What are the main fertilization methods of walnut at present?

   at present, the main fertilization methods of walnut in China are soil fertilization and foliar spraying.

   soil fertilization can be combined with soil ploughing. In order to facilitate the absorption and utilization of root system and maximize the fertilizer effect, fertilizer must be applied to the centralized distribution layer of human root system during soil fertilization. There are the following specific methods, and the most suitable fertilization method can be selected according to the actual situation.

   (1) the annular ditch was dug along the periphery of the canopy projection on the ground. The ditch was 30cm wide, 30cm deep and 15cm deep. The fertilizer and topsoil were mixed evenly into the ditch, and then covered with subsoil. The annular groove should move outward year by year. This method is easy to operate and economical to use fertilizer, but the range of fertilization is small, so it is often used in young walnut trees under 5 years old.

   (2) radiation furrow fertilization is the main fertilization method used in walnut orchards over 5 years old. Generally take the projection of the crown on the ground as the standard, accounting for 2 to 3 inward and 1 / 3 outward, digging 4 to 8 radial ditches with a length of 1 to 2 meters, a width of about 30 centimeters, and a depth of 25 to 30 boxes of meters, fertilizing, covering soil and irrigating in the ditches. The position of fertilizer ditch is staggered every year. When digging trenches, try to avoid injuring large roots with a diameter of more than 1 cm.

   (3) Strip ditch fertilization is suitable for young trees, adult trees and dense planting gardens. It is to dig 2 canopy 3 or equal to crown diameter on one or both sides of the crown projection between walnut trees or rows. The ditch is 40cm wide, 40cm wide, 40cm deep and 15cm deep. The annual rotation of furrow-to-row and plant-to-plant fertilization can be combined with deep soil ploughing. The root injury of this method is relatively less, but the fertilization site is limited, so it can be used alternately with radiation ditch fertilization to expand the fertilizer application area and promote root absorption.

   (4) hole fertilization is suitable for walnut orchards with large crown, wide root distribution and intercropping between rows, and is mostly used for topdressing. Take the trunk as the center, 1 ~ 1. 5 meters away from the trunk. 5 meters away, dig a number of fertilizer holes with a diameter of 30 to 40 centimeters and a depth of about 25 centimeters, apply fertilizer into them, seal the soil and irrigate. This method saves fertilizer and is simple and convenient.

   (5) during the full fruit stage, the root system of the fruit tree has been spread all over the orchard. When applying basic fertilizer, the organic fertilizer can be spread evenly on the ground, and then turn into the soil, the depth is generally about 20 cm. This method is simple and easy, but the disadvantage is that the fertilization position is shallow, which is easy to cause the root system to return.

In addition,    topdressing can also use infiltration irrigation to dissolve soluble fertilizer into water and topdressing with water through drip irrigation or infiltration irrigation system. This method provides fertilizer in time, evenly distributes without harming roots, does not destroy soil structure, and can save chemical fertilizer. This method is also known as "integration of fertilizer and water".

   (6) foliar fertilizer, also known as extra-root topdressing, is to spray a certain concentration of fertilizer solution directly on the leaf surface. This method has the advantages of less fertilizer, fast fertilizer efficiency and high utilization rate. it can meet the nutrient needs of walnut trees in time, and avoid the disadvantage that some elements of soil fertilization will be fixed. Foliar spraying can be carried out at flowering stage, rapid shoot growth period, flower bud differentiation period and after harvest, and foliar spraying can be carried out before 10:00 or after 4 pm in sunny and windless weather. When the temperature is too high, the solution will shrink and leaf burning will occur. In general, the back of the leaf has a strong ability to absorb fertilizer, so the back of the leaf should be sprayed when spraying fertilizer on the leaf surface. The type and concentration of foliar spraying fertilizer are: urea 0. 5%. 3%-0.4%, calcium superphosphate 0. 5%-1%, potassium sulfate 0. 2% zero. 3% (or 1% plant ash extract), boric acid 0. 1% 0.2%, 0.5% ammonium molybdate, 0. 1% copper sulfate. 3% zero. 4%. Spraying 0. 0 at flowering stage of walnut in Shexian County, Hebei Province. 3% boron plus 0. 3% urea can increase the fruit setting rate by 9% ~ 17%. The general principle of foliar fertilizer spraying is that the concentration is low in the early growth stage and high in the later stage. In practical use, small-scale tests should be done first to avoid drug damage caused by excessive concentration. It should be noted that foliar topdressing is only a supplementary fertilization measure and can not replace soil fertilization. If the two fertilization methods are used together and complement each other, the maximum effect of fertilization can be brought into play.