Two Years of Pre-Plant Residual Herbicide Product Efficacy Trials on Texas High Plains Cotton

For both the 2014 and 2015 seasons, five different residual herbicide options were chosen as pre-plant weed control treatments for the trials, including an untreated check.  A later applied herbicide intended to be evaluated alone and as an additional residual herbicide layer was also added making the trials both 10 treatment factorials.  The trials were both replicated four times with small plots utilizing a RBD.  During the 2014 growing season, the field utilized was a conventional tilled while the 2015 trial was placed into a no-till system.  Treatment selection between the two trials varied slightly to fit the tillage system of the field in which the trial was conducted. 

During 2014, the pre-plant herbicides were applied in mid-March while the additional residual herbicide was applied post-planting in early May.  Significant differences between treatments and the untreated check began in late March throughout April.  During May some pre-plant residual herbicides began playing out and were no longer significantly different from the untreated check.  Other herbicides continued to offer significant differences from the untreated check throughout the remainder of the trial.

For the 2015 season, the pre-plant herbicides were applied in late March and the additional residual herbicide was applied post-planting during mid-May.  Numeric trends between pre-plant treatments were noted throughout April, but significant differences in weed populations did not occur until 49 days after pre-plant treatment with several treatments outperforming the untreated check and showing differences between treatments.   This trend continued and deepened for the remainder of the trial. 

The addition of the layered or second herbicide also paid additional significant dividends that lasted throughout the remainder of both trials when compared to both the untreated check and the use of all pre-plant residual herbicides alone.