Waterhemp emergence response to exogenous application of gibberellic and abscisic acids

The exogenous application of phytohormones to manipulate weed seed germination and emergence is a potential avenue for exploring alternative integrated weed management strategies. Greenhouse and field experiments were conducted to investigate the effects of exogenous applications of the phytohormones gibberellic acid (GA3) and abscisic acid (ABA) on waterhemp (Amaranthus tuberculatus [Moq.]) emergence.

In the greenhouse study, all waterhemp populations in sandy soil and three out of five populations in clay soil demonstrated a positive response to increased GA3; however, the response was small, leading to an increase in waterhemp emergence of up to 10% points, and weak (R²_adj < 0.3). Only one population exhibited a small (up to 10 points) and weak (R²_adj = 0.1) reduction in emergence in response to increased ABA in clay soil. The field studies demonstrated no differences in waterhemp and soybean emergence in response to application of GA3 and ABA.

Despite the low to absent efficacy of the exogenous application of GA3 and ABA in manipulating waterhemp emergence in these experiments, our findings provide foundation information for future research on this concept, particularly supporting further research investing the use of GA3 in lighter textured soils.