Causes of Uneven Corn Seedling Sizes in the Same Field and the Same Variety, and How to Prevent Them

Around Qingming, plant melons and beans. In a while, it will be time to plant corn. Attentive farmer friends may have noticed that after corn emerges each year, sometimes the corn seedlings grow large and small. Corn has high per-plant productivity; missing one plant means losing 150-300 grams of yield. People often say “Lose one seedling in spring, lose one jin of grain in autumn.” A 10% loss of seedlings means a yield reduction of 60-80 kg per mu. Therefore, ensuring a full stand of seedlings is the prerequisite for a high-yielding corn crop.

So in the same field, with the same variety, sown at the same time, why do corn seedlings grow to different sizes? The appearance of large and small corn seedlings will affect later yield, so this situation should be avoided as much as possible. Keep these points in mind!

1. Uneven soil moisture

When the weather is dry, soil moisture becomes uneven. In this case, where soil moisture is better, corn emerges early; where soil moisture is poorer, corn emerges late. Early or late emergence will also lead to uneven growth of large and small seedlings. Therefore, when sowing, be sure to pay attention to soil moisture and make a plan in advance.

2. Uneven sowing depth

If the quality of land preparation is poor, the soil surface will be uneven. When mechanical sowing is used, high spots are sown deep, while low spots are sown shallow. In addition, if there are many large clods in the field, the influence of the clods during mechanical sowing will also lead to uneven sowing depth. When soil moisture is good, deep-sown seeds emerge late and shallow-sown seeds emerge early; in dry weather, deep-sown seeds emerge early and shallow-sown seeds emerge late. This causes late emergence and also forms large and small seedlings.

3. Seeds not graded and damaged seeds

The quality of corn seed also affects corn emergence. Some corn seeds are not graded and carefully selected, so the seeds are not uniform in size. This also leads to strong seedlings from large seeds and weak seedlings from small seeds, and large and small seedlings appear from the seedling stage onward.

Damaged seeds. Damaged seeds are easily infected by pathogens, grow and develop slowly, and easily become weak and small seedlings, causing large and small seedlings in the field.

Therefore, when buying seeds, be sure to observe the uniformity of the seeds and the damage rate of the seeds, and prevent large and small seedlings in the corn field starting from seed purchase.

4. Delayed thinning and final singling

After corn emerges, timely thinning and final singling can avoid crowding of seedlings and competition for light, fertilizer and water, which helps cultivate strong seedlings. Thinning is generally carried out at the 3-4 leaf stage. Around the 3-leaf stage, corn is in the “weaning period” and requires good light conditions to help produce more nutrients to supply seedling growth.

If plants are too crowded at the seedling stage, root systems between plants intertwine, and there will be competition for water and fertilizer. Also, seedling leaves overlap each other, which not only affects photosynthesis but also easily causes “seedling overcrowding.” Final singling is generally carried out at the 4-6 leaf stage. If thinning and final singling cannot be carried out on schedule, areas with more seedlings will form thin, weak, tall seedlings, and finally large and small seedlings will appear. So how can large and small corn seedlings be prevented?

1. Choose good seed with high purity and a high germination rate, grade the seeds, sow with plump, uniform large seeds, and treat the seeds with chemicals.

2. Strictly control the quality of land preparation and sowing, achieve high-standard operations, and ensure full and uniform emergence in one sowing.

3. Sow at the proper time. If there is no time to irrigate the soil moisture before sowing, irrigate after sowing with the first watering. Shallow irrigation and even irrigation are required. This is an important measure for preserving seedlings in arid areas.

4. Press the soil after sowing. If soil pores are large after sowing, the seeds cannot easily absorb water, affecting full and uniform corn emergence. Pressing after sowing can increase contact between the seeds and the soil, strengthen the seeds' absorption of soil moisture, help moisture from lower soil layers rise, and increase the moisture content of the sowing layer, so as to help the seeds emerge.

5. Prevent damage from insects, birds and animals. After emergence, promptly control underground pests to avoid missing seedlings. 6. If missing seedlings or broken rows are found, promptly check the seedlings and replant or transplant.

7. If seed fertilizer is applied, keep the seed and fertilizer separate, and strictly prevent burning the seeds and seedlings.

8. After sowing and before emergence, if rainfall is relatively heavy and the ground forms a crust, promptly carry out shallow intertillage, break the hard surface crust, and help the seedlings emerge. But do not damage the young shoots when loosening the soil.