Key Technical Points and Detailed Methods for Topdressing Summer Corn

Because summer corn is interplanted in wheat fields or directly sown after the previous crop is harvested, basal fertilizer is generally not applied, and the amount of seed fertilizer used is also insufficient. Therefore, rational topdressing is crucial.

I. Choose the appropriate topdressing plan

For corn to form a certain yield, it needs to absorb corresponding nutrients from the soil and fertilizer. The higher the yield, the more fertilizer is needed. It is very necessary to choose a suitable topdressing plan according to the yield level and soil fertility conditions. There are 3 topdressing plans available for selection. For high-yield fields with a good fertility foundation and a large amount of topdressing, it is best to adopt the topdressing method of light seedling fertilizer, heavy ear fertilizer, and supplementary grain fertilizer: seedling fertilizer accounts for 30% of the total topdressing amount, ear fertilizer accounts for about 50%, and grain fertilizer accounts for about 20%. For medium-yield fields with a relatively good fertility foundation and a relatively large amount of topdressing, it is advisable to adopt the two-attack fertilization method of applying sufficient seedling fertilizer and heavy ear fertilizer: seedling fertilizer accounts for about 40%, and ear fertilizer accounts for about 60%. For low-yield fields with a poor fertility foundation and a small amount of topdressing, the topdressing method of heavy seedling fertilizer and light ear fertilizer should be adopted: seedling fertilizer accounts for about 60%, and ear fertilizer accounts for about 40%.

II. Keep good control over the timing of topdressing

According to the fertilizer requirement pattern throughout the life of corn, topdressing at the optimal fertilization period can fully exert fertilizer efficiency and play a role in increasing yield and income.

(1) Seedling fertilizer. Seedling fertilizer has the effects of promoting roots, strengthening seedlings, promoting leaves, and strengthening stalks, building a framework for high yield and laying a foundation for large ears. In addition to applying quick-acting nitrogen fertilizer, seedling fertilizer can also be applied together with phosphate fertilizer and potassium fertilizer, and decomposed organic fertilizer can also be applied.

(2) Ear fertilizer. The large trumpet stage of corn is exactly in the period when vegetative growth and reproductive growth proceed together, with vigorous growth and a large fertilizer requirement. Fertilizing at this time can not only meet the nutrient requirements for ear differentiation, but also improve the photosynthetic rate of the middle and upper leaves, so that more nutrients are transported into the ear, promoting more grains and greater grain weight.

(3) Grain fertilizer. From tasseling to flowering, corn shifts to reproductive growth. Applying grain fertilizer can prolong the functional period of green leaves, improve photosynthetic efficiency, increase the accumulation of photosynthetic products, and promote more grains and greater grain weight.

In addition, spraying phosphate fertilizer on the leaves in the late growth stage of corn has a clear effect on promoting the transport of nutrients to the grains and increasing the 1000-grain weight. Generally, use a 0.4%--0.5% potassium dihydrogen phosphate aqueous solution or a 3%--4% clear leaching solution of superphosphate, and spray about 75--100 kg per mu onto the stems and leaves, with significant effects.

III. Master the proper topdressing concentration and placement

Appropriate fertilization concentration and placement can fully exert fertilizer efficiency, reduce fertilizer loss, and achieve economical and effective fertilization. When nitrogen fertilizer is used for topdressing, it must be applied deeply into the soil to fully exert fertilizer efficiency and improve nitrogen fertilizer use efficiency. Generally, deep application of nitrogen fertilizer at about 10 cm is appropriate. Seedling fertilizer should be applied 10--12 cm from the plant, and ear fertilizer should be applied 15--20 cm from the plant, which is beneficial for plant absorption and utilization.