Effects of Compensatory Growth On Palmer Amaranth Biomass and Accumulation and Cotton Yield

Palmer amaranth is a highly competitive weed of field corn, cotton, peanut, and soybean and has been confirmed to be resistant to glyphosate in nearly every agronomic county in GA. Palmer amaranth’s successful establishment in GA cotton fields is due, in part, to the presence of a deep taproot as well as a network of finer, fibrous roots. Because of its rooting structure, Palmer amaranth is able to penetrate compacted soils, thereby gaining access to water and nutrients, more effectively than many commonly grown crops. This contributes to Palmer amaranth’s rapid growth rate (up to inches per day) and competitiveness. The presence of a taproot can also make it difficult to remove Palmer amaranth by hand. Growers, extension agents, and university research personnel have observed instances where: 1) previously pulled Palmer amaranth plants have re-rooted and become reestablished in a field and 2) plants that have been cut back (using hoes or machetes) have re-sprouted from dormant buds and resumed normal growth. Current GA recommendations for Palmer amaranth management stress the need to remove all plants from a field prior to their achieving reproductive maturity in an effort to mitigate the size of the soil seedbank. Plants that escape removal could flower and produce progeny that could severely impact the following year’s crop. This paper will evaluate the potential of Palmer amaranth to grow and develop in cotton following defoliation occurring during a simulated hand-weeding failure.