Corn planting time in a “normal” spring
Yes, a year does make a lot of difference – in 2012, we had 5 percent of the Illinois corn crop planted by April 1 and 17 percent planted by April 9. This year, the April 8 issue of Illinois Weather & Crops from the Illinois office of NASS gives no percentage planted as of April 7, which means that less than 1 percent had been planted. There has been some planting this week, but with soils still cool and rain in the forecast, along with a drop in temperatures into the 30s at night later this week, many producers are proceeding with caution.
According to the Illinois State Climatologist’s office, soil temperature at the 4-inch depth at 10 AM averaged in the mid-30s on March 20, 2013, compared to the upper 50s on the same date in 2012. Soils have warmed since then, but according to the DTN/Illinois Farm Bureau website, ranged from only the mid-50s in southern Illinois to the upper 30s in the northern edge of the State on April 9, 2013. With cool weather returning late this week, soil temperatures are likely to decrease. And wet soils warm more slowly than dry soils, so we may be in for some “patience-requiring” weather.
Cool soils by themselves don’t represent much threat to corn seed, but soils that are both cool and wet slow germination and emergence, and provide an advantage to microbes in the soil that can attack corn seed. Some producers may be inclined to set planting depth a little shallower in an attempt to help with emergence under such conditions. That can help sometimes, but the shallowest-placed seed after planting should never be less than about 1.25 inches deep, and planter settings should seldom be less than 1.5 inches deep. Remember, too, that soil close to the surface both warms faster during the day and cools down faster at night than soil beneath the surface, so the overall effect of shallower placement on temperature experienced by the seed and seedling might not be very predictable.
Compared to the corn that was planted in mid-March last year and suffered frost damage the second week of April, the crop this year should be in little danger of frost damage. Chances of frost drop quickly as April progresses, to very low levels by the end of the month in all but the northern edge of Illinois. That doesn’t mean zero chance – we had frost through much of central and northern Illinois the first week of May in 2005 – but frost through mid- or even late April is not likely to damage corn this year because there won’t be much corn emerged and growing if frost occurs.