Yellow rattle is a hemiparasitic weed that is becoming increasingly problematic in hay fields in the northeastern United States. The biomass of yellow rattle was assessed in two experiments in which commercially available soil amendments were applied to an infested hay field under no-till management. The amendments were applied in the fall of 2010 and 2011 and included wood ash, biochar, hardwood sawdust, lime, and K. Wood ash applied at a rate of 8,967 kg ha⁻¹ (4 tons per acre) had the greatest suppressive effect and reduced yellow rattle biomass the following summer by 86 and 92% relative to the untreated control in Experiments 1 and 2, respectively. Two additional treatments included in Experiment 2, a doubled rate of wood ash and sawdust applied at a rate of 13,450 kg ha⁻¹, also reduced yellow rattle biomass. No other treatments affected yellow rattle biomass. A partial least-squares regression (PLSR) analysis that included aboveground plant community and soil biochemical data explained only 42.4% of the variation in yellow rattle biomass, suggesting that the mechanisms responsible for the suppression of yellow rattle by wood ash and sawdust are complex. Amending hay fields with wood ash or sawdust may be an effective nonherbicide strategy for managing yellow rattle infestations. Additional research will be required to determine the mechanisms and generality of yellow rattle suppression by wood ash and sawdust amendments to the soil.

Nomenclature: Yellow rattle, Rhinanthus minor L. yellow rattle.