The high sweetness of citrus is an important indicator of fruit quality. In recent years, the quality of citrus produced in orange orchards in some places has declined, and the flavor has deteriorated, in addition to the selection of excellent varieties with high sugar content suitable for local water and soil conditions, there are many measures to be implemented in fertilization.
Strengthen canopy management to brighten and sweeten
Focus on the dense change of orange orchards to thinning, and the height of the canopy to short. Make sure to form "independent trees" and "independent branches". The trees and branches are not connected to each other, and the hedge spacing should be kept at least 30~40 cm; The height of the canopy is limited to 2.3 meters, and the canopy is thinned or transplanted to reach the standard of 4 meters ×3 meters between the rows. Promote the pruning technology of large branches, adopt the techniques of hanging, pulling and binding to open the crown; sawing off the central erect branches, opening the skylight, reducing the height of the crown; thinning the upright branches, large branches with small branch angles and over-dense, crossing, and rotating large branches, pruning diseased and insect branches; retracting weak branches or branch groups, making the crown dwarf, and achieving a reasonable combination of main branches, Secondly, the water control 20~30 days before harvest is promoted, and the ground is covered with reflective film, which not only controls water but also supplements light, which is conducive to improving the solid content of fruits.
Changing the partial application of chemical fertilizer to increasing the application of organic fertilizer
The survey found that some citrus varieties with high sweetness lost their original flavor due to the heavy application of chemical fertilizers, which reduced the sugar content and increased the acidity. If a large amount of chemical nitrogen fertilizer and potassium fertilizer are applied, because nitrogen can promote vegetative growth, delay fruit coloring, lighten color, and thicken the peel, so excessive nitrogen application is not conducive to improving the sweetness of fruits.
Potassium promotes fruit enlargement, but too much potassium in the leaves increases fruit acidity and lightens the flavor of the pulp.
In the production of citrus, more organic fertilizer, especially a variety of cake fertilizer and a variety of organic and inorganic compound fertilizer, can not only meet the growth of nitrogen, phosphorus, potassium, but also can supplement magnesium, zinc and other trace elements, but also improve soil acidity and soil bulk density, improve fertilizer utilization, prevent or correct citrus deficiency symptoms, improve soil fertility, thereby increasing its sweetness.
Increase calcium fertilizer
According to research, the acidity of citrus is related to the amount of calcium in the soil.
Citrus with a high calcium content has a relatively low acidity and vice versa. The soil of the southern orange orchard is mostly red loam, the soil is acidic, the pH value is generally 5~6, and the soil is generally deficient in calcium. Therefore, the addition of lime and other calcium fertilizers to the soil of citrus orchards can effectively supplement the calcium content in the soil and supplement the calcium nutrients required in the citrus growth period. Generally, 50~60 kg of quicklime per mu is sprinkled in the orange orchard soil to reduce the acidity in the orange orchard soil, improve the accumulation of sugar and increase the sweetness.
In addition, 2 foliar sprays of chelated calcium increase the sweetness of citrus, improve the taste, and also improve the storage tolerance of citrus.
Spray foliar fertilizer appropriately
In the early, middle and late stages after fruit bearing, potassium dihydrogen phosphate was sprayed once on the upper foliar surface of the fruit tree, which was conducive to sugar increase and storage tolerance, and the sugar-acid ratio was increased and the fruit expansion was facilitated.
The experiment proved that after fruit growth, spraying 2% (w) lime water and 0.4% (w) salt mixture can improve leaf photosynthesis, prevent high temperature damage to fruit, promote coloring, improve quality, and mature 7~10 days early.
Sweetener is applied
(Fluid boron:chelate calcium:glucose = 1:1:5)
The liquid is sprayed on the leaf surface of the citrus with a sprayer, and the front and back sides should be evenly sprayed, and the sugar content of the mandarin orange after harvest is 11.8 degrees, the acidity is 0.7, and the sweetness is increased by 1.6 degrees compared with the non-sprayed solution.
When spraying, it is necessary to grasp the timing, and the first spraying requires that the fruit has grown and begins to turn red, and the spraying amount is 20.5~1 liter per meter. After 10 days, spray again. The test showed that the coloring rate could reach 95% and the sugar content could be increased by 8.5% after spraying the solution.
This method is not only simple to operate, high coloring rate and high sugar content, but also non-toxic, harmless and non-polluting, which improves yield and increases storage resistance.
Change late application to early application of basal fertilizer
In the past, orange farmers Xi used to apply basal fertilizer in winter. If the basal fertilizer based on organic fertilizer is applied in the autumn after harvesting, the early basal fertilizer is easy to ferment and decompose, and is easy to be absorbed by the tree, which is conducive to the decomposition and transformation of organic fertilizer in winter and spring and the continuous release of nutrients. As a result, citrus can send out new roots in time, so as to facilitate the rapid recovery of growth and vitality in the next year. By providing citrus trees with nutrients needed for flower bud differentiation and early flowering and fruiting, it can promote flower bud differentiation and prevent flower and fruit drop, which can significantly improve the yield and quality of citrus fruits.