How to Dry Soybeans

By Dr. Harold Willis

Soybeans above 14% moisture should be dried. The same drying equipment used for other grains can be used for soybeans. At high drying temperatures (over 100 degrees F.) germination rate, oil and protein quality are harmed. In low humidity weather, no artificial heat may be necessary. If the outside humidity is below 70% and temperature above 60 degrees F., good drying will occur. A perforated floor under the grain gives better air distribution than ducts. An air flow of 2-3 cubic feet per minute is recommended.

To prevent seed coat cracking, drying air should be above 40% relative humidity. The relative humidity of air is approximately cut in half for every 20 degrees F. rise in temperature. Say the outside humidity is 100% at 50 degrees F. If you raise your drying air to 70 degrees F., its humidity will be 50% An additional rise to 90 degrees F. will bring the humidity too low, 25%, and many seeds will crack.

About 2,000 BTU of heat are needed to evaporate a pound of water. You can figure the cost and time for drying a batch of soybeans. Using the accompanying table (below), find the pounds of water per bushel you need to dry, and multiply by total bushels. For example, to dry beans with 16% moisture to 12%, 2.8 pounds of water per bushel must be removed. This times 2,000 BTU equals 5,600 BTU per bushel.

soybean moisture chart

To figure drying time, the BTU per hour equals air flow (in cubic feet per minute) times temperature increase. For example, at an air flow of 2 cfm and a temperature increase of 15 degrees F., the heat input is 30 BTU per hour per bushel. Thus to dry our beans from 16 to 12% moisture, we would need:

drying soybeans equation

If you know the drying time and the horsepower required (see table below), you can figure cost at 1 kilowatt hour per horsepower times electricity cost per kilowatt hour. If a heat source other than the motor and fan is used, the electricity or LP cost must be added on.

soybean drying requirements

Learn more about the specifics of soybean storage here.

Source: How to Grow Super Soybeans

Soybean Seed & Genetic Management

By Dr. Harold Willis

The soybean is a truly amazing and versatile crop plant. It is one of the oldest food plants, domesticated by 1100 BC in northeastern China. Its ancestor is a wild vine-like plant which produces tiny, hard seeds that are useless for food unless properly prepared.

In order to best manage soybean production, one needs an understanding of how the plant grows and develops.

Soybean seed development


After being planted in the soil, the seed absorbs moisture, changing from less than 13% moisture to about 50% in several hours. After one or two days the first root (called the radicle) emerges through the seed coat and begins growing downward to establish the root system.

soybean seed management
Soybean seeds after harvest, with the pods.

The upper part of the young plant (the hypocotyl) begins to lengthen, pulling the remainder of the seed upward. About five to fifteen days after planting, the new plant arches through the soil, and the oval seed leaves (cotyledons) open up. The cotyledons provide the seedling with food (that was stored in them) for about a week, plus they soon turn green and begin making a little additional food by photosynthesis. Later they drop off.

Seed germination and emergence is a critical period in the life of a soybean because poor emergence due to a soil crust, cold temperatures or seedling pests or diseases can drastically cut yield.

Pod Development

One or two weeks after the first flowers, the first seed pods appear, with most pods being set within the next three weeks. Inside the pod, three (or sometimes four) tiny seeds begin to grow and develop.

For the next 30 to 40 days, the seeds rapidly fill with food produced in the leaves. The seed-filling period is the most critical in the life of the soybean plant with regard to yield. If weather conditions are adverse, such as drought stress or leaf loss from hail, yields will be cut severely. At this time, the plant takes 30-40% of its total mineral needs from the soil, so soil fertility should be at a peak.

After most seeds have filled, the growth activities of the plant slow down rather suddenly (called senescence). The leaves slow down their photosynthesis and begin to turn yellow, eventually dropping off. Root nodules cease producing nitrogen.


