Cereal Rye Seeding Density Affects Trait Distribution, Population Responses and Termination Efficacy Using a Roller‐Crimper

Weed management in cover crop‐based, organic rotational no‐till (CCORNT) production is achieved via in situ cover crop mulch. However, ineffective cover crop termination impedes this sustainable practise. Cereal rye ( Secale cereale ; CR) is terminated via roll‐crimping, which crushes the vascular tissue along the stem. Previous studies suggested optimal growth stages (GS) to maximise termination efficacy (TE), but the effect of the distribution of individual morphological and ontogenetic traits on roller‐crimper TE has not been described. In a field study in Pennsylvania, USA, we tested the effects of (1) seeding density on CR trait variation, and (2) trait variation effect on TE. We managed CR populations with two factors, seeding rate (150, 300, 600, 900 seeds m −2 ) and sowing arrangement (row, grid). We measured the slenderness and GS of individual tillers and assessed inequality in trait distributions with Gini coefficients. We also quantified stem density and total biomass. Following roll‐crimping, we assessed TE (1 − (surviving stems/initial stem density)) and CR seed production. Cereal rye seeding rate affected all traits assessed. Slenderness and GS were positively correlated with TE, but structural equation models did not support the hypothesis that these traits mediated the positive relationship between seeding rate and TE. In contrast, stem density fully mediated the relationship between seeding rate and TE and was the best predictor of TE. Sowing arrangement did not affect cereal rye traits or TE. Our research suggests increasing seeding rate affected CR trait distributions and increased stem density led to improved roll‐crimping efficacy. Ultimately, increasing seeding rates may minimise the risks in adopting CCORNT production practises.