It is no secret that we have had a devil of a time with weed control these past few seasons. In response we have been getting better and more aggressive in our use of pre-plant herbicides in our primary row crop, cotton.
This is making for an interesting dilemma with such a long (yet welcome) period of wet weather delaying most cotton plantings. Any more delays in cotton planting and many of us will be outside our window for our full potential of profitable cotton crop. This leads many of us to consider alternate crops that do not require as large a production window such as corn or sorghum planted slightly later. So, what can we do about our fields that were aggressively treated with pre-plant residual cotton herbicides?
Dr. Jordan Bell, extension agronomist district 1, Dr. Wayne Keeling, extension agronomist district 2, and myself have been wrestling with the issue in discussions. Dr. Keeling mentioned to Dr. Bell that, “You do not necessarily have to rule out sorghum or even an earlier maturity class corn on Treflan (yellow) ground. Because Treflan is bound very tightly in the soil, you can plant below the herbicide. Well, how deep? That depends on how deep the herbicide was incorporated.
Trash whippers work well to push Treflan soil away from the seed. If you plant below the herbicide, the cotyledon can grow through the herbicide, but if you plant on top of the herbicide, the roots will grow through the herbicide and you will see quick herbicide damage. This can be detected within 4 to 5 days after planting as long as soil temperatures are ideal to promote germination.
The recent rains will not wash away the herbicide and alleviate the problem. It is best to plant under ideal conditions with soil temperatures at 65F for 10 days to ensure vigorous early growth. Planting in the current conditions with cool soil temperatures will result in stressed plants that will be more susceptible to herbicide issues in addition to the other problems such as disease and pest problems.”
Dr. Bell added speaking of the Amarillo region, “I do not think many of our Panhandle producers use as much Caparol and Staple as the Southern High Plains producers so hopefully those will not affect too many acres.”
Our specialist’s thoughts on the issue would fit very well with what I have witnessed in the fields over the years. We definitely want to get below our “yellow” pre-plant cotton herbicides with corn or sorghum plantings into really good planting conditions, and maybe bump our seeding rates a touch. I would caution about bumping seeding rates too much as it is very easy to get too high a plant population by over estimating any loss due to herbicide, especially if we successfully plant below the herbicide layer. Corn and sorghum seedlings do tend to act much more heartily with deeper plantings compared to cotton when it comes to emergence.
It might also do some good to recheck the label for the applied herbicide. We might be concerned over nothing. There are a few pre-plant residual herbicides, some of the ‘white’ herbicides by name, which have both a corn and cotton label.