Glyphosate’s Role in Conservation Agriculture

A balanced review of glyphosate’s position in CA systems — its agronomic importance, risks, resistance issues, and relationship to the future of no-till. Based on a TCS Magazine (France) article originally published 2011.

“Glyphosate was the mainstay of direct drilling, it has become the safety net of conservation agriculture.” — Matthieu Archambeaud, TCS Magazine

Historical Context

Since the beginning of agriculture, tillage served two purposes:

  1. Fertilisation — oxygenation of organic matter
  2. Weed control — burial (ploughing) or mechanical removal

The development of herbicides — paraquat, 2,4-D, then glyphosate — enabled a fundamental shift: weeds could be removed without disturbing the soil. This was the prerequisite for conservation agriculture.

France, weakened after WWII, used intensive mechanisation + mineral fertilisation + new varieties to become a major agricultural exporter. But the system’s environmental costs became apparent: erosion, declining OM, nutrient losses, reduced biological activity, compacted soils unable to tolerate further mechanical damage.

Why Glyphosate Is Central to CA

Glyphosate offers a combination of properties no alternative currently matches in CA systems:

  • No soil disturbance — removes vegetation without triggering fresh weed germination (unlike mechanical destruction)
  • Fast, easy, economic — very low energy consumption vs tillage
  • Effective against a wide range of plants
  • No fresh germination trigger — unlike cultivation, which stimulates dormant weed seeds

“It is thanks to glyphosate that pioneer farmers and technicians are developing efficient, effective and innovative agroecological systems based on living soils. And the more we develop and validate alternatives, the less it will become necessary.”

Risks and Concerns

1. Resistance Development

Systematic, widespread use inevitably drives resistance:

  • France: resistance in ryegrass and fescues populations
  • First French case: vetch in vineyards (intensive, sole-product use)
  • Australia: reintroduced paraquat in “double knock” combination (glyphosate + paraquat) to overcome resistance
  • North/South America: widespread RR GMO cropping accelerating resistance issues

Root cause: Not the molecule itself but the mode and intensity of use. Single-product reliance is the driver.

2. Soil and Biological Impacts

Research by Prof. D. Huber (Purdue University) and Prof. Römheld (Stuttgart):

  • Glyphosate concentrates in soils receiving regular applications
  • May disrupt absorption of manganese, iron, calcium, magnesium by crops — via:
  • Physical chelation of trace elements in root environment
  • Damage to rhizosphere microorganism populations that facilitate mineral uptake
  • RR crops may exude absorbed glyphosate through roots, amplifying effects in the rhizosphere
  • Huber’s hypothesis: glyphosate may suppress plant immune system — death caused by fungi/bacteria that the weakened plant cannot resist
  • Direct seeding concentrates organic matter at the surface, potentially concentrating glyphosate near the rhizosphere

3. Public Perception and Political Issues

Three reasons glyphosate has become a lightning rod:

  1. Massive global use — most widely used herbicide in the world, far beyond CA farmers
  2. Link to GMOs — synonymous with Roundup Ready GM systems
  3. Monsanto’s history — association with Agent Orange and coca eradication spraying in Latin America

The CA Perspective

European CA farmers have been forced to go beyond the simple “GM + glyphosate” model common in South America:

“European agriculture has evolved in a social, regulatory and environmental framework, forcing growers to go further… leading them to increase exchanges with organic farmers themselves, in pursuit of agronomic and technical solutions.”

The CA approach reframes glyphosate:

  • Not a substitute for rotation or cover crop management
  • A tool to control biomass without damaging soil
  • Used to push systems further while reducing risk — e.g., terminating cover crops without a cultivation pass
  • A “safety net” as alternatives are developed, rather than the first resort

Position in the Debate

The article argues that glyphosate should not be treated as either:

  • Completely safe and irreplaceable, OR
  • Something to be banned outright

Rather: reduce use progressively as alternatives develop, without abandoning the product before those alternatives are proven. The goal is to develop technical and agronomic solutions that maximally reduce pesticide use while maintaining viable farming systems.

See Roller Crimper and Glyphosate Alternatives for Cover Crop Termination for developing mechanical alternatives.

Sources

  • [[sources/dd-issue-02]] — “Is Glyphosate the 4th Pillar of Conservation Agriculture?”, Matthieu Archambeaud, TCS Magazine No. 62 (March/April/May 2011), reproduced in Direct Driller Issue 2 (June 2018)

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