1. Some plots, especially those with straw returning to the field, are not compacted or roughed, and the soil is large, which may cause the roots of the wheat seedlings to hang, and the water and nutrients are relatively scarce, causing the wheat seedlings to be small and thin, which may also cause the wheat to be seedlings. , sparse.
Second, excessive seeding density will cause the wheat population to be too large, affecting photosynthesis of wheat, insufficient nutrient supply, resulting in yellowing of leaves. The wheat seedlings are too dense, and the phenomenon of competing for fertilizer, glory, and water competition between the wheat seedlings leads to yellow weak seedlings. It should be sown according to the season and temperature.
Third, the sowing is too deep to cause the wheat to yellow. Due to the deep sowing, the roots of the wheat seedlings are poorly developed and the wheat seedlings are thin.
4. The wheat seedlings caused by improper fertilization are yellow. The organic fertilizers such as farmyard manure and bean cake are not fully decomposed, and the fertilizers are used too much. The fertilization position is too close to the seeds, and the seedlings and seeds are easily burned, resulting in yellowing of the leaves or tips.
5. The yellowing of wheat seedlings caused by soil drought. It mainly occurs in the wheat fields that have not been watered in the case of robbing and sowing.
Sixth, corn stalks returning to the field can play a role in improving soil and fertility. Now the amount of straw is large, and the plough layer is generally less than 20 cm, so that the roots of some wheat in the field are tied to loose straw, which is difficult to get from the soil. Absorbs nutrients, causing yellowing of wheat. Therefore, deep ploughing is advocated and should be ploughed every three years to a depth of 25 cm. In addition, the straw returned to the field without supplementing the nitrogen fertilizer can also cause the wheat seedlings to yellow, and the application of the straw decomposing agent does not increase the application of nitrogen fertilizer, which is prone to the phenomenon of nitrogen stalks and wheat seedlings.
Seventh, underground pests can also damage yellow leaves caused by wheat, such as golden worms and cockroaches. The control methods are chemical dressing and soil treatment.
Eight, root rot, sheath blight, soil-borne mosaic disease and other diseases caused by the yellowing of wheat. Wheat pests and diseases mainly include sheath blight, total erosion and root rot. They are all fungal diseases and can express yellow leaves at the beginning of the disease, but the location of the lesions and the shape of the lesions are different. The sheath blight mainly harms the leaf sheath; the total erosion mainly affects the base and root of the stem; the root rot only occurs in the root. They all depend on soil-borne diseases.
9. The wheat seedlings caused by phytotoxicity are yellow. 1. The amount of seed dressing is large, causing the yellow leaves to die; 2. The herbicide residue of the upper crops, such as farmers applying the nicosulfuron-type herbicide on the corn, even if the normal dosage is used, it should be separated from the wheat planted by the sorghum. More than a month to ensure no impact on wheat.
Ten, the wheat seedlings caused by deficiency syndrome are yellow. Phosphorus deficiency, nitrogen deficiency, manganese deficiency, and potassium deficiency can cause yellowing of wheat.
The nitrogen-deficient yellow-yielding yellow-breasted plants are short and weak, and the tillers are few and weak. The leaves of the seedlings turn yellow and the leaves tip wither, and the old leaves of the lower leaves are yellow and dry. The reason is generally due to the early sowing, the sandy field, the insufficient application of the base fertilizer, and the application of the fertilizer is not timely, and the amount of fertilizer is small, and the yellowing of the wheat seed is most likely to occur. The remedy is: if the wheat seedling stage is deficient in nitrogen, it can apply 10~15 kg of urea per acre, and it will lack nitrogen and yellow after spring. It can be applied for about 5 kg of urea per acre during the rejuvenation period, and 12 to 15 kg of urea per acre during the period of uplifting or jointing. It can also be sprayed on the foliar when the wheat is yellow, and sprayed with 2% urea solution twice, each time about 7 days.
Phosphorus-deficient yellow wheat is deficient in phosphorus, with few secondary roots, less tillering, darker green leaves, yellow tip leaves, blue-green leaves, and purple-yellow leaves. If not remedied in time, it will result in less spikes and less seeds. Thousands of grains are falling. The wheat seedlings are deficient in phosphorus, and 45-50 kg of calcium phosphate can be applied per mu. It can also be sprayed with fertilizer on the foliar surface, spraying 60 kg of 3% superphosphate aqueous solution per mu, interval 7~10 days, even spraying 2~3 Times.
