Does a native and introduced cover crop species differ in their ability to suppress? A study in a table grape vineyard

Authors: Fernando, Margaret; Hale, Lauren; SHRESTHA, ANIL - California State University

Submitted to: International Journal of Pest Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2024
Publication Date: 10/25/2024
Citation: Fernando, M.R., Hale, L.E., Shrestha, A. 2024. Does a native and introduced cover crop species differ in their ability to suppress? A study in a table grape vineyard. International Journal of Pest Management. p. 1-9. https://doi.org/10.1080/09670874.2024.2419902.
DOI: https://doi.org/10.1080/09670874.2024.2419902

Interpretive Summary: Cover crops can serve as a tool for weed management in vineyards when herbicide application or soil disturbance via discing are undesirable. This study compared the use of a native plant species winter cover crop for weed management to that of an introduced plant species and an herbicide-maintained control. We hypothesized that owing to adaptive advantages the native cover crop would outperform the introduced species for weed suppression, which it did in regards to weed biomass, cover: weed ratios, and weed seed bank. However, neither treatment outperformed the herbicide-maintained control, suggesting additional management would be necessary to supplement cover crops for vineyard weed suppression.

Technical Abstract: Cover crops are valuable tools for sustainable agricultural systems due to their numerous benefits for the agroecosystems, in general, and soils in particular. Weed suppression is considered one of those benefits. However, weed suppression by cover crops is often inconsistent. We hypothesized that a native cover crop may have better ability to suppress weeds than an introduced species due to their advantage in adaptability. A study was conducted from 2020 to 2022 in a newly established Autumn King table grape vineyard in a semi-arid region in Parlier, CA, USA. The impact of a native species phacelia (Phacelia tanacetifolia), an introduced species rye (Secale cereale L. ‘Merced’), both as cover crops, and a control without cover crop on weeds was compared. Cover crops were sown in 2019 in the centre 1.8 m of the 3.6 m space between the grapevine rows. The experimental design was a randomized complete block with four replications. Percent cover, weed density, and weed biomass in different seasons were assessed in the inter-row spaces and the vine rows. Soil samples were collected in 2021 from these locations to assess the weed seedbank. In two of the seasonal samplings, after the cover crops had been terminated, percent weed cover was lower in the interrow of the phacelia treatment compared to the control. During the growing season of the cover crops, phacelia plots also showed lower weed biomass and higher cover weed biomass ratio compared to the rye plots with values of 27.7 and 4.0 respectively. However, greater weed seedling emergence was observed in the cover crop plots than in the control plots with mean values of 870, 1740, and 414 plants m-2 in phacelia, rye, and the control, respectively. In summary, the native species cover crops had more potential for weed control compared to the introduced species in this study. However, there was an increase in the weed seedbanks with both cover crop treatments, so additional management practices will be needed for long term weed management in conjunction with cover crops in vineyards.