Glyphosate and GM crops are harming no-till soils
No-Till Farmer is a magazine aimed at farmers who grow GM glyphosate-tolerant corn and soybeans using herbicides instead of ploughing to control weeds. In a revealing sign of the times, the magazine has published an article detailing the serious problems of soil and plant health caused by the application of glyphosate on these GM crops in no-till systems.
The article gives the lie to the regular promotion of no-till farming with GM crops as environmentally friendly – generally on the claimed grounds that by avoiding ploughing it mitigates climate change by reducing the number of tractor passes in fields, thus reducing fossil fuel use, and stores carbon in the soil rather than releasing it into the atmosphere. While the new article focuses on other aspects of no-till farming with GM crops, it makes clear that these systems create a host of negative impacts for farmers and the environment alike.
The paywalled article , written by No-Till Farmer’s senior editor John Dobberstein, draws on the expertise of Robert Kremer, a retired research microbiologist with the USDA-Agricultural Research Service and adjunct professor at the University of Missouri, as well as other researchers.
Noting that “there may be trouble on the horizon for glyphosate,” Dobberstein says that when measured by pounds applied per square mile, the use of glyphosate has increased from less than 1 million pounds in 1974 to 28 million pounds in 1995, and 80 million pounds in 2010. Between 1974 and 2014, 30 billion pounds of glyphosate were applied to US agricultural lands, according to federal data.
Glyphosate lingers in soil
Referring to claims that glyphosate is typically neutralized and degraded by soil microbes after a period of time, Dobberstein notes that in the last 5 years, evidence seems to be mounting through research studies that the herbicide is lingering in the soil environment longer than anticipated and initiating a host of non-target effects.
According to Dobberstein, impacts include absorption by non-target crops through roots, suppression of beneficial mycorrhizal fungi (which enable plants to acquire more nutrients from the surrounding soil and confer protection against diseases), increase in potentially pathogenic microorganisms, reduction in earthworm activity, and chemical residues in soil and water. It could also have negative effects on respiration for soil-dwelling organisms and nutrient immobilization for plants and microorganisms.
One of the main concerns of researchers, Dobberstein writes, is how glyphosate affects soil biological processes and the soil rhizosphere – the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Kremer says that glyphosate is released through the roots of plants and that can suppress the antagonistic microbes that we need to keep pathogens down in soil: “Maybe one of the reasons we see more Fusarium on the roots is because these pseudomonads will suppress Fusarium.”
Effects on beneficial organisms
Kremer adds that glyphosate and GM crops can also negatively affect other beneficial soil organisms, such as small insects and earthworms, which no-tillers have worked hard to bring back.
Kremer says, “This is a concern because these organisms interact with each other helping to decompose organic substances, build up soil organic matter and mineralize nitrogen, phosphorous, sulfur and potassium.”
“We’re all in one big family there, so you can kind of understand if these very small inferior organisms are becoming affected, what does it take before mammals higher in the food chain are affected as well?”
Effects on plants
Glyphosate lingering in the soil can also negatively affect Roundup Ready soybean or corn plants that take in the chemical, Kremer says.
Glyphosate kills weeds by disrupting their protein synthesis, causing them to die. But there’s a secondary mechanism, Kremer says, that causes that plant to become susceptible to opportunistic soil microbes that attack the plant’s roots and eventually kill it.
Kremer explains that glyphosate is systemic and ends up being present throughout the plant, including in soybean pods and seeds. About 30 to 40% of the herbicide reaches the root system of the resistant crops, which includes actively growing root tips. Some of the glyphosate is released out into the soil and enters the environment.
Read the full article at GMWatch.org.