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Canada: Herbicides Glyphosate May Have Negative Impact on Phosphorus Levels

| Editor: Alexander Stark

A new research from McGill University reveals an overlooked impact that the widely used herbicide glyphosate may be having on the environment. The study focuses not on direct health risks associated with the herbicide, but on its contribution to environmental phosphorus levels, an issue that has yet to receive much attention.

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A new study examines how Glyphosate adds to phosphorus levels in soil and waterways.
A new study examines how Glyphosate adds to phosphorus levels in soil and waterways.
(Source: Pixabay / CC0 )

Montreal/Canada — Marie-Pier Hébert, lead author of the study and a doctoral student in the Department of Biology at McGill University, said that no one has thus far investigated the impact of glyphosate use on phosphorus loads in agricultural areas — most likely because pesticides have always been considered a negligible source of nutrients.

In many agricultural areas, decades of phosphorus-based fertilizer use have led to a saturation of the soil’s capacity to hold the nutrient. This increases the likelihood that any additional phosphorus applied to the land will run off into waterways, where it is a known cause of harmful algal blooms and deoxygenation leading to fish death.

Until now, regulations to limit phosphorus pollution have focused on the use of fertilizers, which remain the largest artificial source of phosphorus. But as the use of glyphosate increases — the past two decades alone have seen global use increase 15-fold — the herbicide’s relatively small phosphorus content starts to add up, reaching levels comparable to other sources, like detergents, that have attracted regulators’ attention in the past.

This new study argues that the recent and rapid rise in glyphosate use has magnified its relative importance as a source of anthropogenic phosphorus, especially in areas of intensive corn, soybean and cotton cultivation.

The McGill research team — Marie-Pier Hébert, Vincent Fugère and Andrew Gonzalez — used data from the US Geological Survey and the UN Food and Agriculture Organization to calculate the relative contributions of glyphosate and fertilizers to the total amount of phosphorus being applied to agricultural land in the United States and elsewhere. They also reviewed existing studies to bring to light the mechanisms by which glyphosate contributes to phosphorus levels in the soil and phosphorus outflows to waterways. They conclude that glyphosate use can no longer be disregarded in monitoring and managing phosphorus levels in areas where the herbicide is used extensively.

Reference: Hébert MP, Fugère V, and Gonzalez A. (2019) “The overlooked impact of rising glyphosate use on phosphorus loading in agricultural watersheds,” first published online Dec. 5, 2018. Frontiers in Ecology and the Environment. 17: 48–56.

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