A year studying glyphosate here and overseas on a Nuffield Scholarship has convinced Mid Canterbury arable farmer Hamish Marr it is a vital tool in agriculture. But it comes with responsibilities, and if farmers and growers are arrogant about its use, they risk losing it through political pressure.
Can we farm without glyphosate? Of course we can – we did before, and farmers in some countries don’t use it, Hamish Marr said in a presentation to the Primary Industries NZ Summit last month.
But after spending a year on a Nuffield Scholarship soaking up every piece of information he could find on glyphosate, and talking to farmers, environmentalists, scientists and consumers here and in a number of European countries, Hamish is convinced it can continue to play a vital role for food producers.
To remove it will threaten food security and supply at a global level and there would be unintended consequences. By many estimates, yields would drop by between 20 and 50% both in the field and from processing losses from contamination. By having to return to machine tillage to get rid of weeds and crop residue, soil erosion would increase. That cultivation would result in an estimated increased fuel burn and CO2 emissions equivalent to 2.5 million cars and 11 million cars in the UK and USA respectively.
“In pre-glyphosate times, farmers could cultivate land up to 10 times between crops in order to break the cycle of some weed species, and spell fields for months,” Hamish said.
People would spend months trying to remove grass weeds like twitch or couch with machines. This time taken was time where nothing productive was growing. Over-cultivation of soil is No. 1 contributor to soil erosion. It can also result in soil carbon losses of upwards of 20% per year.
“When roundup was introduced farmers were instantly able to cultivate primarily for seedbed creation. The natural progression was the development of Minimum Tillage and then Zero Tillage or what we call direct drilling.
In the US Midwest, zero tillage has all but eliminated soil erosion that had been as high as 1.5t/ha of soil per year – soil would ultimately end up in the Mississippi river and then the Gulf of Mexico.
Most people equate glyphosate/roundup with weed control. But for arable farmers dealing with residue from a previous crop is every bit as important.
On his Methven farm, Hamish grows 10 different crop species, along with pasture with cattle and sheep in 60 individual fields across 500 hectares.
“We rotate these crops around our farm in a cycle that follows basic agronomic rules around particular crops must follow others to break disease cycles. Rotations allow us the flexibility to apply different management to different areas constantly.”
Some fields will be in yellow brassica seed crops, mustard, bok choi or kale, for example. When this has been harvested it regrows and any seed that falls on the ground germinates. This is the point where glyphosate is used. This ensures that the yellow crop does not go on to be a weed in whatever is sown next.
All agricultural products are traded on purity. If contaminated with unwanted species the product is of little value. If you buy kale seed at the garden centre, you want every seed to be a kale, not a mixture of bok choi, mustard and cabbage.
Most arable farmers in New Zealand are also seed producers and our seed industry is held in very high regard worldwide – in fact we lead the world in the production of some vegetable and grass seeds.
“Roundup is the tool that allows us the agility to move efficiently from crop to crop, in a minimum amount of time, without endangering what follows.”
In Denmark the seed trade has been shown to be virtually impossible without glyphosate.
“In Europe I saw a number of examples of complete crop failure due to lack of pest control options. This is the first component of food wastage and it begins in the field. There is no doubt that yield reductions will result in price increases for food.”
So, what about health issues?
Hamish said there was no scientific proof of a link between medical issues and glyphosate but there are a multitude of correlations including links to kidney problems, celiac disease and gluten intolerance. There is conflict between The UN International Agency for Cancer Research, which in 2015 claimed a probable link with cancer and yet a year later the EU Chemical Agency, similar to New Zealand’s EPA, found no grounds to classify the controversial herbicide as carcinogenic.
“We have all heard about the huge court cases in the US and subsequent payouts by Bayer. These warnings, correlations and findings have led to government legislated restrictions in the EU and in Germany and France, and an outright ban in 2022.
“After talking to many, many people – farmers, consumers, scientists, doctors, toxicoligists, people in the street – it struck me that the negative publicity around glyphosate use has been confused and hijacked by a movement against genetic modification and as a result really has become the victim of its own success and collateral damage.”
