If you had visited the Napa Valley as recently as 5 or 6 years ago, you would have noticed the absence of any vegetation in the vineyards except for the foliage of the vines themselves. Thankfully that's changed. The majority of farmers have now adopted a 'no-till' policy, choosing to plant cover crops or allow native vegetation to proliferate. Even a vineyard floor covered in dandelions would be preferable to a 'scorched earth' approach to farming.
This year I chose to plant a clover mix in our vineyard. Clovers are legumes, belonging to the Fabaceae family, and so are capable of fixing nitrogen from the air. Through a symbiotic association with bacteria from the genus Rhizobium, they convert nitrogen gas (N2) in the atmosphere to ammonium (NH3) that can be readily used by crops. Because rhizobia occur naturally at low levels in most soils, the bacteria must be present on the legume seed at planting, hence the uniform look of the seed in my photograph. They are coated with everything they need to perform this amazing feat of alchemy.
There are arguments for and against the planting of cover crops. On the pro side; they are very beneficial to overall soil health, add organic matter to soil, retard soil erosion and provide shelter for beneficial predatory insects, amongst other things. Naysayers fear; competiton for available groundwater, too much nitrogen fixation (that could result in too much vigour), and the over-wintering of problematic insects...but seeing as I am a proponent of cover cropping, and it's my blog, I'm not going to dwell on the negatives. There is a lot more to this subject than just tossing out a few seeds and calling it good. Cover crop management is quite complex and is a science in itself, but the positive aspects of this practice are to me incontestable. Besides, it was a great day to be outdoors. The weather was fantastic (84F) and V2 accompanied me as I worked...or at least I think she did, if the huge shadow of her large ears just to my side was anything to go by.