Farmers Seek Membership in 100 Bushel Club

www.agrinews-pubs.com
Tom Doran
2010-01-20

URBANA, Ill. — Yield is a journey, not an event, and becoming a member of the 100 Bushel Club requires a better understanding of soybeans.

“If we’re really going to put together a common system that maximizes our yield or at least the probability, I think it’s good to understand this plant and see if we can manipulate the environment to maximize what that plant is doing,” said William Wiebold of the University of Missouri Division of Plant Sciences.

Much attention has focused on seed size, particularly in recent yield contests. However, Wiebold believes seed number is the most important determinant of soybean yield.

Even for the world record soybean yield, only about one-third of the increased yield can be attributed to increased seed size.

“This is not to say that seed size is unimportant, but there is a discouraging link between increased seed number and reduced seed size,” Wiebold said during the recent AgMasters Conference, hosted by the University of Illinois. “So, enhancing soybean yield often means increasing seed number dramatically, while attempting to maintain or slightly enhance seed size.

“Yield is a journey, not an event. If you go through that journey, you have good and bad stretches along the way that can affect that yield. So you gain yield and you lose yield. Yield is complex. That potential yield changes nearly every day of the growing season.”

Although flowers are produced on every stem and branch node of a soybean plant, the majority of the soybean yield is produced in the upper portion of the middle one-third of the soybean canopy.

This portion of the plant canopy is where sunlight is absorbed.

“Almost all of the light captured is in the top third of the canopy. We know that light drives photosynthesis, photosynthesis produces sugar, and sugar is needed for everything the plant does. In particular it is needed to produce yield,” Wiebold said.

“Light drives that yield. What also I think is important here is the product of that light captured — those sugars — don’t move very far in the plant. They’re used right where they’re made. You can’t capture light at the top of the canopy and move that sugar very well down to the bottom parts of the canopy.”

Although producers can learn some things about soybean yield enhancement from other crops, including corn, it is important to understand the unique characteristics of soybeans.

“The primary thing here is that corn produces a single ear. It is relatively easy to increase the ear numbers per acre simply by adding more plants,” the specialist said. “So for corn, increasing yield is often focused on maintaining ear size while pushing plant density.

“Soybean is much different as the plants produce seeds in pods that contain only two or three seeds. It’s not easy to increase that pod number because of the way the plant responds to crowding and plant population.”

Node number becomes important, but what ultimately becomes even more important is the number of pods per node.

“As we crowd those plants together, the number of branches and the number nodes greatly decreases,” Wiebold said. “This is why soybean yield does not change much within a large range of stand densities. Increasing population is a farm more useful tool for corn than for soybeans.”

He noted one other unique characteristic of soybean is the large amount of flower and pod abscission. Under normal conditions, 65 percent or more of the soybean flowers produced abscise and are not harvested as seed containing pods.

The amount of abscission increased with depth into the soybean canopy. The amount of abscission also varies on the individual inflorescences.

Soybean flowers, pods and developing seeds compete with their neighbors for sugars and other nutrients.

All plant stresses aggravate this competition among pods and increase the amount of abscission, according to Wiebold. He used football as an analogy for achieving high soybean yields.

“If you look at the team that’s going to win the Super Bowl, the offensive line has to block right, the running back has to hit the holes, the receivers have to run the right routes, the quarterback has to have the right timing. All of those fundamentals are true, no matter how great you are,” Wiebold said.

“So no matter how great of a farmer you are, you still have to pay attention to the fundamentals, and that’s really what we’re talking about.”

He provided his keys to entering the 100 Bushel Club.

“The most important decision is variety selection,” Wiebold said. “In most situations, I suggest reviewing data over many locations including locations that have low to average yield potential. If you’re going to use a high yield environment, I would select a variety that was tested under those high yield environments.

“By following this process you select for yield stability, which is important because you do not know the conditions your field will experience in any given year.”

He said other characteristics, such as disease resistance, are important, but yield potential in high yield environments should be at the top of the list. Sunlight should be captured as soon as possible, and planting early is important.

“Planting early moves the critical seed-filling period for the soybean crop earlier in the summer when sun power is greater. Narrow rows an also increase light capture,” Wiebold said.

Full canopy closure occurs much earlier in rows planted 7.5 inches apart than rows planted 30 inches apart.

“Selecting an appropriate seeding rate may not seem like it is related to light capture, but you want to make sure you are above your target stand in every place within the field,” the specialist said. “Be knowledgeable about your field and know where emergence problems or reduced plant growth are possible.

“Protect those leaves, particularly in the upper half of those canopies. This means getting out and scout those insects and diseases. You need to know what’s going on in that field and you need to protect it.

“I’m not a real fan of fungicides in many cases, but if you need them, it’s a great tool. The same is true with insecticides. If you need them, they are a great tool. If you don’t need them, you ought not to be spraying.”

He recommended to “treat the soil as if it is alive. Don’t kill it. Watch your compaction.”

“We often forget that nearly one-half of the soybean plant is below ground,” he said. “Root health is essential to plant health.”

An actively thriving soil community of microbes and other living organisms means that roots also will be healthy.

Soils act as banks for water and nutrient storage. Plant roots draw upon these banks as the season progresses.

Good structure, aeration and organic matter are all characteristics of a well-working soil bank. Compaction squeezes the life out of soil and can have season-long or even longer impacts on our soil plants.

“Pamper your plants,” Wiebold said. “The world record holder for soybean yields tells us to keep our soybean plants happy.

“Remember that your commitment to producing 100-bushel yield means that soybean plants will exploit their environment to a much greater extent than in normal fields. One hundred bushels require a lot of nutrients and other kinds of things.”

“If you’re really going to aim at that 100 Bushel Club, you need to know those plants need, how yield is made, and maybe you’ll produce plants like this,” he said while showing a large soybean plant filled with pods from yield contest winner Kip Cullers’ field.

“Making yield is a season long journey. Raising the yield bar and finding a path to the 100 Bushel Club will likely take more than one season.

“As you scout fields, remember to record the appearance of the plants — the good, the bad and the ugly. Write down things that may not seem significant when you see them, but may help explain what went right or what went wrong.

“With good notes you might come closer to your goal next year if you failed to enter the 100 Bushel Club on your first attempt.”


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