This of course highlights a big problem with all agrochemicals whether used commercially or domestically.
It's not difficult to calculate the precise dose for insecticide/herbicide/fertiliser etc but too many of us don't.
- read the label
- read the label
- do a first test with plain water so you know the time taken to empty your sprayer/watering can/dribble bar etc
- do a second test - walk up and down your rows at the speed you normally spray at - much more realistic if you do this with water rather than 'dry'
- with a simple bit of maths you can work out the exact dose of chemicals that you are putting on your land/plants (i reckon to within 5% at least) and make the necessary adjustments (to the concentration or how fast you walk)
- this way you know how long it takes to empty your particular sprayer.
- read the label
- pay heed to safety instructions, and wear the appropriate personal safety equipment if needed (masks/eye shields/gloves/tyvek disposable overalls)
- this is all particularly important if we are buying commercial strength glyphosate (36%) rather than garden centre concentrations (circa 14%)
Probably talking to the converted here, but I do feel that we must take a responsible attitude towards all the chemicals that we use or else the legislators will have just reason to take the draconian measures that many of us object to.
There are too many of us that just 'splash a bit in the bottom of the can', or 'use up the rest at the end of the season' - in fact it's how I used to behave until a kindly market gardener took me to task and spent no more than five minutes chatting to me and putting me on the right track. Previously not only did I 'add a bit extra for insurance', but also often dosed the land 'one extra time just to make sure' (usually because the first application was too early in the season). Now when I use chemicals I am ruthlessly efficient, and use only the correct dose at precisely the right stage of the growing cycle and as a consequence use only 20-35% of what I used to.
One of the factors for us domestic users to consider is that the cost of domestic chemicals is a small part of what we spend on our gardens/allotments, so whilst we pay way over the odds for them, as a percentage of total spend it's quite low, so we may be tempted to adopt bad habits. Hopefully by sharing the way that I've changed my behaviour others will be prompted to do likewise (actually I hope that all who read this are mega-responsible and don't need to make any adjustments)
As an aside - the commercial boys are running to such tight margins and the cost of their consumables are high in proportion, and they often have to live under a tight regulations, that they are often the most efficient users of chemicals.