How To Grow Soybeans And Get Increased Yields

Genus Glycine Willd is divided into two subgenera: Glycine (perennial) and Soja (Moench) (annual). Perennial varieties are extremely diverse in morphology, cytology, and genome structure. They grow up in a wide variety of climatic and soil conditions and have a wide geographic distribution. These types of soybean have a variety of physiological and biochemical characteristics, as well as for the sources of resistance to pathogens.

Taxonomically, both annual wild soybeans (G. soja Sieb. & Zucc.) and cultivated soybeans (G. max (L) Merrill) are the subgenera of Soja. Wild soya (G. soja Sieb. & Zucc.) is usually used in breeding programs due to its high salt tolerance, frost and drought tolerance, high lutein content, etc. Wild soybeans can also be used to create fertile hybrids of cultivated and wild soybeans.

Globally, soybeans are comparable in importance to wheat, rice, and corn. This oilseed belongs to the group of crops that are moderately drought tolerant. Besides, soy products are becoming more common every year in different countries of the world. For example, the production of soybean oil alone has increased by 63% over the last 5 years.

Depending on the demand, the volume of crop production and acreage vary every year. The largest producers of soybeans are Brazil, USA, Argentina, India, and China.

In the last 5 years, U.S. soybean production was the biggest with the volume of 120.52 million metric tons in 2018 – 2019. But in 2020, Brazil has taken the leading position with a production volume of 124 million metric tons.

Soy is a light-loving and heat-demanding crop. The greatest need for heat is during the flowering and bean formation phases. The best temperature for soybean during this period is 21 – 22 ° C. With a decrease to 14 °C, the growth and development of soybeans stops. At the beginning and end of the growing season, the need for heat is lower. At this time, the plants tolerate frosts down to -3.5 °C.

Keep in mind that soybeans also don’t tolerate air drought, especially during flowering and bean formation stages. At very low humidity during this period, new flowers and beans are not formed and the existing flowers and beans fall off. Besides, soy is also demanding in terms of light. The lack of lighting lengthens the stems and leads to the inability to form shoots and beans.

Soybeans use 2 – 3 times more nutrients than grain crops, which means they grow well on fertile and cultivated soils. On other soils, soybeans can give a high yield only when high doses of fertilizers are applied.

A thick layer of water-permeable soil that is rich in phosphorus, calcium, and humus is considered ideal for growing soybeans. Soy also grows better on neutral and slightly acidic soils (pH 5.5 – 6.5). Besides, this crop is demanding on its predecessors. The highest yields of soybeans are obtained after winter wheat. But it is not preferable to sow soybeans after legumes and sunflowers due to the danger of spreading bacteriosis and other diseases. The best soil temperature for planting soybeans is around 12 °C.

Here are the main growth stages of soybeans.

0. Germination

At this stage, the hypocotyl reaches the soil surface and breaks through the soil surface.

1. Leaf development

At this stage, the cotyledons completely unfold, and the leaves develop. The stage lasts until 9 or more leaves unfold.

2. Formation of side shoots

This is when the first side shoot of the plant is visible. This stage lasts until 9 or more side shoots appear.

3. Inflorescence emergence

At this stage of soybean growth, the first flower buds become visible and enlarge, until the petals appear.

4. Flowering

This stage starts when the first soybean flower opens and ends when the first pods are visible.

5. Development of fruit

This stage starts when 10% of pods reach their typical length. It ends when 80% of pods reach their typical length and the individual beans become easily visible.

6. Ripening of fruit and seed

This stage continues until 80% of pods are fully ripe and the beans are hard.

7. Senescence

This is the last stage of soybean plant growth when the plants die.

Land preparation for planting soybeans should be differentiated according to the soil type, predecessor, weediness of the field, and soil moisture. Steps in land preparation include the main tillage in fall (deep plowing), pre-sowing cultivation in spring, and post-sowing cultivation.

Depending on the predecessor, a number of additional treatments are carried out before and after the main cultivation. If the predecessor is cereal crops (wheat, barley), soil preparation consists of stubble plowing, deep plowing and, depending on the degree of weediness of the soil, disking in fall. Stubble plowing is carried out in areas heavily infested with perennial weeds.

The timing and depth of the main plowing have an impact on the yield. To provide a suitable soil layer for sowing in spring, the main cultivation should be carried out to a depth of 20 – 23 cm.

