Introduction to the fertilization period of walnut trees

According to the performance of fertilizer and fertilization period,    can be divided into two categories: base fertilizer and topdressing fertilizer.

   1. The base fertilizer is mainly rotten organic fertilizer, which is the basic fertilizer that can supply walnut with various nutrients for a long time. Base fertilizer is usually applied in autumn and as soon as possible after fruit harvest and before defoliation. If it is too late in autumn, it can be applied in spring. The application of basal fertilizer in autumn can promote flower bud differentiation, root growth, improve the nutrient storage level of trees, and be beneficial to branch and leaf growth, flowering and fruit setting in the coming year. The sooner base fertilizer is applied in autumn, the better. In the young walnut country, the human base fertilizer can be applied in combination with deep ploughing, and the adult garden can apply the base fertilizer and irrigate once after the base fertilizer is applied in the whole garden.

   2. Topdressing is an available fertilizer which is replenished in time according to the needs of tree growth and development on the basis of base fertilizer. Give priority to quick-acting chemical fertilizer. Topdressing can provide the nutrition needed for the growth and development of trees in the same year, which is not only conducive to the high yield and high quality of strong trees in that year, but also lay the foundation for the growth and fruit in the coming year. High temperature and rainy areas or sandy soil, fertilizer is easy to lose, topdressing should be a small number of times. The times of topdressing for young trees should be less, generally 2-3 times a year, with the increase of tree age and fruit, the times of topdressing increase, and adult trees generally 3-4 times a year. The three main topdressing periods of walnut are as follows:

   (1) the first topdressing of early bearing walnut was carried out before the female flower blossomed, and the fruit walnut was carried out at the early stage of leaf expansion. Mainly available nitrogen fertilizer, such as urea, ammonium sulfate and so on. Topdressing in this period can promote flowering and fruit setting, which is beneficial to the growth and development of new shoots. For walnut trees entering the full fruit stage, quick-acting nitrogen and phosphorus fertilizers must be applied before sprouting in spring, and the amount of fertilizer should account for more than 50% of the total amount of topdressing in the whole year, otherwise the lack of nutrition in the early stage will hinder the growth and development of the tree, affect flowering and fruit setting.

   (2) the second topdressing of early bearing walnut was applied after female flower blooming, and late bearing walnut was applied at the end of leaf expansion. Give priority to nitrogen fertilizer, combined with appropriate amount of phosphorus and potassium fertilizer. At this time, topdressing can promote fruit development, reduce fruit drop, and be beneficial to branch growth and Lignification. The amount of fertilizer applied should cover 30% of the total amount of topdressing in the whole year.

   (3) the third topdressing was carried out after the hard kernel of the fruit in late June for the walnut entering the fruiting stage. Mainly phosphorus and potassium fertilizer, combined with a small amount of nitrogen fertilizer. The main purpose of topdressing in this period is to meet a large number of nutrients needed for kernel development, improve nut quality, promote flower bud differentiation, and lay a good foundation for flowering and fruit setting in the coming year. The amount of topdressing should account for 20% of the total amount of topdressing in the whole year.

   in addition, the determination of specific fertilization period is also affected by the nutrition and water status of the soil. For barren soil, multiple topdressing in spring is very important, while fertilization times can be reduced in fertile soil with high organic matter content. Soil water content will affect the exertion of fertilizer effect, and fertilization is often harmful but not beneficial when soil is short of water, so the fertilization period should be determined according to whether water can be supplied or not, and fertilization should be applied in the rain period in water-deficient areas.