Pesticide “ghosts” can haunt organic farms for decades

Most commercial crops grown around the world are treated with pesticides. But some farms are now switching to organic practices to avoid the risks that pesticides pose to human and environmental health.

However, new research shows that past pesticide use can still “haunt” fields that have long been converted into organic farms. Published recently in Environmental Science and Technology, the study shows that fields that have long been dedicated to organic farming still glowed with pesticide residue upon examination.

Beneficial microbes in the soil also appeared to be negatively affected by pesticides even years after their initial application. In all, the study sheds light on the extent of the environmental damage that pesticides can cause.

Effects of past pesticide use still linger in organic fields

Some organic farms today operate on land previously treated with pesticides. And while studies on the impacts of pesticide use on the environment are not lacking, it remains unclear whether pesticides have a lasting presence in organic farms that were once conventional ones.

To shed light on that matter, a team of European researchers studied the presence and abundance of 46 widely applied pesticides in soil samples taken from 100 agricultural fields across Switzerland, 40 of which were managed with organic farming practices.

The team wanted to determine whether the farming methods used influenced the occurrence of pesticides. The team also evaluated how the duration of organic management affected the occurrence and concentration of pesticides in the soil. In addition, they studied the effects of pesticide residues on indicators of soil life.

Interestingly, the researchers found pesticide residues in all of the soil samples, including those taken from the organic farms that were converted from conventional ones over two decades ago.

In particular, they found residues of multiple herbicides and one fungicide in the samples taken from the fields that were later managed with organic practices. However, they also found that the longer the fields were under organic management, the fewer the number of synthetic chemicals found in the soil.

They also found lower microbial abundance and decreased levels of a beneficial microbe in soil that had higher numbers of pesticide residues. This finding suggests that the residues negatively impact soil health. (Related: Scientists: Long history of fertilizer use on land is threatening our water quality today.)

However, the researchers pointed out that some of the pesticide residues present in the samples collected from organic fields may have come from nearby conventional fields. The residues could have contaminated the organic fields by traveling through the air, water or soil.

To sum up, the findings show that ubiquitous pesticide use can negatively affect soil health in the long term, so much so that even organically managed fields may still contain pesticide residues long after they have been converted from conventionally managed ones.

The findings also show that the persistence of pesticides is grossly underestimated. The researchers said future work should examine the synergistic effects of pesticide residues and environmental stressors on soil health. Such studies may shed light on the extent to which pesticide residues affect soil microbes and processes.

Organic farming still has its benefits

The study suggests a grim future of pesticide residues persisting for years after farmers have transformed their fields to practice organic agriculture. But that does not mean organic farming is a futile endeavor.

Pesticides protect crops by destroying organisms that can damage them. However, pesticides are notorious for causing severe health effects and illnesses, ranging from respiratory diseases to cancer. Pesticides also harm beneficial insects like honeybees. They can also leach into the soil and contaminate groundwater supplies.

Conventional farming sets the stage for such health and environmental problems because it promotes the widespread use of pesticides. In contrast, organic farming entails avoiding the use of pesticides, as well as considering the long-term effect of agricultural practices on the soil and the environment.

So although pesticides can persist long after conventional farms have gone, practicing organic farming can still greatly benefit the environment by not adding to the chemical load already contaminating fields. And the longer farmers keep their fields clean and pesticide-free, the safer both insects and humans will be.

Go to OrganicFarming.news to learn more about the advantages of organic farming.

Sources include:

ScienceDaily.com

FAO.org