Productivity , Economics , and Fruit and Soil Quality of Weed Management Systems

11 Organic tree fruit producers often rely on tillage in the tree row to control weeds and disrupt 12 rodent pest habitat. This inexpensive practice can potentially damage the trees’ trunk and roots, 13 thereby reducing yield and fruit quality. In contrast, mulching under the trees to suppress weeds 14 often improves tree performance but at a high initial installation cost, whereas flame weeding 15 and organic-compliant herbicides can control weeds without disturbing the soil. These three 16 systems of weed management in the tree row were compared in commercial, certified organic 17 apple and pear orchards in Washington State, USA, to determine the effectiveness for weed 18 control, and the impacts on tree performance, soil organic matter, and economic return of each 19 system when taking into account both the cost of the weed control itself and its impact on fruit 20 yield and quality. Mulching produced a large net economic benefit relative to tillage, more so in 21 the apple orchard that had sandier soil than in the pear orchard on a loam soil. Flame weeding 22 was similar to tillage in cost, whereas organic herbicides proved extremely expensive and 23 relatively ineffective. Tillage did not lead to a decline in soil organic matter over three seasons, 24 nor did mulching increase it. Overall, mulching led to better tree performance and economic 25 returns but was not a successful stand-alone weed control practice over three years. A 26 combination of flaming and tillage and/or mulch may offer the best overall results. 27 28