Present cooler climate circumstances are posing challenges for growers to get cereal rye cover crops terminated. Nevertheless, for growers planning to plant soybeans into the rye cover crop, there could also be a perk to letting the rye cover crop accumulate extra biomass — the perk being that cover crop biomass may help with weed suppression. The power of cereal rye to suppress weeds is instantly associated to the biomass accumulation on the time of termination.
Iowa State College carried out discipline experiments at Ames and Boone in 2019-20. A cereal rye cover crop (Elbon selection) was drill-seeded at 60 kilos per acre within the second week of October 2019 and terminated with Roundup (glyphosate 1.12 kilos acid equal per acre) at totally different timings in spring 2020 (Desk 1). No cover crop plots have been stored fallow till soybean planting.
Within the discipline trial carried out in Ames, comparisons have been made between totally different cereal rye termination timings on weed suppression. The cover crop terminated 14 days after soybean planting collected better biomass and offered larger ranges of marestail (horseweed) and waterhemp suppression in comparison with termination dates of seven days earlier than soybean planting or at soybean planting.
Within the discipline trial carried out in Boone, comparisons have been made between a cereal rye cover crop that was terminated on the time of soybean planting versus a no cover crop remedy. Cereal rye collected 4,658 kilos per acre biomass and offered better than 30% discount in waterhemp emergence in the course of the rising season in comparison with no cover crop plots.
Along with reductions in waterhemp, the cover crop residue diminished the scale and biomass of the waterhemp vegetation on the time of a post-herbicide software. The cover crop resulted in better than 65% discount in waterhemp seed manufacturing in contrast with no cover crop plots.
On this research, soybean emergence, development, cover improvement and grain yields weren’t affected when the cereal rye cover crop was terminated at soybean planting in comparison with no cover crop plots.
Biomass and residual herbicides
Based mostly on the outcomes from the 2020 discipline research, terminating the cereal rye cover crop at or after soybean planting didn’t get rid of the necessity for a preemergence soil residual herbicide. A residual herbicide (Prefix 32 ounces per acre) utilized on the time of cereal rye termination, with glyphosate as a burndown program, offered better waterhemp control six weeks after soybean planting, in comparison with a glyphosate-only burndown program, or when Prefix 32 ounces per acre was utilized at submit timing.
A residual herbicide with a number of websites of motion utilized as pre together with a high-biomass cover crop termination would scale back choice stress on submit herbicides, a finest administration apply to handle herbicide resistance.
Though not noticed within the 2020 discipline trials, a excessive biomass cover crop (delayed termination) might trigger bodily tie-up of the soil residual herbicide for an extended interval, thereby lowering the supply within the soil the place preemergence herbicides are lively.
Making use of the preemergence herbicide early submit reasonably than with the burndown remedy could also be another possibility, particularly for waterhemp control later into the season. Nevertheless, this technique limits preemergence merchandise that may be utilized following soybean emergence.
Ongoing analysis and on-farm trials carried out over a number of places in Iowa will assist in better understanding the cover crop termination timing by herbicide interactions and the impact of local weather variables throughout years.
In conclusion, cover crops can not reliably substitute different types of weed control, however this built-in weed administration technique would scale back herbicide choice stress whereas bettering weed control with herbicides when herbicide-resistant weeds are an issue.
Jha is an affiliate professor in agronomy and Extension weed specialist at ISU.Supply: ISU ICM Information, which is accountable for the data offered and is wholly owned by the supply. Informa Enterprise Media and its subsidiaries aren’t accountable for any of the content material contained on this info asset.