The Allelopathic Effects of Palmer Amaranth (Amaranthus palmeri) on the Growth and Phenology of Crop Plants.

Kayla L. Broster, Kaylee L. Agney, Joe L. Mattews, and Karla L. Gage

Department of Plant, Soil and Agricultural Systems

Abstract

The allelopathic effects of Palmer amaranth (Amaranthus palmeri) on the growth and phenology of crop plants.

Illinois is an important producer of corn and soybeans, with corn accounting for more than 54 percent of Illinois’ income from agricultural industries. Weeds, such as Palmer amaranth (Amaranthus palmeri), left uncontrolled in agriculture fields can result in crop yield loss. Palmer amaranth is becoming more common in the Midwest, and is evolving resistance to multiple herbicide modes of action. In addition to competing with crops, Palmer amaranth is known for having allelopathic interactions, potentially resulting in increased yield loss. Allelopathic effects, which are biochemical interaction between plants, have been observed between Palmer amaranth and several plant species, however, effects on corn and soybeans are unknown. Therefore, the objective of this study was to determine the allelopathy of Palmer amaranth on multiple plant species. A greenhouse study was conducted using corn and Palmer amaranth residue and four plant species. Corn residue was the control since it is known to have no allelopathic effects. Tomato germination has been shown to be sensitive to Palmer amaranth allelopathic compounds, so the tomato plants were used as comparisons.  Corn, soybean, tomato, and Palmer amaranth seeds were planted  in  10-cm pots in the greenhouse, and equal amounts of  corn or Palmer amaranth residues was added to the surface of the pots. The first plant to germinate was recorded and all other germinating seedlings were removed to prevent competition. Growth rates were recorded for 6 weeks. The data indicates Palmer amaranth residue has an effect on germination and growth rate.