Desherbage - Weedkilling

We thought long and hard about how we would go about weeding between the vines (grass grows between the rows and we cut that with a shredding attachment but you can’t use that to get stuff that grows between the vines). Being determined not to use pesticides unless essential we reviewed the various alternative options and made a few visits to see them in action. There are basically three choices. (1) spray, (2) use a kind of mechanical weeder or (3) (frighteningly) use a huge machine that uses butane gas to burn the tops off the weeds. As usual in these situations, no single choice is without its problems and after much circular debate and against an impending need to take urgent action we decided to use a sprayer – we also took the decision to spray a thin swathe with (only) glyphosate which is systemic but becomes inert immediately it touches the soil (avoiding the previous harsher treatment that kills seeds as well). This will be friendlier than that used before we arrived but could mean that we have to do an extra spraying, oh well…..The choices don’t stop there though, even for this kind of basic spraying there is a multitude of options – rear mounted, side mounted, front mounted, discussions needed about capacity and throughput, oh dear. With the aid of the man from local equipment supplier we plumped for a front-mounted sprayer.

The sprayer consists of a big green tank on the back of the tractor with a pump that is powered by the tractor, this sends pressurised solution to an upside-down-U-shaped contraption with two baskets on the end containing spray jets. The inverted U straddles the vines and you simply (hmmm) drive along and press a button to start spraying – oh and the whole lot moves up and down (using a hydraulic control in the cabin) because it needs to be kept at the right height.

The other aspect to this job is the need to understand the technicalities of spraying properly. Firstly the tractor speed is checked by timing it over 100m. Having a constant and repeatable speed is the first requirement – the equipment vendor recommends 5.6kph and I take his advice even though it seems worryingly fast given the precision that will be needed to avoid uprooting anything. Having determined the tractor speed the spray jets need to be calibrated (the rate of fluid sprayed per minute at a fixed pressure setting) - done by setting everything going and actually collecting the water sprayed out of the jets. Finally all this data has to be combined in a formula along with information translated from the product packaging to get the appropriate dilution.