By Kent Thiesse
Across the Corn Belt, the possibility of this year’s corn (and soybean) crops falling prey to the first frost is a key concern.
Average first frost dates range from September 20 in northern Minnesota to October 15 in southeast Minnesota and eastern Iowa. With delayed planting across parts of Minnesota, Iowa and South Dakota, corn and soybeans reaching maturity by those dates could be doubtful.
The level of growing degree units accumulated at the University of Minnesota Southwest Research and Outreach Center at Lamberton as of August 26 (1,938) is 6 percent below normal and 350 GDUs behind last year’s standings.
Additionally, less than a third of Minnesota’s corn crop had reach “dent” stage by that date, well behind normal. For most commonly grown corn hybrids, physiological maturity takes another three to four weeks after dent stage, and with the run of cooler temperatures lately, that could take even longer.
Corn is considered safe from a killing frost once the corn reaches physiological maturity, which is when the corn kernel reaches the “black layer” stage. At that stage, kernel moisture is usually at 28 to 32 percent. Ideally corn should be at 15 to 16 percent kernel moisture for safe storage in a grain bin until next spring or summer.
Even beyond the corn reaching maturity in the coming weeks, favorable weather conditions will be required to allow for natural dry-down of the corn in the field, in order to avoid high corn drying costs this fall. It is likely that a high percentage of the 2019 corn crop will be stored in farm grain storage until next year.
Soybeans are also in dire need of favorable growing conditions through September in order to beat out the first frost. Timely rainfall during August should be favorable for soybean growth and pod setting; however, that advantage has been somewhat offset by the extremely cool weather during much of the month.
Based on the August 19th USDA Crop Progress Report, only 55 percent of the corn crop and 60 percent of the soybean crop in Minnesota is rated good-to-excellent, well-below crop ratings for mid-August in recent years. The higher crop ratings for corn in surrounding states were 65 percent in Iowa, 73 percent in North Dakota, and 62 percent in South Dakota.
The “good-to-excellent” for soybeans were 61 percent in Iowa, 63 percent in North Dakota, and 56 percent in South Dakota.
Nationally, 53 percent of the corn crop and 56 percent of the U.S. soybean crop was rated “good-to-excellent” on August 19, which compares to 68 percent for corn and 65 percent for soybeans in 2018.
Highly variable yields across regions are now expected in Minnesota and surrounding states. Statewide yield estimates from the recent “Pro Farmer” crop tour came in well under the yield estimates in the last USDA Crop Report, although those numbers are likely to become closer together with later reports based on recent history.
The 2019 Minnesota corn yield was projected at 173 bushels per acre in the USDA report, compared to 167 bushels per acre in the “Pro Farmer” (PF) tour. Other estimated 2019 statewide corn yield estimates were Iowa at 191 bushels per acre (USDA) and 181 bushels per acre (PF) and South Dakota at 157 bushels per acre (USDA) and 140 bushels per acre (PF). USDA is estimating the 2019 national average corn yield at 169.5 bushels per acre, compared to a projection of 163.3 bushels per acre (PF).
The situation is similar for 2019 soybean yield estimates. Minnesota is projected at 45 bushels per acre in the USDA report, compared to 42 bushels per acre by Pro Farmer. Other estimated 2019 statewide soybean yield estimates were Iowa at 55 bushels per acre (USDA and PF) and South Dakota at 45 bushels per acre (USDA) and 39 bushels per acre (PF). USDA is estimating the 2019 national average soybean yield at 48.5 bushels per acre, compared to a projection of 46.1 bushels per acre (PF).
Differences in those two sets of estimates could be significant because they represent a large difference in the total 2019 corn and soybean production levels, which could impact grain market prices in the coming months. The current difference between the USDA national corn yield estimate and the Pro Farmer estimate is a difference of 6.2 bushels per acre. Based on the USDA estimate of 82 million harvested acres of corn in the U.S. in 2019, that yield difference represents over one-half billion total bushels of corn.
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