Dissipation and persistence of aminopyralid and its impact on winter wheat development in soils under different...

The residues of the herbicides applied to a primary crop may be phytotoxic to subsequent harvests, requiring a study of their dissipation and persistence in soils under different environmental management. Research on the dissipation and persistence of the herbicide aminopyralid has been limited to conventional soil management practices in field settings, with no studies conducted under alternative agronomic management methods. Therefore, the objective of this study was to investigate the effect of different agronomic management practices (soil type, application of green compost (GC) as organic amendment, herbicide dose, and irrigation regime) on the dissipation and persistence of the herbicide aminopyralid applied to a winter wheat crop under greenhouse conditions. Two soils with different characteristics (SA and SB) were amended with GC at 2.5% (w/w) (SA + GC and SB + GC). Wheat was sown in pots with unamended and amended soils. Each soil with one control (Control, without herbicide) and two herbicide doses (D1, agronomic dose, and D2, double agronomic dose) received two irrigation regimes (AR, average rainfall, and MR, minimum rainfall). The dissipation curves were obtained and the data were fitted to different kinetic models to calculate half-life values (DT₅₀, days). The dissipation rate of aminopyralid was higher in SB (DT₅₀ = 7.7 days) than in SA (DT₅₀ = 8.6 days) under AR, falling within the range of values determined for its dissipation in the field. The dissipation rate in amended soils (SA + GC and SB + GC) increased compared to unamended soils, and the DT₅₀ values decreased from 1.7 to 3.3 times. The DT₅₀ values in SA and SB + GC increased from 1.2 to 1.6 times when D2 was applied. In general, soils under AR had a higher aminopyralid dissipation rate and lower DT₅₀ values than soils under MR, in which the herbicide was more persistent at 90 days. Our results show that the agronomic practices also impact upon wheat development, being negatively affected by acidic soil (SA), the higher herbicide dose (D2), and water stress (MR) under greenhouse conditions. Overall, herbicide persistence was higher in soils under minimum irrigation, which should be considered in order to estimate the fallow period for reducing herbicide carryover and protecting rotational crops under future climate scenarios.