Selectivity through equipment design was a logical response to some selective post-em herbicides for weed control in minor crops, and especially row crop vegetables, not being re-registered for use. Micron Sprayers designed the first Varidome in response to the impending withdrawal of Dosaflo (metoxuron) which left vegetable growers with a very limited choice of selective post-em herbicides to control weeds (including volunteer potatoes) in crops such as onions, carrots, parsnips and leeks.
On-going haemorrhaging of selective post-em herbicides for minor crop use is leaving increasing numbers of agricultural and horticultural crops in need of equipment able to accurately apply broad spectrum herbicides, such as Monsanto Roundup Ace (glyphosate 450g/l), onto weeds growing between plant rows and beds with minimum risk of spray drift. Development of the Micron Varidome – a shrouded, low volume (typically 50 to 150 l/ha), inter-row CDA (Controlled Droplet Application) sprayer for the safe removal of weeds growing inter-row using broad spectrum herbicide fulfils this requirement.
The 3 point linkage Varidome, normally front mounted, requires only a 12 volt power supply which is usually supplied by the battery of the carrying vehicle. The Varidome is offered as either a single or 3-bed unit to suit the grower needs. The Varidome is equipped with two types of shrouded CDA head, the wider Vegedome and the much slimmer stream-lined Vegemiser. The Vegedome caters for weed control in the wider gap between the beds and the wheelings, whilst the Vegemiser targets weeds growing in the narrow gaps between plant rows on the bed and also on the shoulder of the bed if required. Both feature Micron CDA rotary atomisers to produce optimum sized spray droplets for maximum spraying efficiency.
Interest in the Varidome has already spread from root crop vegetables into oilseed rape, maize, soft fruit and flower bulbs. An example of this alternative use is a-single bed machine being used for the last two seasons in soft fruit (strawberries and raspberries) in Norfolk. Weeds growing in virtually any row crop situation can be safely removed using the Micron Varidome.
On-going Varidome development at Micron Sprayers is being driven by continuing and accelerating loss of selective post em herbicides and the need to deliver precise selectivity in weed control for an expanding range of crops. Simultaneous technical improvements are focussed on refining and automating the Varidome system, which by its very nature already delivers highly accurate herbicide placement with minimum risk of spray drift.
One of the more recent users is a Scottish vegetable farmer growing parsnips and Brussels sprouts. A single-bed Varidome unit with 6 heads was delivered during spring 2010. It has initially been used with 5 heads operating for one complete season in parsnips. The additional head was purchased to better suit his needs for weed control in the Brussels sprout crop. This Varidome features latest developments for the unit, which now means each Vegedome and Vegemiser head assembly is equipped with its own individual peristaltic pump with a bespoke designed electronic controller.
These new developments (electronic controller and individual peristaltic pumps) serve to equalise the pressure and therefore the flow rate across the total number of CDA heads on the Varidome, which allows the use of machines using up to e.g. 20 spray heads.
The operator now has at his or her fingertips the ability to set different flow rates for different heads according to different weed infestations across the swath width, including the wheelings and wider gaps between the beds, and the much narrower gaps between the rows of crop growing on the bed. Weed assessments are made visually by the operator who now has the ability to vary flow rate individually at each head whilst on the move. Standard tank capacity is 60 litres for a single bed Varidome and 300 litres for a 3-bed machine.
There is much wider interest and definite possibilities for selectivity in weed control by equipment design, rather than by chemical, for use in crops such as oilseed rape, maize and flower bulbs.
According to Micron’s UK sales manager Terry Royston "this is only scratching the surface for future use of the highly versatile and adaptable Micron Varidome". The Varidome can be used in any crop where spacing between the beds and the gaps between the rows on the bed falls between 8 cm and 80 cm. The CDA head units are mounted on a round-profile bar so all the operator has to do to treat a different width is physically slacken a lock nut and rotate the unit to the desired width.
The Micron Varidome is the ultimate in precision application, accurately targeting small weeds, early post-em, growing alongside equally small crop plants. This is all possible due to the precise placement of exact doses of broad spectrum herbicide, all under the protection of a shrouded CDA head to eliminate spray drift. The electronic controller and each head assembly, now with its own peristaltic pump, refine an already precise system. Pressure and flow rate for each CDA head is equalised across the entire spray width of the unit while the ability to set dedicated flow rates for each CDA head provides ultra-accurate pesticide placement, weed control and chemical efficiency.
