium fertilizers applied is generally 3:2:2. The fertilizer amount accounts for about 40%-50% of the annual fertilizer amount. For late-maturing varieties, it can be applied earlier, before fruit harvest. Taking a tree yielding 35 kg of loquat fruit as an example, 0.75-1.0 kg of imported compound fertilizer and 10-12 kg of chicken manure should be applied per loquat tree.
② Pre-flowering fertilizer is applied in September-October, when autumn flower bud differentiation has basically ended and flower clusters begin to appear, to provide the nutrients needed for flowering and fruiting and for the growth of vegetative autumn shoots, promote good flowering and improve the cold resistance of the plant. It is based mainly on organic fertilizer. The ratio of nitrogen, phosphorus and potassium fertilizers is generally 5:4:5. The fertilizer amount accounts for about 30%-40% of the annual fertilizer amount. Apply 10-13 kg of chicken manure per tree.
③ Spring shoot and fruit-sizing fertilizer is applied in February-March after fruit thinning. The role of this fertilization is to promote the growth of spring shoots and roots, supply the nutrients needed for young fruit growth, promote the enlargement of young fruit, reduce fruit drop, and promote and fill out the spring shoots. Quick-acting fertilizers are used together with compound fertilizer; the ratio of nitrogen, phosphorus and potassium fertilizers is generally 3:4:3. If the soil is relatively rich in phosphorus, or if the amount of fruit borne at the time is relatively small, the proportion of phosphorus fertilizer can be reduced. If tree vigor is not strong, the proportion of nitrogen fertilizer is increased. The fertilizer amount accounts for about 20% of the annual fertilizer amount. Apply 30-50 kg of decomposed dilute human manure and urine per tree, plus 0.3-0.6 kg of imported compound fertilizer and 0.25-0.5 kg of potassium fertilizer. February is the period of the greatest root growth of the year, so the fertilization depth should be shallow to avoid damaging the roots.
In Putian, Fujian, loquat growers apply 30-35 kg of chicken manure per tree after fruit harvest, combined with plowing and earthing up. When a loquat tree bears much fruit, during the rapid fruit enlargement period, apply 30-35 kg of chicken manure per tree. When a loquat tree bears much fruit, before the rapid fruit enlargement period, spray foliar fertilizer solution 2-3 times (0.2%-0.4% monopotassium phosphate, 0.2-0.4% urea and 0.2-0.3% potassium sulfate), spraying once every 10 days.
(2) Fertilization methods. The effectiveness of fertilization for loquat is closely related to the fertilization method. The absorbing roots of the loquat tree are mainly concentrated in the soil layer outside the outer edge of the canopy projection, so in production the fertilization site is at the canopy drip line. The chemotropic nature of the loquat root system can also be used by applying fertilizer slightly away from the place where roots are concentrated, guiding the roots to grow deeper or spread outward and expanding the root range. In addition, the characteristics of the fertilizer should also be considered; for example, phosphorus fertilizer has poor mobility and is easily fixed by red soil. Therefore, phosphorus fertilizer should be applied deeply and in holes, applied in the root zone, to improve the absorption and utilization rate of phosphorus fertilizer. When applying superphosphate or bone meal, it should be mixed with barnyard manure, stable manure or human manure and urine and composted, then applied after decomposition for a better effect. The soil fertilization methods commonly used in loquat orchards are:
① Ring fertilization, also called circular fertilization. Dig a ring-shaped trench slightly outside the outer edge of the canopy, apply fertilizer into it, and then cover with soil. The trench for base fertilizer should be deeper, 40-50 cm; the trench for topdressing should be shallower, 15-30 cm. The fertilization trench should be moved outward year by year. This fertilization method has the advantages of being simple to carry out and economical in fertilizer use. However, it easily cuts some faster-growing horizontal roots, and the fertilization range is relatively small; this should be noted when choosing it.
② Disk fertilization. With the main trunk as the center, rake the soil open into a disk shape. The part near the main trunk is shallow, and the farther from the main trunk, the deeper it is. There is also the practice of making only a flat-bottomed fertilization disk. The raked-out soil is piled around the outside of the disk to form a ridge at the edge. After fertilization, cover with soil again. Because this method applies fertilizer relatively shallowly, water can easily damage the roots, so it is suitable for topdressing. But long-term use of this fertilization method will cause the loquat tree root system to move upward.
③ Radial trench fertilization. With the trunk as the center, dig 6-8 radiating strip trenches outward starting 60-80 cm from the trunk, 20-30 cm deep, and apply fertilizer in the trenches. Change the trench positions every other year or every other application to increase the absorbing surface of the loquat tree root system. This method damages fewer roots, and if combined with ring fertilization, the fertilization effect is better. But when digging trenches, large roots should be avoided so as not to damage them.
