Effectiveness of living and compostable mulches for weed control in Pacific Northwest highbush blueberry

When managed properly, living mulches in many horticultural systems can effectively suppress annual weed growth while not negatively affecting crop productivity. Compostable plastic mulches (CM) also show promise for weed control in many crops, and are currently being investigated for usefulness in berry production systems. In a newly-transplanted blueberry trial, 'Draper' plants were transplanted from 3.8-L pots into the field in March 2015. Greenhouse-grown living mulch plants, creeping buttercup (Ranunculus arvensis) and sweet woodruff (Galium odoratum), were transplanted to a density of 10.8 plants m^-2 at the same time as blueberry. Other plots were treated with 5 cm of sawdust or by CM (black spunbond polylactic acid plastic) to cover all bare soil. Soil in the fifth treatment was left bare. CM provided good to excellent weed control, reducing weeding time 97% in May and 82% in July compared to bare ground plots. Sawdust also reduced weeding time by 70 and 66% in May and July, respectively, compared to bare ground plots. Living mulch did not reduce weeding time in May of the establishment year compared to bare ground plots, but weeding time was reduced by about 70% in July. In a separate trial in established 'Duke', creeping buttercup and sweet woodruff were transplanted as described above in March 2015 and their effects on weeds and blueberry were compared to those from sawdust mulch. Living mulches did not affect hand-weeding time, fifty-berry weight, or berry yield in July of the living mulch establishment year.