Soil Biota Adversely Affected by Interaction of Inputs and Practices in Chemical-Intensive Agriculture
(Beyond Pesticides, October 14, 2016) A recent study has shown that the interaction between pesticides, tillage and soil fertilization can have an effect on soil organisms. The study demonstrates that simple evaluations of pesticide exposure on single organisms does not give a complete picture of pesticide risk, and the authors of the study conclude that a more realistic risk assessment was needed to fully encompass the complex factors that can influence the effects of pesticides.
The study, titled Pesticide Interactions with Tillage and N Source, Effects on fauna, microoganisms and selected ecosystem services, monitored soil biota during two cropping seasons of winter wheat. The researchers studied pesticide effects in both moldboard plowed soil and directly seeded (no-till) soil. Either mineral fertilizer or cattle slurry was applied to the soil, along with either a fungicide, an insecticide, or both. Following the application of pesticides in the spring, and again after the winter wheat harvest in September, researchers studied how the populations of earthworms, springtails, mites and microbial life were affected. Researchers observed a negative effect due to pesticide treatment on mites, and generally found that all taxonomic groups were affected negatively, especially following insecticide treatment.
When looking at the effects of direct seeding versus plowed, and the addition of cattle slurry versus mineral fertilizer, researchers found that there was a higher population of soil biota in the soil under direct seeding versus plowed soil, and a positive effect from the addition of cattle slurry as opposed to the mineral fertilizer. Pesticide effects on soil organisms were also examined after the incubation of soil columns. Researchers found that soil biota populations were greater in the soil that had been directly seeded compared to plowed soil.
According to the conclusion of the study, ‚ÄúThis project demonstrated a complex interaction between management factors that should be considered in risk assessments, for example by supplementing traditions dose-response tests with more realistic test systems that can also take indirect effects into account. Negative effects of pesticides on populations occurred in this project mainly at highly elevated doses, but also sublethal effects, and changes in species composition, are important, as loss of biodiversity can reduce the robustness of cropping systems towards, e.g., climate change.‚ÄĚ
Other studies have demonstrated the detrimental effects that a wide range of pesticides can have on earthworms and other soil biota. A 2015 study demonstrated that glyphosate, the controversial and toxic active ingredient in Roundup, reduces activity and reproduction in two species of earthworms and increases soil nutrient concentrations to dangerous levels. Another study on worms found that chronic and/or acute exposure to glyphosate and/or mancozeb promotes neurodegeneration in GABAergic and DAergic neurons in Caenorhabditis elegans, a type of roundworm. In 2014, researchers also found that earthworms exposed to fungicides in conventionally farmed soil are at a stark disadvantage to worms in land managed organically. Earthworms exposed to the fungicide epoxiconazole ¬†are able to detoxify the chemical, but gain half as much weight as worms from an organic farm, where their population is also 2 to 3 times higher.
Soil biota is ¬†essential to ecosystem functioning because it ¬†breaks down organic matter, enables chemical elements to be reused, and fixes ¬†nitrogen, which is necessary for nutrient cycling in ¬†the ecosystem. A study published in February 2016 reveals ¬†that a decrease in soil biota impacts the services that healthy soil provides. The study finds that soil microbial diversity ¬†positively relates to multi-functionality in terrestrial ecosystems. Simply put, when soil diversity is high, the soil can function more efficiently and provide a multitude of ecosystem services. Any loss in microbial diversity will likely reduce multi-functionality, negatively affecting ¬†the services provided by soil, such as climate regulation through atmospheric carbon sequestration, fertility, and productivity. A ¬†further decline in soil biodiversity has adverse economic ¬†impacts as well. The European Academies‚Äô Science Advisory Council (EASAC) estimates soil organisms and their role in agricultural productivity to be worth $25 billion a year, globally.
One way to protect soil biota, other wildlife, biodiversity, and the ecosystem as a whole from the harmful effects of pesticides is to support organic agriculture over conventional, chemical-intensive farming. Beyond Pesticides supports organic agriculture as effecting good land stewardship. The pesticide reform movement, citing pesticide problems associated with chemical agriculture, from groundwater contamination and runoff to drift, views organic as the solution to this serious environmental threat. It is impossible to discuss the ecological benefits of organic agriculture without discussing the devastating effects of conventional agriculture.
Conventional, or chemical-intensive, agriculture relies on toxic pesticides that contaminate air, water, soil, and living things; organic agriculture does not allow the use of toxic pesticides. Chemical-intensive ¬†agriculture relies on synthetic chemical fertilizers that reduce soil organic matter and contaminate waterways; organic agriculture does not permit the use of synthetic ¬†fertilizers and relies instead on nutrient sources that tend to be less soluble and more stable in the soil, because of the expectation that healthy soil will produce microbes that ¬†can make the nutrients naturally available over a longer period of time.
To learn more about the impacts of pesticides on wildlife (which includes soil biota), visit Beyond Pesticides‚Äô Wildlife Page ¬†for a ¬†discussion of how organic systems protect ¬†wildlife from the dangerous impacts of pesticides, encourage them to flourish, and restore the natural balance that is unable to exist in chemical-intensive ¬†agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.