Forage harvest and re-crop considerations following these drought conditions
Vince M. Davis, Extension Weed Scientist
Due to the drought conditions, some growers are considering harvesting their corn and/or soybean crops earlier than normal as a forage this year, and furthermore some are considering planting a second crop to produce more biomass for a fall forage harvest. There are three important herbicide related considerations for these situations:
- Has enough time elapsed between previous herbicide applications and the harvest of the corn or soybean crop as a forage?
- Are there any herbicide rotational crop restrictions for another crop you are considering to plant next?
- Even if the time between herbicide application and fall planting is ‘okay’ regarding re-crop restrictions, are there still concerns of herbicide carryover from residual herbicides because of little rainfall received throughout the season?
The first and best recommendation is to make certain you review the annual herbicide application records, and pay attention to the dates of these applications. Moreover, check those herbicide labels for the intervals needed following application before crop foliage to be feed as a forage. These restrictions are often different than the pre-harvest intervals for grain. There are also tables in the 2012 “Pest Management in Wisconsin Field Crops” manual A3646 to help you out with finding this information. Table 2-4. “Forage, grazing, and grain harvest intervals for corn herbicides, page 54” lists these intervals for many popular corn herbicides, and Table 3-3. “Forage and grain harvest intervals for soybean herbicides.” lists these intervals for many popular soybean herbicides.
Additionally, Appendix Table 2 lists the planting intervals required for many rotational crops. Please review this table (as well as herbicide labels) for restrictions against any plans to re-crop this fall. For instance, I have heard that fall seeded oats and peas are among some of the popular choices discussed to plant for a fall forage crop. Several popular corn herbicides, like atrazine, would prevent this option for two years. Moreover, due to lack of rainfall, the potential for herbicides to ‘break down’ or degrade in their biological activity in the soil also decreased. If their breakdown decreased, then their chance to be biologically active and injure sensitive vegetation(crops) planted following the application increases.
In short, before making any re-crop decisions, please review your application records and review these tables and your herbicide labels to insure you won’t have a failure in a succeeding crop establishment.
Click below to view Tables 2-4.