Rising CO2 can alter fodder–weed interactions and suppression of Parthenium hysterophorus

Three C grass (Setaria incrassata, Astrebla squarrosa and Bothriochloa decipiens) and one C legume (Clitoria ternatea) suppressive fodder species, were re-evaluated against the growth of the C Parthenium hysterophorus under an ambient (390 μmol mol) and an elevated atmospheric CO concentration (550 μmol mol). Under the elevated atmospheric CO, shoot dry biomass and suppression index (SI) value of the C S. incrassata were both reduced by 32% and 0.7 respectively, while those for A. squarrosa were reduced by 23% and 0.3. In contrast and under the same elevated atmospheric CO concentration, the shoot dry biomass and SI of the C B. decipiens were increased by 8% and 0.1 respectively, while those for the C C. ternatea were increased by 38% and 0.8. Our results suggest that C fodder plants along with certain C species could be utilised for the effective management of P. hysterophorus under the future elevated atmospheric CO conditions. However, this system needs more fodder species to be investigated. Our results suggest that rising CO per se may alter the efficacy of suppressive fodder management of an invasive C species, P. hysterophorus