Many soils have a poor natural fertility and low organic matter levels and can become easily degraded through intensive agricultural practices.
When a soil becomes degraded, fertiliser, water and amendment (e.g. lime and gypsum) inputs generally increase which is a further cost to both the grower and the environment.
The surface application of mulch and/or compost is being increasingly used in vineyards since they are proving to be viable economic options with a range of potential benefits.
Which product too choose, and how should it be applied
It is important to identify why you want to apply mulch and/or compost since the potential benefits are only achievable if the correct product is used at the correct rate of application.
Since the choice of product will depend on the specific needs of the vineyard, the following factors should be considered:
Where the primary objective is to conserve soil moisture, suppress weed growth, reduce topsoil temperature fluctuations and/or minimise erosion, coarse-textured mulches are recommended. The coarseness in texture allows water and air to reach the soil easily.
Where the primary aim is to improve soil health (i.e. physical, chemical and biological properties) and fertility, composts are recommended. These generally have a finer texture than mulches and as a result, water can be prevented from reaching the soil if the material is applied too thick.]
Application rate and frequency
For coarse-textured mulches, aim to achieve a depth of about 50–75 mm
(no greater than 100 mm), and a band width of at least 500 mm.
For finer-textured composts, aim to achieve a depth of about 25 mm (no greater than 50 mm) and a band width of at least 500 mm.
When using compost as a sub-soil conditioner, the nutrient content of the product in relation to vine requirements should be used to determine application rates.
Depending on the type of product used, soil type, environment and management practices, a 3 to 5 year benefit can be realised before a further application is required.
Benefits of using Mulch and Compost in the Vineyard
Benefits of Mulch
- Improved soil water retention and water use efficiency / less irrigation requirements
- Reduces solar radiation and wind speed at the soil surface, thereby reducing water loss through evaporation.
- Additional increases in organic matter through decomposition, improves soil structure and hence, soil water storage, aeration and drainage.
- Reduced weed growth / less herbicide requirements
- Suppresses the emergence and growth of weeds. Weed suppression increases as the thickness of the layer increases.
- Reduced fluctuation in topsoil temperature / less heat damage and vine stress
- Buffers changes in topsoil temperature and radiation, thereby promoting a more even temperature regime for root survival and fruit ripening. Darker products generally heat up more than lighter products.
- Reduced soil and nutrient loss / less vineyard inputs
- Protects topsoil from the direct impact of rain and wind, thereby reducing erosion and land degradation.
Benefits of Compost
- Improved soil health and vine performance / less vineyard inputs
- Under suitable environmental conditions, increases topsoil organic matter and humus levels with subsequent improvements in soil physical, chemical and biological properties. Benefits include improved soil aggregation and structure, water infiltration and aeration, water and nutrient holding capacity and soil organism population, diversity and activity.
- Micro-organism activity in the rhizosphere (area immediately surrounding roots) is particularly beneficial.
- Improved soil fertility / less fertiliser requirements
- Contains nutrients (particularly N, P, K) present in both inorganic and organic forms. Inorganic nutrients become available immediately, while organic nutrients are released slowly over time as material undergoes further microbial decomposition. The decomposition rate of organic matter and subsequent release of nutrients is determined by climate, soil types and management practices.
- Reduced pests and diseases issues / less chemical inputs and reduced risk of crop loss.
- Increases the population, diversity and activity of beneficial soil organisms which reduces the risk of pathogen growth and may also increase vine resistance to diseases.
Factors to consider and assess when using mulch and compost
- The needs of a vineyard should be assessed on an individual block basis depending on soil health, vine growth and crop productivity, and fruit and wine quality specifications.
- The use of mulch and/or compost banded under vine in combination with mid row cover crops is a highly beneficial synergy for improving soil health, organic matter and nutrient levels.
- Monitor soil moisture content, particularly when using mulch, to manage irrigation scheduling requirements.
- Monitor vine nutrient status and check for deficiency symptoms associated with ‘nitrogen drawdown’ when using mulch since the Carbon: Nitrogen ratio may be high.
- Compost can influence vegetative growth and fruit composition through the addition and improved soil availability of nutrients.
- Consider monitoring changes in soil health attributes (especially those associated with biology) when using compost.