This four-year trial undertaken on the Mornington Peninsula from 2014 to 2018 investigated the use of compost under grapevines to determine system responses.

There is a large amount of research showing the benefits of applying compost to soil and this trial has focused on improving parameters such as:

• Soil health, evidenced by the soils ability to bounce back after herbicide is sprayed
• Water savings from improvements in water infiltration and reducing evaporation during warmer months
• Reduction to input costs by less herbicide applications
• Improvements to vine balance
• Improvements in winegrape quality

Method

Compost was spread at a rate of 25m3/acre using a fine compost and a composted mulch – one row of each product. In between a control row of no compost and standard management practice of herbicide application was in place.

Summary of results

Overall, the results showed that improvement in soil condition leads to better plant health and reduced water stress. As an example, one vineyard recorded irrigation savings of 20% in summer 2016 (dry year) where the control row used 2ml/ha and the fine compost block used 1.6ml/ha from November to March. This amounted to savings of 416,000l/ha.

In 2017, winegrape quality traits were measured by Vintessential Laboratories. Earlier ripening berries were observed in the rows with compost or compost mulch in three out of four vineyards. Autumn rains pose an issue through increase disease pressure so early ripening is desirable in the cooler climate of the Mornington Peninsula.

Bunchzone temperatures were warmer in cold nights on mulched rows and these nights lead to accelerated acid loss.

The layer of mulch acted as a weed suppressant for at least 3-6 months and reduced the need for herbicides during this time.

The following additional benefits to applying compost under vine were also observed:

• Healthier canopies with less senescence at veraison
• Mulch has a beneficial effect on leaf area of medium sized leaves which are the most productive leaves as they supply nutrients to the grapes later in the season.
• More fibrous roots in the top 300mm soil profile
• Mulch has a beneficial effect on colour
• Following harvest, the vine leaves held on longer with mulch than the control.

Since the trials began, over 37 vineyards have reported the trial or adoption of applying compost mulch under vine, resulting in over 193 hectares under this improved practice.

Acknowledgements

The trial was funded by the Australian Government’s National Landcare Program and was run in conjunction with the Western Port Catchment Landcare Network, the Mornington Peninsula Vignerons Association and the Australian Organics Recycling Association.

We gratefully acknowledge the invaluable contributions made by Declan McDonald, Soil Scientist with SESL, Erika Winter, Grapelinks Consultant and Tyson Lewis, Mornington Peninsula Vignerons Association.

Guide to compost use in vineyards

The below document provides guidance to wine growers on the application of compost or mulch on their vineyards. It is based on the results of the compost under vines trial.