The corn bracts are short and can't cover the cob, what's the matter?

Recently, growers in Liaoning, Heilongjiang, Shanxi and many other places reported the strange phenomenon of short bracts in corn. The specific manifestation is that the length of the corn shafts is normal, but a part of the shafts are exposed and not wrapped by the bracts. The length of bracts in some plots is only one-third of the length of ears; in some plots, the length of bracts is half the length of ears. There are basically no grains on the exposed shaft.

In fact, the problem of lax corn bracts occurs every year, especially last year in Henan, Shandong and Tianjin. This phenomenon is more serious in the red shafts, and the white shafts rarely occur.

The scientific name of maize incomplete bracts is "corn dew top". Maize dew top refers to that the bracts of the female ear of corn are shorter than the cob, which cannot cover the cob and exposes a part of the cob.

Because the bracts are short, the grains are exposed, which affects the grain filling and leads to reduced yield. In addition, the short bracts are prone to insect pests, such as the double-spotted firefly beetle biting the silk and the chafer biting the grains, which can also cause a reduction in production.

1. What are the reasons for the short corn bracts and what causes

Corn outcrops are mainly caused by the uneven growth of each period. Although the bracts and cobs of maize female ears develop and grow at the same time, the bracts stop growing first, and the normal growth of the ears will exceed the length of the bracts, causing the top to appear.

The main causes of slow growth and insufficient growth of bracts are:

1. Drought and water shortage: The jointing period is the corn ear differentiation period. The high temperature and drought during the jointing period cause the differentiation of bracts and ears to be out of step, resulting in short bracts.

2. Weather reasons: rainy weather, insufficient light and temperature, reduced photosynthesis, resulting in slow growth of bracts, insufficient growth, and less than the proper length, but the ears grow normally beyond the bracts, resulting in dew.

3. Excessive dense planting: Excessive planting density causes poor ventilation and light transmission conditions in the later stage of corn growth, which affects the normal growth of corn.

4. Variety factors: individual varieties are more sensitive to environmental changes, and the development of bracts and ears will not be synchronized when climatic conditions change.

5. Reason for the agent: spraying chemical control agents or triazole agents before tasseling can also cause the development of bracts and ears to be out of sync.

6. The soil lacks micro-fertilizer. Boron deficiency in the soil will adversely affect the formation of maize male flower pollen and the pollination activity. When zinc is deficient, white spots appear on the leaves of old seedlings, and they expand rapidly, forming local white areas and necrotic spots, and the internodes are shortened, which can also cause abnormal growth and development of ears.

2. How to prevent the occurrence of short corn bracts

1. Strengthen the management of fertilizer and water: one is to apply ear fertilizer early, before and after tasseling, and the other is to prevent drought. When the female ears emerge, there should be no water shortage to ensure the normal growth of bracts.

2. Pay attention to the selection of varieties: the red shaft varieties of maize are less resistant to high temperature (the American line is the most sensitive, and the Asia-Europe line is relatively better). When high temperature is encountered, "the ears and bracts cannot be covered", and even severe "grain missing" and Severe "balding" phenomenon and reduced production.

It is reported that the corn white and red (white shaft plus red shaft) mixed sowing technology has achieved good results. Enhance hybrid genes and re-hybridize on the basis of hybridization. "Double hybridization" has stronger resistance to stress. The 2:2 mixing of white shaft and red shaft is beneficial to increase the thousand-grain weight and increase the yield significantly.

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