Ⅰ

Topdressing period

The best period of topdressing for maize is from jointing to ear differentiation (June 20-27). At this time, maize has expanded 7-12 leaves, which is the period from the growth and elongation of female ears to the differentiation of female florets, which is the key period to determine the length and diameter of maize ears. At this time, topdressing can meet the needs of nutrients for jointing and booting, promote ear differentiation and make maize ears large and more grains.

Ⅱ

Topdressing method

There are three top dressing methods commonly used in Maize Production: ridge and platform application, and then ploughing and wading soil immediately; Dig pits between artificial ridges and plants, apply them deeply, cover them with soil, and then plough and wade to cover them; Ridge and furrow topdressing. The best effect of these three top dressing methods is to manually dig pits, Wade ditches and cover soil. This will achieve good application effect due to deep fertilization, strict coverage and high fertilizer utilization rate, and will increase the yield by 2% - 11% compared with that of Fertilizing on ridge. The second is ridge and furrow topdressing. This method has the advantages of saving labor and trouble. The disadvantage is that the fertilizer is slightly far from the root intensive area, which is not conducive to the corn root system to fully absorb the fertilizer. Therefore, when in use, we must plough and wade the shallow ditch, apply fertilizer and cover the soil, and cover the fertilizer tightly to avoid volatilization, loss and waste. Sometimes, when the ridge is not tightly sealed, the fertilizer is exposed, resulting in serious loss and waste. The topdressing depth and distance from the plant of maize should be 7-10CM, which is conducive to the absorption and utilization of maize roots. If it exceeds 10cm, it will affect the effect of fertilizer application, and if it is less than 5cm, it will cause seedling burning. After fertilization, the soil shall be covered in time or combined with shovel.

Ⅲ

Topdressing times

Most of the corn is topdressed once at the 9-11 leaf stage, about before and after June 25. If the amount of topdressing is large, it is best to topdress twice (jointing booting fertilizer and ear grain fertilizer). The distribution principle of two topdressing is that the first should account for 2 / 3 of the total Topdressing and the second should account for 1 / 3. Light soil such as sandy soil has poor fertilizer and water retention, so it is necessary to apply a small amount of topdressing for many times to prevent nitrogen leaching.

Ⅳ

Topdressing quantity

The topdressing of maize should be appropriate according to soil fertility, fertilizer demand characteristics of varieties and growth period of varieties, so as to meet the needs of maize growth and development. For plots with low soil fertility, the amount of topdressing should be increased, otherwise, the amount can be appropriately reduced. In high fertility plots, the amount of urea is 15-17 kg / mu; For medium fertility plots, the amount of urea is 18-20 kg / mu; In low fertility plots, the amount of urea is 21-23 kg / mu. In addition, the topdressing amount is also different due to different density and cultivation methods. If the planting density is large, the topdressing amount should be increased; If the corn ridge is close to two rows or two plants, the amount of fertilizer should be increased, and 35-40 kg of urea should be applied per mu. If potassium fertilizer is not applied to base fertilizer and mouth fertilizer, 3-4kg potassium chloride or 4-5kg potassium sulfate can be applied per mu together with nitrogen fertilizer for the first time.

Ⅴ

Other matters

In case of soil drought, the topdressing time shall be determined according to the weather forecast, and it is best to topdressing before rain. The amount of topdressing should also be appropriate according to the growth and seedling situation of corn. The plots lacking fertilizer should be supplemented in time to increase the amount of topdressing. For the late maturing plots of greedy green, we should increase the application of phosphorus and potassium fertilizer to promote the maturity of corn as soon as possible.