Chapter 30

Cover Cropping in Vineyards

Types of Cover Crops

Many types of plants can be used as cover crops. Grasses (including cereals) and legumes and are the most extensively used, but there is increasing interest in brassicas (such as rape, mustard, and forage radish) and continued interest in others, such as buckwheat. Some of the most important types of cover crops are discussed below. Choosing a cover crop depends largely upon the objectives in the overall vineyard management plan.


Legumes are broad-leaved, annual or perennial species known for their ability to fix atmospheric nitrogen (inert gas) into usable forms. Nodules on the roots are the "factories" that house nitrogen-fixing bacteria (Rhizobium spp.) that form a symbiotic relationship with legume roots. Nitrogen accumulations by leguminous cover crops range from 40 to 200 pounds (18 to 90 kg) of nitrogen per acre. The portion of green-manure nitrogen available to grapevines is usually about 40 to 60 percent of the total amount contained in the legume. If growing legumes it is better to incorporate them into the soil when they are blooming to get the maximum addition of nitrogen.

Carbon-to-Nitrogen Ratio

Legume-based cover crop systems can also play an important role in the short- and long-term cycling of soil nitrogen and carbon in an agroecosystem. Legumes are generally lower in carbon and higher in nitrogen than grasses.

Cool Season and Warm Season Legumes

Cool season (winter) annual legumes are generally planted in the fall and provide forage in late fall and spring. These plants flower and produce seed in late spring and die soon after seeds mature. Cool season annual legumes differ substantially in their preferred soil characteristics, growth distribution, cold tolerance, bloat potential, and reseeding potential.


Grass cover crops produce high biomass and dense fibrous root systems preventing soil erosion. Grasses are higher in carbon than legume cover crops. Because of their high carbon content, grasses break down more slowly than legumes, resulting in longer-lasting residue. As grasses mature, the carbon-tonitrogen ratio (C:N) increases. This has two tangible results: The higher carbon residue is harder for soil microbes to break down, so the process takes longer, and the nutrients contained in the cover crop residue usually are less available to the grapevines.

Carbon-to-Nitrogen Ratio

Grass-based cover crop systems can also play an important role in the short- and long-term cycling of soil nitrogen and carbon in an agroecosystem. Grasses are generally higher in carbon and lower in nitrogen than grasses. This higher C:N ratio results in slower breakdown of grass residues. Initially, soil nitrogen availability may be substantially decreased following their incorporation into the soil.

Cool Season and Warm Season Grasses

Grasses are often described by their growth cycle through a year: cool season and warm season grasses. The main growing period for cool-season grass is in spring and fall when soil temperature is 50 to 65 degrees F (10 to 18°C), and the air temperature is 60 to 75 degrees F (16 to 24°C).


Brassicas used as cover crops include mustard, rapeseed, and forage radish. They are increasingly used as winter or rotational cover crops in vegetable and specialty crop production, such as potatoes and tree fruits. Rapeseed, also known as rape, grows well under the moist and cool conditions of late fall, when other kinds of plants are going dormant for winter.


Buckwheat is a summer annual that is easily killed by frost. It will grow better than many other cover crops on low-fertility soils.

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