The Australian Wine Research Institute

Background

Several different tools are used by wine-grape growers across Australia to manage undervine weeds without chemicals. Most growers use a combination of different tools to achieve good weed control.

Mulches are spread undervine to help with moisture conservation and to add nutrients to the soil. High rates of mulch can also help to suppress weed growth. Various organic materials can be used as mulches.

Figure 1. Straw mulch spread undervine using a Kuhn Primor Straw Blower (image courtesy of Steve Schiller)

Action

Straw mulch suppresses weed germination by blocking sunlight from the weed seeds and their germinants. Some crop species that are used to make straw produce allelopathic chemicals, which can help to suppress weed growth. Generally, wheat or triticale straw is used, as their rate of breakdown is slower than other crops.

Advantages and disadvantages

Advantages: Straw mulch use provides long-term weed control (two to three years). It can be used in blocks with large or excessive stones where other tools cannot be used, and where tillage and mowing are difficult. Straw helps keep the soil surface cool and protected from evaporative water losses. It provides a source of carbon and does not disturb the soil, which can contribute to improved soil health. There is no risk of damage to vines from this practice.

Disadvantages: Straw mulch can increase frost risk in frost-prone areas and increase fire risk. It can create issues with trafficability, particularly in narrow rows (<2 m) and may be disturbed by grazing animals or flooding. Straw mulch can also harbour snails and other pests. In vineyards of low fertility, nitrogen drawdown caused by the straw can reduce vine growth unless supplementary nitrogen is applied.

Table 1. Advantages and disadvantages of straw mulch

Considerations

When considering which weed control tools to use, it is important to base the decision on each vineyard’s individual characteristics. Factors such as soil type and condition; slope; rainfall and water availability; weed pressure; vine age, vine vigour; fruit end-use targets; weather conditions and compatibility with existing infrastructure and equipment should all be considered.

When considering straw mulch, it is important to consider its impact on vineyard trafficability, particularly in vineyards with narrow rows, as well as the impact on frost and fire risk.

It’s recommended to check the straw supplier’s spray diary to ensure the chemicals used in the straw production are not going to adversely affect vine growth (e.g. Lontrel®). Growers should also make sure the straw is free from weed seeds and pests.

Table 2. Ease of using straw mulch on different soil types