Agronomy Blog

Seeding Large-Seeded Soybeans

by User Not Found | May 7, 2018

We have been wrestling with an industry-wide issue in soybean seed this year. Quite a bit of seed has been very large with a couple of varieties checking in at nearly 2000 seeds per pound.  Another issue we have faced, is low germination percentages. While the majority of our soybean seed is meeting the industry standard of 90% germination, there are some lot numbers testing between 80% - 85%.  For the areas of the country that are still on the front end of bean planting, I would like to discuss what caused this and give some recommendations on how to set yourself up for success in planting large, lower-germination soybean seeds.

The main reason we have encountered these seed conditions is due to weather.  The issues began with the extremely dry conditions early to mid-season.  This reduced the amount of branching in soybeans, reducing the number of nodes per plant, thereby reducing the number of flowers and pods.  As the season progressed and soybeans began to fill pods, we had very late rainfall in seed production fields.  For the most part, plants had already set the number of pods and number of seeds per plant.  Late rainfall could only add yield to already existing seeds, which caused them to swell and enlarge.  The late season moisture also made potassium available to the plant that had been unavailable due to dry soils earlier in the season.  The rapid uptake of late season moisture and potassium resulted in very large seeds.  To exacerbate this issue, as the soybean seeds experienced cycles of drying and re-wetting from the late season rain showers, the seed coats began to lose their plasticity.  Since the seeds were still enlarging, some seed coats experienced growth cracks.  These growth cracks have reduced the quality of some seed.

To set yourself up for success in getting these soybeans up and out of the ground this spring, there are several things you can do.

Planter adjustments.Ensure your planter is able to handle larger soybean seed.If using a drill, you can plug every other feed cup and further open the metering gates to reduce damage by the metering system.It would also be wise to lower the feed cup if your drill has that option.If you are using a finger pickup planter, you may need to change to seed metering plates with larger cells for larger beans.If using a vacuum planter, changing your discs and adjusting your vacuum pressure might be necessary.In all cases, check your operator’s manual for specific recommendations.

Seed Handling.Mechanical injury to fragile seed coats can continue to happen after the seed leaves the warehouse.If I have seen it once, I have seen it a thousand times.People will throw bags of seed like they are bags of feed.Several seed companies have a “three inch” rule when bagging and handling seed.They do not want bags of seed being dropped more than three inches when stacking seed.Remember, these bags contain living organisms.Please use caution when loading and unloading them multiple times in and out of the back of your truck.If you are using a seed tender, make sure your brush auger is being gentle with the seed.If you are seeing a high number of split beans after tendering them into your planter, you are further damaging the seed.As always, add the appropriate amount of graphite/talc to improve flowability.

Planting practices.There are several things to consider.Soil conditions are king when it comes to planting.Make every effort to plant into the best soil conditions you can, whether it is no-till or conventional till.Planting depth is another issue.If there is plenty of moisture in the soil, consider planting slightly shallower to get better emergence.However, in several areas we are looking at very dry soils and drought conditions.Soybeans must imbibe 50% of its weight in water in order to germinate.Therefore, the larger the seed the more water must be imbibed.In droughty soil conditions, this may negatively impact germination and emergence.In these conditions you need to plant into at least ½ inch of moist soil to promote uniform emergence.Also consider seed treatments.While seed treatments will not help you improve the germination of reduced quality seed, it will help protect from further losses due to fungi and insects.

Re-evaluate your planting populations.No matter the size of the soybean, the same soybean variety will have the same genetic material.Therefore, it also has the same yield potential.Larger seed has larger cotyledons and larger energy reserve.On the one hand, this larger energy reserve will help the seed emerge in difficult conditions.On the other hand, the larger cotyledons are more difficult to lift out of the soil and more energy is needed.Increase your populations to get the seeds closer together within the row to provide more of a “team effort” during emergence.Additionally, you might need to raise your populations in order to compensate for a 5% - 10% reduction in germination.An evenly spaced, uniform stand of 100,000 plants per acre is generally considered the threshold necessary to avoid replanting.

Every year is different.  This year will be different than any other year.  Every year also has its own set of challenges.  If you have any questions or concerns about your LG Soybeans, please do not hesitate to call your District Sales Manager or your Agronomist.  We would love to answer any questions you may have.  Thank you for your business and please continue to have a safe spring! 

Resources and Additional Information
http://msue.anr.msu.edu/news/recommendations_for_planting_large_soybean_seed
https://crops.extension.iastate.edu/files/article/OptimumPlantPop_000.pdf

Note: The information in this issue is based upon field observations and third-party information. Since variations in local conditions may affect the information and suggestions contained in this issue, LG Seeds disclaims legal responsibility therefore. Always read and follow label instructions. LG Seeds and design are trademarks of SCA Limagrain.

Download a copy of this Technical Bulletin:Tech_377 - Seeding Large Seeded Soybeans