Biomass carbon and nitrogen input from cover crops in an irrigated vineyard in Okanagan Valley, Canada

Abstract

Context and purpose of the study – The use of cover crops in vineyards has been encouraged by positive effects on wine grape yield and sensory attributes, and improved soil function. This study examined the efficacy of three alleyway and three undervine cover crop treatments in an organic vineyard in the semiarid Okanagan Valley, Canada in 2021.

Material and methods – Superior cover crop species were selected based on previous greenhouse and field species screening experiments. Three alleyway and three undervine cover crop mixtures were established in 2021. The vineyard was equipped with drip lines for irrigating vine rows, and undercanopy sprinklers for irrigating alleys. The dry biomass of cover crops and weeds, and carbon and nitrogen accumulation of the cover crop treatments were measured in the 2021 season and are reported here.

Results – Alley cover crops produced different dry biomass and biomass carbon content in order of ryegrass+tillage radish+white clover (1656 kg/ha and 650 kg C/ha) > fescue+white clover (952 kg/ha and 393 kg C/ha) > winter rye+hairy vetch (431 kg/ha and 184 kg C/ha). The proportion of cover crops dry biomass to total groundcover biomass in alleys followed a similar order. The tissue nitrogen content of the cover crops in alleys was the greatest in ryegrass+tillage radish+white clover (45 kg N/ha) and the lowest in winter rye+hairy vetch (15 kg N/ha).  Total alley dry biomass nitrogen content (cover crops + weeds) was between 50 to 65 kg/ha in cover crops plots, which was significantly greater compared to control (weeds only) plots with nitrogen content of 34 kg/ha. Undervine cover crops produced different dry biomass and biomass carbon content in order of Ladino white clover (2029 kg/ha and 839 kg C/ha) ≥ lentil (1409 kg/ha and 603 kg C/ha) > annual ryegrass+birdsfoot trefoil (155 kg/ha and 64 kg C/ha). The tissue nitrogen content in undervine cover crops was the greatest in Ladino white clover (67 kg N/ha) followed by lentil (36 kg/ha) and annual ryegrass+birdsfoot trefoil (2.6 kg N/ha).  Ladino white clover was more effective in suppressing the weeds (55% total biomass) followed by winter lentil (30% total biomass) and annualryegrass+birdsfoot trefoil (4% total biomass) under the vines. We concluded that white clover, tillage radish, and perennial ryegrassmixture in alleys and Ladino white clover under vines were best suited to irrigated vineyards in this region.