Ag Weather Forum

The Monday, August 12 round of USDA reports will add some clarification to the crop outlook scenario in this extremely varied season. Ahead of those numbers, here are some thoughts on potential corn yield impact from the late plantings that we saw in much of the northwestern Corn Belt this year. These comments are from Iowa State University extension agronomist Roger Elmore in a farm magazine article earlier this summer:

“Lower yields – Certainly late planting normally reduces corn yields. Based on actual experimental data from 2010 and 2011 and from simulated crop model results across four Iowa locations, yield potentials of early-season hybrids range around 75 to 85% when planted on June 11th, and from 50 to 70% when planted on June 25th. These are relative to a typical April 30th planting date with full-season hybrids. Yield potentials in Central and SE Iowa were on the high side of these ranges and those of NW and NE Iowa were on the low side of the ranges as you might expect.

Lighter kernels - Frost prior to physiological maturity, limits kernel weights resulting in reduced yields. In addition, kernel dry-down rates slow. Table 1 includes physiological maturity dates for hybrids with a range of maturities planted at three dates at four Iowa locations based on computer model simulations. Also included is the probably of a frost occurring on that date. Depending on the hybrid and location, June 11th planting provides reasonable opportunities for a crop to mature before frost.

Wet grain – An obvious result of late planting either with or without a death-dealing premature frost is wetter grain. Grain is physiologically mature when it reaches around 35% (± 2%) moisture. Remember that grain matures physiologically slightly before the black layer forms. Crop drying costs will increase.

At least two concerns surface when we think about late-maturing corn in addition to the concerns about frost, kernel weights, and wet grain mentioned above. First, many fields have multiple planting dates and thus plants of various developmental stages due to replanting in ponded areas and side-hill seeps among other things. At harvest, (you can) expect large ranges in grain moisture across fields like this. Variability like this may affect yield monitor calibrations as well as artificial grain drying processes. You may need to compromise combine adjustments in these situations too, or make on-the-go adjustments. Second, scouting fields before harvest is even more important this year than normal. Stalk quality, stalk rots, ear retention, and standability will likely vary considerably among hybrids and the wide range of planting dates. Schedule harvests based on accurate scouting.

Preparing for the 2013 corn harvest will be important to your success in terms of profitability as well as reducing you stress level in difficult years like this.”

Bryce

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