Abstract
The influence of soybean row width and glyphosate application timing was determined on survival, biomass, and seed production of cohorts from a mixed population of Palmer amaranth and pusley species (Florida and Brazil pusley) along with soybean seed yield. The first Palmer amaranth and pusley cohort comprised plants that emerged from soybean planting through the V3 (3 wk after soybean emergence [WAE]) soybean stage (cohort 1). The second cohort comprised plants that emerged between the V3 to V6 (5 WAE) soybean stages (cohort 2), and the third cohort emerged after the V6 through the R2 soybean stage (cohort 3). Glyphosate at 840 g ae ha −1 was applied at V3; V6; V3 and V6; and V3, V6, and R2 in rows either 19 or 97 cm wide. A nontreated control was included for comparison in each row width. Sequential glyphosate applications at V3 and V6 or at V3, V6, and R2 soybean stages resulted in 1 to 3% survival of cohort 1 compared with 23 to 28% survival after a single glyphosate application. Vegetative biomass production by cohort 1 accounted for 71% of the total pusley biomass produced in the nontreated plots. Cohort 1, 2, and 3 contributed 68, 31, and 1%, respectively, of the total 37,900 seeds m −2 produced by pusley plants in nontreated plots. Delaying a glyphosate application to the V6 stage resulted in higher biomass and more than twice the seed produced from cohort 1 when compared with cohort 2. Glyphosate applied at V3 and V6 stages prevented pusley seed production from cohort 1, and an additional glyphosate application at the R2 stage prevented seed production from cohorts 2 and 3. No Palmer amaranth emergence occurred after the V6 soybean stage in either row width. A single glyphosate application at the V3 or V6 stage eliminated cohort 1 of Palmer amaranth in narrow rows. Palmer amaranth plants from cohort 1 in wide rows that survived the V3 glyphosate application produced 3.3 g m −2 biomass and 600 seeds m −2 . Averaged over years and row widths, soybean yields after sequential glyphosate applications were 2,490 to 2,640 kg ha −1 compared with 1,850 to 2,020 kg ha −1 after a single glyphosate application at the V3 or V6 stage. This research confirms that sequential glyphosate applications are superior to a single application for minimizing pusley and Palmer amaranth survival, biomass, and seed production along with an improvement in soybean yields.
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Claims 11
Claim · model-written summary
Sequential glyphosate reduced first cohort survival to 1 to 3%, versus 23 to 28% after one application.
- Taxon
- soybean
Glycine maxe0 - Treatment
- Sequential glyphosate applications at V3 and V6 or at V3, V6, and R2e0
- Outcome
- survival of cohort 1e0
- Value
- 1 to 3%e0
- Comparator
- a single glyphosate applicatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sequential glyphosate applications at V3 and V6 or at V3, V6, and R2 soybean stages resulted in 1 to 3% survival of cohort 1 compared with 23 to 28% survival after a single glyphosate application.”
Claim · model-written summary
First cohort accounted for 71% of pusley biomass in untreated plots.
Not reportedTaxon
Verbatim
e0“Vegetative biomass production by cohort 1 accounted for 71% of the total pusley biomass produced in the nontreated plots.”
Claim · model-written summary
First pusley cohort produced 68% of seed in untreated plots.
Not reportedTaxon
Verbatim
e0“Cohort 1, 2, and 3 contributed 68, 31, and 1%, respectively, of the total 37,900 seeds m −2 produced by pusley plants in nontreated plots.”
Claim · model-written summary
Delayed glyphosate gave higher first cohort biomass and over twice as much seed as second cohort.
- Treatment
- Delaying a glyphosate application to the V6 stagee0
- Outcome
- biomass and more than twice the seed produced from cohort 1e0
- Direction
- highere0
- Comparator
- cohort 2e0
Not reportedTaxon
Verbatim
e0“Delaying a glyphosate application to the V6 stage resulted in higher biomass and more than twice the seed produced from cohort 1 when compared with cohort 2.”
Claim · model-written summary
V3 and V6 glyphosate prevented first cohort pusley seed production.
- Treatment
- Glyphosate applied at V3 and V6 stagese0
- Outcome
- pusley seed production from cohort 1e0
- Direction
- preventede0
Not reportedTaxonComparator
Verbatim
e0“Glyphosate applied at V3 and V6 stages prevented pusley seed production from cohort 1”
Claim · model-written summary
An R2 glyphosate application prevented seed production from cohorts two and three.
- Treatment
- an additional glyphosate application at the R2 stagee0
- Outcome
- seed production from cohorts 2 and 3e0
- Direction
- preventede0
Not reportedTaxonComparator
Verbatim
e0“an additional glyphosate application at the R2 stage prevented seed production from cohorts 2 and 3.”
Claim · model-written summary
Palmer amaranth did not emerge after soybean V6 in either row width.
- Taxon
- soybeanGlycine maxe0
- Outcome
- No Palmer amaranth emergencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No Palmer amaranth emergence occurred after the V6 soybean stage in either row width.”
Claim · model-written summary
One V3 or V6 glyphosate application eliminated first cohort Palmer amaranth in narrow rows.
- Treatment
- A single glyphosate application at the V3 or V6 stagee0
- Outcome
- cohort 1 of Palmer amaranthe0
- Direction
- eliminatede0
Not reportedTaxonComparator
Verbatim
e0“A single glyphosate application at the V3 or V6 stage eliminated cohort 1 of Palmer amaranth in narrow rows.”
Claim · model-written summary
Surviving first cohort Palmer amaranth in wide rows produced 3.3 g m −2 biomass.
Not reportedTaxon
Verbatim
e0“Palmer amaranth plants from cohort 1 in wide rows that survived the V3 glyphosate application produced 3.3 g m −2 biomass and 600 seeds m −2 .”
Claim · model-written summary
Surviving first cohort Palmer amaranth in wide rows produced 600 seeds m −2.
Not reportedTaxon
Verbatim
e0“Palmer amaranth plants from cohort 1 in wide rows that survived the V3 glyphosate application produced 3.3 g m −2 biomass and 600 seeds m −2 .”
Claim · model-written summary
Soybean yielded 2,490 to 2,640 kg ha −1 after sequential applications versus 1,850 to 2,020 after one.
- Taxon
- soybeanGlycine maxe0
- Treatment
- sequential glyphosate applicationse0
- Outcome
- soybean yieldse0
- Value
- 2,490 to 2,640 kg ha −1e0
- Comparator
- a single glyphosate application at the V3 or V6 stagee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soybean yields after sequential glyphosate applications were 2,490 to 2,640 kg ha −1 compared with 1,850 to 2,020 kg ha −1 after a single glyphosate application at the V3 or V6 stage.”
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