The answer lies in the soil

Soil health is a huge subject area, and the characteristics that can impact the growth of vines are varied. The structure of the soil, its pH, nutrient and organic matter content along with bulk density, microbial diversity and respiration can all have a massive impact on the success of a vineyard’s crop.

Improving soil biology is always a current issue, but even more so now that the government has recognised the importance of encouraging activities that improve soil health. The Sustainable Farming Incentive was launched last year as part of DEFRA’s Environmental Land Management schemes. The overhaul of the EU farming subsidy system has been referred to by environmentalist George Monbiot as the “one genuine benefit of Brexit.”

The incentive pays producers who conform to certain standards – in relation to arable and horticultural soils, as well as a variety of other areas – and by doing this they acknowledge them as a public good. £1 billion will be spent “to support food production while protecting habitats and wildlife.” In 2023, more standards will be added to the scheme, including nutrient management and integrated pest management.

New ways to maximise outputs are continually being investigated. Research funded through DEFRA’s Farming Innovation Programme is ongoing to find ways to increase productivity and sustainability in UK grape growing, for example. Led by NIAB at the East Malling Research Vineyard as well as on commercial sites, the £350k project is investigating the impact of cover cropping and mechanical weeding strategies on soil health.

“It is still quite early in the project,” said Root & Soil Biologist with NIAB, Dr Flora O’Brien. “We are currently focussing on the importance of cover crop establishment methods; how to achieve a good cover crop stand, and its impact on soil health. Regarding sustainability, the most desirable option is to use a direct drill with little or no cultivation, however, the existing grass sward and weed population can often be problematic and outcompete the cover crops. We are looking at how to best manage this and will monitor the impact on both the vines and soil health.”

One outcome of the two-year research project will be guidance on bespoke cover crop mixes to control nematodes, alleviate soil compaction and improve soil nutrition. This will be supported by recommendations supporting the transition to net-zero carbon emissions. It is envisaged that bringing up standards of soil health will address some of the causes of inconsistent yields and low juice quality.

Cover crops and green manures that are currently in use in UK vineyards include:

◆ Beans and clover for nitrogen

◆ Mustard and phacelia for carbon storage

◆ Linseed and oats for deep rooting

◆ Daikon radish planted in the winter as the deep-rooting varieties help with drainage and compaction

◆ Vetch and lucerne help to add nutrition to the soil

◆ Cocksfoot or ribgrass are deep-rooting grasses that assist with soil structure.

Identifying areas of the vineyard that perform differently and understanding why certain vines have issues with, for example, drainage or excessive growth is key to selecting the correct cover crop mix.

While cover crops are known to improve soil fertility by fixing nitrogen, suppressing weeds and preventing soil erosion, they are often ignored by commercial growers who fear that they may harbour insect pests, create more maintenance and increase competition for nutrients and water. This research may help to provide solid evidence that the practice of cover cropping actually brings more benefits than drawbacks.

Increasing the organic matter content of your soil is an indisputable way of improving soil health. The manual addition of manures and composts is one way of securing those benefits for your soil.

The British Standard Institution has produced a specification for compost materials known as BSI PAS100. It applies across the UK and aims to improve confidence in composted material by helping to identify products that are safe and reliable.

“Some 15 years ago the PAS100 product landed and is now freely available from numerous suppliers,” says agronomist Julian Searle. “Several suppliers also spread in fruit row crops for a fee – FGS Agri, and Bournes are two examples. Trials at NIAB-EMR with AHDB demonstrated conclusively that at a sufficient rate, spread to the rows only, water and nutrient availability was significantly improved to depth as well as providing a useful mulch against immediate water loss.”

In some areas, composted manure is available as an option too. Julian recommends spreading every vineyard one year post-planting and, if not restricted by the NVZ regulations that control the amount spread, to the planted row only.

When applying compost or manure, there are a number of factors to take into consideration:

◆ The timing of organic amendments can affect their availability and impact on soil health. Application in the autumn or winter can allow for nutrient release before the growing season. However, spring applications can also be beneficial as they enhance soil biology and provide nutrients to the vines.

◆ The application rates and distribution are important to avoid nutrient imbalances or excesses as well as to keep within the water regulations. The application rate will be dependent on the type and quality of the amendment, and the vineyard’s nutrient needs. Even distribution is important to ensure uniform nutrient availability across the vineyard.

◆ Each type of amendment comes with its own strengths and weaknesses. Fresh manures may have a high nutrient content, but they can also contain weed seeds or pathogens. Well-aged composts provide a slow release of nutrients and enhance soil structure, but may cause too much vigorous growth in the vines.

“Quality