Why do returning-green wheat plants still turn yellow after watering and fertilizing?
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Why returning-green wheat is still yellow even after watering and fertilizing
Author: Article source: Agricultural Science and Technology News Published: 2018-02-09 Views:
Right now is the wheat returning-green stage, the best time to apply returning-green water and returning-green fertilizer, but some fields, after watering and fertilizing, show a temporary return to green and then continue to yellow. What exactly is the reason? Below, the different causes of wheat yellowing are analyzed, in the hope that the right remedy can be applied early.
Cause one: excessive irrigation volume combined with low-lying terrain causing salinization, with a relatively waterlogged state lasting more than 5 days. Organic matter decomposes slowly, nutrients cannot be absorbed in time, causing wheat seedling leaves to yellow, growth to slow, root development to be hindered, and rooting to be shallow; in severe cases, root rot and seedling death also occur.
Remedial measures: For low-lying fields, water lightly, using the standard that wheat seedlings can be pulled out easily; for fields already over-watered, open ditches to drain water and deepen and clear the field drainage ditches.
Cause two: potassium-deficiency yellow seedlings, along with heavy nitrogen application. Unlike weak seedlings from nitrogen deficiency, yellowing of wheat seedlings from potassium deficiency often occurs in sandy soil fields, and the edges of the beds are more affected than the middle; yellowing wheat seedlings generally start from the leaf tip and then extend downward along the leaf margin, with a clear boundary between the yellow patches and the normal parts, forming mosaic-type yellowing; yellow leaves often soften and later lie flat on the ground.
Remedial measures: For potassium-deficient wheat fields, generally 5-10 jin of potassium fertilizer can be applied per mu as a top dressing. Since nitrogen fertilizer was applied previously, nitrogen or nitrogen-potassium fertilizer need not be applied again, or, combined with pest and disease control, 2% potassium dihydrogen phosphate can be sprayed on the leaves.
Cause three: magnesium deficiency or copper deficiency. In magnesium-deficient wheat, the veins of the middle and lower leaves lose green, with residual green spots forming strings. In copper-deficient wheat, the upper flag leaf yellows, becomes thinner, and twists and droops into tip yellowing disease; old leaves bend, leaf tips wither into a spiral shape, and gray spots appear on the lower part of the leaf sheath.
Remedial measures: Heavy application of nitrogen fertilizer will cause obstacles to the absorption of medium and trace elements; the nitrogen fertilizer rate should be reduced, and attention should be paid to the application of medium and trace elements.
Cause four: wheat infected with root rot. Wheat root rot is prone to occur during the growth period; root rot at the seedling stage is accompanied by leaf spots. Root rot occurring in the later stage of wheat causes premature senescence, many shriveled grains, ear rot, and black embryo, and in severe cases reduces yield.
Remedial measures: A large amount of pathogenic bacteria accumulates in the soil of continuous wheat cropping fields; deep plow once in the next season. The higher the seed-borne pathogen rate, the higher the seedling disease incidence and disease index. At sowing, use triadimefon or Likxiu seed coating treatment; at the returning-green stage, combined with watering, drench the roots with hymexazol or metalaxyl-hymexazol.
Cause five: wheat infected with yellow dwarf virus disease. New leaves begin to yellow from the leaf tip, and the leaf color is golden yellow to bright yellow, with the yellowed part accounting for 30%-50% of the whole leaf.
Remedial measures: Wheat yellow dwarf disease has a high probability of occurrence in warm winters and cold springs; the main task is to control wheat aphids and planthoppers, especially in wheat fields near roadsides and ditches.
Cause six: encountering a late spring cold snap, with low-temperature freeze damage caused by not watering thoroughly. Wheat encountering a low temperature of -5°C to -8°C before jointing, or a low temperature of around 0°C after jointing, is prone to freeze damage.
Remedial measures: Before the cold wave arrives, promptly irrigate dry wheat fields to ensure sufficient soil moisture, so as to reduce low-temperature freeze damage. For affected fields that were not watered thoroughly, after the cold wave passes, irrigate again promptly, and water sufficiently and thoroughly.
Cause one: excessive irrigation volume combined with low-lying terrain causing salinization, with a relatively waterlogged state lasting more than 5 days. Organic matter decomposes slowly, nutrients cannot be absorbed in time, causing wheat seedling leaves to yellow, growth to slow, root development to be hindered, and rooting to be shallow; in severe cases, root rot and seedling death also occur.
Remedial measures: For low-lying fields, water lightly, using the standard that wheat seedlings can be pulled out easily; for fields already over-watered, open ditches to drain water and deepen and clear the field drainage ditches.
Cause two: potassium-deficiency yellow seedlings, along with heavy nitrogen application. Unlike weak seedlings from nitrogen deficiency, yellowing of wheat seedlings from potassium deficiency often occurs in sandy soil fields, and the edges of the beds are more affected than the middle; yellowing wheat seedlings generally start from the leaf tip and then extend downward along the leaf margin, with a clear boundary between the yellow patches and the normal parts, forming mosaic-type yellowing; yellow leaves often soften and later lie flat on the ground.
Remedial measures: For potassium-deficient wheat fields, generally 5-10 jin of potassium fertilizer can be applied per mu as a top dressing. Since nitrogen fertilizer was applied previously, nitrogen or nitrogen-potassium fertilizer need not be applied again, or, combined with pest and disease control, 2% potassium dihydrogen phosphate can be sprayed on the leaves.
Cause three: magnesium deficiency or copper deficiency. In magnesium-deficient wheat, the veins of the middle and lower leaves lose green, with residual green spots forming strings. In copper-deficient wheat, the upper flag leaf yellows, becomes thinner, and twists and droops into tip yellowing disease; old leaves bend, leaf tips wither into a spiral shape, and gray spots appear on the lower part of the leaf sheath.
Remedial measures: Heavy application of nitrogen fertilizer will cause obstacles to the absorption of medium and trace elements; the nitrogen fertilizer rate should be reduced, and attention should be paid to the application of medium and trace elements.
Cause four: wheat infected with root rot. Wheat root rot is prone to occur during the growth period; root rot at the seedling stage is accompanied by leaf spots. Root rot occurring in the later stage of wheat causes premature senescence, many shriveled grains, ear rot, and black embryo, and in severe cases reduces yield.
Remedial measures: A large amount of pathogenic bacteria accumulates in the soil of continuous wheat cropping fields; deep plow once in the next season. The higher the seed-borne pathogen rate, the higher the seedling disease incidence and disease index. At sowing, use triadimefon or Likxiu seed coating treatment; at the returning-green stage, combined with watering, drench the roots with hymexazol or metalaxyl-hymexazol.
Cause five: wheat infected with yellow dwarf virus disease. New leaves begin to yellow from the leaf tip, and the leaf color is golden yellow to bright yellow, with the yellowed part accounting for 30%-50% of the whole leaf.
Remedial measures: Wheat yellow dwarf disease has a high probability of occurrence in warm winters and cold springs; the main task is to control wheat aphids and planthoppers, especially in wheat fields near roadsides and ditches.
Cause six: encountering a late spring cold snap, with low-temperature freeze damage caused by not watering thoroughly. Wheat encountering a low temperature of -5°C to -8°C before jointing, or a low temperature of around 0°C after jointing, is prone to freeze damage.
Remedial measures: Before the cold wave arrives, promptly irrigate dry wheat fields to ensure sufficient soil moisture, so as to reduce low-temperature freeze damage. For affected fields that were not watered thoroughly, after the cold wave passes, irrigate again promptly, and water sufficiently and thoroughly.
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