When preparing land for farming in spring, early spring harrowing is carried out. If the soil condition before the spring pre-sowing treatment is not very good (there are lumps), cultivation is carried out with harrowing to a depth of 6 – 8 cm to break the lumps before they dry out. It is undesirable to cultivate the soil to greater depths since soybeans do not tolerate deep planting of seeds and are very demanding to a firm seedbed. Re-cultivation is carried out 7 – 10 days before sowing.

The choice of the optimal time for planting soybeans depends on several factors. First of all, on the sufficient and stable heating of the soil in spring. Soybean, in comparison to other field and spring crops, is a crop of late sowing due to the increased temperature requirements during the period of seed germination and emergence of seedlings.

When determining soybean planting dates, ensure that the seed bed is heated to 8 – 10 °C at this period, and severe frosts are no longer expected. Besides, that is when a lot of weeds emerge: wild oat, wild radish, bindweed and others, which is an indirect indicator that the field is ready for crop planting.

The warmer the soil, the faster the shoots appear from the moment of sowing. It is also critical to take into account the calendar period of possible return of frosts. Exposure to temperatures below -3 °C is destructive to soybean seedlings.

The choice of the optimal sowing time for varieties of different groups of ripeness should also be based on the field moisture, including the amount and distribution of precipitation.

It is important that during the period of bean formation and seed filling, the water supply of the crops is sufficient. On heavily weedy fields, a delayed, late sowing of soybeans is preferable to destroy weeds in the pre-sowing period.

Before planting soybean, it is critical to select only large and medium seeds and carry out seed treatment to increase resistance to diseases and pests.

The sowing technology must be selected according to the degree of contamination of the field. On clean and herbicide-treated fields, drill sowing is used, which makes two or three inter-row treatments unnecessary. In other cases, sow with a row spacing of 45 cm.

The recommended soybean planting depth is 3 – 4 cm, and the seed rate varies significantly according to local conditions. It is increased if the field is fertile enough and well provided with moisture, and if there is a lack of moisture, it is reduced. Usually, it is 130 – 135% of the required plant density, and the seed rate falls in the range of 70 – 120 kg / ha.

Soybeans begin to absorb elements necessary for development from the soil quite early. To obtain a high yield, it is necessary to fertilize the plants at the flowering stage.

Soybean fertilization is carried out in three stages: basic, pre-sowing, and top dressing. Mineral fertilizers for soybeans are phosphorus and potassium that are applied in autumn, and nitrogen is applied in spring. During the main stage of fertilization, nitrogen must be applied half as much as phosphorus. If nitrogen is applied in large quantities at the beginning of the growing season, it will not remain there until the flowering phase when it is extremely necessary. That is why it is better to apply it as a top-dresser.

Soy reacts differently to phosphorus depending on the acidity of the soil. If the soil analysis has not been carried out, 26 – 42 kg / ha are applied. Phosphorus is especially necessary in the initial phases of plant growth – from germination to tillering. This element is important for the formation of nodules and a large number of generative organs.

Sometimes phosphates are located in the soil close to the seeds, but they do not negatively affect them. However, potassium used in the form of potassium chloride can be bad for young seedlings. That is why potassium is recommended to be used during pre-sowing seed treatment. Potassium is also needed in the phase of bean formation. During this period, the plants need this element more than phosphorus and nitrogen.

The amount and rate of mineral fertilizers for soybeans depends on the saturation of the soil with nutrients, as well as on the planned harvest.

The use of only one nutrient can negatively affect the cultivation of this crop. The use of fertilizers comprehensively stabilizes both the deficit and the surplus of nutrients.

The water requirements of soybeans depend on the growing season, variety, irrigation method, and rainfall. The average need of soybeans for irrigation is 367 mm. However, the demand for the amount of water used for irrigation varies depending on soil moisture reserves.

In soybean cultivation, sprinkler irrigation is common practice for plants planted on a leveled surface. If the crop is sown on raised ridges, furrow irrigation is used. Drip irrigation is either not used in soybean cultivation or is used very rarely. However, the choice of irrigation method is also determined by such factors as the source of irrigation, surface topography, and soil content.

Drip irrigation not only reduces water consumption compared to sprinkling but also maintains a higher soil temperature, which contributes to higher germination and seedling growth rates. Although surface and subsurface drip irrigation systems can be used, in the case of subsurface drip irrigation at low depths, high humidity and low oxygen content in the soil can lead to hypoxia.

Irrigation should be applied taking into account the stage of crop development, weather conditions, and the state of soil moisture required for soybean.

