Food Plots: Determinate vs Indeterminate Soybeans

Soybeans are a warm-season, annual legume and are one of the most marketed and divisive food plot foods. They can also be one of the best deer attractants and highest sources of protein for deer (upwards of 20-30%). That doesn’t necessarily mean it’s the right solution for every property, but in addition to figuring out the difference between all the brands and labels, you also need to decide if you want determinate (regular) or indeterminate (forage) soybeans.

Growth Stages

Before understanding determinate vs indeterminate soybeans, it’s important to understand the stages of soybean growth. After a 30-40 day vegetative stage of growth, soybeans enter their reproductive stage in which pod formation begins.

Once flowering beings, it usually takes around 30 days to begin forming pods and another 40-50 days to hit maturity. This gives soybeans a full cycle of around 130 days, or just over 4 months, in perfect conditions. For more information on the various stages of soybean growth, I highly recommend checking out this free resource from Purdue University.

Determinate (regular) soybeans stop growing on the main stem as soon as they enter R1. They will continue to develop leaves on branches but will not grow in height. This also means that if a deer comes by and eats the main stem after entering R1, the plant is likely going to fail to produce any significant forage or pods. Indeterminate (forage) soybeans on the other hand will continue to go through its vegetative and reproductive states until the first freeze. This means they’ll continue to produce forage and can grow upwards of 4-5 feet tall as long as they aren’t eaten down to the ground. If leaves or the main stem are eaten, they’ll split and continue to push more branches, leaves, and flowers as conditions allow. One final thing to note is soybeans being determinate or indeterminate doesn’t affect how palatable deer find soybeans.

The Farmer’s Approach

If you draw a horizontal line right through the United States, you’ll likely find that soybeans planted south of that line are determinate. Although there is a much longer growing period in the south, most farmers want to make sure their harvest happens before the heavy rains, storms, and hurricane season that hits in August. Determinate soybeans are a great choice since you know (within a small variance) exactly how long it will be between planting and harvesting. You’ll start to see a wider usage of indeterminate soybeans north of the horizontal line. The north has shorter growing seasons and farmers want to get the most out of what they can. In the north, some fields might not get planted until June and the season can end in August or go through October. The opposite can also happen where you can plant in early May and get growth through September.

The Hunter’s Approach

I believe that you shouldn’t go all-in with soybeans. They are a tough plant to grow and maintain, and they’re expensive when compared to other food plot alternatives. Due to their attractiveness to deer, the size of the field you would need before the deer eat them all the way down (and usually before prime hunting season) is prohibitively expensive. In addition to the expenses, as a hunter your food plot would be competing with manicured ag fields produced by farmers who do this for a living.

I have previously planted soybeans in a small 3/4 acre plot protected by a dual zone fence. It worked great as a 1-2 week attractant when I removed the fence, but the deer herd completely decimated the plot in that time. This 1-2 week period also threw off any previously established patterns to other parts of the property. In my opinion, soybeans are best planted in a later summer mix with things like winter peas, rye, and brassicas. The goal would not to be produce pods but to produce young, green soybean leaves. Unless you have thousands of acres, it’s unrealistic to think your food plots are growing or otherwise influencing the local deer heard with soybeans. It’s also too expensive and risky to dedicate whole plots to soybeans. Think about it, if you had $100 for a food plot would you put well over 50% of that budget towards one food plot attractant like soybeans that will not last until prime hunting season or would it be better to put 20% towards 4-5 different food plot seeds with varying levels or attractiveness at different periods that last the entire hunting season and even the late winter seasons when deer need food the most? This is how small land owners can influence the deer herd.

If you decide to go with indeterminate soybeans, it really comes down to if you want them to be glyphosate-resistant (Roundup Ready) or not. If so, you’ll be looking at spending a little more and likely looking at Eagle Seed forage soybeans. Otherwise if you don’t need glyphosate-resistant soybeans, you can go with something like Loredo or Tyrone forage soybeans. In either case, the most effective indeterminate soybean food plot I ever planted was successful because I implemented a dual-zone fence strategy. Make sure to include that in your list of expenses too and make sure to set your expectations to have that food plot wiped out well before the rut.