For generations, the standard measure for corn growth was “knee-high by fourth of July,” 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 highercorn by July 4 is a more typical, and has resulted in some very good corn yields in most areas in recent years. It is difficult to get exceptional corn yields in the southern half of Minnesota if corn is only knee high or smaller on July 4.
In most of Minnesota and Iowa, the 2013 growing season started out later than normal, with most corn planted in the month of May; however, much of earlier planted corn has rebounded nicely with some fairly good growing conditions in mid-late June. In recent weeks, excessive rainfall and severe storms in many areas has to some crop challenges with large drown-out areas in fields, significant hail damage, and further delays with late panting of soybeans. Most corn in southern Minnesota and northern Iowa that was planted by mid-May will exceed knee high by July 4, and some will exceed waist high; however, no corn will be approaching shoulder high, which occurred in many parts of the region in 2012.
In southeast Minnesota, northeast Iowa and western Wisconsin, a considerable amount of 2013 corn was not planted until late May or early June, leaving the crop development well behind normal. As a result, there will be a significant amount of corn in this region that will fail to reach knee highby July 4. What this means in agronomic terms is that the corn in this region is two to three weeks or more behind normal development. This increases the likelihood that a large amount of corn could have maturity issues this fall, and that the 2013 corn crop is much more susceptible to a normal or earlier than normal first frost. It also increases the odds of wetter corn at harvest, which will likely lead to higher corn drying costs this fall. There are also thousands of prevented planting  corn acres in this region that will not be planted in 2013.
Corn and soybean development in most areas continues to run behind normal, due to cooler-than-normal temperatures through most of May and early June; however, conditions have improved in recent weeks. The accumulation of growing degree units (GDUs) at the U of M Southern Minnesota Research Center totaled 790 from May 1 through June 30, 2013, compared to a normal GDU accumulation of 868 on June 30, resulting in most corn development being a week or more behind normal development. By comparison, there were 994 GDUs accumulated by June 30, 2012; 837 GDUs in 2011, and 871 GDUs in 2010. GDU accumulation has been even slower in many areas of southeast Minnesota, which along with the very late planting dates, has lead to the extremely slow start for corn and soybeans in that region.
June rainfalls have been quite variable across the region, with most areas of Upper Midwest receiving adequate to excessive amounts of rainfall during June. Total rainfall at the Waseca Research Center in the month of June was 6.67 in., which compares to a normal June rainfall of 4.22 in. The total precipitation for 2013 through June 30 at Waseca is now at 24.91 in., which is +8.34 in. above normal, and is about 150% of the normal rainfall amount for the first six months of the year. Many areas of Southeastern Minnesota have received more than double their normal precipitation amount from April 1 to June 30, with several locations setting all-time records. Any concerns with continuation of drought conditions into the 2013 growing season have pretty much disappeared.
Some portions of Southern Minnesota have received frequent excessive rainfall amounts during the month of June, which has lead to some large drown-out areas of fields. The excessive rainfall has also lead to problems for timely applications of post-emergence herbicides for weed control, and has caused some leaching of available nitrogen in the soil profile. There are many areas with yellow, chlorotic-looking soybeans, due to the excessively wet soil conditions. Close to maximum levels of stored soil moisture exist in most areas of southern Minnesota, so any major rainfall events can quickly result in large amount of standing water in crop fields.
The severe winter-kill to alfalfa fields across the Upper Midwest has been another serious problem in many areas. The shortage of hay production in 2013, combined with the late and delayed planting in some areas, could lead to some very tight feed supplies for livestock producers in the hardest hit portions of the region during the coming months