Cover crop, or cover crops can be defined as a non-economic crop which is deliberately grown in combination with the cash crop to enhance it (Chuck A Ingels and Karen M Klonsky (1998, p.3). In vineyards, cover crops are grown between the rows of vines which, via their grapes, provide the cash crop.
Types of cover crops: Ingels and Klonsky (ibid.) say most cover crops are classified as winter or summer annuals, which germinate and die in one year or less, or perennials, which live for three or more years. Often, cover crops are also classified based on taxonomy, mostly being either legumes (Fabaceae family) such as clovers and vetches, or grasses (Poaceae family) such as barley and fescues. Other plant types used as cover crops include brassicas (Brassicaceae family) and phacelia (Hydrophyllaceae family). In addition, weeds are often simply allowed to grow and be managed like a cover crop. This “resident vegetation” offers some of the benefits of a sown cover crop, such as improved water penetration, although the plant species may vary greatly and may include undesirable weeds, the authors say.
Why cover crops?: They stabilise and improve soil structure, prevent erosion, improve water and nutrient retention, make access to the vineyards easier in wet weather, and enhance soil micro-biology (Welte, 2002).
Their flowering component attracts and feeds beneficial insects and improves pest management by increasing beneficial organisms and the presence of of non-host plant species (Welte, 2002).
Their roots oxygenate the soil and subsoil according to their rooting depths (Welte, 2002).
They improve the soil structure and increase soil organic matter and soil protein, transforming organic soil matter to humus and/or conserve nitrogen, increase soil nutrient content and soil fertility and crop nutrition (Welte, 2002).
They reduce soil compaction, increase water infiltration and water holding capacity, increase soil micro- and macro-organism activity (bacteria, fungi, worms), suppress soil and plant pathogens and provide health to soil and vine, decrease nutrient and trace element leaching, protect young vines from wined damage and reduce the risk of wind and water erosion (Welte, 2002).
They promote biodiversity above ground (Andreas Welte: 2002, Vol 55).
Plants used as cover crops: Alfalfa. | Alyssum. | Barley (Hordeum vulgare). | Blando Brome. | Brassica or crucifer family. | Broad beans (Vicia faba). | Chicory. | Crimson clover (Trifolium incarnatum). | Crucifer–see Brassica. | Daikon radish. | Egyptian clover. | Einkorn. | Grasses. | Legumes. | Lucerne. | Mustard. | Oats (Avena sativa). | Plantain. | Red clover. | Rye (Secale cereale). | Serradella. | Spelt (Triticum spelta). | Squarrose clover (Trifolium squarrosum). | Tansy phacelia (see also Phacelia). | Wheat.
Chuck A. Ingels & Karen M. Klonsky, ‘Historical and current uses’ in Cover cropping in Vineyards, A Grower’s Handbook’, University of California Division of Agriculture and Natural Resources, Publication 3338, 1998, p.3.