Weeds can be controlled by one of two means, cultivation or chemicals. For decades, fields would be left fallow for a year so that the farmer could cultivate the field regularly, killing the weeds. Cultivation controls weeds when no other crop is growing on the field, whereas chemicals control weeds while crops are growing. Through breeding and science, crops have been created to be tolerant to chemicals and therefore less soil cultivation is needed to control weeds. Previously summerfallowed land is now used to grow crops, with chemicals being the most common way of controlling weeds.
Despite weed control, weeds are still an issue
Since weeds typically germinate earlier than planted crops, grow at faster rates than the surrounding crops and produce way more seeds, proper weed control is necessary for farmers. Weeds like the palmer amaranth are a particularly noxious weed in the southern United States, which can produce up to one million seeds per plant per summer. Kochia, a common weed in Western Canada is capable of producing 25,000 seeds a summer. A good yielding variety of wheat typically produces 25-30 kernels of wheat per plant per season, with an exceptional yield of 40 kernels. When weeds are able to produce 1,000 – 25,000 times more seeds than a crop, it doesn’t take long to see why poor weed control practices can quickly become a big problem for farmers.
Weed wielding yield wasting
If not properly controlled, weeds lower crops yields. For small farmers in developing countries, poor weed control has been identified as the single biggest cause for low yields. Weeds germinate earlier and grow faster than most crops, allowing them to steal a crops nutrients from the soil and sun, reducing the crops’ yield. Yield losses of 20-80% are common in parts of sub-Saharan Africa when proper weed control practices are not followed.
In Canadian fields, yield losses are not at the levels in Africa but are higher than one might expect. Wild oats have been a problem weed for decades in Western Canada and in the worst case scenario, have reduced wheat yields by 38%. A more typical yield loss due to wild oats ranges from 5-20%.
The cost of weed seed
The presence of weed seeds in harvested crops also cost farmers money when it comes to selling their crops. At the elevator, a grain sample is taken and tested for the percentage of weed seeds. This is known as ‘dockage’ and the volume of weed seeds per tonne of grain is deducted from the amount of money the farmer receives for the grain. Weeds at the point of sale can be a double whammy to farmers. Not only do weeds reduce a farmer’s yield, but also the money received at the point of sale.
