All chemicals that are applied during food production have impacts on the environment, regardless of whether they have been synthetically developed or derived from natural sources. In an ideal world, no chemicals would need to be applied to crops to ensure sufficient food production, however crops are constantly under threat from pests such as weeds, insects, and diseases. Inefficient control of weeds allows them to flourish, taking moisture and nutrients away from seeded crops. Inefficient control of insects and diseases both result in lower yields. If weeds, insects, and diseases are not efficiently controlled, the combined loss in some crops can reach 100%.
Chemicals are classified by the pests they control. Herbicides control weeds, insecticides control insects, and fungicides control plant diseases. These three groups of chemicals are collectively known as pesticides. Each pesticide relies on different chemistry, which results in each pesticide having a specific pest target, such as specific groups of insects or weeds. Pesticide chemistry for synthetic pesticides has significantly advanced over time, with the result being less active ingredient needed for application while reducing impact on the environment.
The organic sector has rejected the use of synthetic pesticides but heavily relies on naturally-derived pesticides. There are well over 100 pesticides eligible for application on organic crops. Many in the organic sector advocate that since their pesticides are naturally-derived, they are somehow safer for the environment. Comparing the toxicity of organic herbicides against those of synthetic herbicides provides some interesting insights into the organic sector’s claims.
Weed Control and Herbicide Use
Prior to the commercialization of genetically modified (GM) crops in the mid-1990s, tillage was the leading form of weed control. At this time, fields would normally be tilled prior to seeding which controlled all weeds that had germinated. While conventional agriculture has shifted away the use of tillage as a form of weed control, organic agriculture still heavily relies on this outdated practice. Organic crop production also relies on tillage to incorporate what is known as ‘green fertilizer’. Green fertilizer is when a crop is allowed to grow to a short height and then it is tilled into the soil to provide nutrients. Fields incorporating green fertilizer require numerous tillage passes to best ensure the nutrients are successfully integrated into the soil.
In the mid-1990s, herbicide availability was limited in some crops, such as canola. There was a lack of efficient in-crop herbicides, so many farmers would incorporate herbicides into the soil via tillage. Soil incorporated herbicides had higher impacts on the environment, as quantified by the Environmental Impact Quotient (EIQ). Cornell University developed a methodology for assessing the environmental impact of pesticides known as the EIQ. It is derived from assessing the impacts of a pesticide on the applicator, consumers through exposure to groundwater and post-harvest residues, and ecological impacts on fish, birds, bees, and other beneficial species.
Due to the sometimes limited in-crop weed control options in the early 1990s, farmers would frequently make an application of glyphosate prior to seeding fields as a way of controlling weeds that had germinated prior to seeding. This was done to ensure that weeds would not outcompete the seeded crop for nutrients and moisture, which is often in short supply some years.
The top five in-crop herbicides utilized in the early 1990s in Saskatchewan are identified in the table below. These five herbicides accounted for about 73% of total cropping acres, with other numerous herbicides accounting for the remaining acres.
Table 1: Top in-crop herbicides used from 1991-1994
Herbicide | EIQ value | Grams applied per hectare |
|---|---|---|
MCPA | 15.6 | 330 |
2,4-D | 8.3 | 280 |
Buctril M | 6.1 | 168 |
Hoegrass | 16.9 | 291 |
Treflan | 14.5 | 563 |
Source: LIKA ET AL. 2024
Following the adoption of GM and mutagenic canola varieties that were tolerant to the application of in-crop herbicides, this significantly changed crop production practices. Tillage was removed as farmers were able to gain efficient weed control through the application of in-crop herbicides. This change resulted in both the EIQ value and the grams applied per hectare declining. Top herbicides at this time included glyphosate (Round Up), glufosinate (Liberty), clethodim (Select), imazamox (Raptor), and 2,4-D. Table 2 highlights in-crop herbicide use from 2016-2019.
Table 2: Top in-crop herbicides used from 2016-2019
Herbicide | EIQ Value | Grams applied per hectare |
|---|---|---|
Round Up | 10.5 | 324 |
Liberty | 11.6 | 248 |
Select | 1.2 | 49 |
Raptor | 0.9 | 158 |
2,4-D | 6.3 | 297 |
Source: LIKA ET AL. 2024
This example shows that when it comes to the use of synthetic herbicides, there has been declines in the amount of herbicide active ingredient applied per hectare, along with lower environmental impacts. By contrast, organic herbicide use relies on compounds that can have higher environmental impacts, as well as being applied at rates that significantly exceed those of synthetic rates (Table 3). These leading organic herbicide options all have higher environmental impacts than those of synthetic herbicides. Given the general ineffectiveness of organic herbicides, the application rates needed are considerably higher than those of synthetic herbicides. The application rates of some organic herbicides are nearly 100 times higher than those of synthetic herbicides. When these higher application rates are coupled with the higher EIQ, it becomes very apparent that organic crop production using naturally-derived herbicides has a far higher impact than the use of synthetic herbicides.
Table 3: Organic herbicides
Herbicide | EIQ value [1] | Grams applied per hectare |
|---|---|---|
Copper sulfate | 61.9 | 1,234 [1] |
Acetic acid (vinegar) | 12.2 | various |
Ammonium | 23.6 | up to 10,800 [2] |
Pelargonic acid | 15.3 | 8,000-13,500 [3] |
Sources: 1 – Cornell University EIQ Calculator. 2 – Webber et al. 2011. 3 – Health Canada 2019.
Future of Crop Innovations
As crop innovations increase at a more rapid pace following the adoption of gene editing technologies, the potential for even further reductions in herbicide use exists in conventional crop production. More crops will become herbicide tolerant, increasing farmers’ options for the application of more benign herbicides at rates lower than those of previous herbicides. This provides a promising future for conventional crop production.
These gains will not be experienced by organic crop producers as their industry has politically decided to reject gene-edited crops as being eligible for organic standards. This is incredibly odd as current organic crops have been developed through the use of mutagenic technologies and gene editing is simply an advancement of earlier mutagenic technologies. This will result in the organic sector being forced to rely on the use of more toxic herbicides at vastly higher rates of application, resulting in much higher environmental impacts than there needs to be.
