Preemergence Herbicide Treatments Behind the Cotton Planter

Apr 20, 2021

By Steve Li

Cotton planting will be in full swing in just another week or two. One thing that I cannot emphasize enough is to START CLEAN (free of weeds), particularly in no-till fields. A single-pass burndown treatment is often not enough. It is hard to kill everything in no-till fields with a single burndown treatment, particularly when weeds are tall and thick. A second-pass pre-plant burndown treatment, or a follow-up application of Gramoxone with soil herbicides behind the planter is needed to START CLEAN. Otherwise, some weeds that “appear to be dead” may recover and regrow. Sometimes burndown treatments only injure foliage and the readily visible plant canopy (leaving growing points, crowns, and roots alive); resulting in weeds that fully recover in a few days to exert competition to the crop.

Dr. Steve Li, Auburn Weed Scientist

I recommend using two-way mixes as PRE treatments. They provide both a broader weed control spectrum and longer duration control. A few effective treatments I’ve evaluated in recent years include:

Reflex + Cotoran (best treatment on broadleaf weeds such as sicklepod, morning glory, teaweed and pigweed)
Reflex + Warrant* (best treatment on annual grasses and pigweed)
Reflex + Brake (best treatment on pigweed)
Cotoran + Warrant* (best treatment on heavy soils where Reflex does not fit well)
Cotoran + Brake (best treatment for pigweed and broadleaf weeds on heavy textured soils).

*Application of Warrant herbicide is legal in Florida, but it cannot be sold in Florida

Use rates for these herbicides in two-way mixes on sandy loam soils are: Reflex 8-10 oz/A, Cotoran 1 pt/A, Warrant 2 pt/A, Brake 16 oz/A. Rates for these herbicides in two-way mixes on silt loam soils are: Reflex 10 oz/A, Cotoran 1.5 pt/A, Warrant 2.5 pt/A, Brake 20 oz/A. Rainfall or irrigation within 3-4 days after application is needed to properly activate these herbicides.

If you run into a dry spell in May and there is no chance of rain in the next 7-10 days after planting, one alternative is to apply PRE-treatments over smooth, prepared seed beds prior to planting … just ahead of rain that will eventually come. The purpose is to get herbicides activated by rainfall, then utilize the moisture to get a crop stand after the rain. A pass by a strip-till may facilitate cotton emergence by breaking any crust layer at the soil surface caused by heavy rain and reduce herbicide injury.

Source : ufl.edu

Video: Dr. Emerson Nafziger: Nitrogen Fertilizer Rates for Corn

The Crop Science Podcast Show, Dr. Emerson Nafziger from the University of Illinois breaks down decades of nitrogen research. From the evolution of N rate guidelines to how soil health and hybrid genetics influence nitrogen use efficiency, this conversation unpacks the science behind smarter fertilization. Improving how we set nitrogen fertilizer rates for rainfed corn is a key focus. Discover why the MRTN model matters more than ever, and how shifting mindsets and better data can boost yields and environmental outcomes. Tune in now on all major platforms!

"The nitrogen that comes from soil mineralization is the first nitrogen the plant sees, and its role is underestimated."

Meet the guest:

Dr. Emerson Nafziger is Professor Emeritus of Crop Sciences at the University of Illinois at Urbana-Champaign, with degrees in agronomy from Ohio State, Purdue, and Illinois. His research has focused on nitrogen rate strategies and crop productivity. He co-developed the Maximum Return to Nitrogen (MRTN) model, which is widely used across the Midwest. His research spans N response trials, hybrid interactions, crop rotation effects, and yield stability.