(1) Causes of bald tip formation
In addition to the genetic characteristics of maize varieties, there are six main reasons: First, lack of nutrition. Phosphorus deficiency in soil affects cell division. Especially in the filament elongation period, the slow elongation of phosphorus-deficient filaments affects pollination. If the panicle top grain is small and unusually white, it is characterized by phosphorus deficiency and potassium deficiency, especially potassium deficiency. The second is spikelet degradation. The spikelets at the top of the ear are degenerated and deformed, and sometimes bisexual flowers or male flowers develop but female flowers do not develop, which affects the normal pollination of corn and makes it difficult to bear fruit. Third, the filament developed late. Filaments at the top of the spike develop late, and silking is delayed, so they are often not paired with male flowers when flowering, resulting in failure to bear fruit. Fourth, it is dry and short of water. Drought occurred during maize flowering and pollination, and the interval between male and female flowers was prolonged, which led to missing the peak of pollen propagation in the tassel when the filaments were elongated, resulting in poor pollination and affecting fruit setting. The fifth is excessive close planting. Excessive planting density causes poor ventilation and light transmission conditions in the late growth stage of corn, which affects the normal growth of corn. Sixth, the soil lacks micro-fertilizer. Boron deficiency in soil has adverse effects on pollen formation and pollination activities of maize male flowers. When zinc is deficient, white spots appear on the leaves of old seedlings, which expand rapidly, forming local white areas and necrotic spots, shortening internodes, easily causing abnormal growth and development of fruit ears, leading to baldness.
(2) Main technical measures to prevent corn baldness.
The first is to select fine varieties. Select coated seeds with high yield, full seeds and strong vitality, which are suitable for local planting. The planting density is generally around 4000 plants, so it is best to plant in wide and narrow rows to avoid weak seedlings caused by uneven fertilizer, water and light. The second is rational fertilization. Nitrogen, phosphorus and potassium are combined to apply micro-fertilizer. Topdressing should be applied to plots with low fertility, but attention should be paid to topdressing before and after, so as to prevent greed and cheap, and late ripening. It is necessary to control watering at seedling stage, promote young panicle differentiation, shorten the interval of tasseling and spinning, and increase pollination opportunities. We should re-apply base fertilizer and skillfully apply ear fertilizer in fertilization. Before maize heading 10 day, 40 ~ 50 kg urea is usually applied per mu, and zinc fertilizer is sprayed when the female ear begins to spin. The third is to strengthen water management. Corn is sensitive to water before heading 15 days. When the soil water content is lower than 80% of the maximum field water capacity, water management should be strengthened to facilitate maize pollination and filling. The fourth is artificial pollination. At the peak of maize flowering, it is necessary to seize the time when the dew dries in the morning and the male flowers begin to loose a lot of powder. Pull rope method or plant shaking method can be used once every 2 ~ 3 days for 2 ~ 3 times in a row to prevent baldness.