In some regions of the state, there are some problems with corn emergence, primarily due to heavy rain around May 1 and 6.
To evaluate eroded or poor stands, the following information may provide assistance. It was gleaned from an article written by retired U-M Extension corn specialist Dale Hicks, with additional input provided by Jeff Coulter, current Extension state corn specialist. For a website, search for "Minnesota Extension Corn Emergence."
-Evaluating the Stand Potential. Dig out 10 consecutive seeds and evaluate their potential to emerge. Some coleoptiles may have ruptured and that lets the seedling "leaf out" underground. Count these as dead. (The coleoptile is the "pointed" shoot that emerges from the seed. The first leaf emerges from the coleoptile.) Seeds, roots and shoots that are soft should be counted as dead. Determine the percent of the 10 seeds that are likely to emerge and determine the potential plant stand. If 8 of the 10 seeds would emerge, then the stand should be 80% of the expected stand. Repeat this procedure several times to evaluate the stand for the "field". Large gaps in the stand result in more yield loss than evenly spaced losses. If there are a lot of large gaps (2.5 feet or more), add 5% to the yield loss.
-If the expected stand is less than 22-24,000 plants per acre in this example, then the decision is more difficult. Some references suggest a stand that is 75% of the intended stand is more economical to keep than replanting. Consider the cost to replant. Maturity might be later and grain might be wetter and cost more to dry. Consider how your replant cost balances with yield prospects, corn prices, and any crop insurance replant payments. Consider whether any soil applied herbicides might create problems for reseeding. Past experience also counts.
-Surface Soil Condition. If plants are not up, but seeds are germinating and still alive, then breaking up the surface crust can help emergence. The rotary hoe is the best tool for this task. Operate the rotary hoe with a good speed and inspect the job it is doing. Rotary hoeing can be done on corn from before emergence to about an 8 inch height. If corn is just about to emerge, there may be an occasional plant that is injured because a tine hits the corn shoot. Rotary hoeing can reduce stands by 1-4%. With corn that has just spiked (coleoptile coming through), it is probably best to rotary hoe in the afternoon when the seedlings are less turgid and less likely to snap off. Rotary hoeing usually works best when the soil is flat, dry and limited crop residue. Optimal operating depth is considered 0.5 to 0.75 inches.
-A harrow might work better than a rotary hoe when the surface is rough and/or has lots of residue. By harrow, we're talking about a 1/4 or 5/16 inch diameter spring tooth about a foot long mounted on a bar. A drag could be considered with caution. There are several different kinds of drags and some can be too aggressive. Some drags will move soil into wheel tracks or other depressions and cover the seedling deeper. If a pre-emergent herbicide has been applied, moving soil might increase the herbicide rate above the seed. Some drags might plug with trash and cause damage by gouging or "bulldozing soil."
-Regardless of the tool used, run the equipment for a short distance at a normal speed and stop to look at the results. Evaluate whether you're getting the desired outcome, or adjustments are needed, or the task shows no benefit. If you continue, check again occasionally.
-By Dan Martens, U-M Extension Educator