The Case NOT to Water Soybeans

The Case NOT to water soybeans from Central Valley Ag on Vimeo.

by Keith Byerly

by Keith Byerly

I know that for the most part, the month of June has been Hot and Dry for most of us. There have been a few occasional reprieves, but by and large, we have seen very little rain in most places. And in the beginning and middle of the month, we saw a lot of people eager to pump water. I could go into another AquaSystems rant on this, but honestly, I think we saw the trigger pulled too early in many cases. However, I am confident that it hasn’t been time to water soybeans yet. And I think that history makes a pretty good case for that.

I think that there is plenty of research out there now that goes with what we have learned by trial and error. We need to delay irrigation on Soybeans until early pod formation (end of July). As long as we can catch some rain, our crop can get by to that point. Many people don’t believe this until they have had a moisture probe, but our soybeans root down more than our corn does in most years. If we do not give the soybeans too much supplemental water along the way, they will easily root down to 30” in an average year.

Watering soybeans in June except when in drought-like conditions leads to taller soybeans that have more biomass. This will often manifest itself later on in the season as lodging, or we will see diseases like white mold set in because of lots of leaves and a lack of airflow.

We started out this growing season in almost all areas with a full soil profile. Now for my sand farming friends, that might only mean 2” of water in Three Feet of soil, but from the rest of you, it’s typically between 3.5”-5” of water. So let’s do a little math. Soybeans will use about 20” of water in a growing season. About half of that water is used in August, since from R3 to Maturity takes 9” give or take. Up until we hit R1, we are using a short 1” of water per week. That means with a full soil profile and occasional rainfall; we have this soybean crops needs filled pretty well.

Now of course, here is where AquaSystems comes into play. When it’s dry, it’s a tricky proposition to irrigate beans in June and July. How they are rooting down, moisture levels throughout the profile and daily use are all pivotal in making the call. Coincidentally, those are all things that AquaSystems can help you with. My take home for the day is this, all of our CVA regions have a couple of fields that your FSA or ACS Regional Specialist can share data on. It is too late to add a probe for this season, but, working with our team, we can help you with an idea of what to do.

History has taught us that building a bunch of vegetative material on our soybeans is not a recipe for higher yields. However, managing our irrigation is the recipe for better yields, better plant health, and better profitability. I have watched enough soybean soil moisture probes in June and July the past five years to know two things. First, observing soil moisture probes in soybeans in June and July is boring compared to August and September when water use jumps, and yield is being determined. Second, watching soil moisture probes in soybeans can be enlightening if you look for the management opportunities, and not just when to irrigate. So engage in a conversation with us about Soybean irrigation, and I ask you to be slow to pull the trigger and make sure it is your best choice before you do so.