A major portion (about 90 percent) of the Minnesota corn acres are planted but only ten percent has emerged. For soybeans, only 28 percent of the acres are planted and only a very few (1%) have emerged. Cold seed zones do not promote germination and emergence.
Growers are anxious to see the plants emerge so they can evaluate the stands and may be wondering if they'll need to replant, but we believe it's too early to consider that. We need to remind ourselves of the soil and weather conditions that we had in 2002. Corn seed lay in the ground 30 days, and in some cases, as long as 40 days. Plant stands were not what growers intended or wanted, but the yield potential of lower than optimum stands is usually higher than that of a later planted, full stand. And to jog our memories, the state average yield of 157 bushels per acre was a record corn production for Minnesota. The 2002 soybean situation was similar (a record yield of 43.5 bushels per acre); however, like in 2005, the soybean crop was planted relatively late, statewide.
Germination and growth are temperature driven. When the temperature around the seed is less than 50° F, there is little to no growth activity for either corn or soybean. The optimum temperature for germination is about 70°, but germination will and does occur when temperatures are lower. Normally in May, there is a portion of the day when the seed zone temperature is higher than 50° and this portion increases as each day passes. The average soil temperature at the two-inch depth for May is graphed in an earlier Crop News.
The number of days that's normally needed for corn germination and emergence is also graphed in the same article, "It's corn planting time." Because of the wet and cold soil, days to emerge and emergence date will be later than normal for average conditions. And, the time for soybean emergence will also be longer.
Fungicide Seed Treatments for Soybean
Many have questioned whether this year would have been an ideal year to have invested in a fungicide seed treatment for their soybeans. While these products are unlikely to hurt soybean stands and subsequent yields, they do not guarantee positive results. Seed treatment trials in Minnesota have provided positive results infrequently. Although there are many possible explanations, it is likely that the short active period for these fungicides (up to 14 days) is too short for very slow emerging soybean crops. A more detailed description of fungal diseases of soybean is available on the Soybean diseases website
Emerged corn fields are not dark green; but, again, it's cold and wet. Color will change very quickly when good growing conditions return.
What Can A Grower Do?
Be patient. Evaluate seed condition in the field. If seeds are not rotting, then we would expect emergence to occur when soils warm some. If a major portion of the seed is rotted, then plan to replant when conditions allow for planting. If replanting is necessary, then consider maturities that are appropriate for the planting date. Maturity suggestions are given in Hybrid maturities considerations for delayed corn planting.
Other articles that may be useful to growers are:
Guidelines for late-planted corn and soybean in Minnesota
For more information, visit Extension's corn production website: http://z.umn.edu/corn.