The Australian Cooperative Research Centre for Viticulture report on Improving Soils in Vineyards (CRCV report) discusses soil issues, such as  soil salinity, crusting and hard-setting, which results in poor water and nutrient movement into the root zone as well as poor root growth and impaired root function. And can also trigger erosion on slopes as the smooth soil surface increases the rate of water run-off from irrigation and heavy rainfall events.

Crusting occurs when soil aggregates are broken down by the impact of water droplets, resulting in soil particles setting into a hard crust, in the top 10mm of soil, ⁽¹⁾. Soil aggregates under the crust are protected from further impact caused by water droplets. The crusting prevents the movement of fertilisers and water through the soil profile.

Hard-setting (CRCV report) is similar to crusting as it is caused by the breakdown of soil surface aggregates by water droplets or flooding, but the effect extends to depths greater than 10mm. To identify at risk areas, note areas of ponding and areas where the soil remains saturated at the surface for several weeks following heavy rain.  

Applications of saline water or highly saline ground water as well as a build up of salts from fertiliser applications can cause sodium accumulation in the upper soil profile in vineyards. High levels of sodium causes weak soil structure, where soil aggregates disperse upon wetting. Even soils irrigated with good quality water can be leached of components, such as calcium, which assist in binding clay particles together.

The CRCV report suggests soils most prone to hard-setting and/or crusting usually have low levels of organic matter as well as a soil chemistry imbalance.

Organic Matter

Soil structure improvements can be made with changes in soil management practices as well as regular applications of organic matter and gypsum.

Organic matter plays an important role in binding soil particles together  and protects the soil surface from the physical impact of water. As organic matter decomposes, the compounds produced assist in maintaining aggregate stability.

The Western Australian Wine Institute report on Managing Grapevine Nutrition and Soil Health, outlines straw, cover crop trimmings, mulches, and compost are examples of organic matter that can be used in vineyards.

Regular annual applications of gypsum encourages the flocculation of clay particles into aggregates, preventing soil crusting and hard setting of soils occurring. Gypsum also encourages soil structure improvements, aeration and allows water to drain more freely through soil profile.

For salinity issues, the calcium in gypsum displaces sodium from the clay colloids, removing it from the soil profile.  This promotes better overall soil structure to allow sufficient infiltration of water and movement of nutrients through the soil profile.

Talk to your fertiliser advisor about the benefits of using gypsum in your vineyard. Gypsum is BioGro certified. Gypsum- it all starts with healthy soil.

References

1. CRCV Improving Soil in Vineyards report https://www.awri.com.au/wp-content/uploads/2014/09/on-farm-trials-manual-2-1.pdf

2. The Western Australian Wine Institute report on Managing Grapevine Nutrition and Soil Health, https://winewa.asn.au/wp-content/uploads/2020/04/Grapevine_Nutrition_LR_2.pdf

3. Gypsum as an Agricultural Amendment, General Use Guidelines, Bulletin 945, Ohio State University, W A Dick, L Chen, 2011