A detailed explanation of the soybean growth process: from sowing, germination, flowering and pod formation to maturity
Soybean is one of China's important food crops. It is an annual herbaceous plant of the genus Glycine in the legume family (Fabaceae). It is cultivated throughout China and is also widely cultivated around the world. Over its life it goes through six growth stages: seed germination and emergence, seedling growth, flower bud differentiation, flowering and pod formation, seed filling, and maturity. Let's take a look at the soybean growth process together below!
Emergence stage
The radicle of the soybean seed first emerges from the micropyle of the ovule. When the radicle has elongated to the same length as the seed, it is called germination. The hypocotyl elongates, the seed coat falls off, and the cotyledons emerge above the soil surface as the hypocotyl elongates. When the cotyledons unfold, it is called emergence. Under suitable conditions, emergence occurs 4-6 days after sowing. When more than half of the cotyledons in the field have emerged from the soil, it is the emergence stage.
Seedling stage
From emergence to flower bud differentiation is the seedling stage. After emergence, the 2 cotyledons unfold, and the young stem continues to elongate. The 2 opposite simple leaves above then unfold; this is called the simple leaf stage. As the young stem keeps elongating, when the first compound leaf appears it is called the 3-leaf stage. During the 3-leaf stage, the aboveground part grows relatively slowly, while the underground root system grows relatively quickly and forms root nodules. By the end of this stage the root system has taken preliminary shape and begins to require more water and nutrients. The seedling stage lasts about 20-25 days, accounting for 1/5 of the entire growth period. This period is the root-growing period, and attention should be paid to controlling seedling growth and strengthening field management so as to achieve full, uniform, and strong seedlings, laying the foundation for a high yield.
Flower bud differentiation stage
From the beginning of flower bud differentiation to the first flowering is the flower bud differentiation stage, generally lasting about 25-30 days. When 4-5 compound leaves have appeared, branching begins at the lower part of the main stem, and flower buds differentiate at the same time. The process of flower bud differentiation begins with the appearance of a hemispherical flower bud primordium, followed by the formation of sepals in front of it, then the formation of the tube, and then the differentiation of the keel petal, wing petal, and standard petal. The ring-shaped stamen primordia differentiate successively, and in the center of the stamens the pistil begins to differentiate, with ovule primordia appearing. Subsequently, the ovule and anther primordia differentiate, the floral organs gradually grow, and finally flower buds, pollen, and embryo sacs form one after another, completing flower bud differentiation. During the flower bud differentiation stage, the plant enters a period in which reproductive growth and vegetative growth proceed together. At this time, fertilizer and water management must be strengthened, while attention should be paid to coordinating vegetative growth and reproductive growth so as to achieve the requirements of strong plants, many branches, many flower buds, and healthy flowers.
Flowering and pod formation stage
From the first flower to the last flower is the flowering stage. The flowers are very small and are borne in leaf axils or at the top of the stem. The number of flowers borne on each flower cluster varies with variety and cultivation conditions. The rate of flower and pod abscission is high, so the number of pods set per flower cluster is relatively small. Soybean flowering occurs mostly from 6-9 a.m. It generally takes 3-7 days from bud appearance to flowering. After the ovule is fertilized, the ovary gradually expands to form a soft, small green young pod. When the pod reaches 1 cm in length, it is called pod formation. The growth of the pod is first in length, then in width, and finally in thickness. The flowering and pod formation stage is the period of most vigorous soybean growth, the period when water and nutrients are needed in the greatest amounts, and it also requires sufficient light. On the basis of full seedlings, strong seedlings, and many branches in the earlier stage, fertilizer and water management should be strengthened during the flowering stage, and good aeration should be maintained, so as to achieve the requirements of many flowers, many pods, and many seeds and to reduce flower and pod abscission.
Seed filling stage
From the beginning of enlargement of the seeds inside the pod until they reach their maximum volume and weight is the seed filling stage. Within 10 days after flowering, the accumulation of dry matter in the seeds increases slowly, and then increases very rapidly over the following 7 days. Most of the dry matter is accumulated over about 21 days after that. The seed filling stage lasts about 30-40 days. When seed filling is complete, the moisture content of the seeds is about 90%. The seed filling stage is an important period for soybean seed formation. At this time, whether soybean growth is normal will determine the number of seeds per pod, the seed weight, and the chemical composition of the seeds. At this time, drought or excessive rain causing waterlogging can cause dead pods and shriveled seeds and reduce seed weight, seriously affecting yield. Ensuring normal seed development requires meeting two conditions: the plant itself has abundant stored matter, the root system does not senesce, and the assimilation of the leaves is vigorous; there must also be an adequate water supply.
Maturity stage
The soybean leaves turn yellow and drop, the seeds dehydrate, and the inherent characteristics of the variety appear. At this time, the seed moisture content has dropped below 15%, until a slight rattling sound is heard inside the pods when the plant is shaken; this is the maturity stage. At this time, soil moisture should be reduced to accelerate the drying of the seeds and plants, making timely harvest easier, while also preventing excessive fertilizer and water from causing delayed senescence and late maturity, which would affect timely harvest and crop rotation. In this period, clear and dry weather can promote maturity and help improve quality.