May 11, 2017
Monitor Stands in Early Planted Corn
This certainly has been a challenging spring for farmers trying to get crops planted in many areas. Between prolonged rainy conditions and soil temperatures taking a plunge, there just weren’t a lot of good opportunities to get crops planted in April. On the positive side, I think area farmers might have set a record for the number of acres of corn that were planted in a short time, May 5-9, until more rain forced them out of the fields for a couple of days.
Those farmers who did get something planted earlier this spring will want to keep a close eye on the stand in those early planted fields. Under these less than ideal conditions, there are several things that can go wrong in the field. Those include:
• Imbibitional chilling injury - the seed itself is injured by a rapid uptake of water in cold soils
• Rotted seed prior to germination
• Rotted or discolored seedlings after germination, but prior to emergence
• Damping off of seedlings after they emerged, and
• Root or hypocotyl decay.
Chilling injury is a physical injury to the seed when it takes up, or imbibes, cold soil moisture. This is most serious when soils are cold in the 24 to 48 hours after planting, and is less of a problem if soil temperatures drop later after planting. The other problems can all be caused by several common soilborne pathogens. Unfortunately there is not hybrid resistance for these diseases which include Pythium, Fusarium, and Rhizoctonia.
Some things you can do include improving drainage in fields that are prone to flooding or waterlogged conditions after precipitation or waiting to plant these fields until soil conditions are warmer and promote rapid seed germination and emergence. The most common method for disease management is the use of seed treatment fungicides.
While seed treatment fungicides provide protection during the first few weeks after planting, some diseases may develop later if we have extended periods of inclement weather and poor growing conditions or under severe disease pressure.
To decide if you need to replant areas or fields with poor stands, take stand counts from at least three representative areas in a field. Count the number of healthy plants in 1/1,000th of an acre. If you are in 30 inch rows, that’s the number of plants in 17 feet, 5 inches of rows at each location. Average these numbers to get an average remaining stand. If you have an average of 24 plants from the counts you took at several locations, that indicates you have a final stand of 24,000 plants per acre.
Then do a google search for “Evaluating Hail Damage to Corn in Nebraska” and the first link should be to a Nebraska Extension publication (http://extensionpublications.
Using the example above, if you counted an average of 24 plants in 1/1,000th of an acre, you’d add a zero to 24 and have 240 plants in 1/100th of an acre when using this chart. If you planted for an original stand of 34,000 plants per acre, or 340 on the chart, then your estimated yield reduction would be 10%. Before you replant, you need to consider the existing yield potential based on the remaining plant stand, the calendar date, and the cost of seed, additional pesticides, tillage and fuel.
For more information on seedling diseases and assessing whether to replant, visit the Nebraska CropWatch website (http://cropwatch.unl.edu) or contact your local Nebraska Extension office.