The very dry weather pattern in many areas of southern and western Minnesota in late July and early August could have an effect on 2014 corn and soybean yields in some portions of the region. The level of crop deterioration was probably limited, especially on heavier soil types, by cooler-than-normal weather during that period. The other big challenge in many areas of the Upper Midwest is the continued cooler than normal temperatures, and lower-than-normal accumulation of growing degree units (GDUs). This raises concerns that some of the 2014 corn and soybean crop may not reach maturity prior to the first killing frost, especially in areas with very late planting dates this past spring.
There was some very beneficial rainfall in many areas of southern and western Minnesota in the last two weeks of August, which should still be a positive factor for a majority of the soybean acres, and will help the corn mature more naturally. At the U of M Research and Outreach Center in Waseca, a total of 1.55 inches of rainfall had been received during August, as of 8-28-14, which compares to a normal August rainfall total of 4.75 inches at Waseca. Waseca received only 1.19 inches of rainfall in July, which was 3.23 inches below normal, after accumulating 12.94 inches of rainfall in June, which was 8.25 inches above normal. For the year, Waseca has received 28.49 inches of rainfall through August 28, which is about 2.75 inches above normal.
By comparison, the U of M Research and Outreach Center in Lamberton, had received 13.25 inches of precipitation from May 1 through August 25, compared to a normal level of 13.55 inches. Lamberton received just 1.17 inches of rainfall in July, and had 2.88 inches in August (as of 8-25-14), after receiving 7.39 inches of precipitation in June. As of August 15, there were only 2.32 inches of available soil moisture in the top 5 feet of soil at Lamberton, which is similar to 2013, and is only slightly more than the drought year of 2012. Most of the available soil moisture was at the 3-5-foot soil depth. The normal amount of available soil moisture in mid-August is 4.23 inches.
Of course rainfall amounts and timeliness of rainfall events have been quite variable across the region in 2014. Some localized areas of southern and western Minnesota, especially in west-central Minnesota, have received more timely rainfalls during early August than other portions of the region. Many areas of south-central and southwest Minnesota have received rainfall amounts similar to those listed at Lamberton, and were experiencing rather dry conditions until the recent rainfalls. Due to the variability of the rainfall events from farm-to-farm, and even from field-to-field, we are likely to see a wide variation in crop yields across the region in 2014, even in the same county or township.
The development of the corn and soybean crop in many areas of Minnesota remained behind normal in late August. Temperatures and accumulation of GDUs in the Upper Midwest have been somewhat below normal throughout most of the 2014 growing season. The slower-than-normal accumulation of GDUs, together with much later-than-normal planting in some locations, has lead to some significant crop maturity concerns in portions of the region. The total accumulated GDUs from May 1 through August 28 at the U of M Research and Outreach Center at Waseca was at 2,009, which is surprisingly only about 34 units behind normal GDU accumulation. The GDU accumulation is much further behind normal in some other areas of Minnesota. As of 8-28-14, Waseca had not recorded one day in August above 90° F, which is very unusual.