The newly formed seeds contain about 90% moisture. As the seeds fill with food, moisture content decreases to about 60-65%. When seeds are mature (filled), the moisture content is 45-55% and the pods and stems of the plant are yellow or brown. The mature seed itself will also be completely yellow when mature (if it is a yellow-seeded variety).

In warm, dry weather, seed moisture will continue to drop to about 13-14%, when the crop can be harvested. In some varieties especially, the dying plants tend to lodge, making harvesting difficult, and in some varieties, pods tend to split open (shatter), dropping the seed and reducing harvestable yield.

As soybean seeds lose moisture they change from large, kidney bean shaped to smaller and nearly round. When dry, the seed contains about 40% protein, 21% oil, 34% carbohydrates and 5% ash.

Soybean Varieties

There is an amazing number of soybean varieties. Just about every valley in China, Japan and Korea grows its own variety, adapted to local conditions. A collection of over 10,000 strains of soybean seeds is maintained by the USDA. A glance of an assortment of these seeds reveals seeds of every color and description — some red, some green, some black, some brown, some speckled or streaked, some large and some tiny.

The great majority of soybean varieties grown commercially today is for animal feed and oil production (for food processing and industrial uses). Most are yellow-seeded field varieties. Other varieties can be obtained for special uses: forage and hay (with an abundance of stems and leaves; small-seeded black and brown late varieties) and human food (large-seeded, various-colored varieties).


Commercial hybrid soybean seed is very difficult to produce. This is because of the way the soybean reproduces: it is self-pollinating. Hybrids are made by soybean seed breeders, but it is a laborious, expensive process. From various ancestral and hybrid varieties, the commercial varieties are developed, both by agricultural experiment stations and private seed companies.

Seed quality

Varieties are developed to produce high yields of good quality seed, to mature properly for the geographic area, to be resistant to lodging and shattering, to be cold and drought tolerant, and to resist diseases and pests.

Factors of seed quality may include low numbers of defective or shriveled seeds, high germination rate, high oil and/or protein content and human food value.
Soybean seeds sold by reliable seed dealers should come with certain important information: the variety, the Maturity Group number, percent
inert matter, percent weed seed, percent other crop seed, germination rate and resistance to diseases and/or pests. The U.S. Plant Variety Protection Act of 1970 and the earlier Federal Seed Act, as well as state seed laws, provide standards and protection to dealers, but some private growers may not adhere to these standards. Anyone can save some seed to grow the next year, but this is no assurance of quality.

Selecting a Variety

In selecting which variety you wish to plant, assuming you are growing field soybeans, you need to consider several things. First, buy the best quality seed you can find. Certified tested seed is usually worth the cost. You can test for germination rate by counting out 25 whole seeds and roll them up in a damp cloth. Keep in a warm (70 to 80 degrees F.) place. Sprinkle with water if necessary to keep the cloth moist. After five or six days, unroll the cloth and count the seeds that have germinated out of 25. Multiply by 4 and divide by 100 to get the percentage germination.

Be sure to get seed of a Maturity Group adapted to your area. You may want to vary slightly the maturity group depending on soil type (an early variety for cool, wet, fine-textured soils and a later variety on coarse, well-drained soils). Avoid early varieties in fields where tall broadleaf weeds may get out of hand. If you want to follow the soybeans with fall-seeded small grains, use an early-maturing soybean.

One way to allow for uncertain weather conditions is to plant more than one maturity, either in different fields or as a seed blend, a mixture of varieties. That way at least one variety should give a reasonably good yield. If you save your own seed to replant, you will not get the same proportion as what was in the blend.

Select a variety that is shatter and lodging resistant, especially if you intend to plant high populations, since the plants will grow taller, more slender stems.

Disease and insect resistance may be important if these have been a problem in your area; however, by improving your soil’s fertility and structure, most such problems should disappear.

Indeterminate varieties should be used in the North, and determinate varieties do not do well in soils that crust. For wide rows, bushy varieties are best, to fill in the space quickly.

