The two best ways to bring nutrition and fertility to your vineyards are compost and cover crops. These fit into our philosophy of making the best wines from our unique site, with minimal chemical intervention, and of working with rather than against nature. Today I want to share what is happening in terms of cover crops, which have grown well with the alternating warmth and rain we have experienced in the last month.
Regenerative farming for the future
Cover cropping is not the cheapest or easiest way to provide nutrition. But if we want to still be farming in 100 years then we need to use more regenerative rather than extractive and polluting practices in winegrowing and in agriculture more generally. We also know the vines are actually not what require the most attention. Rather, it is the soil that we need to farm, that is the engine which allows grapevines and all other plants to grow well. One aspect of this is cover crops, which not only provide nutrition for our vines but support a diverse microbial ecosystem and healthy soils.
We hand sow non-GMO seeds beginning at the end of March. We inoculate the nitrogen fixers with a mixture of milk, compost, and mycorrhizal microbes which kickstarts the symbiotic relationship between plant, microbe, and soil.
At Iona this year our program included twelve species which each have a unique function. I have always preferred mixes, as I think the diversity is beneficial to the microbial and insect populations in a vineyard.
In choosing which crops to plant in which blocks we use precision agricultural principles and take into account the vine age, crop, growth, soil type, soil structure, any nutrient excesses or deficiencies and our longer term goals with that block.
Diverse and precision agriculture
All our blocks get at least one cereal, and this year we have planted Korog (triticale), Rye, and Saia Oats. Cereals produce a lot of biomass quickly, which adds organic matter and carbon into the soils. White mustard has a similar role, but it also attracts beneficial insects and repels nematodes.
We have sown Daikon radish everywhere this year. It is a large taproot, so it helps open the soil and reduce compaction. Our cows enjoy munching on them as do we, it makes a delicious Vietnamese-inspired pickle.
My favourite group of plants are the legumes, and we have planted seven. Legumes actually fix nitrogen into the soil by taking it out of the air, replacing the use of artificial, synthetic fertilisers. They do this in association with symbiotic fungi in the soil. Our legumes include bitter lupins (which will be beautiful when in bloom), faba beans (used where the vines need extra growth), vetch (which can grow in more austere or rocky soils), serradella (another beautiful one, also grows very long root systems), and forage peas (which use the taller plants as their trellis).
One new approach we are experimenting with is a permanent under-vine cover crop, something that is not very competitive to the grapevines but can supress problem weeds and grasses. This year we are trialling medics and clover. The goal here is to reduce the need for either chemical or mechanical weeding, and to therefore improve the structure and condition of the soil. Using life to manage life!
Cheers,
Viticulturist & Assistant Winemaker