Science took the main commodity crops – corn, soy, lucerne, cotton and canola – and made them resistant to insects and also to glyphosate – meaning you could spray glyphosate over green crops without fear of damaging them. The insect resistance bred into these crops comes from the naturally occurring and organically certified fungus Bacillus thuringiensis, which is toxic to many insect pests. Seed companies named this modification BT for short. The introduction of BT crops immediately led to a reduction in insecticide use across North America.
The same thing happened with glyphosate. In producing roundup ready crops, the seed companies effectively substituted more targeted herbicides – dicamba, atrazine and 24D – out of the food chain.
“Novel plant breeding has all but eliminated insecticide and selective herbicide use on millions and millions of hectares of food producing crops and we haven’t been told about it at all. Bringing in a benign product like glyphosate should have been a win/win for farmers and consumers.”
“Two things went wrong. Firstly, the seed companies didn’t pass the good news story on to the consumers. And the amount of glyphosate being used now in countries with roundup ready crops has increased by a factor of 15 and people are alarmed by this.”
While roundup ready and BT crops are a big deal and a success, no one really foresaw the social issues that we are experiencing now. Agricultural science assumed that swapping good for bad was the end point but it hasn’t worked out that way. What has actually happened is that testing has improved out of sight and when coupled with increased use in GM countries, residue levels have increased.
“People are very very wary of roundup and GMO and there is a huge movement that has snowballed worldwide as a result without actually understanding the back story.”
Hamish said he spent most of 2019 looking for the big breakthrough piece of research that would tell him that roundup was as dangerous as some claim. “I couldn’t find it.”
What he did witness was the industrial agriculture in North America, with no diversity, and heavily regulated Europe, “where restrictions are so tough that farmers could not survive without subsidies.
“Both are not sustainable. Those two examples have taught me to respect the privilege we have and realise how important the use of glyphosate is strategically in modern farming systems and that actually we don’t use a lot in this country.”
“Nevertheless, we owe it to our consumers to minimise residues where possible.”
For many people, farming practices are a mystery and if we want to keep using tools such as glyphosate, we need to explain them better “and bring people with us”.
The gist on Glyphosate
- Glyphosate (aka ‘Roundup’) is a broad spectrum herbicide.
- Developed by Monsanto in 1974, it was popular with farmers and gardeners almost instantly.
- Many scientists declared it as the chemical of the century because it’s a broad spectrum, non-selective herbicide with very low toxicity, virtually no soil residue and a zero plant back period. That all means it has a very wide target range and works simply by disrupting the production of an amino acid found only in plants. In mammals it is expelled rapidly in urine.
- Glyphosate is broken down very quickly in soil – although this has some environmental qualifications attached to it. Because of this breakdown, farmers and gardeners are able to replant crops and pastures almost immediately following application without fear of crop failure through root absorption.
- Unlike in many other countries where crops are grown to feed centrally housed livestock, most of our country is in pasture and much of that pasture is not renewed regularly. So glyphosate is only applied to around 6% of our farm land.
Questions of toxicity
One of the key attributes of glyphosate is its low toxicity.
Toxicity in any product is measured by a metric known as an LD 50, LD meaning lethal dose and 50 standing for the lethal dose required to kill 50% of a test population. It is expressed in milligrams (mg) injested per kilogram of liveweight. The lower the number the more toxic the substance.
Table salt has an LD50 of 190, so the lethal dose for someone who weighs around 90kg is therefore 19 grams, Caffeine an LD50 of 367, white vinegar an LD50 of 3600, glyphosate an LD50 of 5600 and Vitamin C, LD50 of 11,000.
There are no alternatives to glyphosate that tick all the boxes. People have tried steam weeding, electrocution and even using boiling water. But they don’t stack up for the scale required.
“In Europe farmers have tried white vinegar; it’s in the house so it must be safe, right?,” Hamish said. “But think of its toxicity and this fact – a 1% solution of roundup will shut down 90% of species on its label. White vinegar requires a 20% solution, virtually concentrated at 1.5 time the toxicity. The authorities have been very quick to ban white vinegar for weed control in Europe for environmental and health reasons.”