If you use a grain drill for planting, avoid seed lots with many large seeds, which do not flow well through the drill. Use seed lots with 2,400 seeds per pound or less. Small-seeded varieties have some advantages: the seedlings emerge better through crusted soil, fewer pounds of seed are needed to establish a certain plant population, and it is often easier to produce high quality grain (because smaller seeds suffer less damage during harvesting and handling).

You can often get valuable advice on selecting varieties from your agricultural research and extension personnel or from seed dealers. They may have performance test results which can be a rough guide of what to expect from a variety.

Saving Seeds

If you want to replant your own seed, save out the needed amount. Seed should be dried to about 13% moisture and kept in ventilated containers (cloth bags, cardboard boxes, or glass jars with cheesecloth covers). It should be stored in a dry, ventilated area at cool temperatures (not higher than 70 degrees F. or lower than 32 degrees F.). Keep away from mice and rabbits.

Seed should maintain a good germination rate for the first year (80 to 85%), but after the second year of storage, germination may drop to 65%. Test the germination rate before planting.

Source: How to Grow Super Soybeans

Measuring Soybean Quality

By Dr. Harold Willis

Soybean plants that grow poorly or produce poor quality seed represent potential problems. Measuring quality of soybean plants and seeds is essential.

Sometimes the reason for poor quality soybeans is a low rate of photosynthesis, possibly due to cloudy, cool weather — or the opposite extreme, heat and drought. Nutrient deficiencies may contribute. Unfavorable soil conditions — waterlogging and poor aeration — can also disrupt normal plant functions.

Healthy plants will produce more nutritious food and seeds with more protein and oil. High quality seed will have a higher test weight.

measure soybean quality

Tools for measuring soybean quality

A handy tool to help you monitor the health of your growing plants is a refractometer. This is a precision instrument which quickly measures the percent sugars in a plant’s sap, while you are standing in the field. In general, the higher the sugar content, the higher the protein and oil content, since sugars are later turned into protein and oil. Fairly inexpensive, refractometers are routinely used in the food industry, by canneries, wineries and breweries, for example, to measure the quality of the fruits and vegetables they buy from the farmer or of the foods and drinks they manufacture.

Using a refractometer is easy. Just squeeze a drop or two of juice from the stem or leaves of the plant onto the glass prism of the refractometer, close the “lid” and look through the eyepiece. The sugar content is read on a numbered scale in units called brix (same as percent).

By comparing with standard readings or with past readings you have made, you can see how your crops measure up that day. Be careful to always take a reading from the same part of a plant (upper mature leaves and stems are good) each time and at the same time of day. The sugar content will vary in different parts of the plant, at different times and in different weather conditions (higher on warm, sunny days in the afternoon). Sometimes a sick plant will have a high sugar reading in the early morning, whereas a healthy plant should not.

corn quality refractometer

Standard refractometer readings for soybeans and peas:

  • Poor: 4
  • Average: 6
  • Good: 10
  • Excellent: 12

Find out what’s wrong

You can’t really tell what is going on in your fields while driving by at 50 miles per hour. You need to stop and walk through your fields and carefully observe what is happening. Look for telltale signs of insect damage or mineral deficiency in your plants. Check their sugar content with a refractometer. Are there isolated problem areas in a field?

Most important, check your soil. Carry a shovel and occasionally dig down and turn up a shovelful of soil. Is it loose and friable, or tight and hard? Is there a hardpan six inches under? Are there earthworms, and fungi in last year’s residues? Does the soil have that good rich smell of humus? Is there a weed problem?

Dig up the root system of a plant. Are the roots a healthy white color or discolored with decaying spots? Are there plenty of nitrogen-fixing nodules on the upper roots? Are the nodules a healthy pink inside?

These are all things you should notice and questions you should be able to answer about your fields. If you spot a problem, figure out its cause and work to overcome it. The basic place to begin is the soil.

