The discussion below relates to vineyards that are irrigated. Dryland has its own challenges but weed management is not one of them.
The vineyards on Spier are in their second year of conversion to organic status and then to biodynamic status. I have been managing my dryland Chenin vineyard according to biodynamic principles since 2005. I produce my straw wine from this vineyard.
In my limited viticultural experience the two biggest problems faced by organic/biodynamic vineyard mangers are feeding the plant and weed management. Feeding the plant is a subject for another day. Within weed management the tricky part, in our experience, is the berm or the bankie.
The berm needs to be kept with as little plant material on as possible so as to first allow no competition for the vine and second allow light to penetrate the canopy and and air to move freely. The air flow is almost most important because conditions conducive for fungal diseases need to kept to a minimum as we don’t have the weapon of a systemic fungicide in our arsenal.
With conventional management nothing beats glyphosate (I lie, rye grass does) but organic/biodynamic vineyard managers can’t/won’t/are not allowed to use that tool. Also we don’t want our soils without Zinc, Managanese or Iron (glyphosate chelates these minerals and we have the soil tests to prove it).
Most organic/biodynamic managers use the mechanical method of either using various tractor drawn implements to rid the berm of weeds or use labour to hoe the berm clean. Our problem with this is that the soil is left bare and bare soil is between 8 and 20 Celsius hotter than covered soil so then we need to use more water and the microbes get hurt.
Our biological method was inspired by Nick Kotze of Agricol, improved by Bennie Diedericks (082 452 7263) and is being perfected by my colleague Orlando Filander.
Our biological method was inspired by Nick Kotze of Agricol, improved by Bennie Diedericks (082 452 7263) and is being perfected by my colleague Orlando Filander. The first thing to do is to clean the berm mechanically. As soon as possible after harvest. Turn on the irrigation to see where the dripline is and then clear a hoe width on that dripline. Then mix Subterranean Clover seed, obtainable from Agricol, and some compost and apply this mix through a 2 litre Coke bottle in your newly created trough. Water regularly to give the clover a chance to get growing before the winter rains stimulate the other weeds to grow. The above photo was taken on the 22nd of May.
Above is one our better examples, taken on the 6th of September, of where the sub clover has established and is covering the berm and not allowing too much competition to grow on the berm. Please don’t forget that clover is a legume that is fixing Nitrogen for plant growth into the soil.
There are some other areas where we have not established the sub clover that well and accordingly there is more competition that has grown through the sub clover and we have had to use weedeaters to cut them back.
There are some other areas where we have not established the sub clover that well and accordingly there is more competition that has grown through the sub clover and we have had to use weedeaters to cut them back. The photo above was taken on the 27th of October and shows where we want to get to with all our vineyards. The sub clover has almost entirely died, only after burying it’s seed. So not only did it fix Nitrogen whilst living, it has created a mulch to keep the soil cool and finally it has reseeded itself which absolves us of that duty next year. Every year that subclover blanket gets thicker and fixes more Nitrogen.