How many days after corn planting do seedlings emerge? When is the best time to apply a topdressing fertilizer?

　　Every year around mid-May, farmers are gearing up: the winter wheat harvest is just around the corner, and it’s time to start planning for corn planting. Many farmers have already begun selecting seeds and purchasing fertilizers. In this article, we’ll focus on how many days after corn sowing seedlings typically emerge, when topdressing is most effective, and how to apply it properly.

　　 1. How many days after corn planting do seedlings emerge?

　　After corn seeds are sown:

　　Swelling and germination of the embryo can be observed as early as day 1.

　　A week later, these tiny sprouts emerged from the soil; under the sun’s rays, the tender yellow shoots gradually turned green.

　　Around 27 days, the seedlings gradually grow larger and begin to elongate.

　　At 52 days, the silk threads begin to emerge, and male pollen appears at the top; around 90–100 days, after pollination, the ear grows larger and larger, while the silk threads gradually dry up or fall off, eventually developing into the mature ear.

　　 II. When is the best time to apply a topdressing fertilizer to corn?

　　Applying a topdressing fertilizer at the appropriate time enables corn to absorb nutrients quickly and efficiently, thereby promoting growth and increasing yield.

　　The optimal timing for topdressing corn is from the jointing stage to the tassel‑differentiation stage. At this point, the plant has developed 7–12 leaves, and the female inflorescence is undergoing elongation and differentiating into female florets—making it a critical period that determines ear length and ear thickness. Applying fertilizer at this stage meets the nutrient demands of jointing and ear initiation, promotes ear differentiation, and results in larger ears with more kernels.

　　Most corn is top-dressed once at the 9–11 leaf stage; if a larger amount of fertilizer is applied, two top-dressings are recommended—one at the jointing–booting stage and another at the tasseling–grain-filling stage. The allocation between the two applications should be two-thirds for the first and one-third for the second. On light soils such as sandy soils, which have poor nutrient‑ and water‑retention capacity, fertilization should be applied in small, frequent doses to minimize nitrogen leaching.

　　 III. How to Apply Topdressing Fertilizer to Corn

　　The three commonly used methods of topdressing are deep application in furrows, broadcast application on the ridge surface followed by plowing to incorporate the fertilizer, and hole‑fertilization between plants. At the time of topdressing, the plant roots have already begun to develop; when using mechanical equipment, care should be taken to minimize root injury, the application depth should not be excessive, and the lateral distance from the plant should also be appropriate. In general, for corn, a topdressing depth of 10–15 cm and a lateral distance of 10–12 cm are recommended.

　　1. Deep application in the ridge‑furrow system. When corn has 7–8 leaves, at a depth of about 40 cm, use the fertilizer‑spreading blade of the seeder to make deep furrows, delivering the fertilizer directly into the bottom of the ridge‑furrow. This approach addresses the traditional problems of shallow topdressing—resulting in poor soil coverage, significant root damage, and low fertilizer use efficiency—while minimizing fertilizer volatilization. By applying fertilizer early and deeply during the seedling stage, this method enhances fertilizer utilization.

　　2. Broadcast fertilizer on the ridge surface and cover it with a heavy plow. During the third intertillage, apply the fertilizer directly onto the ridge tops, then use a heavy plow to incorporate it into the soil. The drawback is that the fertilizer is placed above the root zone; adequate moisture after application is essential for it to be effective.

　　3. Side‑ditch fertilization between plants. This method allows for application at the desired depth, enabling deeper root penetration and enhancing the plant’s ability to absorb nutrients and water, as well as improving drought resistance and lodging resistance. However, side‑ditch fertilization requires considerable manual labor and is difficult to implement over large areas; it is best suited for vegetables and cash crops.