When is the best time for topdressing corn? What kind of fertilizer do you use? (method, quantity, number)

Corn takes a long time to absorb fertilizer and needs a large amount of fertilizer, so the application of base fertilizer and seed fertilizer alone can not fully meet the needs. So when is the best time for corn topdressing? What kind of fertilizer do you use? One of the key problems of topdressing is to grasp the critical period and the highest efficiency period of nutrient absorption by crops, and to carry out scientific topdressing in the peak period of nutrition as far as possible, so as to improve the utilization rate of fertilizer and give full play to its role in increasing production.

Topdressing period

The best period of topdressing for maize is from jointing to panicle differentiation (June 20-27), when 7-12 leaves have been unfolded, which is the key period to determine ear length and diameter from female ear growth and elongation to female floret differentiation. Topdressing can meet the nutrient needs of jointing and booting, promote ear differentiation and make maize ears larger and more grains.

Topdressing method

There are three common methods of topdressing in corn production, that is, spreading fertilizer on the ridge, then immediately ploughing and covering the soil; deep application of the planing pit between the plants of the artificial ridge, covering the soil and then ploughing the ground; and topdressing in the ridge and furrow. The best effect of these three topdressing methods is artificial ploughing and trench covering, which will achieve a good application effect because of deep fertilization, strict coverage and high fertilizer use efficiency, which will increase the yield by 2% and 11% compared with the application of fertilizer on the ridge.

The second is ridge and furrow topdressing, the advantage of this method is labor-saving and labor-saving, and the disadvantage is that the fertilizer is a little far away from the dense root area, which is not conducive to the maize root system to fully absorb fertilizer. Therefore, when in use, we must plough the shallow furrow and cover the soil and cover the fertilizer strictly to avoid volatilization loss and waste. Ridge spread sometimes due to lax ridge sealing, fertilizer exposed outside, resulting in serious loss and waste. Maize topdressing depth, distance from the plant should be 7-10 cm, this is conducive to the absorption and utilization of maize roots, if more than 10 cm will affect the effect of fertilizer application, less than 5 cm will cause burning seedlings. Cover soil in time or combine with shovel to cover soil in time after fertilization.

Times of topdressing

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

Topdressing quantity

Topdressing of maize should be based on soil fertility, characteristics of fertilizer requirement of varieties and growth period of varieties, so as to meet the needs of maize growth and development. The plots with low soil fertility should increase the amount of topdressing, otherwise the amount can be reduced appropriately. The urea dosage is 15-17 kg / mu in high fertility plots, 18-20 kg / mu in medium fertility plots and 21-23 kg / mu in low fertility plots. In addition, due to different density and cultivation methods, the amount of topdressing is also different. The amount of topdressing should be increased when the planting density is high, and the amount of fertilizer should be increased for those with large ridges and double rows or close to each other, 35-40 kg urea per mu. If the base fertilizer and mouth fertilizer are not applied potash fertilizer can be applied together with 3-4 kg potassium chloride or 4-5 kg potassium sulfate per mu for the first time.

What kind of chemical fertilizer is used for topdressing?

Topdressing mostly uses urea or compound fertilizer, and its amount varies with different spring and summer corn. The amount of spring corn is generally about 33.0% of the total amount of nitrogen fertilizer, and the amount of topdressing can account for about 50% of the total amount of nitrogen fertilizer in the soil with partial sand texture and poor fertilizer conservation performance. Summer corn due to stubble re-sowing, generally do not apply base fertilizer, the amount of fertilizer is not large, topdressing is even more important, most or all of the nitrogen fertilizer is used as topdressing. The topdressing must be guaranteed twice, the first time after the seedling is fixed, we should pay close attention to promoting the seedling fertilizer, this time the topdressing should be based on nitrogen and phosphorus quick-acting chemical fertilizer, which can achieve the goal of both seedling emergence and stable growth. The second topdressing should be in the big trumpet stage after jointing, mainly heavy topdressing nitrogen fertilizer, the amount of which is twice as much as that of the first nitrogen fertilizer, in order to ensure a large amount of nitrogen in the panicle differentiation stage. Topdressing should take the method of hole covering soil to put an end to spreading and surface application, so as to prevent volatilization from causing waste.

Other matters

In the case of soil drought, the time of topdressing is determined according to the weather forecast, and it is best to topdressing before the rain. It is also necessary to apply appropriate amount of topdressing according to maize growth and seedling conditions, and fertilizer deficient plots should be applied in time to increase the amount of topdressing. For greedy green late-maturing plots, it is necessary to increase the application of phosphorus and potassium fertilizer to promote corn ripening as soon as possible.