Rising CO2 makes cover crops more vulnerable to herbicides, not less
Files MC, Aranha BC, Fipke MV, Elias DB, Camargo ER
Climate Adaptation
If you grow cover crops to build soil health, this research shows that a warmer, higher-CO2 future could make those same crops more easily damaged by residual herbicides, even as one of them, Persian clover, keeps doing the useful work of helping soil microbes clear the chemicals away.
Researchers grew Italian ryegrass and Persian clover in soil treated with three common herbicides, under both today's CO2 levels and the higher levels expected in the future. Persian clover consistently helped soil microbes break down the herbicides faster, but surprisingly, plants grown under future high-CO2 conditions got bigger yet became more easily hurt by the same herbicide doses. In other words, more CO2 made the plants grow more but also made them weaker against herbicide stress.
Key Findings
Persian clover residues boosted herbicide dissipation in soil by about 15-30% compared to fallow soil after 40 days, while ryegrass showed little improvement.
Elevated CO2 increased shoot biomass in both species but lowered their herbicide tolerance, cutting GR50 values by 12-31% (e.g., ryegrass dropped from 64.5 to 44.6 g a.i./ha).
Cover-crop identity mattered more than CO2 level for herbicide breakdown: Persian clover consistently raised microbial respiration and herbicide degradation, while elevated CO2 increased plant sensitivity without improving soil remediation.
chevron_right Technical Summary
Scientists found that cover crops like Persian clover help soil microbes break down common imidazolinone herbicides faster, but rising CO2 levels make both clover and ryegrass more sensitive to these herbicides rather than more resistant.
Abstract Preview
Original paper
Elevated CO2 increases cover crop sensitivity to imidazolinones but does not substantially alter post-cultivation soil dissipation.
This study evaluated the effects of elevated (700 ± 50 µmol mol-1) and ambient (400 ± 50 µmol mol-1) atmospheric CO2 concentrations on soils treated with imazapyr, imazapic and imazethapyr using It...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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