Here are the most common soybean pests and the ways to protect the crop from them:

Bean seed fly

The larva of this pest damages the cotyledons, growth point, and stems. As a result, young plants wither and die out.

Protection measures:

• Placement of seeds in wet soil
• Sowing in the optimal time
• Application of hexachloride in the soil before sowing

Sitona weevil

This soy beetle damages the cotyledons, primordial, and sometimes the first trifoliate leaves. The activity of weevils increases in the warm weather of 14 – 15 °С. Plants damaged by the weevil significantly slow down in growth.

Protection measures:

• Insecticides application
• Removal of soybean from areas occupied by perennial legumes

Beet webworm

Mass damage by the caterpillars of this pest to all parts of soybean plants is observed mainly in the second half of summer, when the caterpillar devours almost all the leaves on the soybean.

Protection measures:

• Soybean pesticides application
• Weed control

Thrips

Soybean thrips larvae are found mainly in flowers and young leaves. Sucking the juice from the flowers, thrips negatively affect the development and fertilization of plants.

Protection measures:

• Stubble plowing
• Deep winter plowing

Marbled Clover

In late summer and autumn, the caterpillar of this pest mainly damages the beans and seeds by gnawing round holes in the green beans.

Protection measures:

• Fall plowing
• Insecticides treatment

Here are the most common soybean diseases and the ways to protect the crop from them:

Fusarium wilt

During the flowering period, this disease affects the upper part of the plant. The beans crack and dry out. Adult plants greatly slow down in growth, the seeds are small and wrinkled. Crop density decreases, leading to significant yield losses. The development of this disease is especially severe in fields that are also infested with soybean cyst nematodes.

Protection measures:

• Fungicides application
• Seed treatment before planting

Canker

This seedling disease is transmitted through seeds and crop residues and affects all parts of the soybean. Small black spots or stripes appear on stems and leaves. The leaves curl up, and the veins turn brown. When infected at an early stage, seedlings die. Rainy weather in spring and summer promotes the rapid development of the disease.

Protection measures:

• Fungicides application
• Selection of resistant varieties
• Burning of plant residues

Bacteriosis

This disease causes dark brown spots to appear on leaves and stems. The beans are covered with oily brown spots and crack.

Protection measures:

• Seed treatment
• Weed control
• Fungicides application

Noble rot

The rot appears in the form of light spots on stems and leaves. The stems eventually break, the plants wither, and the leaves rot and fall off.

Protection measures:

• Removal of plant residues from the field
• Seed treatment

Soybeans are harvested during the period of full ripeness, after the leaves begin to dry out, fall off, the stem and beans turn brown, and the moisture content of the seeds decreases to 14 – 18%. The perfect soybean harvest time is when the seed moisture is 13-14%. In this case, the grains can be easily threshed without injuring them.

The main method of harvesting soybeans is direct combining with low cutting levels. For harvesting, a special soybean harvesting machine is used, which guarantees minimum crop losses.

Usually, soybeans are harvested at a height of 6 – 7 cm. In most cases, the cause of a large yield loss is an incorrectly selected cut height, late mowing, and varieties with a low bean attachment. After harvesting, the seeds must be immediately cleaned and dried.

Soybean yield depends not only on the number of plants per acre, but also on the number of beans and grains in each of them, as well as their mass. And the number of beans depends on the length of daylight hours and moisture during their formation.

The average soybean yield per acre ranges from 41 to 47 bushels. And the highest soybean yield ever was harvested by Randy Dowdy and accounted for 190.23 bushels per acre.

Soybean prices depend on the volume of its production, the state of the global market, and the demand on products that are made from it. In 2020, the average soybean price per bushel is $10.4350.

Here are the recommendations to follow if you want to increase soybean yields:

• Adding one more pod per plant. Doing this can help increase yields by 2 bushels per acre.
• Seed treatment with fungicides and insecticides to ensure strong plants and protect soybeans from diseases and pests. This will allow for healthy development of plants that will contain more pods.
• Planting early. This will help the plant to develop as many nodes and stems as possible. And since the nodes carry the pods, more pods means more seeds and greater yield.
• Narrower row spacing. Row spacing of 15 – 20 inches has proven to increase yields and help plants to respond to management better.
• Foliar fertilizers. Plants get most of their nutrients from the soil, but a certain amount of nutrients applied together with herbicides or fungicides can help the plants to overcome short-term deficiencies and stimulate metabolism and root activity underground. All this leads to plants ability to retain more pods, which means more seeds.