Organic Options for Managing Weeds in Highbush Blueberries

Abstract

Weeds are especially problematic in highbush blueberry which has a long establishment period, shallow-fibrous roots, and poor competitive ability in obtaining water, nutrients and sunlight. Commercial approaches in certified organic blueberry fields compared horticultural management methods in two New Jersey sites. The trials utilized both new and established blueberry blocks having trickle or overhead irrigation. Commercial methods investigated included rotary cultivation, mowing, propane flaming, cover crops, landscape fabric, and various mulches. Mulch comparisons included pine bark mulch, hardwood mulch, coffee grinds, cocoa grinds, municipal leaf mulch, and composted tea leaves. 3' × 12' plots were replicated 4 times in 4 adjoining rows. Applications of 3-4 inches of these mulches within the crop row to a new planting of Duke highbush blueberry have provided a combined weed control level of ca. 95% without landscape fabric and ≈98% with landscape fabric during 2003. Walkway weed suppression in new plantings was achieved with the establishment of two types of fine leafed turf fescues and monthly mowings. Bare ground percentage decreased from 80% to <2% within one year's time as these fine fescues gradually out-competed annual weeds for space. These fescue cover crops increased ground coverage from 8% to >95% over the seven month growing season. Such varieties were selected because they have good germination, require little water, use limited nitrogen and can squeeze out weeds through allelopathy. Applied research studies indicate that several suitable methods can be utilized for effective weed management in organic highbush blueberry production systems.