Thirty years ago, maybe even more recently that that, it wasn't hard to find a farmer who didn't want to plant corn until May 10 and soybeans until May 20. Likely they didn't have so many acres to plant, but many days went by in those years when equipment sat still when today it would be in the field.
This spring unfolded and offered the opportunity for many to push the envelope, planting both corn and soybeans in late March and into early to mid-April. At least a few of the soybeans planted early were replanted, although it appeared to vary with soil type and conditions. Some soybeans planted on light soils, such as along creek bottoms, in central Indiana during late March are doing very well.
One big rain now takes the season form early to right on time to late, especially for corn planting. That's the risk you took if you passed on the early April window of planting. Yes, cold temperatures returned. But farming is a gamble, as they say.
The Purdue University Corn & Soybean Field Guide, 2012 edition, has numbers based on averages for what happens to corn yields planted after May 10. The sweet spot in the table in that booklet is the last week of April at 28,000 to 32,000 plants per acre. Before that and after that, yield potential is estimated at something less than 100%, even at optimum stands.
By May 10, getting 96 to 97% of yield is still possible, on average, at the aforementioned populations. But on 200 bushel per acre corn land, that's dropping six to eight bushels per acre, which can be $30 to $40 in extra revenue off the top.
If rain keeps you out to May 20, corn planted then can be expected to yield about 91% of its' original potential. Now we're talking yield drops of 18 bushels per acre, or up to $90 per acre at $5 corn. If you've still got 500 acres that don't get planted until then, that's $45,000 in lost revenue.
One two-inch rain may stand between you and those statistics. If you haven't planted everything yet and conditions are right, should you be planting? You decide.