Manifestations of deficiency and toxicosis of walnut

The key of    scientific fertilization is to accurately judge the surplus and deficiency status of nutrient elements and tree nutrients in soil. The basis of fertilization includes morphological diagnosis and nutrition diagnosis.

   morphological diagnosis is to judge the amount of nutrient elements and guide fertilization according to the external morphological characteristics of fruit trees. A wealth of experience is required for morphological diagnosis. In general, large and many leaves, thick and thick green leaves, stout branches, full buds, uniform results, good quality, high yield and stable yield show that the nutrition of the tree is normal, otherwise the reason should be clear and measures should be taken to improve it. The common walnut deficiency and toxicosis are described as follows for reference.

When    was nitrogen deficient, the leaf color was lighter at the beginning of the growing period, and gradually turned yellow, the leaves were sparse and small, the leaves often fell ahead of schedule, the growth of new shoots was small, the tree potential was weak, and the flower and fruit drop was serious; in serious cases, the top branchlets of the plant died and the yield decreased obviously. However, a similar phenomenon may occur under drought and other adverse conditions. Excessive application of nitrogen fertilizer often leads to the growth of technical leaves, the insufficiency of tissue, the postponement of fruit ripening, the decrease of storage tolerance and the aggravation of physiological diseases.

When    is deficient in phosphorus, the tree is generally very weak, the leaves are sparse, the small leaves are slightly smaller than normal, the leaves appear irregular yellowing and necrosis, and the leaves fall in advance. Excess phosphorus can affect the absorption of nitrogen, potassium and exercise, reduce the activity of iron in plants and soil, turn leaves yellow and cause lobular disease caused by zinc deficiency.

The symptoms of potassium deficiency in    were mostly on the leaves in the middle of the technical strip, which turned gray at the beginning (similar to nitrogen deficiency), then wavy leaf margin, light gray (or bronze color) on the back, reduced leaf and shoot growth, and reduced nuts.

When    was deficient in calcium, the root system was short, thick and curved, and the tip soon became brown and withered, and the aboveground parts first appeared on the young leaves, the leaves were small, rough, the leaf margin was deformed, and often appeared spots or necrosis, and in serious cases, the technique strip withered, and the physiological diseases of calcium deficient fruits were aggravated. Too much calcitonin, iron, manganese, zinc, boron and so on are easy to be transformed into unavailable state, resulting in element deficiency.

When    is iron deficient, the young leaves lose chlorosis, the mesophyll is yellowish green, and the leaf veins are still green. In severe iron deficiency, the leaves are small and thin, yellow or milky self-color, and even develop into scorched or shedding. Because iron is not easy to move in the tree, the young leaves at the top of the shoot are the first to show iron deficiency.

When    is zinc deficient, the sprouting period of shoot tip bud is delayed, and the leaves are small and yellow, showing tufted shape, which is called "leaflet disease", the new shoots are thin and the internodes are short; in severe cases, the leaves gradually fall off from the base of the new shoots, the technical strips die and the fruit becomes smaller.

When    is boron deficient, the growth of the tree is slow, the technical strip is slender, the internodes become shorter, the leaflets are irregular, sometimes in the shape of sepals, and in severe cases, the tip strips die. Excessive boron can cause poisoning and tissue necrosis. the symptoms first appear in the leaf tip and gradually expand to the leaf edge, and in severe cases, the necrotic part expands between the veins in the leaf, and the lobule edge is rolled up and scorched.

   magnesium is the main component of chlorophyll. When magnesium is deficient, chlorophyll can not be formed, showing chlorosis. First, yellowing occurs at the leaf tip and both leaf edges, and gradually extends to the base of the leaf, leaving a v-shaped green area. The yellowing part gradually withered and became dark brown.

When    was deficient in manganese, it showed a unique symptom of chlorosis, the chlorosis developed from the main vein to the edge of the leaf, the chlorotic part was rib-shaped, and the tip leaf was still green. In severe cases, the leaves become smaller and the yield becomes lower.

When    was deficient in copper, the leaves at the top of the new shoot first lost green and turned yellow, then scorched, the technical strip shrunk slightly, and there were small dark brown spots on the top of the new shoot. The fruit whitens slightly and the nucleolus shrinks seriously.

   nutrition diagnosis is a widely used method to determine and adjust the fertilization of fruit trees abroad. Nutrition diagnosis can timely and accurately reflect the nutritional status of the tree, analyze the deficiency or excess of various nutrient elements, distinguish the similar symptoms caused by different elements, and detect them as early as possible before the symptoms appear. Therefore, scientific fertilization based on nutritional diagnosis can ensure the normal growth and development of fruit trees. Nutrition diagnosis includes leaf analysis and soil analysis, which is to determine the content of mineral elements in leaves according to the unified standard method, and to determine the amount of this element by comparing with the standard value of leaf analysis. then, according to the local soil nutrient status (that is, the results obtained by soil analysis), fertilizer efficiency index and the interaction between mineral elements, we can scientifically formulate fertilization plan and fertilizer ratio to guide fertilization.