Under-vine De-vigor Clover Pasture

Comely Bank vineyards are in their fourth year working with an under-vine clover mix. Kiwi Seed agronomist Hamish Stace caught up with Comely Bank’s vineyard manager, Brent Carmody, to have a look at the persistence and management of their innovative pastures.

The primary focus for Comely Bank in establishing this particular type of under-vine seed mix is to reduce vegetative vigor of vines. This lifts the quality and flavour profile of fruit come harvest time. The sowing has occured over multiple years which has the added benefit of directly comparing different age pastures in the same season.

Although both grass and clover mixes have been tried, Brent reports his preference for a straight clover mix. The clover is more manageable, and also has superior soil health benefits.

Under-vine clover at Comely Bank Vineyard, Marlborough. © 2021 Brent Carmody

De-vigor
The difference in canopy growth is immediately apparent walking through the vineyard; Brent says this translates to around 2-3t/ha at harvest time. When the aim of a block is quality over quantity, this yield sacrifice rewards the grower with a huge quality improvement in the fruit.

Soil improvement
Clover cover crops have proven benefits in nutrient cycling and soil structure, improving microbial biomass and particulate organic matter. Clovers also fix 40-90kg N per hectare per year.

Soil moisture
Brent reports reduced water requirements with the under-vine pasture. The likely explanation for this is that the amount of water lost through plant transpiration is less than the amount lost to evaporation from bare earth when the irrigation process is considered. When the drippers begin irrigating a block with bare earth below the vine, the first part of the irrigation period is spent watering soil near to the surface to water holding capacity, for it to eventually drop and spread to become available to the vine roots. With the under-vine pasture, evaporation and soil drying effect is minimised so the water goes straight to work irrigating the pasture and vine roots.

Management
Brent has devised a line-trimmer style implement which is mounted to the front of the tractor. It trims just above the irrigation line, and does so in the same pass as the regular inter-row mowing, at the normal mowing speed. The vineyard is winter-grazed as per usual.

Two year old under-vine clover pasture, Comely Bank Vineyard, Marlborough. © 2021 Hamish Stace

Sowing
Vineyard owner Jeff Hammond has perfected the sowing technique that works best at Comely Bank. They have tried all manner of approaches, including fert spreader, and a hand broadcaster powered by an electric drill. When sowing small clover seeds under-vine using a modified drill or broadcaster, it can be difficult getting the rate right without running the seed out halfway down the row. To manage this, growers will often add a bulking medium to the seed mix, such as meat and bone meal.
The solution that has worked for Jeff though is a modified outlet on a watering can, walking down the row and scattering on to the under-vine. This allows for a high level of control of sowing rate and seed placement. When sown at the right time, this method also achieves a great seed strike.

Managing Expectations
The fourth year under-vine pasture does show a level of weed ingression which suggests that a 4-5 year under-vine renewal plan would be required to keep the clover content at the desired level.

Looking to the future
Overall, Brent, Jeff and the team at Comely Bank are happy with how things are going. The key lessons have been:

- Pasture height control is necessary to keep plants well below the canopy
- Clover-only mixes are the most manageable
- Good strike and establishment is crucial to the success of the pasture in following seasons
- For a long-term outlook, a reseeding cycle of five years might be required

Kiwi Seed are working on an under-vine pasture mix which will minimise the draw on vine resources and focus instead on a low growing height and weed prevention - a living weed mat. Have a chat with with us if you're interested in de-vigoring your vines or sowing a living weed mat for your vineyard.