Agronomic guidelines for late planted silage corn
Management adjustments are needed when planting silage corn late in the growing season.
Yield potential of corn planted very late in the growing season (e.g., July) is less than corn planted on time in Michigan. However, corn can still produce more than 5 tons of dry matter per acre when planted in July. The feeding value of silage corn is at least equal to other summer annual grasses when planted this late. This makes corn an excellent “emergency” forage in a growing season like 2019.
Based on information across the northern Corn Belt, some agronomic guidelines for maintaining best possible forage yield and quality in late planted silage corn are outlined below. Follow these guidelines in keeping with your field and equipment situations.
If using late planted silage corn in a prevented planting situation, your crop insurance agent may require additional adjustments to qualify silage corn as a cover crop. You must consult your agent to obtain these details.
Relative maturity of hybrids
Use a full-season or long-maturity hybrid for corn planted in July or later. University of Wisconsin research shows that corn whole plant fiber digestibility declines from prior to flowering until around R3 (milk) growth stage before recovering and peaking at R5.5 (half milkline). Since corn planted July or later has very little chance of reaching maturity before frost and hence will not achieve peak quality, targeting harvest before the digestibility decline is recommended. This timing is easier to achieve with a long maturity hybrid.
Seeding rate and row spacing
If possible, use a narrow row spacing (less than 30 inches) combined with increased seeding rate (more than 36,000 seeds per acre) for optimum silage yield with fast canopy closure and weed suppression. If a narrow row planter is not available, criss-crossed rows can help with faster canopy closure. Plant half the seeding rate in normal row direction followed by splitting the rows or planting at an offset (perpendicular or at an angle) from the original row. Make sure your silage chopper will be able to handle the planting arrangement used.
Reducing nitrogen fertilizer to match yield potential will reduce cost of production and avoid application of more nitrogen than late planted corn can use. According to University of Wisconsin, 40-60 pounds nitrogen per acre might be enough for July-planted silage corn. Weed control programs will also need adjustment. For details, see Michigan State University Extension article, “Weed control recommendations for late and prevented planting.”
If planting into a field that is not the normal corn rotation under emergency conditions, check labels for any pesticides applied to the field during the previous 18 months to make sure there are no restrictions on feeding the harvested forage to livestock.
Harvesting corn silage that will probably be immature presents another set of challenges, which will be addressed in the second part of this article.
We thank Joe Lauer of University of Wisconsin for assistance with this article.
MSU Extension offers additional educational resources and programs to help farmers as they deal with delayed planting seasons at https://www.canr.msu.edu/agriculture/delayed-planting-resources.