Flooding during the growing season spreads Echinochloa colona seedling emergence towards summer

Background and aims Floods could promote hydrophyte weed species recruitment in cultivated lowland fields in temperate regions of the world. This study tested whether different flooding regimes change the amount and timing of Echinochloa colona seedling emergence. Methods We did a series of three annual crop-free experiments in mesocosms taken from agricultural wetlands located in the Pampas region and subjected to cultivation during dry years to test if Echinochloa colona (L.) Link. seedling emergence, aboveground biomass and seed production per area could be affected by flood regimes differing in duration and timing. Results Flooding or intermittently flooding-drawdown conditions during the growing season did not increase cumulative emergence compared to drained controls at field capacity; however, flooding affected the seedling emergence pattern by skewing emergency peaks towards mid-summer. Notably, an abundant subaquatic E. colona seedling emergence was observed in spring (≈ 2500 seedlings m ^− 2 ) in constantly flooded mesocosms. In the second experiment we found that even after prolonged and frequent flood pulses that decreased seedling emergency, E. colona seed production was enough to replenish the soil bank. In a third experiment we revealed that long winter floods, before the growing season, decreased total seedling cumulative emergency yet did not change the emergence pattern of seedlings. Conclusion The extended temporal window of E. colona recruitment due to flooding can complicate its field control and should be included in weed emergency models to accurately forecast E. colona seedling recruitment to advise weed control and management decisions.