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ISHS Acta Horticulturae 1133: XI International Rubus and Ribes Symposium

Weed control increases growth, cumulative yield, and economic returns of machine-harvested organic trailing blackberry

Authors:   E.K. Dixon, B.C. Strik
Keywords:   landscape fabric, weed mat, Rubus, economics, certified organic, weed management, cost
DOI:   10.17660/ActaHortic.2016.1133.50
A trailing blackberry planting was established at Oregon State University's North Willamette Research and Extension Center (Aurora, OR, USA) in 2010 to evaluate cultivar and weed management practices for a machine-harvested, processed fruit market. The planting was 0.4 ha in size and was certified organic (Oregon Tilth) in 2012, prior to the first harvest. Treatments studied were cultivar ('Marion' and 'Black Diamond') and in-row weed management [non-weeded, hand-weeded, and a porous, polyethylene ground cover (weed mat)] during establishment and three fruiting seasons (2012-2014). On average, plants growing in hand-weeded and weed mat plots produced 50% more primocanes than those in non-weeded plots, but the resulting floricane biomass was 50% higher in weed mat plots than either hand-weeded or non-weeded plots. This difference in plant growth response to the weed management treatments led to weed mat plots producing 36.1 t ha-1 of cumulative yield, 25 and 100% greater than the hand-weeded and non-weeded plots, respectively. Weed control (either with hand-weeding or weed mat) increased average berry weight compared to the non-weeded plots. Weed mat required a high initial investment to install, but only 16 h ha-1 to maintain over the study period (labor was valued at US$ 15 h-1). The non-weeded and hand-weeded treatments required 25 and 215 h ha-1 of labor to mow tall weeds prior to harvest or hand hoe, respectively. Total cumulative costs, including materials and installation (weed mat) over the 5 years were US$ 3,302 ha-1 for weed mat, US$ 3,231 ha-1 for hand-weeded, and US$ 370 ha-1 for non-weeded. Despite the relatively low cost of the non-weeded management strategy, low yield significantly reduced net returns (gross fruit sales - weed management costs). The hand-weeded and weed mat management strategies increased net returns by 40 and 71% compared to non-weeded, respectively. Weed mat had a 22% greater cumulative net return than the hand-weeded treatment. Weed mat increased growth, yield, and net returns and appears to be an excellent option for weed management in machine-harvested organic trailing blackberry.

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