Ground cover

This can be:

  • temporary, i.e., planted in the autumn and destroyed in the summer: costly unless the plant can re-seed itself (often used in Napa & Sonoma with field mustard – produces classic ‘golden vineyard’ look by early spring) due to a short life-cycle or strip-tillage, where some of the plants are allowed to grow to seed.
  • Permanent: planting permanent cover crop or allowing natural vegetation to grow.

Cover crop

Best sown in the autumn after careful soil preparation at high seed rates. Must stop using residual herbicides well before. The criteria for selecting cover crop:

  • Quick to establish
  • Adapted to soil and climatic conditions (particularly drought in some areas)
  • Correct level of vigour
  • Hard wearing
  • Provides good cover
  • Leguminous? E.g. red fescue and white dwarf clover
  • Low growth habit
  • Can re-seed itself
  • Secondary crop?

Is often the case that mixtures of crops are used.

Natural vegetation

This is well-suited to the conditions, cheap and leads to greater biodiversity, but can be difficult to manage and harbour pests.

It is important to manage cover crop properly:

  • Mow very closely before budburst (frost)
  • Mow again a couple of weeks before flowering to boost vigour
  • Allow to grow at veraison
  • Alternate row mowing will allow better biodiversity

Note that some cover crops will not survive close mowing. As crops get more mature, their biomass increases and they become woodier, thus taking longer to break down when mown or incorporated into the soil.

Advantages & disadvantages of ground cover

Advantages Disadvantages
  • Increased bearing capacity (trafficability) of the soil, particularly in wet weather
  • Good soil structure: high organic matter levels and roots break up soil, reducing compaction
  • Leguminous plants (clovers, medics and vetches) can reduce fertiliser requirements
  • Control of vine vigour due to competition with water
  • Encourage deep rooting in vines
  • Reduced erosion risk & increased water infiltration
  • Suppression of undesirable weeds by competing for light
  • No dust or mud problems
  • Surface mulch is formed, which can trap moisture in the soil
  • Reduced nitrate leaching
  • Possibility of secondary crop
  • Aesthetic
  • Environmentally acceptable, can increase biodiversity
  • Promotes soil life
  • Reduction in vine vigour can be excessive, particularly with young vines, poor and shallow soils or dry climates (<650 mm annual rainfall)
  • Humidification of microclimate, encouraging fungal diseases
  • Cooling of microclimate, discouraging ripening
  • Inefficient use of fertilisers
  • Increased spring frost risk
  • High maintenance costs compared with herbicide control, particularly as under-row area usually has to be controlled separately
  • Can be too slippery on slopes

Generally regarded as a quality method, and gaining in popularity for low density highly mechanised vineyards. Is it suitable under cold-climate conditions?
Good compromise could be to apply alternate rows of cover crop / cultivation, changing around every few years.