Screening Cover Crops for Sustainable Grape Production in Ontario, Canada.

Cover crops have been increasingly adopted by the temperate region grape growers as an effective tool to improve long-term productivity and environmental sustainability. A suite of cover crops was evaluated in 2014 and 2015 for their impact on soil properties, soil mineral nitrogen (N), cover crops biomass, and grape yield and quality in three major grape growing regions of Ontario, Canada (Prince Edward County (PEC), Niagara and Lake Erie north shore (LENS)). Treatments include annual ryegrass (AR, control), annual ryegrass+red clover (AR-RCl), annual ryegrass+forage radish (AR-FR), creeping fescue+microclover (CF-MC), and a mixture of cover crops including oats and Italian ryegrass, red clover, alfalfa, alsike clover, and forage radish (SuperMix).  Each treatment replicated three times. Soil samples were collected once at budbreak for soil properties (0-15 cm depth) and four times during the growing season for mineral N (0-30 cm depth; bud break, flowering, veraison and harvest).  The AR+RC and AR+FR treatments had the highest biomass in the PEC region, and AR+FR had the highest biomass in the NE and LENS regions. The CF+MC treatment generally had poor growth overall. Weed suppression was greatest in cover crop treatments with high biomass. The differences in soil properties among treatments were not significant in two years. Soil nitrate concentrations among treatments or sampling date in each location were not different in 2014. The AR+RC and SuperMix treatments had significantly higher soil nitrate concentrations compared with the AR treatment only in Niagara and PEC in 2015. Nitrate concentrations were the highest in the veraison stage and the lowest in the bud break and flowering stages in Niagara in 2015. Nitrate concentrations were highest in the bud break stage and lowest in the veraison and flowering stage in PEC 2015. Grapes yields did not affect by treatments except AR treatment in 2014 at PEC had significantly less grape yield than other treatments. Effect of cover crops on yield quality parameters (Brix, TA and YAN) was not significant. The AR+RC or AR+FR in the PEC region and AR+FR in the NE and LENS regions showed promising preliminary results (high cover crop biomass and weed suppression) with minimal cost differences from annual ryegrass.