Why is wheat yellowing?

After wheat has returned to green, yellowing often occurs. The main reasons for this phenomenon are drought, large amount of straw returning, lack of fertilizer, disease, insect damage and freezing damage.

drought. The yellowing of wheat caused by drought means that when the water absorbed by the wheat roots from the soil is difficult to compensate for the transpiration consumption, the balance of water balance in the wheat is imbalanced, and its growth and development are affected by yellowing and death in severe cases. The field performance is consistent with the yellowing of the whole wheat field. The tillers are born slowly, the leaves are grayish green, the growth is slow or stagnant, the new leaves are short, and the roots are small and thin. This type of wheat often occurs in the bottom of the sputum, rushing to sow, running through the wind, there is no field to seal the frozen water.

Corn stalks are returned to the field. Corn stalks can be directly returned to the field, which can play the role of fertility and soil improvement. However, the requirement for returning straw to the field is one mu and two mu, with nitrogen fertilizer and deep ploughing 25 cm. Now the peas returning farmer is actually one mu. One acre, the ploughing layer is less than 20 centimeters, and some are not equipped with nitrogen fertilizer. In this way, the roots of some wheat in the field are tied to the loose straw after emergence, and it is difficult to absorb nutrients from the soil, causing the straw to be cooked and the wheat seedlings to compete for water and fertilizer. After the spring wheat is watered in the spring, the soil is solid, and the wheat seedlings are suspended and yellowed, even dead.

Lack of fertilizer. Wheat nitrogen deficiency or insufficient phosphate fertilizer can cause yellowing of wheat. The yellowing of wheat in the form of nitrogen deficiency means yellowing of wheat due to premature planting, prolonged winter, insufficient application of base fertilizer or low nitrogen content in base fertilizer and poor fertilizer retention. The field performance is as follows: the plants are short and weak, the tillers are few and weak, and the leaves of the seedlings turn yellow and the leaves are withered, and the old leaves of the lower leaves are yellow and dry. In this case, 5 kg of urea should be applied per mu in the rejuvenation period , and 12-15 kg of urea should be applied per acre during the period of uplifting or jointing . If necessary, it can also be combined with foliar spray fertilizer , and spray 2% concentration per mu. The urea solution is 30-50 kg, and sprayed again after about 7 days. The lack of phosphate fertilizer in the base fertilizer of wheat, the insufficient application of phosphate fertilizer or the lack of phosphorus in the soil often cause the wheat to be deficient in phosphorus and yellow. The field performance is as follows: the secondary roots are few, the tillers are few, the leaves are dark green, the leaves are yellow, the new leaves are blue-green, and the leaves are purple. If the wheat is deficient in phosphorus and yellow, if it is not remedied in time, it will result in less spikes, less seeds, and a decrease in 1000-grain weight, which will seriously affect the yield. When the wheat seedlings are deficient in phosphorus, 10 kg of diammonium or 45-50 kg of superphosphate can be applied per mu. If necessary, it can also be combined with foliar spray fertilizer. Spray 3% of superphosphate solution 60 kg per acre , interval 7 -10 days, even spray 2-3 times

Disease. According to field observations, the diseases causing yellowing of wheat are mainly wheat root rot and sheath blight. The main symptoms of wheat root rot are: root rot, leaf spot, stem dead, and neck dead. After the spring wheat returned to green, the field appeared to be yellow and the plant height was uneven. After the wheat sheath blight is susceptible to the seedling stage, the diseased part is dark green spots at the beginning, and then gradually enlarges into a cloud-like large spot. In the early stage after the jointing of wheat, the stalk-like lesions with light brown edges and grayish-white edges appear on the leaf sheath near the surface of the lower part of the plant. After the lesions are enlarged, the stalks can be formed into stalks, which seriously cause the base. It turns black and even rots and leads to dead plants. Wheat root rot may be in the early stages, with 12.5% Li Wo fruit or 20-30 g 40-50 g of 20% aqueous triadimefon 50-60 kg, pulling spraying head aligned wheat stem base portion 15 days, once every twice. 5% of free wheat sharp Jinggangmeisu agent 7.5 g Water to 100 kg, or 12.5% with 20-30 grams of Li Wo fruit 50 kg of water spray. The field with serious disease will be prevented once every 7 to 10 days.

Freezing damage. After the wheat returns to green in spring, the cold resistance is reduced, especially after the jointing, it is very sensitive to low temperature. When it encounters bad cold weather and the temperature drops to normal plants, it is vulnerable to freezing damage. After the wheat is subjected to freezing damage, the symptoms are generally expressed from the growth cone, and the frozen growth cone is initially opaque, and then the cell disintegrates and deforms. In the field, the leaves are dark green, and the leaves are like boiled with boiling water. The leaves of the frozen light are chlorotic and yellow, and then dry, and the upper part is dry or the whole plant is dead.