BLOOMINGTON, Ill. — Soybeans and corn are often put into the same management strategy bucket, but the “soy factory” is more complex.
“We try to lump the soybean into the same category as the corn plant, and what pushes the needle on yield on corn we try that on soybean and we end up scratching our head because we have a hard time of making the soybean react to the management that we wanted it to react to. So, we chalk the soybean plant up as either very stubborn or too complex and it’s just going to do what it’s going to do,” said Dustin Bowling, AgriGold western agronomy manager.
One difference between the two crops is corn is a sprinter and soybeans are like long-distance runners due to the difference in their photosynthesis characteristics, said Bowling during an Illinois Soybean Association-hosted webinar.
Soybeans fall into the C3 pathway of photosynthesis. They breathe carbon dioxide in through their stomates, fixes a three-chain carbon molecule and breathes out oxygen.
When it gets hot or the soybeans have some other stress, the stomates close and the plant is not able to continue the carbon-fixing process within its cells.
“Soybeans are just wired differently.”— Dustin Bowling, AgriGold western agronomy manager
On the other hand, corn has a C4 pathway of photosynthesis that breaks down the carbon dioxide through the stomates and fixes a four-chain carbon molecule. They continue to fix carbon within the plant when the stomates close and stop the process of breathing out water and respiration.
“Because of a corn plant’s C4 pathway and its metabolism, it operates like a sprinter’s level metabolism. It’s going to be very reactive to all the nutrients you give it. It’s going to react very quickly, and it’s going to keep pushing towards the goal at a much faster rate, accumulated a lot more carbon and a lot more natural resource fixation along the way,” Bowling explained.
“Whereas our soybean plants are like the cross-country runner with the long game in mind and they chug along at a steady pace. That means they’re not as reactive to some of the management practices that we’re used to on the corn side. Soybeans are just wired differently.”
Fueled By Nutrients
The foundation of building a successful soybean factory is fertility. Soybeans required 17 nutrients to produce high yields.
Nitrogen, phosphorus, copper and potassium are the raw materials used to produce grain. Sulfur, calcium, boron and manganese are all secondary nutrients that are necessary to help the plant grow properly.
“You combine those 17 nutrients with sunlight and you have an effective soybean factory,” Bowling said.
Bowling compared soybean production to the four quarters of a football or a basketball game in terms of how the plant reacts to different factors throughout the entire growing season.
The opening kickoff is in the form of early planting and stand establishment. A soybean plant needs more time to get to its goal.
“Think about how big a soybean plant can get if it’s planted April 15 at a lower population, let’s say 80,000 seeds per acre. You have an extra 30 days between April 15th and May 15th for root development, shoot development and nutrient uptake,” Bowling said.
“By the time you get to May 15th you’re already thinking you should probably plant 120,000, 130,000. By the time you get to June 15th it takes a lot more factories in order to equal a very similar amount of pod production and seed production you might get out of that one plant back on April 15th.”
Soybeans are more cold-tolerant than what was once thought and can survive cold spells if the seed is planted in soil with a 50-degree temperature. Seeds treatments also make a difference with cooler soil temperatures.
“The other thing is we have written off for a long time is the fact that starter fertilizer just doesn’t work on soybeans. I truly believe it’s because we were doing starter trials in May. From May 14th to June 1st there’s virtually no response to starter fertilizer. If you go April 5th planting date to April 23, all of a sudden you’re up into four to almost five bushels per acre yield gain,” Bowling said.
“In cold soils, you have a lot less microbiology activity in the soil. The warmer it gets, the more active the soil gets. So, I think there’s a number of reasons we’re getting good responses in earlier planting soybeans as we look to push planting dates earlier. We can start to do some different management practices that’ll pay.”
It’s the most forgiving quarter of growth.
“Think about what we do with soybeans in the vegetative stage. We burn them with Cobra, we roll with rollers, there’s a relatively low need for a lot of nutrition and as long as you don’t damage the plant below the cotyledons you’ll get those auxiliary buds to break out every time,” Bowling said.
“Get the herbicide programs done during the second quarter of growth before bloom starts because when you go into bloom it is a major shift in the soybean itself.”
The soybean factory has to be operating 24 hours a day at its highest efficiency in the second half of the growing season. R1 flowering marks the beginning of the third quarter.
“The nutrient demand skyrockets. The plant starts its reproductive process and probably the biggest thing I’ve notice is when your soybean starts blooming they’re not very tall,” Bowling said.
“Not only does the soybean plant have to get those reproductive processes starting, it still has to put on two-thirds of its overall plant height starting at R1. It’s like building a ship as you’re sailing down the river. It takes all hands on deck to get this done. That’s why we looked at the R1 timeframe to do that micronutrient mix because the demand curve for nutrition is amazing.”
He referred to research on nutrient uptake for 101 bushel per acre soybeans that was conducted by Rutgers University. The uptake of nitrogen, phosphorous and potassium is miniscule for the first 51 days compared to during full bloom, early pod and soft seed. Less than 9% of the nitrogen is used in the first 51 days and 91% beginning at full bloom through soft seed.
“All in all making sure that we’ve got the soybean plant operating at its highest capacity during the third quarter is huge because that’s really where all of the yield gains really come from,” Bowling added.
Pod formation marks the beginning of the last quarter.
“The source-to-sink relationship begins to change, when it goes from blooming and pod creation to actually filling seed. All the available nutrients begin to move to the seed,” Bowling said.
“There’s a huge opportunity for foliar feeding during the R1, R2, R3 pod phase. We see that every time we increase the pod fill length of time with fungicides, the longer we can keep this process going, the heavier our soybeans can get.”
Water usage also peaks to help move the nutrients from the plant tissue to the seed in the pods and September heat will provide a strong finish.
“It’s an animal that we can certainty corral. The more we understand the soybean the more we can push it to its limits. We need to build the best factory as early as we can and we need to focus on those key innings throughout the season,” Bowling noted.
“At the end of the day, water and sunlight in the second half is going to drive your success and making decisions to get that done is going to ultimately put your soybean factory and your plants in general in a position to win.”