Seedbank persistence of Palmer amaranth (Amaranthus palmeri) and waterhemp (Amaranthus tuberculatus) across diverse geographical regions in the United States

Authors: KORRES, NICHOLAS - University Of Arkansas; NORSWORTHY, JASON - University Of Arkansas; YOUNG, BRYAN - Purdue University; REYNOLDS, DANIEL - Mississippi State Extension Service; JOHNSON, WILLIAM - Purdue University; CONLEY, SHAWN - University Of Wisconsin; SMEDA, REID - University Of Missouri; MUELLER, THOMAS - University Of Tennessee; Spaunhorst, Douglas; GAGE, KARLA - Southern Illinois University; LOUX, MARK - The Ohio State University; KRUGER, GREG - University Of Nebraska; BAGAVATHIANNAN, MUTHUKUMAR - Texas A&M University

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2018
Publication Date: 7/2/2018
Citation: Korres, N.E., Norsworthy, J.K., Young, B.G., Reynolds, D.B., Johnson, W.G., Conley, S.P., Smeda, R.J., Mueller, T.C., Spaunhorst, D.J., Gage, K.L., Loux, M., Kruger, G.R., Bagavathiannan, M.V. 2018. Seedbank persistence of Palmer amaranth (Amaranthus palmeri) and waterhemp (Amaranthus tuberculatus) across diverse geographical regions in the United States. Weed Science. 66(4):446-456. https://doi.org/10.1017/wsc.2018.27.
DOI: https://doi.org/10.1017/wsc.2018.27

Interpretive Summary: Palmer amaranth (Amaranthus palmeri) and tall waterhemp (Amaranthus tuberculatus) are two problematic weed species in Midwest and Mid-south soybean production. Both problematic weed species have evolved resistance to herbicides commonly applied in soybean. Knowledge of the effects of burial depth and burial duration on seed viability and consequently seedbank persistence of Palmer amaranth and tall waterhemp ecotypes can be used for the development of efficient weed management programs. This is of particular interest given that both species can produce large quantities of seed and replenishment the soil seedbank. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0- and 15-cm) for a maximum duration of three years. Each year, seeds were retrieved and seed damage and viability were evaluated. Greater seed damage averaged across seed origin, burial depth, and year was recorded at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for Palmer amaranth and tall waterhemp, respectively. The site differences for seed persistence was probably due to higher volumetric water content at these sites. Seed death was directly proportional to burial depth, whereas the percentage of viable seeds recovered after 36 months on the soil surface ranged from 4.1 to 4.3% compared to 5 to 5.3% at the 15-cm depth for Palmer amaranth and tall waterhemp. Seed viability loss was greater in the seeds placed on the soil surface compared to the buried seeds. The greatest influence of seed viability was time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species could focus on reducing seed shattering, enhancing seed removal from the soil surface or adjust tillage systems.

Technical Abstract: Knowledge of the effects of burial depth and burial duration on seed viability and consequently seedbank persistence of Amaranthus palmeri (Palmer amaranth) and Amaranthus tuberculatus (tall waterhemp) ecotypes can be used for the development of efficient weed management programs. This is of particular interest given the great fecundity of both species and consequently their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0- and 15-cm) for three years. Each year, seeds were retrieved and seed damage and viability were evaluated. Greater seed damage averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for Palmer amaranth and waterhemp, respectively. The site differences for seed persistence was probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (a=0.001) whereas the percentage of viable seeds recovered after 36 months on the soil surface ranged from 4.1 to 4.3% compared to 5 to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus. Seed viability loss was greater in the seeds placed on the soil surface compared to the buried seeds. The greatest influence of seed viability was time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species could focus on reducing seed shattering, enhancing seed removal from the soil surface or adjust tillage systems.