Why do wheat seedlings turn yellow? Failure to deal with it in time can easily lead to dry leaves

SummaryThe common reasons for wheat seedlings turning yellow include improper sowing, pesticide damage, fertilizer damage, pests and diseases, and lack of elements. The pests and diseases of wheat seedlings are mostly sheath blight and take-all, white grubs, wireworms and mole crickets, etc., while element deficiencies are mostly phosphorus deficiency, nitrogen deficiency and potassium deficiency, etc.

After wheat seedlings emerge in spring and winter, situations such as sparse seedlings, weak seedlings, yellow seedlings and dead seedlings will occur. The reasons causing these situations include improper sowing, pesticide damage, fertilizer damage, pests and diseases, and element deficiency, etc.

1. Improper sowing

1. Too high a density at sowing can easily cause the wheat population to be too large, which will affect the photosynthesis of wheat, nutrients cannot be supplied in time, and ultimately lead to yellowing of the leaves.

2. If the distance between each wheat seedling is too dense, situations such as competition for fertilizer, water and light will occur, ultimately leading to weak and yellowing wheat seedlings.

Remedial methods: If the plot is too dry, water it in time to promote normal growth of the wheat seedlings. Or if the density is too high, causing oversowing, carry out manual thinning of seedlings to increase ventilation and light transmission, and deep plow to cut roots to reduce water and fertilizer absorption and promote strong seedling growth.

2. Pesticide damage

1. When mixing pesticides with wheat seeds, excessive pesticide dosage will cause the leaves of wheat seedlings to turn yellow and die.

2. Land that has previously grown other crops and has been treated with herbicides will retain residues and cannot be immediately used to plant wheat. If planted immediately, it will cause wheat seedlings to turn yellow.

Remedial methods: If the problem is not serious, it can be left untreated, and after secondary roots grow out, the wheat seedlings will naturally turn from yellow to green. If the problem is serious, water to remedy it, and loosen the soil after watering.

3. Fertilizer damage

Applying farmyard manure, bean cake and other organic fertilizers that are not fully decomposed to wheat seedlings, or using too much seed fertilizer, or placing fertilizer very close to the wheat seeds, will all cause wheat seedlings and seeds to be easily burned by fertilizer, directly leading to yellowing of the leaves or leaf tips.

Remedial methods: Water and leach every week, and water about 1-3 times consecutively according to the specific fertilizer damage situation.

4. Pests and diseases

There are many pests and diseases that cause yellowing and death of wheat seedling leaves. They are generally sheath blight and take-all, and the three pests white grubs, wireworms and mole crickets.

1. Sheath blight: During the wheat seedling stage, it damages the underground stems of wheat, hindering the transport of water and nutrients, gradually developing upward over time, and finally causing the leaves of wheat seedlings to turn yellow.

2. Take-all: When wheat seedlings are damaged at the seedling stage, their primary roots and the base of the roots will turn dark brown, the color of the upper leaves of surviving wheat seedlings will become lighter, the lower leaves will become yellow, the wheat plants will become short and small, and the roots can be easily broken off.

3. Mole cricket: In autumn, it bites off the young roots and tender stems of wheat or bites them into a tangled mass, thereby causing wheat seedlings to die, and it can also move on the soil surface, separating the roots of wheat seedlings from the soil and causing wheat seedlings to turn yellow.

4. White grub: September-October in autumn and April-May in spring are the peak periods of its damage. It bites off the root stems of wheat seedlings, causing the seedlings to turn yellow and die.

5. Wireworm: During the larval stage, it bites and eats germinating wheat seeds and the root stems of wheat, and can also bore into the junction of seeds or root stems, causing wheat seedlings to form dead-heart seedlings and thus causing the whole plant to turn yellow and die.

6. Root rot: Root rot is very likely to occur at the wheat seedling stage, causing wheat seedlings to turn yellow, and when it becomes serious it will cause wheat seedlings to die and the roots to rot completely.

Remedial methods: After root rot occurs, 70% thiophanate-methyl wettable powder can be used at 800-1000 times dilution for root irrigation along the rows.

5. Element deficiency

1. Nitrogen deficiency: It will cause wheat seedling plants to be short, thin and weak, with few and very weak tillers, and can easily cause the leaves of seedlings to turn yellow, leaf tips to wither, and old leaves to turn yellow and fall off.

Remedial methods: Apply about 10-15 kg of urea per mu as topdressing, or about 7-12 kg of ammonium bicarbonate as topdressing. After greening up, if nitrogen deficiency still occurs, continue to apply about 15 kg of urea per mu, or when wheat seedlings turn yellow, spray 2% urea solution on the leaves, and apply a second time after an interval of about one week.

2. Phosphorus deficiency: It will cause wheat seedlings to have very few secondary roots and tillers, the leaf color to be dark green, the leaf tips to turn yellow, newly grown leaves to be blue-green with purple-red leaf tips, and ultimately lead to small wheat spikes and few grains.

Remedial methods: After phosphorus deficiency occurs, apply about 7-10 kg of diammonium phosphate per mu, or about 10-20 kg of superphosphate, or spray 80 kg per mu of a 3%-5% superphosphate aqueous solution on the leaves, spraying once every one week to 10 days, for 2 to 3 consecutive sprays.

3. Potassium deficiency: It generally starts with yellowing at the tips of old wheat leaves, then follows the leaf veins downward, and the yellow spots are very obvious, showing mosaic-like yellowing. In the later stage, the yellowed leaves will cling to the ground, and the stems of the wheat plants will be thin and weak, making lodging and premature senescence likely.

Remedial methods: If remedying at the wheat seedling stage, apply about 5-10 kg of potassium chloride or potassium sulfate per mu in furrows, or apply about 30-50 kg of plant ash per mu. If remedying in the middle and late stages of wheat growth, spray a 10% plant ash solution on the wheat leaves per mu, spraying once every week, for 2-3 sprays.

6. Other reasons

Poor soil fertilizer retention capacity, infertile soil, and insufficient base fertilizer when sowing seeds will cause wheat seedlings to turn yellow due to long-term lack of fertilizer.