④ Strip trench fertilization. Open strip trenches on both sides of the canopy drip line, or open strip trenches between rows or between plants in the loquat orchard. The trench for base fertilizer should be deeper, 50-60 cm; the trench for topdressing should be shallower, 15-30 cm. Then apply fertilizer into the strip trenches and cover with soil. At the next fertilization, the other two sides can be used instead, moving outward year by year, combined with deep plowing, to mature the soil. This is a relatively good fertilization method.
⑤ Whole-orchard fertilization. For mature loquat orchards, the loquat tree roots have already spread throughout the whole orchard, so fertilizer can be evenly broadcast over the whole orchard and then turned into the soil. If whole-orchard fertilization is combined with strip trench fertilization or radial trench fertilization, the fertilizer effect can be brought into fuller play. This method applies fertilizer relatively shallowly and easily causes the loquat root system to move upward.
⑥ Foliar topdressing, also called leaf surface spraying. Foliar topdressing is a method in which fertilizer is dissolved in water and sprayed directly onto loquat leaves so that the leaves directly absorb and utilize the nutrient elements. The foliar topdressing method is simple and easy to carry out, uses a small amount of fertilizer, and is absorbed and utilized quickly. Foliar topdressing plays an important role in preserving flowers and fruit, promoting fruit development, improving quality, correcting nutrient deficiency symptoms, increasing fertilizer efficiency (preventing chemical or biological fixation in the soil) and regulating loquat tree vigor. However, foliar topdressing has a short duration of action and can only play a supplementary role; it cannot completely replace soil fertilization.
Leaves are the center of the physiological and biochemical activities of the loquat tree. The stomata and cuticle on the leaves have the ability to absorb nutrients. During the growing period, the underside of young leaves has a relatively strong ability to absorb nutrients. Usually, the absorption of nutrients by leaves, like that by roots, is such that under acidic conditions anions are easily absorbed, while under alkaline conditions cations are easily absorbed. The trace elements used in foliar topdressing are mostly fertilizers of a simple substance. The suitable spraying concentration of various fertilizers is shown in Table 4-5. When foliar topdressing is carried out in spring, the concentration can be slightly higher; when carried out in the high-temperature and dry seasons of summer and autumn, the concentration should be appropriately lower to avoid fertilizer damage. When multiple fertilizers are mixed for use, the suitable concentration should be reduced proportionally. In addition, foliar topdressing can also be carried out in combination with spraying pesticides for pest and disease control, but attention must be paid to the acidity and alkalinity of the fertilizer types and pesticide types; acidic and alkaline ones cannot be mixed.
⑦ Special fertilization. In some hilly and mountainous areas, soil erosion is serious and nutrient elements are leached out, easily causing deficiency symptoms. In addition, acidic soil is often deficient in phosphorus and calcium, while alkaline soil is often deficient in iron, and supplementation by soil fertilization is not very effective. For this reason, some special fertilization methods are used, which can achieve relatively good fertilization results.
First, root-sleeving fertilization. The period for root-sleeving fertilization should be during the root growth and absorption period; the effect is relatively good 5-7 days after flowers fade. The concentration used is generally slightly lower than that used for foliar topdressing. The method is: use a 10 cm x 15 cm plastic bag containing 100-200 ml of fertilizer solution; at about 30-50 cm inside the drip line on the east, south, west and north sides of the loquat canopy, dig out a bundle of fibrous roots with many new roots; insert it into the plastic bag filled with fertilizer, and tie the bag opening tightly to prevent water evaporation. This method has a relatively good effect on correcting deficiency symptoms.
Second, infusion fertilization. Infusion fertilization is generally carried out in early spring when the sap is flowing, during the flower bud sprouting period, and one month before the fruit ripening period. It can preserve flowers and fruit and promote fruit development and flower bud differentiation. The fertilizer solution is 0.5 L of water, 6 g of urea, 4 g of monopotassium phosphate, plus 4 g of boric acid in early spring, a trace amount of triacontanol, and 3 g of ferrous sulfate when iron is deficient. Its device resembles a hospital infusion bottle. The method of making it is: use a plastic bottle to hold the fertilizer solution, making sure it does not leak after the cap is sealed. Insert two needles into the cap and connect rubber tubes; one rubber tube 40 cm long is used for air intake, and another rubber tube 60 cm long is then connected to a needle inserted into the tree body. Use a nail to make a hole in the main trunk of the loquat tree 20 cm above the ground, reaching deep into the xylem. Then, hang up the bottle, insert the needle into the hole, and after seeing the liquid seep out, seal the small hole tightly with white wax.
Third, drip irrigation fertilization. The drip irrigation fertilization method is also an advanced fertilization and irrigation technique. It has the advantages of timely fertilizer supply, even fertilizer distribution, no root damage, protection of soil structure, less labor use and less fertilizer use. However, at present there are commonly problems in production such as water quality failing to meet requirements, easily causing emitter clogging, and so on. Further technical improvement is needed before it can be widely applied in production.