Tillage index predicts weed seedling recruitment depth

Abstract

The influence of tillage on the depth of weed seedling recruitment has implications for species competitive ability, weed management strategy development, and the modeling of weed emergence; characterization of this relationship could aid in the creation of field-specific models of weed seedling recruitment. A tillage index based on the percentage of residue cover remaining on the soil surface after tillage events was assessed for 44 zero-tillage and 44 conventional-tillage fields across Manitoba, Canada. This index was related to in situ measurements of seedling recruitment depth from the same fields for five annual weed species. The modeled relationship was linear and unique for each species (R2 values ranged from 0.38 to 0.71). The relationship did not differ between pre- and post-seeding measurements, or between years, except for green foxtail. Slopes of the regression lines were greater for species such as volunteer wheat, which can recruit from a great range of depths. The results of this study show that recent tillage strongly influences mean weed seedling recruitment depth, and that the recruitment depth of summer annual weed seedlings is related in a continuous and reliable manner to a simple estimation of the relative level of tillage (including seeding) applied in one season. Key words: Recruitment depth, tillage index, weed emergence, weed seedlings