Phenology marks the strength of life activities and the absorption and consumption of nutrients by fruit trees. According to the observation of 32P markers on apple, peach, jujube and other fruit trees in Hebei Agricultural University, it is found that the distribution of nutrients in trees is the organ that meets the most vigorous life activities, that is, the growth center, also known as the nutrient distribution center. With the development of phenology, the distribution center has also shifted. In the budding and flowering stage, young leaves, branches and flower organs need nutrition most; In the period of rapid fruit expansion, the fruit needs nutrition most; In the flower bud differentiation stage, the bud needs the most nutrients. According to the experimental report of Shaanxi Fruit Research Institute, fertilization at flowering and fruit-setting stage can still improve the fruit-setting rate when the fertilizer consumption exceeds the general production level. Missing this fertilization period will often aggravate the physiological fruit drop. This shows that suitable fertilization, that is, grasping the validity period of fruit tree fertilizer, is the key to rational fertilization. At the same time, the overlapping phenology of fruit trees affects the amplitude of distribution center and the contradiction between nutrient distribution and supply and demand.

Fruit trees need different nutrients at different phenological stages of the annual cycle. Generally speaking, when budding, budding and spreading leaves, the most nitrogen is needed. The demand for potassium increased in the middle growth stage and the rapid fruit expansion stage, and 80% ~ 90% of potassium was absorbed during this period. The absorption of phosphorus is the least in the early growth stage, gradually increases after flowering, and then changes little.

Different fruit trees need fertilizer most at different times. For example, from germination to rapid fruit expansion, the absorption of nitrogen gradually increased until the fruit rapidly increased and gained weight. Another example is that citrus fruit trees absorb nitrogen almost all year round, but the absorption peak is in the summer when the temperature is high; Phosphorus absorption is mainly in the vigorous growth period of new shoots, and rarely in winter; The absorption of potassium is mainly in May ~165438+1October.

Root activity is also one of the signs that determine the fertilization period. Generally, the roots of deciduous fruit trees begin to grow and absorb before germination. Therefore, fertilization should be carried out before germination, which is premature and easy to lose; Too late will lead to excessive growth of branches and fruit drop. Nitrogen supply should be carried out at the peak of shoot growth and root growth in the middle and late stage, otherwise it will promote the growth of secondary branches and affect fruit setting, flower formation and safe overwintering. The growth of roots and branches of evergreen fruit trees is related to the regional climate. In some areas, roots begin to move before germination, some areas sprout three times a year, and some areas sprout four times a year, which is warm all year round. Therefore, fertilization must also be based on the active period and peak time of roots and branches.