The high sweetness of citrus is an important indicator of the quality of the fruit. In recent years, the quality of citrus produced in some local orange gardens has declined, and the flavor has deteriorated. In addition to selecting high-quality varieties with high sugar content suitable for local soil and water conditions, there are many measures to be implemented in fertilization.

The application of chemical fertilizers is to increase the application of organic fertilizer. The survey found that some sweet citrus varieties were heavily applied with fertilizer, the sugar content decreased, the acidity increased, and the original flavor was lost. If a large amount of chemical nitrogen fertilizer and potassium fertilizer are applied, nitrogen can promote vegetative growth, delay fruit coloration, lighten color, and thicken the skin. Therefore, excessive nitrogen application is unfavorable for improving the sweetness of the fruit. Potassium can promote fruit enlargement, but excessive potassium in leaves will increase the acidity of the fruit and make the flavor of the flesh lighter.

In the citrus production, more organic fertilizers, especially various cake fertilizers and multi-organic inorganic-inorganic compound fertilizers, can meet the nitrogen, phosphorus and potassium needed for growth in time, and can also supplement trace elements such as magnesium and zinc. Improve soil acidity and soil bulk density, improve fertilizer utilization, prevent or correct citrus deficiency symptoms, increase soil fertility, and thus increase its sweetness.

Change the late application for early application of base fertilizer. In the past, orange farmers were used to applying base fertilizer during the winter. If the base fertilizer based on organic fertilizer is applied in the autumn after harvesting, the early base fertilizer is easy to be decomposed and decomposed, which is easy to be absorbed by the tree body, which is beneficial to the decomposition and transformation of organic fertilizer in winter and spring and continuous release of nutrients. So that the citrus will send out new roots in time to help restore growth and vitality quickly next year. Due to the supply of citrus tree flower bud differentiation and nutrients required for early flowering, it promotes flower bud differentiation, prevents the occurrence of falling flowers and leaves, and can significantly increase the yield and quality of citrus fruits.

Add calcium fertilizer. According to research, the acidity of citrus is related to the amount of calcium in the soil. High calcium content The citrus has a relatively low acidity and is therefore relatively high. The soil of the southern orangery is mostly red loam soil, the soil is acidic, and the pH is generally between 5 and 6. The soil is generally deficient in calcium. Therefore, the application of calcium fertilizer such as lime to the citrus garden soil can effectively supplement the calcium content in the soil and at the same time complement the calcium nutrients required in the citrus growth period. Generally, 50-60 kg of quick lime per acre is applied to the soil of the orangery to reduce the acidity in the soil of the orangery, and increase the accumulation of sugar to increase the sweetness.

Spray foliar fertilizer reasonably. In the early, middle and late stages after fruiting, a mixture of 0.2% calcium dihydrogen phosphate and 0.2% sodium dihydrogen phosphate was sprayed on the upper leaves of the fruit trees. Spraying calcium dihydrogen phosphate is beneficial to sugar and storage; spraying sodium dihydrogen phosphate is beneficial to increase the ratio of sugar to acid, and potassium dihydrogen phosphate is beneficial to fruit expansion. In the high temperature mature period, it is necessary to spray 100-200ppm "Sweet Treasure" solution in moderation. Tests have shown that after fruit growth, spraying 2% lime water and 0.4% salt mixture can improve leaf photosynthesis, prevent high temperature damage, promote coloration, improve quality, and mature 7-10 days earlier.

Formulated with sweeteners. In 700 kg of water, a boron fertilizer equivalent to 200 g of pure boron, 2.4% of sucrose, and 0.7 g of calcium chloride are added, and after dissolution, it is a "sweetener". The liquid was sprayed on the leaf surface of the citrus by a sprayer, and both sides were sprayed evenly on both sides. After harvesting, the sugar content of the mandarin orange was 11.8 degrees, and the acidity was 0.7. The sweetness was increased by 1.6 degrees compared with the case where the liquid was not sprayed. . According to the test, 99.57% of ammonium thiosulfate and 0.43% of sodium lauryl sulfate were mixed, and 20,000 times of clean water was added thereto, and the mixture was allowed to stand overnight, and then the fruit was sprayed. When spraying, it is necessary to grasp the timing. The first spraying requires the fruit to be long enough to start in red, and the spraying amount is 0.5-1 liter per square meter. After 10 days, spray again. Tests have shown that after spraying the solution, the coloration rate can reach 95% and the sugar content can be increased by 8.5%. The method not only has simple operation, high coloring rate, high sugar content, but also is non-toxic, harmless, non-polluting, increases yield, and increases storability.