Follow the Field Update #3 – Soybean Flowers & Corn GDDs

Follow the Field presented by A Farm Kid's Guide to Agriculture

It’s Follow the Field Friday! Not much to update other than the hot weather has been great for the crops – they need as much sunshine as they can get after the slow start this spring. Ironically, we wouldn’t be upset over a nice rain or two, either.

This was a busy week here in Stanford. The 4-H club I help lead runs a food pantry in town. We discovered on Tuesday that one of the two refrigerators we have in the food pantry stopped working, which was especially inconvenient as this weekend is the monthly food pantry distribution. Fortunately, we hadn’t gone for our monthly food pickup at the food bank yet since that’s normally scheduled for Wednesday mornings, but we were still left scrambling to figure something out so the refrigerator outage wouldn’t affect our patrons. We shared our predicament on our Facebook page Tuesday night and put out the call that we were searching for a used refrigerator to replace our old one. First thing Wednesday morning, we received a phone call from the church next door offering us use of their refrigerator so we could still pick up and distribute our normal quantity of refrigerated items during food bank pickup on Wednesday. Then we received another call from an individual wanting to cover the cost of a replacement refrigerator, which was a huge blessing as we weren’t quite sure where we were going to find the funds to purchase the replacement. We received several messages all day Wednesday with links to used refrigerators for sale all over the area. We went to look at one Wednesday evening and ended up purchasing it and bringing it back to the food pantry on Thursday evening. How cool is it that our rural community was able to come together so quickly to support the food pantry?

Anyway, here are the field updates.

7/12/19 UPDATE:

COVER CROP SOYBEANS (56 DAYS)

If you recall from previous updates (week 1 and week 2), these soybeans were planted on May 17th into a standing cover crop. I’m happy to report that you can barely see what’s left of the cover crop anymore.

soybean height on July 11 2019

The soybeans didn’t gain much in height this week, but they did begin filling out and are beginning to close the canopy between rows. Because of the cover crop, we didn’t see many issues with weeds after the soybeans were planted, and the canopy will suppress any weeds that might poke through the cover crop mulch later this summer. There are still plenty of Japanese beetles hanging around and munching on the beans, but there isn’t enough leaf damage to warrant an insecticide application yet. There are also a few bean leaf beetles in this field, so we’ll continue to keep scouting and make sure there are no big pest problems.

soybean canopy

Soybeans mature based on day length. The longest day of the year, or the summer solstice, was on June 21, with every day afterwards becoming slightly shorter. This triggers the maturity process in soybeans. So even though they were planted late, they’re beginning to flower. This is what we consider the R1 growth stage, also called beginning flower. The plant will advance to the R2 stage, or full flower, once more flowers appear. Most varieties of soybeans grown in Central Illinois are indeterminate soybeans, which means that these soybeans will continue vegetative growth and will put on more leaves and grow a little taller even though it’s begun flowering.

soybean flowers

CORN (38 DAYS)

It’s amazing how quickly corn grows. Two weeks ago today, this corn was 16 inches tall. Last week, it was 25 inches tall. Now it’s outgrown my yardstick.

Corn height on July 11 2019

We measure corn growth potential in what we call heat units or growing degree days (GDDs). To explain this simply, we use a formula to determine the number of GDDs in a given day to help measure the potential for plant development. There are a few rules about the highest maximum temperature (86°F) and the lowest minimum temperature (50°F) to use based on what conditions corn will grow in. That formula is as follows:

  • Daily Average Temperature (°F) = (Daily Maximum Temperature °F + Daily Minimum Temperature °F) / 2
  • Daily Corn GDD (°F) = Daily Average Temperature °F – 50 °F

So if we wanted to figure out yesterday’s accumulated GDDs, we would use the observed maximum temperature (or high) of 85°F and the observed minimum temperature (or low) of 63°F.

  • Daily Average Temperature = (85°F + 63°F) / 2 = 148 / 2 = 74°F
  • Daily Corn GDD = 74°F – 50°F = 24 GDDs

between the rows of cornThis corn is a 113-day hybrid, which is an indicator of how long it’ll take this hybrid to mature. There are hybrids out there with later maturities and earlier maturities. Farmers determine which hybrid of corn to plant based on where they live and their planting date. If we would’ve had to wait one more week to plant this corn, we probably would have switched to an earlier maturity, like a 105-day corn.

This 113-day corn will require about 2600 GDDs to bring it to maturity in our area, so these warm days are really helping.

NO-TILL SOYBEANS (34 DAYS)

These soybeans are still quite a bit smaller than their earlier-planted counterparts, but they’re making good progress and look good for their growth stage. There still aren’t any noticeable pest issues, which is a really good thing for us right now. These soybeans have not yet flowered, but I expect that will begin within the next week. For now, we’ll hope that they keep growing well and can fill out with more branches and leaves so that they can hold more pods and produce more soybeans this fall.

soybean height on July 11 2019

Soybean rows

That’s this week’s update. I’ll be back with more photos next week – looks like I’ll need to bring the measuring tape to measure the corn. 😊

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