The potassium-deficient yellow-supplemented potassium-deficient wheat seedlings often start from the tip of the old leaves and then extend down the veins. The macula is partially visible and is mosaic-like yellowing. Under the yellow leaves, the late stage is attached, the stems of the diseased seedlings are small and thin, prone to premature aging and easy to fall. Potassium deficiency wheat field, in the wheat seedling stage, 7.5~10 kg of potassium chloride or potassium sulfate per mu of ditch, or 30~50 kg of wood ash per acre; 10% of per acre of leaf surface in the middle and late stages of wheat growth The grass ash leaching solution, or 0.2 kg ~ 0.3% potassium dihydrogen phosphate aqueous solution 60 kg, even spray 2 ~ 3 times, interval 7 ~ 10 days, the control effect is very significant.
11. The wheat is yellowed due to poor soil and poor quality. The soil is poor, the soil fertility is poor, the bottom fertilizer is insufficient at the time of sowing, and the wheat seedling turns yellow due to long-term lack of fertilizer.
12. The wheat seedlings caused by soil compaction are yellow. The soil compaction caused poor ventilation, which made the root vigor of the wheat seedlings worse, and the root absorption capacity was weakened, resulting in yellow and small leaves, and the tillers could not appear on time.
Thirteen, continuous low temperature, less light time, wheat seedlings overall weak, affected by low temperature freezing damage showed leaf yellow. The control measures are to strengthen management after the arrival of the cold current and spray the foliar fertilizer .
Methods for preventing seedling yellow, slim, and dead seedlings in wheat seedlings:
1, the correct purchase of varieties
Don't be tempted to be cheap, and don't plant new varieties on a large scale. It is best to go to old farmer's stores and buy those that have already been promoted.
2, soil preparation
Before the land preparation, we must smash the straw of the former crop, the length of the smash should not exceed 5 cm, and if there are many stalks, it should be scattered in time, deep burying and buried, then rotary tilling the soil, compacting the soil, and combining the soil preparation. Apply appropriate amount of nitrogen fertilizer to avoid nitrogen competition with wheat seedlings during straw decomposing.
3. Drainage protection
Pay attention to clearing the ditch and ensuring that the energy can be discharged and the stain can be lowered. When the soil moisture is suitable, it is suitable to use the sown wheat to cultivate the loose soil, which can enhance the soil permeability, increase the ground temperature, promote the soil microbial activity, and improve the root absorption capacity.
4, do a good job of pest control
After the winter, the weather turned cold and the damage of underground pests was reduced. To control underground pests, seed dressing and soil treatment methods can be used before planting, and roots or poisonous soil can be applied after emergence. The key to prevention and control of wheat seedling diseases is the treatment of seeds before sowing, which can be prevented by seed coating agents.
Management of winter wheat measures
1. Watering and replenishing, and soiling the soil. Promote close contact between wheat roots and soil to ensure that roots absorb enough nutrients from the soil. Timely application of appropriate amount of nitrogen fertilizer, it is recommended to apply 10-15 kg of urea per mu while returning straw.
2. Control the sowing depth. Maintain a seeding depth of 3-4 cm to prevent too deep or too shallow.
3, in addition to treatment of pests and diseases. To control aphids, Laodelphax sinensis, and spider mites, we must first eliminate the weeds in the fields and destroy the habitats of the pests, and then use 1000% omethoate to dilute 1000 times for spraying; and control the red spiders to use 50-100 ml of Daqinling. Spray 30-40 kg of water.
4. Remove the weeds in the field in time, or spray herbicides to control the weeds.
5, timely topdressing. In the case of seedlings with yellow and weak seedlings, high-nitrogen fertilizers should be applied in time for rejuvenation, such as Jinzhengda synergistic urea 36-6-6, 20-30 kg per mu, supplement nutrients, and promote the transformation of wheat from yellow to green.
6, root spray fertilizer. Use 1-2% aqueous urea solution or potassium dihydrogen phosphate solution, foliar spray, supplement nutrition, reduce yellowing.
More pesticide encyclopedia , please pay attention to China Pesticide Network
(Source: Good Agricultural Resources Network)
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