Allelopathic Potential and Weed Control Dynamics of Winter Cover Crops in Southeastern United States Corn Production

Abstract

Corn production is limited by multiple factors, including weeds. Sole dependency on herbicides has led to multiple problems. Therefore, integrated weed management is crucial to reduce sole dependency on herbicide. Cover crops have the potential to suppress weeds through physical mulch, competition, and allelochemicals. Therefore, a growth chamber experiment was conducted to understand the influence of cover crops extract allelochemicals effect on the radicle length of weeds such as morningglory (Ipomoea spp.), sicklepod [ Senna obtusifolia (L.) H.S. Irwin & Barneyby], Palmer amaranth [ Amaranthus palmeri S. Watson], and corn. Treatments included a control, cereal rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), Italian ryegrass (Lolium multiflorum Lam.), lupin (Lupinus alba L.), and radish (Raphanus sativus L.). Results indicated the allelopathic effects of cover crops differed among weed species and runs; however, not completely selective. Furthermore, a greenhouse experiment was conducted with five treatments: control, cereal rye, radish, and mixture of above-mentioned cover crops in two runs to understand the allelochemicals potential of dried residue of cover crops in density and biomass of troublesome weed species. Weed species were morningglory, sicklepod, and Palmer amaranth. Results showed that dried cover crops significantly suppressed the sicklepod counts and biomass, and Palmer amaranth counts. However, Palmer amaranth biomass, morningglory counts and biomass was not significantly inhibited by treatments. Furthermore, to understand the influence of winter cover crops on the critical period of weed control (CPWC) in corn, a field experiment was conducted in two locations: Wiregrass Research and Extension Center (WG) and Gulf Coast Research and Extension Center (GC) in 2023-2025. Treatments included weedy winter fallow, cereal rye, wheat, crimson clover, white lupin, radish, and a five-way mixture. The subplot included durations of weedy regime and weed-free regime for 0, 2, 4, 6, 8, and 10 weeks after planting. Results showed the varied results of CTWR, CWFP, and CPWC across the location and year. In WG, wheat showed the shortest CPWC in both years (1.35 weeks in 2025 and 1.1 weeks in 2024), followed by mixture (6.02 weeks) in 2025 and radish (2.69 weeks) in 2024. In GC, the mixture had the shortest CPWC with 0.84 weeks, followed by radish (2.23 weeks), cereal rye (3.02 weeks), lupin (4.95 weeks), and wheat (5.65 weeks), compared to weedy winter fallow (5.76 weeks). Cover crops influence the beginning and ending time points of the weed management window. In addition, cover crops help to suppress the weed biomass as compared to weedy winter fallow. Thus, cover crops as a tool of integrated weed management strategies have the potential to help producers reduce frequent herbicide applications with weed control and achieve greater yield.