Cotton (Gossypium Hirsutum L.) response to pendimethalin formulation, timing, and method of application

Authors: GREY, TIMOTHY - University Of Georgia; Webster, Theodore

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 5/1/2013
Publication Date: 6/12/2013
Publication URL: http://dx.doi.org/10.5772/56184
Citation: Grey, T.L., Webster, T.M. 2013. Cotton (Gossypium Hirsutum L.) response to pendimethalin formulation, timing, and method of application. In: Price, A.J., Kelton, J.A. editors. Herbicides-current research and case studies in use. 27-46.

Interpretive Summary: Palmer amaranth has rapidly become one of the most important weeds of agronomic crops in the southern US. One of the factors linked with this recent change in the importance of Palmer amaranth is the changing weed management practices. Adoption of conservation tillage and abandonment of deep cultivation favors Palmer amaranth with its small seeds that germinate at shallow soil depths. One of the tenets of managing herbicide resistant weeds is the use of multiple herbicide mechanisms of action. Conservation tillage has been problematic, as many of the preemergence herbicides are intercepted and bound by the cover crop residues before they can act on the germinating weed seedling. One alternative method to spraying pendimethalin herbicide with water as a method of field application is to apply it to the surface of fertilizers and then spread in tandem, reducing application cost by eliminating one trip across the field. Some concerns for fertilizer impregnated with pendimethalin include uniform spraying of herbicide on the fertilizer, even distribution in the field, fertilizer penetration of plant residues to reach the soil surface, and activation. Field studies determined that there was no appreciable crop injury, adverse cotton growth, or yield loss for any method of application or pendimethalin formulation. The applications made to emerged cotton plants exhibited significant crop injury and decreased yield for cotton with the emulsifiable concentrate (EC) formulation of pendimethalin relative to the micro-encapsulated (ME) formulation; treatments that were sprayed in water had greater injury than fertilizer-applied treatments. Based on injury, cotton plant height, and final yield data, pendimethalin ME caused less injury than pendimethalin EC, and fertilizer application of both formulations was less injurious than spray application.

Technical Abstract: Cotton growers are constantly seeking ways to reduce inputs. An alternative method to spraying pendimethalin herbicide with water as a method of field application is to coat it on fertilizers and then spread in tandem, reducing application cost by eliminating one trip across the field. Some concerns for fertilizer impregnated with pendimethalin include uniform spraying of herbicide on the fertilizer, even distribution in the field, fertilizer penetration of plant residues to reach the soil surface, and activation. Field studies conducted in 2005, 2006, and 2007 evaluated cotton response to pendimethalin formulation and timing and method of application. Treatments were made at four different application timings, prior to plant emergence (PRE), at seedling emergence (AE), to 3rd leaf (3LF), or to 6th leaf (6LF) cotton. Pendimethalin formulation comparisons were made for an emulsifiable concentrate (EC) with 0.41 kg ai/L and a microencapsulated aqueous capsule suspension (ME) with 0.47 kg ai/L. Pendimethalin EC or ME were applied as spray in an aqueous solution of water, or impregnated on fertilizer which was mechanically spread. A non-treated control was included for comparison. There was no appreciable crop injury, adverse cotton growth, or yield loss for any PRE treatment for any method of application or pendimethalin formulation. The AE and 3LF application treatments exhibited significant crop injury and decreased yield for cotton that had pendimethalin EC applied, much greater than pendimethalin ME, with spray-applied treatments having greater injury than fertilizer-applied treatments. Significant yield loss was observed for the pendimethalin EC when applied as AE or 3LF spray treatments. Based on injury, subsequent height, and final yield data, pendimethalin ME caused less injury than pendimethalin EC, and fertilizer application of both formulations was less injurious than spray application. The PRE and 6LF applications for either formulation had no observed crop response and no effect on yield as compared to the nontreated control.