Winetech Technical Yearbook 2022

PHOTO 3. This mulcher is an example of an implement that chops up cover crop and pruning shoots and spreads the mulch on the berm. (Photo: Francois Viljoen.) nutrients are thus lost. Organic material also serves as nutrient source for micro-organisms which improve soil health. The use of mulches therefore holds multiple advantages, like water conservation, suppression of weeds, soil improvement in terms of carbon content and microbial activity, and ultimately improved yield and quality in water-scarce areas (photo 2). The type of material used, must be fibre-rich to retain its shape for an extended period in the sun, wind and weather. The most common option is to spread out one small bale of hay between three vines; approximately 1 000 bales per hectare. At a purchase price of R17 to R20 per bale it is a staggering amount, even if it lasts for two to three years. The cost of buying organic materials like hay or wood chips for establishing a mulch, is currently the biggest limiting factor preventing its widespread application. Most producers currently applying this practice, produce their own hay and other organic materials. ALTERNATIVES The cultivation of cover crops in the work row is a generally common practice and we currently have commercial species that can be successfully cultivated under various conditions. According to Fourie (1994), a good cover crop stand can produce up to seven tons of dry material. Species like triticale in particular is known for good fibre production. In 2020, results from the Gen-Z cover crop demo sites (Barenbrug seed) in the Paarl area found that different cover crop combinations were able to yield seven to 10 tons of dry material per hectare. It is thus possible to produce large amounts of dry material in the vineyard at relatively low cost. Pruned cuttings is a further source of material, and at an average vigour, 0.6 kg dry shoots are produced per metre of cordon, thus around two tons per hectare. Mechanisation in the vineyard has advanced significantly over the past few years and this has seen the introduction of implements for finely cutting the cover crop and shoots into a mulch and spreading it on the berm. An example of this can be seen in photo 3. In this way a mulch is placed on the berm, but the work row is cut to a stubble (unless the cover crop can form regrowth), which can in turn lead to summer weed problems in the row. This practice is not recommended for dry areas, as evaporation of water in the work row will increase. The cover crop’s fibre content is also not optimally developed using this approach, and if cut

PHOTO 4. A medics cover crop was established early in the winter on the berms of this vineyard in the Stellenbosch area. (Photo: Emma Carkeek.) too finely, it will not last long on the berm. Nutrients are however released faster from the green, mulched cover crop. Producers have also been performing trials with living mulches over the last few years. Medics, already established early in the year on the berms, are mostly used for this. Photo 4 shows a vineyard where medics had been established early autumn on the berms, and photo 5 shows the same vineyard in springtime. The medics species grow until spring, past the vines’ budding period, and it is important to check the vines for any symptoms of competition. It is consequently not a good option for dryland vineyards. POSSIBLE SCENARIOS AND COST OF THE OPTIONS The following table indicates possible scenarios where mulching can add value to yield and quality. The purchase cost of materials is expensive, but the materials can also be produced by producers themselves, which will lower the cost.

PHOTO 5. Medics naturally dying off on the berm after setting seed.

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WINETECH TECHNICAL YEARBOOK 2022