by Matt McIntosh
Fields are just large gardens. Similar to your flower patch, weeds can be a big problem.
Controlling weeds can be tough, though. With a huge range of species and growth habits, farmers use a variety of methods to wrangle weed populations before they get out of hand.
One common method is to apply herbicides at strategic points in the growing season.
What are herbicides?
The word “pesticide” refers to three categories of chemicals for farmers: fungicides, insecticides, and herbicides. The first is used to stop the spread of fungal pathogens, the second gets rid of crop-damaging insects, while the latter is used to keep weeds out of the field.
Herbicides come in many forms. Some naturally occurring compounds can, and indeed are, used for this purpose. Herbicides manufactured to have specific properties – these are called “active ingredients” – are also widely used.
Farmers generally apply herbicides with the use of a sprayer, which is a piece of equipment equipped with a tank, hoses, and nozzles. Depending on the design, sprayers can either be driven themselves, or be pulled through the field by a tractor.
Why weeds are a problem
Weeds bring many, many problems to the field. First and foremost, they compete with crops for nutrients, water, and sunlight. This hurts both the quality and the amount (yield) of crop which farmers can harvest.
They can also spread over huge distances and infest fields very quickly by releasing tens or hundreds of thousands of seeds per plant. Because the combines used to harvest crops separate and disperse plant residue from the valuable crop seeds, tiny weeds seeds can also use the combine to spread themselves even further.
Harvesting a really weedy crop is also more time-consuming, harder on the machinery, and more costly overall for the farmer.
Before a herbicide can be used by farmers, Health Canada and the federal Pest Management Regulatory Agency have to deem it safe for people and the environment. In addition, reviews of approved products occur every fifteen years, if not earlier, to account for new scientific information.
Farmers must purchase approved products for use on the farm. Regulations also dictate that herbicides be accompanied by very specific information about the product, including what amount of it should be used and how it should be applied. Farmers follow these instructions to ensure they protect their crops without damaging them or the wider environment.
Other ways to control weeds
Farmers consider many things before using herbicides, such as what the weather looks like, if the crop in the field could be damaged, and whether the type of herbicide being used will work on the types of weeds present in the field.
Not every herbicide will work on every weed. Some weed species have even developed resistance to specific types of herbicides as a result of repeated exposure to specific products.
Herbicides are not the only way farmers control weeds. Changing the type of crop grown in a field from year to year, for example, helps keep the same weed species from gaining a larger foothold. Using different kinds of herbicides helps ensure weeds don’t develop resistances.
Tilling the soil can also make a big difference, although doing so too often or aggressively can damage soil health. Indeed, many farmers use herbicides specifically so they have to disturb the soil less often, if at all. Other options include planting cover crops – that is, crops planted to protect the soil – which help smother weeds before they get a chance to grow.
Just like the old days, farmers can also manually remove weeds. However, doing so is very time-consuming and labour intensive. But with the right equipment, manual weeding could be a great option for some farm businesses. Companies and growers around the world are developing weeding robots for just this reason. But, for now, herbicides remain one of the most affordable and efficient ways for farmers to control weeds on a large scale.