I spotted an old friend in a local restaurant having dinner with his wife and stopped by to say hi. It was April 21. I'd been no-tilling soybeans that day for a neighbor. The friend works off the farm, but still farms about 600 acres.
"Planted soybeans? Are you nuts? It's way too early for that!"
"The ground worked very well," I countered, meekly.
"The soil is still cool. It's downright cold. I've been that route before. They won't come up. You're crazy!"
His wife gave him the 'calm down' look. I thought he was my friend. Friends can disagree. We parted on friendly terms. I certainly wasn't the only person planting soybeans in Indiana that week. Nevertheless, I decided to look back at some data to see if maybe I was crazy.
Beck's Hybrids have conducted date of planting studies for soybeans for the past 12 years at their home farm near Atlanta, about 30 miles north of Indianapolis. It's part of their practical farm research program. They don't apply statistics to results, but they publish results no matter how they come out.
As with corn, last year was topsy-turvy. But even including last year, here are their findings based on a 12-year average. The top yielding window, at 107% of the average yield for the entire study over 12 years, is April 3 to 7! Second high is April 9-13, at 104%. That's followed by March 21 to March 31 and April 15 to 28, at 102%. Maybe I didn't plant early enough!
May 1 to 11, often thought to be a prime planting period, and it is, was next, at 101% of average. May 14 to 27 was respectable, at 98% of average. Yield potential slipped to 91% of average at May 29 to June 1, and bottomed at 85% for June 5-17.
Yes, last year the results were different, Beck's sources note. Highest yield for an average of two varieties came on beans planted May 27, at 71.8 bushels per acre. Second last year were beans planted June 5, at 69.9. Historically, early April plantings in this study, even with last year included, have outyielded early June plantings by 14 bushels per acre.
May 20 posted 67.9 bushels per acre, followed closely by the March 21 planting at 67.4- explain that one! April 24 and May 11 finished in a dead heat, at 64.3, lowest yield in the plot last year.
I'll place my bets on the long-term average. This data and results from other sources say planting soybeans in April works.