In this series of articles about cover crops we’ve, so far, taken a closer look at cereals and legumes.  The third major plant group commonly used as beneficial cover crops are the brassicas.   The family Brassicaceae includes flowering plants that are generally known as the mustards and the crucifers.

Well-known crucifers of the genus brassica are cabbages, broccoli, cauliflower and rapeseed.  The family also includes turnips, radishes and horseradish.  However, it is the lush-growing mustards that are commonly used as cover crops.

Why do we use Brassicas as Cover Crops?

The brassicas provide a unique and interesting benefit as a cover crop – they provide a natural fumigant in the soil and make a contribution to holistic pest management.  The plants contain high levels of natural sulphur which is released as it decomposes, and this can play a role in keeping populations of detrimental nematodes in check.  It’s important to note that while brassicas as cover crops can play a role in natural pest management, they need to be used in conjunction with other strategies.

As part of our holistic BioLOGIC® approach, Avondale’s natural pest management system also includes making use of broad spectrum nutrition, building humus in the soil. Natural nematode control is hugely linked to the balance of the carbon/ nitrogen ratio, if you get this correct we find that the occurrence of detrimental nematodes is greatly reduced.  When we were first balancing Avondale’s soils and building thriving communities of life in our soil, we included a range of mustards in our cover crop mixes.  However, now that we have achieved balance in our soils, our communities of life are self-regulating and, for the past six years, we haven’t needed the help of brassicas to keep pests such as nematodes in check.

Apart from their fumigation effect, brassicas are also of benefit in the cover crop mix because:

  • they bring much-needed diversity to the vineyards
  • the fibrous root structures of the mustards penetrate compaction in the soil at the mid-range level
  • with their fast, lush growth, mustards provide excellent soil coverage and provide a significant amount of biomass
  • they also provide sulphur-rich organic matter
  • mustards flower prolifically, usually in yellow, and they draw useful insects into the vineyards

Conventional farming has long favoured keeping the soil bare except for the crops.  The barrenness of the monoculture landscape is mirrored by a dearth of life in the soil.  Avondale’s BioLOGIC® system takes a fundamentally opposite approach.  We make use of ten different types of cover crop mixes that result in great diversity of plant life amidst our vines.  The cover crops, in turn, provide shelter and food for a vibrant diversity of micro-organisms that make up the community of life.  Over time, a healthy, diverse community of life becomes self-regulating and sustains balance, requiring minimal intervention to ensure the healthy conditions required to produce organically-grown, delicious grapes.