What should you do if corn seedling leaves turn yellow and wilt after fertilizing?

Corn tastes sweet and can be used in all kinds of dishes, such as corn pancakes and corn juice. It is also the main raw material for industrial alcohol and liquor, so corn seedlings are planted in large quantities across both northern and southern China. So why do corn seedling leaves turn yellow? And what should you do if they wilt after fertilizing?

1. Corn seedling leaves turn yellow for the following reasons:

1. Sowing too deep. Sowing too shallow makes it hard for seedlings to emerge, while sowing too deep produces weak, yellow seedlings. Sowing depth should be controlled at 3-5 cm.

2. Not thinning and setting the seedlings in time. After corn emerges, thin the seedlings when the corn has 3-4 leaves and set the seedlings when it has 6-7 leaves, to avoid crowding among the young plants and competition for fertilizer, water and light, which produces weak, diseased and yellow seedlings.

3. Insufficient watering. If watering is insufficient before or after sowing corn, the seeds cannot get enough moisture, which in turn affects normal germination and emergence; a prolonged period before emergence produces weak seedlings and yellowing at the seedling stage.

4. Waterlogged seedlings. Corn at the seedling stage often coincides with the rainy season, and poor drainage in low-lying plots or water pooling in areas compacted during wheat harvest causes yellow seedlings.

5. Disease. If the seedling stage meets long periods of low temperature and rainy weather, it can cause the occurrence and spread of corn seedling blight. Seedling blight mostly begins at the two-to-three-leaf stage; the diseased seedlings' leaves turn yellow and dry up, with scorched edges, and the leaves gradually turn yellow and dry from the bottom upward; there are few root hairs, the root system turns brown and develops poorly, producing yellow, weak seedlings.

6. Insect pests. The main insect pests at the corn seedling stage include cotton bollworm, wireworm, aphids, armyworm, thrips, Swedish stem fly, cutworm, and the mealybug Trionymus hagendorfi. The mealybug nymphs and female adults gather at the base of the stem near the soil surface, on the roots and inside the leaf sheaths of corn seedlings, sucking sap, so that the leaf sheaths of the affected corn turn yellow and dry up first.

7. Herbicide damage. Improper use of herbicides, arbitrarily increasing the herbicide dosage, blindly mixing them with other pesticides, using too high a concentration, sharing sprayers, and the effect of counterfeit or substandard herbicides on the following crop can all cause yellow corn seedlings.

8. Nutrient deficiency. Corn is a zinc-sensitive crop; zinc deficiency produces white-flowered seedlings that look like yellow corn seedlings.

2. Wilting of corn seedlings is caused by fumigation from ammonia released by the breakdown of urea.

Because corn seedlings are still small, with tender leaves close to the ground, and because a large amount of urea is applied and it is applied on the soil surface, in hot seasons watering only a little at the surface cannot leach the granular urea down into the deeper soil; it can only dissolve a large amount of urea at the surface. Calcareous soil is on the alkaline side, and the dissolved urea molecules break down fairly quickly at high temperatures, producing large amounts of ammonia and carbon dioxide, which fumigates the seedlings.

In this situation, for plots with the conditions for it, water first, then cultivate and earth up. This both dilutes the nitrogen fertilizer and aerates the soil to promote root growth. For plots without the conditions for irrigation, immediately carry out deep cultivation followed by earthing up; this both keeps the nitrogen in place and reduces ammonia volatilization, and also removes soil moisture to encourage roots to grow downward. Case note: urea is a high-concentration nitrogen fertilizer, and when used as a top dressing, the amount applied at one time should be appropriate. Calcareous soil is on the alkaline side, so when urea and ammonium nitrogen fertilizers are used as top dressing, they must be covered with soil.