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First, shape diagnosis
1. Boron deficiency. The top buds stop growing, gradually wither and die, the roots are underdeveloped, the leaves are dark green, the leaves are small, thick, shrinking, the plants are dwarfed, the flowers are not well developed, the fruits and ears are not real, the buds are shed, the roots and berries are Corrosion or necrosis. Such as broccoli root swelling, radish hollow, heart rot and so on.
2, lack of mo Plant growth is poor, the plant shape is short, the veins are green, or the leaves are twisted. For example, the edge of the tomato leaves curls upwards, forming white and gray spots and falling; the cabbage forms elongated and deformed leaves.
3. Zinc deficiency. In the early stage of maize, zinc deficiency appeared on the leaves, and gradually the leaves were chlorotic, and "white bud disease" appeared. At the late stage of growth, the ears were short of grains and bald.
4. Manganese deficiency. The illness begins with the new leaves. The leaf flesh of the new leaves of the dicotyledonous crops is green and yellow, while the veins are still green; gray spots or brownish green spots appear on the leaves of the monocotyledonous leaves, which gradually become strips along the midrib and lateral veins. And necrosis.
5, lack of iron. It is characterized by "greenness deficiency". At the beginning, the leaves of the young leaves are green and yellow, the veins remain green, and the whole leaves are green. Later, the whole leaves are yellowish white. Because iron has little mobility in the body, it is generally expressed as the new leaves are chlorotic, while the old leaves remain green.
6, lack of copper. When the grass crop lacks copper, the tip of the leaf turns white, the edge is yellow-gray, and when it is severe, it cannot be headed.
Second, the external root spray application diagnosis. The external root spray application is to prepare a soluble salt containing trace elements into a certain concentration solution, spray it on the leaf of the diseased plant, or apply it on the diseased leaf, or immerse the diseased leaf in the solution for 1-2 hours, 7 -10d to observe the recovery of diseased leaves. If the diseased leaves recover or the leaf speed of the new leaves is significantly accelerated and the leaf color is normal, it can be confirmed that the plant disease is caused by the lack of a certain trace element. Generally, the spraying concentration of trace elements is: boric acid or borax 0.1%, ammonium molybdate 0.01%-0.1%, zinc sulfate 0.02%-0.1%, manganese sulfate 0.1%, ferrous sulfate 0.75%-1.0%, copper sulfate 0.02%. -0.04%. In order to facilitate the infiltration of trace elements into the plant body, a neutral spreading agent may be added to the spray solution.
Third, the injection diagnosis method. There are methods such as vein injection and twig injection. First, the salt of a certain trace element is formulated into a solution. The concentration is generally 0.1%-0.2%, and the copper sulfate is not more than 0.1%. Then the filter paper or cotton is used to make the tweezers, one end is placed at the stem incision, and the other is placed in the stem. In the test tube with trace elements, it was taken out for 7-12 hours, and after 10 days, the growth and disease changes of the diseased plants were observed and confirmed. Or take a leaf of the diseased plant, cut off the leaves on both sides along the main vein, leaving only the main vein and some residual mesophyll, immediately immersed in the test tube containing the trace element solution for 1-2 hours, and then remove it. After a few days, observe whether the color of the adjacent diseased leaves is restored. normal.
Fourth, chemical analysis and diagnosis. The chemical analysis diagnosis is to determine the active constituents of trace elements in the soil and the trace elements in the plants by chemical methods, and judge the critical indicators.
There is a complex relationship between soil, crops and nutrients. For general crops, the water-soluble boron in the soil is less than 0.5mg/kg, the plant will show symptoms of boron deficiency, and the beet can be increased to 0.75mg/kg, rapeseed and cotton. Then they were reduced to 0.4 mg/kg and 0.2 mg/kg, respectively. It can be seen that in order to make the determination of the abundance and deficiency index of trace elements in soil have guiding significance in production, it is necessary to make detailed and comprehensive research based on local soil conditions and crop types. Chemical analysis of plants is generally carried out in the early stages of crop growth and when the symptoms of deficiency are not obvious. It has been determined that for mature leaves, when the contents of trace elements such as molybdenum, boron, manganese, zinc, copper and iron are less than 0.1, 15, 20, 20, 4, 50 mg/kg, respectively, it can be diagnosed as deficiency.
Therefore, to determine which trace elements are missing from vegetables, we should combine the plant and soil data, and refer to the diagnostic results of plant shape and spraying to select the correct diagnosis. Provide scientific basis for the rational application of trace element fertilizer.
Although trace elements are small in crops, they are a component of enzymes or coenzymes in plants. They have strong specificity and are indispensable or inseparable parts of normal growth and development of crops. Therefore, when the crop lacks any trace elements, growth and development are inhibited, resulting in reduced yield and quality, and even loss in severe cases. The following is a brief description of the lack of symptoms and diagnostic methods for several trace elements.
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