Adapted From: Bugg, R.L., and M. Van Horn. 1998. Ecological soil management and soil fauna: best practices in California vineyards. Pp. 23-34 in: R. Hamilton, L. Tassie, and P. Hayes (eds). Proceedings of the Viticulture Seminar: Viticultural Best Practice, Mildura Arts Centre, 1 August, 1997, Mildura, Victoria, Australia. Australian Society For Viticulture And Oenology, Inc., Adelaide, South Australia, Australia.
Cover crops are important tools for ecological vineyard management and used to promote soil life, prevent soil erosion , add N, improve soil structure, manage soil moisture, enhance trafficability during wet weather, suppress resident vegetation, and to promote beneficial arthropods. Improperly selected or managed cover crops may reduce vine growth and yields, or grape quality, and increase frost problems.
There is a rich array of cover-cropping options. In vineyards, a wide range of species may be used, including several annual and perennial plants that can be managed to self-regenerate. Winter-annual grasses and legumes are often used.
Many vineyardists in North Coast counties manage winter-annual resident vegetation as a cover crop intended to protect the vineyard soil from erosion during the most intense winter rains. Tillage by mid-March and thereafter at intervals is intended to provide vegetation-free middles until fall rains enable the winter-annual cover crop seeds to germinate. With such a schedule, only early-maturing, low-growing, low-biomass herbaceous plants can complete their life cycles.
Seeded winter-annual cover crops include large-seeded mixes with vetches, field pea, bell bean and oat. These are often tilled under at peak bloom. Small-seeded mixes managed without tillage often include 'Blando' brome (soft chess) and several legumes: burr medic and various clovers: crimson, Persian, rose, and subterranean.
Proper management ensures success of a cover crop:
- Disk to prepare good seedbed;
- Inoculate and broadcast seed;
- Incorporate seed using a drag: 1.25 cm depth is a good compromise depth if there is a mixture of large- and small-seeded species;
- Irrigate as needed to establish and maintain.
- Mow at appropriate heights and times for various purposes: to reduce weeds, prolong flowering, postpone maturation, increase biomass production, reduce frost threat, or to kill the cover crop.
California native perennial grasses used in vineyards include several bunchgrasses and a few sod-forming species. These present both challenges and opportunities to winegrape vineyardists. In general, these grasses are suitable in vineyards that are dry-farmed or irrigated by sprinkler or drip systems, and may be used with some difficulty in those that are irrigated by flood or furrow. Difficulties that may arise in the use perennial grasses include:
- The relatively high price of seed relative to most other cover crops;
- Poor seedling vigor makes establishment difficult where high seed densities of vigorous winter-annual species occur;
- Possible increases in pocket gophers, necessitating special vigilance and an intense trapping program;
- Possible excessive devigoration of vines through competition for soil moisture or nitrogen, necessitating careful matching of soil type, rootstock vigor, native perennial grass phenology, seeding pattern, and irrigation system.
Some advantages include the following:
- One-time establishment cost for native perennial grasses may be amortized over a ten-year period;
- Some native perennial grasses are summer dormant, drought tolerant, and have low stature;
- Fibrous roots of perennial grasses absorb nitrate, bind soil, add soil organic matter (humus);
- Native perennial grasses may reduce weeds;
- Pollen of grasses is food for some lacewings and predatory mites;
- Some native perennial grasses work well with winter-annual legumes;
- Perennial grasses provide excellent trafficable surfaces that allows vehicles entry for critical fungicide applications during wet springs.
Recommended Reading: Ingels, Chuck A., R.L. Bugg, Glenn T. McGourty, and L. Peter Christensen, eds. 1998. Cover Cropping in Vineyards: A Grower's Handbook. University of California, Division of Agriculture and Natural Resources. Publication 3338.
Robert L. Bugg
Assistant to the Director
U.C. Sustainable Agriculture Research and Education Program
University of California
One Shields Avenue
Davis, CA 95616-8716
U.S.A.
530-754-8549 PHONE
530-754-8550 FAX
rlbugg@ucdavis.edu