Soybean Secrets: Unlocking Higher Yields
Season 1, Episode 2
Soybean Secrets: Unlocking Higher Yields
What’s holding your soybeans back? In this episode, we sit down with Alex Renk, head of soybean selection and research at Renk Seed, to explore the full range of strategies to boost your yield. If you’re looking to push your crop to its full potential, this one’s for you.
Intro
When we want high yields in soybeans, we usually come at it by thinking about adding yield. That is probably not the right mindset. The proper way to think about soybeans is how to not lose yield.
Soybeans are pretty adaptable to conditions and they always try their best to produce the most seed. The plant doesn’t demand much up until flowering. At that point, it will try to put on as many flowers as possible. From these flowers, it will start putting on pods. Here is where things get crucial. With adequate nutrients and moisture, it will fill every pod it can with three or more beans. Any stresses with these will eat away at this ideal, either by aborting pods or beans inside the pods. The less stresses, the better the soybean will maintain its yield.
Soil
High-yielding soybeans want to be fed properly. Soybeans use a lot of phosphorous (P) and potassium (K). Nitrogen levels can be ignored, unless you have extremely high levels. You should be relying on nitrogen-fixing bacteria for your source of nitrogen. These little wonders can take atmospheric nitrogen and convert it for soybeans to use. If you remember your high school chemistry, then you know the atmosphere is made up of 78% nitrogen. When nitrogen levels are too high, this can suppress the nitrogen-fixing bacteria from colonizing the roots of the soybeans and will hurt yield.
Now that we have restricted sulfur dioxide coming from our energy production (the old acid rain), we are seeing a renewed need for sulfur (S) to be available for soybeans. Soybeans do respond well to sulfur, but sulfur takes time to be available for use by soybeans. In-season application will not be a benefit. It needs to be applied in prior years.
Regular soil sampling for P, K, and S levels is very important. Trying to make up for deficiencies through in-season banding or foliar feeding is a tough sled. The waxy protective coat on soybeans and the compact root mass restricts the plants’ ability to absorb large quantities of nutrients applied in season.
Micronutrient applications can work. For example, certain acres in Michigan can use a shot of magnesium. I would be looking at these applications only if you know you have known deficiencies.
On average, soybeans planted early show roughly a 4-bushel advantage over soybeans planted later.
Plant early
Common practice is to plant corn first and then follow with soybeans. To maximize yield, this is not the right way to do things. On average, soybeans planted early show roughly a 4-bushel advantage over soybeans planted later. The reason for this is a longer growth window, encouraging extra nodes to develop on the plant. Nodes are where pods are set. In turn, having more nodes can generate more top-end yield.
Caution: planting early has increased risks. There is a much higher risk from Sudden Death Syndrome and white mold. An early spring freeze of soybeans will result in replanting. Factor this into your planting strategy.
Seed does matter
With Renk being a seed company, we might be a little biased towards seed selection. Okay, a lot biased. There are very good reasons for this.
Some problems are best addressed through seed. Iron deficiency chlorosis in certain western acres can only be handled economically by variety tolerance. White mold tolerance in varieties can go a long way toward defusing potential white mold disasters. Having brown stem rot resistance takes out a subtle yield robber. Having varieties that carry the Peking gene for cyst nematodes can really help yield in high-infestation acres.
There can be huge differences in yield potential among varieties. Breeding has been marching forward and we commonly see 2-bushel gains with each new breeding class.
Seed treatment is also very important if you are chasing high yields. Planting early means having treatment with fungicides to fend off Sudden Death Syndrome, pythium, phytophthora, fusarium, and other early-season diseases. This is also your chance to make sure you have enough nitrogen-fixing bacteria for your soybeans. These should be components of your seed treatment.
Seed treatment is also very important if you are chasing high yields.
Proper planting
For high yields, proper planting also comes into play. Seed is very expensive and I would like to see people use it wisely. I think a planter does the best job as it puts the seed at a more uniform depth and spacing. Keeping your harvest population above 90,000 per acre helps not lose yield from poor stands. My rule of thumb is 140,000 planting population unless you have a great seed bed.
In theory, the narrower the row the better yield. However, narrow rows also tend to increase pressure from diseases, primarily white mold. You will also suffer some yield loss from sprayer wheel traffic. For most, standard 30” rows are just fine.
Planting depth should be ¾” to 1½”. I prefer more towards ¾”. The soybean has to push the entire seed out of the ground and if you plant too deep, that can be imperiled.
There is no guarantee they will do any better than earlier varieties but I think they give the highest chance of utilizing late August rains when earlier maturing soybeans are done filling.
Which maturity?
Is high yield your goal? If so, then I would recommend leaning towards full-season maturities. There is no guarantee they will do any better than earlier varieties but I think they give the highest chance of utilizing late August rains when earlier maturing soybeans are done filling.
Spraying
Weed control is always important. Any weed presence competes with soybeans for water, nutrients, and sunlight. Eliminate them with extreme prejudice.
