Alternative Weed Management Tools in Organic Vineyards: Efficacy, Costs, and Carbon Emission Estimates.

Weed management in organic vineyards in the San Joaquin Valley (SJV) is a challenge because of the costs involved and the need for compliance with local air quality regulations. Studies were conducted from 2010 to 2013 in organic raisin and winegrape vineyards at two locations in the SJV. Weed management practices included steam, French plow (raisin vineyard only), Bezzerides tree and vine cultivator, and an organic herbicide (Greenmatch®). These treatments were followed by a second treatment of steam, organic herbicide, or hand weeding. Non-weeded controls were also included. The mechanical (plow and cultivator) treatments provided the greatest level of weed control. The time required to hand hoe mechanically cultivated plots was also lower than the other treatments. Steam and herbicide only suppressed weeds for 2-3 weeks, and the time needed to hoe these plots were similar to the non-weeded control plots. The mechanical treatments also were 2-4 times more cost-effective than steam or herbicide. Therefore, mechanical treatments were the most effective and economical weed control methods, though none of the treatments affected vine growth, mid-day stem water potential, petiole nitrate concentration at bloom, grape yield, or quality. The mechanical weed control methods also had lower carbon emission (CE) values than the steam and organic herbicide treatments. Between the two mechanical weed control methods, the tree and vine cultivator had lower CE than the plow. In areas with strict air quality and other environmental regulations, such as the SJV, these types of analyses may have important implications.