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Determinate vs Indeterminate Soybeans

Forage Soybeans vs Regular Soybeans.

There are two types of soybeans grown across the United States, indeterminate and determinate. Growth of both types is similar during the vegetative growth phase until flowering. Once soybeans begin to flower, indeterminate and determinate plants differ dramatically in stem growth habit. Indeterminate plants continue to develop leaves on the main stem and branches throughout flowering. Determinate plants cease growth on the main stem at the R1 stage but leaves continue to develop on branches until the beginning seed (R5) growth stage.

Here is a great video by AgPhD that maybe can better explain this using some visuals.

So many in the wildlife business are familiar with Eagle Brand roundup ready soybeans. These are Indeterminate soybeans. The benefits of these are they grow tall, produce a large amount of forage and if not grazed too close to the ground, will regrow. The downside of eagle brand soybeans is that they won’t produce pods in many of the northern United States and if they do it’s rolling the dice as to how much pod fill there will be. Because they hold their leaves until a killing frost, they are not a type of soybeans that one would be able to overseed fall brassicas into it.

Real World Soybeans are a determinate pod bean that is moderately tall and has some palatability benefits and a lower shattering score. The pods hold tighter to the plants. These beans can be overseeded into them as they will drop leaves because of day length. Many people want to compare Real World Soybeans to Eagle Beans but they are not the same type of soybean. Ask yourself, are you looking at having a heavy pod producing soybean or a Indeterminant growth forage soybean. All soybeans deer will consume but there are traits that make all soybeans either less palatable or more palatable and very few people look at disease packages of the soybeans they purchase. I will discuss that at another time.

For those who want to overseed brassicas or other cover crops into soybeans, you want a soybean that drops it’s leaves early to reduce the canopy. This will result in a faster growth pattern for the overseeded forages. I have clients using soybeans as low as a .6 maturity just so they could overseed into them in early to mid August.

So, my challenge to everyone is to determine what type of soybean works best for your own particular situation. For those who practice plot rotation, what soybean might fit your program? As we move ahead, there will be less straight glyphosate (roundup ready) soybeans on the market for the average consumer to buy. With the new approval of roundup soybeans with the dicamba trait, there will be stricter regulations on these soybeans. You will need to look at using correct sprayer nozzles and water applications per acre to minimize drift.

With so many round up resistant weeds out there, other tank mix chemicals won’t touch weeds like palmer amaranth, water hemp, lambsquarters and giant rag weeds. This is another reason why I strongly recommend people to not use roundup soybeans and roundup ready corn year after year. If you are going to plant roundup soybeans, make sure you are not stunting weeds, but doing complete kill.

A couple other options for people that are looking for alternatives would be a mix I put together that has forage soybeans, an early pod beans, lablab and cowpeas. It explodes out of the ground and as a result canopies fast. Very few people have to spray this mix. If you do need to spray it, you can use pursuit or if grasses are the only issue, use clethodim. A last option would be to use non roundup pod forming soybeans or indeterminate non round up ready soybeans like Tara, Tyrone or Laredo’s. Again, you could use pursuit or clethodim as herbicide options. You would be getting out of the roundup rotation and in essence would have “refuge”. Refuge is a term all crop farmers are well aware of as you are not allowed to plant 100% roundup ready on your farms.

I hope this gives you all some food for thought.

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