White mold requires cool temperatures with moist conditions. You can skip fungicide for white mold control IF you don’t have these conditions in late June and early July. Spraying a fungicide for white mold can be very tricky. White mold infests plants through soybean flowers. Preventing white mold means that you need to spray right as the soybeans start to flower and follow up with another spray right before pod set. Once white mold is in the plant, it is too late.
You should look at spraying right before pod set with other diseases. Know that using fungicides can give a net benefit.
The elephant in the room: Do you know what the best part is about farming? Doing everything right and then either getting too much rain or not enough!
Soybeans in the Midwest need moisture at two key times during the growing season. Early on to germinate and get out of the ground. Then again during pod fill. Between those two times, as long as the plants survive, you should do just fine with yield. If moisture is plentiful, the plants will be taller but the number of nodes will be the same. Moisture during pod fill is the most crucial ingredient to deciding yield. Go to church. Buy a cloud seeder. Don’t sell your soul—it is not worth 10 extra bushels.
Pushing the envelope
Although I am not going to recommend it myself, there is some evidence you can beat up the growing point of the soybean plant in hopes of causing the plant to branch. Thus, you increase the number of nodes. In turn, this could increase overall pod set. This is done by rolling soybeans and/or spraying them with an herbicide like Cobra. In addition to adding more nodes, you will delay maturity and maybe put the plants in a better moisture situation.
Rolling emerged beans is a delicate process. It is easy to do more harm than good. Same with spraying Cobra. While I know some can pull it off, I would still stick with the less risky options mentioned above for increasing soybean yields.
Conclusion
Proper seed selection, along with early planting into nutrient-rich soil, is the basis for successful results. Once those plants get going, minimizing yield-robbing stresses is critical. With good moisture in August, beans can put up some great yields.
... minimizing yield-robbing stresses is critical.
Frost and Cold Temperature Damage to Small Soybeans
Frost and Cold Temperature Damage to Small Soybeans
- Soybeans respond differently to frost compared to corn because the growing point is exposed to weather as soon as the cotyledons emerge.
- Understanding the effects of weather conditions on soybean at different growth stages can help determine the best management options.
Soybeans vs. Corn
Soybeans are more susceptible than corn to frost and cold temperatures. The growing point for corn remains below ground until corn reaches about V5 (5 visible leaf collars) growth stage. Comparatively, the growing point for soybean is above ground and exposed to the elements as soon as the cotyledons emerge.
If the main growing point (also called the apical meristem) is damaged, soybeans have a greater ability to recover than corn. Soybean plants can produce new growth auxiliary buds found at each node. When this regrowth occurs from the node where the cotyledons or unifoliate leaves were attached, it has been referred to as psi syndrome due to the shape.
Will the Soybean Plant Make It?
Frost damage to soybean plants can occur when temperatures range between 28 to 32 °F. Temperatures of 29 to 30 °F may be tolerated for short periods of time when soybeans are in the VE (emergence) to VC (unrolled unifoliate leaves) growth stages. Several days of cool temperatures can harden a plant, and when this occurs, temperatures of 28 °F may be tolerated. Complete death (buds, stems, and leaves) is not expected until temperatures remain at 28 °F for an extended period of time for sensitive plants. Soybeans in the VC stage are slightly more frost tolerant compared to soybeans in the V1(first-trifoliate) and V2 (second- trifoliate) growth stages. Soybeans with emerged trifoliate leaves (V1 and V2 growth stages) become more susceptible to temperatures below 32 °F for any extended time.
Patience is needed to determine if an individual soybean plant is likely to survive a frost. It helps to wait a few days before evaluating the potential for new growth at the auxiliary buds. In Figure 1, the plant on the left has been injured by frost for 24 hours and may have tissue death below the cotyledonary node. The plant on the right was injured by frost, but only down to the area above the cotyledonary node, allowing for regrowth from the auxiliary buds at that node. The growth from those auxiliary buds will be similar to that of the original plant had it not been damaged by frost. The odds of the injured plant on the right producing a respectable yield potential are very good.
Figure 1. Examples of frost damage to soybeans. Plants with severe frost damage that begins below the cotyledonary bud (left) may have tissue death. If regrowth at the cotyledonary node is seen (right), plants may contribute to yield.
Will the Soybean Plant Make It?
Replanting a field of frost-damaged soybeans demands more consideration since soybeans are more susceptible than corn to frost and cold temperatures. However, soybeans can tolerate stand reductions fairly well. Often, if a soybean stand is evenly distributed, replanting is not recommended unless populations are less than 100,000 plants per acre. As the season progresses, vigilant scouting should continue for seedling blights and environmental damage in soybean fields, especially those damaged by frost.
There are many resources available addressing soybean early growth and survival. Additional information on evaluating soybean early growth and survival can be found in the video blog developed by Extension Specialist Shawn Conley at https://ipcm.wisc.edu/blog/2014/05/new-video-soybean-emergence-and-germination-common-issues/.
Sources: Berglund, D.R. 2004. Spring frost damage to crops could be a problem. News. North Dakota State University. www.ext.nodak.edu. 120601023004
For additional agronomic information, please contact your local seed representative. Developed in partnership with Technology Development & Agronomy by Monsanto.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. ©2017 Monsanto Company.120601023004. 051215SEK
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