Source: How to Grow Super Soybeans

Harvesting and Storing Soybeans

By Dr. Harold Willis

The soybean is a hardy, not-too-particular plant and can do reasonably well in a variety of soils and soil conditions, but to produce high yields of top quality soybeans, you need to get your soil into really good condition. And then, at the end of the growing season comes the most important part of soybean production — harvesting.

Harvesting Soybeans

The beans contain 45-55% moisture when mature (filled) and must dry down before being harvested. When field mature, seeds, pods and stem turn yellow. About four to nine days later, all pods on the plant have turned brown. At this point, seed moisture is about 33%. With good drying weather, the beans should be ready to harvest four to five days after this. They should be at 13-14% moisture, but with careful combining, beans of higher moisture can be successfully harvested. Shattering losses are very high below 13% moisture.

Grain elevators or seed dealers will usually measure moisture content of grain if you do not have your own meter. As a rough indication, a well dried (13% moisture) soybean will split in two easily when tapped with a hammer.

harvesting soybeans


If dry-down is not likely to occur rapidly, chemical desiccant (drying) sprays can be used. Weeds are also killed at the same time. Early harvested beans usually command a higher market price, and field losses are lower with early harvest. But the desiccant kills the plant, and should not be used before seed maturity has been reached or significant yield reduction will occur. The chemicals used for drying include sodium chlorate, a powerful oxidant, and the herbicide Paraquat. Many specialists question the practice of using desiccants, and mention of the practice here does not constitute endorsement.

Reduce losses

It is very important to keep harvesting losses to a minimum in a high-value crop. Lodging and shattering losses can be partially reduced by planting resistant varieties and appropriate populations. Shattering is more likely the longer the plants stand in the field, especially with alternating wet and dry weather.

It is extremely important that the combine be adjusted and operated properly. Keep the machine in good repair. Adjust reel speed to 25% faster than ground speed. Six-bat reels feed more evenly than four- or five-bat reels.

Operate the cutterbar as close to the ground as possible. Use a pick-up reel with lodged soybeans. Generally ground speed should not exceed three miles per hour to prevent stripping of beans from the stalk; slower speeds are necessary if plant height is uneven.


Avoid excessive impact of harvested grain on hard surfaces, since dry soybeans crack easily. Run conveyors as full and as slowly as possible. Use cushion boxes to absorb impact from long drops. Warm up cold beans by aeration before transfer, since cold beans crack more easily. Soybeans above 14% moisture should be dried.

Soybean Storage

Stored grain must be kept cool and dry to prevent mold and insects from attacking. Damaged grain is also a detriment; insects seldom feed on whole soybeans. Foreign matter is often a source of mold growth. Soybeans lose and gain moisture quickly, so it is important that storage bins are well aerated to prevent moisture migration from warm areas and condensation in cool areas. Either drying fans or bin aeration fans can be used. Aerate at a rate of 0.1 cubic foot per minute per bushel of bin capacity.

In the fall, you should aerate continuously when the outside temperature is 10-15 degrees F cooler than the grain temperature until the grain reaches
40 degrees F. In the winter, aerate for 24 hours every two weeks when the outside temperature is 10 degrees F higher or lower than grain temperature. The 24 hours aeration need not be continuous.

In the spring, aerate continuously whenever the outside temperature is 10 to 15 degrees F warmer than grain temperature until grain temperature reaches 60 to 65 degrees F. All of this is made easier if you have automatic controls on your aeration system.

Saving seed

If you want to replant your own seed, save out the needed amount. Seed should be dried to about 13% moisture and kept in ventilated containers (cloth bags, cardboard boxes, or glass jars with cheesecloth covers). It should be stored in a dry, ventilated area at cool temperatures (not higher than 70 degrees F or lower than 32 degrees F). Keep away from mice and rabbits.

Seed should maintain a good germination rate for the first year (80 to 85%), but after the second year of storage, germination may drop to 65%. Test the germination rate before planting.

Source: How to Grow Super Soybeans