Base fertilizer is the fertilizer applied before the growing season, which is mainly based on base fertilizer and slow-release organic fertilizer all year round, such as manure, compost, dry cake, green manure, weeds, garbage, pond mud and filter mud. After being applied to soil, it needs to be decomposed into small molecular nutrients by soil microorganisms: it will be absorbed and utilized by crops. Combining deep tillage with soil improvement can supplement soil organic matter content. In order to exert fertilizer efficiency as soon as possible, some available nitrogen fertilizers and phosphate fertilizers can also be mixed when applying base fertilizer. Applying a small amount of lime combined with base fertilizer can adjust soil pH value. It is better to apply base fertilizer in autumn than in spring, and it is better to apply fertilizer in early autumn than in late autumn or winter. At this time, the sugar orange consumes a lot of nutrients after flowering and fruiting, and it is in the stage of recovery and accumulation, which is also the peak of root growth, which can make the roots cut off by fertilization and soil improvement easily heal and grow new roots.

Step 2: Topdressing

Topdressing, also known as topdressing, is a temporary supplementary fertilizer to make up for the lack of base fertilizer during the growth of sugar oranges. Topdressing is mainly quick-acting inorganic fertilizer, such as urea. After being applied to the soil, it can be easily absorbed by plants, which can timely supplement the needs of the growth of sugar oranges in the current year, ensure the robust growth of trees, and make the flower buds differentiate well, laying the foundation for the growth results in the next year. The period and frequency of topdressing should be determined according to local soil conditions, tree age and bearing capacity of trees and fruits. Generally, loam with fertile soil can be applied less, and sand should be applied less and frequently; Fertilization frequency of young trees and flourishing trees is less than that of adult trees; Trees with many fruits can be topdressed many times; Trees with little or no fruit can be planted less or not. Top dressing of sugar orange is divided into the following periods.

A large number of sugar oranges bloom in spring, coupled with the growth of branches, which consumes a lot of nutrients. Although some nutrients were accumulated on the trees last year, the soil temperature was low in early spring, and the ability of roots to absorb nutrients was weak, which still could not meet the needs, and the contradiction between supply and demand of nutrients was more prominent. Therefore, it is necessary to apply an appropriate amount of quick-acting fertilizer to weak trees and flowering trees in early and mid-February, which can obviously improve the fruit-setting rate, promote the growth of branches and leaves, turn leaves green, enter the functional period as soon as possible, and enhance photosynthetic capacity. It should be noted that if the trees are flourishing, or the number of flower buds is small, it is not appropriate to apply fertilizer before flowering, otherwise it will cause a large number of fruit drops because of promoting the growth of branches. This kind of topdressing should be combined with nitrogen, phosphorus and potassium, and more nitrogen fertilizer should be applied appropriately.

The application period of fruit-stabilizing fertilizer is consistent with the physiological fruit drop and summer shoot emergence of sugar orange. The main purpose of fertilization at this time is to improve the fruit setting rate and control the occurrence of summer shoots. In addition, because flowering consumes a lot of nutrients, if the nutrition is insufficient, it is easy to cause a lot of physiological fruit drop. Therefore, fertilization has the function of stabilizing fruit when flowers wither, that is, applying appropriate amount of available nitrogen fertilizer from late April to early May, combined with phosphorus and potassium fertilizer to supplement the consumption of nutrients by sugar oranges, can reduce physiological fruit drop and promote the rapid expansion of young fruits. It should be noted that the application of nitrogen fertilizer should not be excessive, so as not to promote a large number of summer shoots and aggravate physiological fruit drop.

July-September is a period of rapid fruit expansion, and it is also a long period of germination of autumn shoots. At this time, the quality of fertilizer and water conditions determines the yield of that year, and also relates to the quantity and quality of autumn shoots. Autumn shoots are good fruiting branches in the second year, which is very important for the yield in the second year. In order to ensure the fruit expansion and the quality of autumn shoots, we should apply fruit-strengthening and shoot-promoting fertilizer in early July, combine with drought-resistant irrigation, apply appropriate amount of available nitrogen fertilizer, and increase the proportion of phosphorus and potassium fertilizer, which is conducive to promoting the rapid fruit expansion, increasing the yield, promoting the maturity of autumn shoots and promoting the differentiation of flower buds. At this time, the air temperature and soil temperature are high, which is at the peak of root growth, with a large number of roots and strong root absorption capacity, which is an important period for sugar orange fertilization.

After a year of growth, flowering and fruiting, sugar orange, the fruit picking fertilizer, consumes a lot of nutrients. Apply fruit fertilizer in time after fruit harvesting, mainly with available nitrogen fertilizer and phosphorus and potassium fertilizer. Used to make up for nutrient deficiency caused by a large number of fruits, especially suitable for weak trees that consume more nutrients. It is very important for restoring tree vigor, increasing nutrient accumulation, improving tree overwintering, preventing defoliation and promoting flower bud differentiation, and is very important for the next annual output.