Good Crop Growing Conditions in Most Areas


June 29, 2020



For generations, the standard measure for corn growth was “knee-high by July 4th, which meant that the corn plant should be able to produce a crop for that year. Of course, most farmers a couple of generations ago had much lower yield goals for their corn than the farmers of today. Today, “waist-high” or higher corn by July 4th is a more typical and has resulted in some very good corn yields in most areas of the Upper Midwest in recent years, except for 2019. It is difficult to get exceptional corn yields in the region, if corn is only “knee-high” or smaller on July 4th.


In much of Minnesota and Iowa, the 2020 growing season started out earlier than normal, with most corn planted in the last half of April and first week of May. In recent weeks, excessive rainfall and severe storms with wind and hail has resulted in crop damage and poor growing conditions in some locations. Most corn in Southern Minnesota and Northern Iowa that was planted by early-May will not only exceed “knee-high” by July 4th but will likely exceed “waist-high”. Some of the corn planted in April in areas with favorable growing conditions will likely approach or exceed “shoulder-high” by July 4th, which has not occurred in most parts of the region since 2015.


Corn and soybean development in most areas of Southern Minnesota and Northern Iowa continues to be slightly ahead of normal, as of late June, due to earlier than normal planting dates and above average temperatures in June. The accumulation of “growing degree units” (GDU’s) is one measurement of crop development. The total GDU accumulation at the U of M Southern Minnesota Research Center from May 1 through June 24, 2015 totaled nearly 800 GDU’s, which is about 7 percent ahead of normal and compares to a GDU accumulation of only 633 on the same date in 2019. In most areas of Southern Minnesota, the 2020 GDU accumulation in late June is probably the highest since the drought year of 2012.


The old saying “rain makes grain” may hold true in many instances, but excessive rainfall amounts in late June could result in crop loss in portions of South Central and Southeast Minnesota, along with adjoining areas of Western Wisconsin. Some local areas within this region received 5-8 inches of rain or more on June 28 and 29. This has caused considerable standing water in fields, which could result in some crop damage. Some farm operators with farmland in the flood plain that avoided the initial crop loss this Spring could now experience flooding and crop loss due to the rising rivers and streams. Interestingly, most portions of Southwest Minnesota and the very dry areas of West Central Minnesota received very little rainfall during the two days.


June rainfalls have been quite variable across the region, with most areas of Upper Midwest receiving adequate to excessive amounts of rainfall during June; however, there were some very dry areas beginning to develop in portions of Central, West Central and Northwest Minnesota by late June. Total rainfall at the Waseca Research Center as of June 24 was 3.27 inches; however, Waseca received another 1.54 inches overnight by 8 AM on June 29, with rain continuing. This will put the total rainfall for June very close to the normal June rainfall of 4.69 inches. The total precipitation for 2020 at Waseca is now just below 17 inches, which is just slightly above normal for the first six months of the year. Some areas of South Central and Southeastern Minnesota have received much higher amounts of precipitation in the month of June, while many portions of Western Minnesota have received lower rainfall amounts during the month.



Stored soil moisture levels, which were near capacity prior to planting this Spring, have likely stayed near maximum levels in most areas of Southern Minnesota by late June. As a result, any major rainfall events can quickly result in large amount of standing water in crop fields. The wet field conditions and recent frequent rainfall events in some areas has resulted in problems for timely applications of post-emergence herbicides for weed control. The excessive rainfall can also result in some leaching of available nitrogen in the soil profile; however, drier weather conditions in early June allowed corn roots to move deeper into the soil profile. There are also some areas with yellow, chlorotic-looking soybeans due to the excessively wet soil conditions, which should improve with some warmer and drier conditions. On the other hand, many areas of the region have experienced nearly ideal growing weather in the month of June and have crop conditions that are good to excellent.


Based on the June 22 weekly USDA Crop Progress Report, 85 percent of the corn crop and 81 percent of the soybean crop in Minnesota was rated “good-to-excellent”. Only 2 percent of the corn and soybeans were rated in “poor” condition. This is the best late June crop ratings in Minnesota in several years. Iowa also had excellent crop ratings on June 22, with “good-to-excellent” ratings on 85 percent of the corn and 84 percent of the soybeans. Other States with “good-to-excellent” ratings of 80 percent or more for corn included Nebraska, South Dakota and Wisconsin. The corn ratings in the Eastern Corn Belt were not as robust, with Illinois., Indiana and Ohio all below 60 percent on corn ratings that were “good-to-excellent”. North Dakota had 72 percent of the corn crop in the higher rating.


Nationally, 72 percent of the U.S. corn crop was rated “good-to-excellent on June 22, which compares to only 56 percent on approximately the same date in 2019. Only 5 percent of the U.S. corn crop was rated “poor-to-very poor”, compared to 12 percent a year ago. In the June 22 USDA report, 70 percent of the U.S. soybean crop was rated “good-to-excellent”, which compares to 54 percent in 2019. Similar to corn, only 5 percent of the 2020 soybean crop is rated “poor-to-very poor”, compared to 10 percent a year ago. In 2019, a large portion of the “poor-to-very poor” corn and soybeans were located in Southwest Minnesota and Eastern North and South Dakota, due to late planting and excessive rainfall.



Note — For additional information contact Kent Thiesse, Farm Management Analyst and Senior

Vice President, MinnStar Bank, Lake Crystal, MN. (Phone — (507) 381-7960);

E-mail — Web Site —



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