When is the latest planting time for corn?

To know the planting time of corn, we first need to understand the growth habits of corn. The corn growth period is relatively short, and during the growth period it requires warmth and plenty of rain. Corn consumes a large amount of water; if rainfall is low and irrigation water is insufficient, yields will decline or even be completely lost. If the first autumn frost arrives too early, the corn will be damaged by freezing during the maturation period, which will also reduce yields.

Corn Planting Time

Corn is divided into spring corn and autumn corn according to different planting times. Spring corn is sown in late April to early May and can be harvested in late August. Autumn corn must be sown no later than mid-July and is harvested in mid-to-late October. Throughout the life of corn, according to morphological characteristics, reproductive characteristics and physiological characteristics, it can be divided into several different growth stages, and each stage includes different growth periods. These different stages and periods each have their own characteristics and are also closely related to one another.

1. Seedling stage

The corn seedling stage refers to the period from sowing to jointing, and is a vegetative growth stage dominated by rooting and the differentiation of stems and leaves. The growth characteristics of this stage are: the root system develops relatively quickly, but the growth of aboveground stems and leaves is relatively slow. For this reason, the central task of field management is to promote root development and cultivate strong seedlings, achieving the “four seedling” requirements of early seedlings, sufficient seedlings, uniform seedlings and strong seedlings, laying a good foundation for high corn yields. This stage is further divided into the following two periods.

① Sowing period: the seeds germinate and break through the soil to emerge. At this time, attention should be paid to planting density and improving sowing quality; do not cover with too much soil, as this affects emergence. 30-40% of the nitrogen fertilizer and all of the phosphate fertilizer and potassium fertilizer; in some areas, zinc fertilizer and sulfur fertilizer can be applied in appropriate amounts. After thinning to a stand, the field is cultivated; in the Heilongjiang region, spring drought is prone to occur, affecting the emergence rate. Mild drought is beneficial to root development and downward growth; in cases of extreme drought, irrigation should be carried out. When a living seed is buried in the soil, when the outside temperature is above 8 degrees, the moisture content is about 60% and the aeration conditions are relatively suitable, it generally emerges after about 10 days. When it grows to the three-leaf stage, the nutrients stored in the seed are exhausted, which is called the “weaning period”; this is the first stage of the corn seedling stage. At this stage, soil moisture is the main factor affecting emergence. In addition, the sowing depth of the seed directly affects the speed of emergence. Seedlings that emerge early are generally stronger than those that emerge late. According to experiments, for every 2.5 cm increase in sowing depth, the emergence period is delayed by an average of one day, so the seedlings are weaker.

② Three-leaf stage: from emergence and the three-leaf stage until the jointing stage, the seed grows roots and differentiates stems and leaves; stem and leaf growth is relatively slow, while root development is rapid. At this time, attention should be paid to promoting root growth and strong seedlings, ensuring early emergence, a high emergence rate and uniform emergence. The three-leaf stage is the first turning point in the life of corn, when corn shifts from autotrophic life to heterotrophic life. From the three-leaf stage to jointing, because the plant's root system and leaves are not well developed, the nutrients absorbed and produced are limited, and seedling growth is slow; the main activity is the growth of roots and leaves and the differentiation of stem nodes. The corn seedling stage fears waterlogging but not drought. Waterlogging can, at best, affect growth and, at worst, cause seedling death. Mild drought is beneficial to root development and downward growth.

2. Jointing stage

Apply 60-70% of the total nitrogen fertilizer as a top dressing. For those with good growth, apply it all at once at the large trumpet stage; for those with poor growth, apply it in two applications at the jointing stage and the late large trumpet stage. The fertilization depth is required to be 10 cm, and soil should be covered in a timely manner.

3. Large trumpet stage

From the jointing stage and the large trumpet stage until the tasseling stage, the stem internodes rapidly elongate, the leaves rapidly expand, the root system develops, and the female and male ears differentiate. At this time, attention should be paid to promoting leaves, strengthening stalks, preventing lodging and increasing ear growth. The period from jointing to tasseling in corn is called the ear stage. Jointing is the second turning point in the life of corn. The growth and development characteristics of this stage are: vegetative growth and reproductive growth proceed simultaneously, that is, the vigorous growth of vegetative organs such as leaves and stem nodes and the strong differentiation and formation of reproductive organs such as female and male ears. This period is the most vigorous stage of growth and development in the life of corn, and it is also the most critical period for field management. For this reason, the central task of field management at this stage is to promote the enlargement of the middle and upper leaves and a sturdy stalk and high-yielding appearance, so as to achieve the goal of more ears and larger ears. Use foliar fertilizer.

4. Tasseling stage

The period from tasseling to maturity in corn is called the tasseling stage. When corn tassels and sheds pollen, all leaves have already unfolded and the plant has reached its final length. The growth characteristics of this stage are: the growth of the vegetative body basically stops, and the stage centered on reproductive growth begins, marking the third turning point in the life of corn. For this reason, the central task of field management at this stage is to protect the leaves from damage and premature aging, strive for more kernels and heavier kernels, and achieve a high yield.

5. Maturity stage

Corn enters the stage of flowering, pollination, fertilization and endosperm mother cell division. At this time, attention should be paid to protecting leaves and roots, preventing lodging and preventing aging, and increasing the number of kernels and kernel weight.