FEATURE BY ANTHONY KING | 20 DECEMBER 2023
Turkey, ham, roast potatoes, buttered parsnips and carrots, all swimming in gravy. A fraction of what makes it to the Christmas dinner tables is organic produce, as Anthony King explores.
Organic farming makes up less than 3% of the total farmed area in the UK. That compares with 26% in Austria, 20% in Sweden and around 10% in Spain. Organic production gained traction in the 1970s with the publication of Rachel Carson’s book Silent Spring on the harms from the indiscriminate use of insecticides. This also yoked organic to the environmental movement, with consumers often buying organic food for perceived (unproven) health benefits in avoiding pesticide residues. Yet the strongest motive for adopting more organic farming lies elsewhere – with the environment.
‘I’d say the strongest benefits for low-input agriculture are for soil health and biodiversity,’ says Gareth Morgan, Head of farming policy at the Soil Association, a UK charity. Wildlife is under pressure around the globe, including in Europe. In Germany, for example, a 75% fall in flying insect biomass over 27 years was recorded in 63 protected areas surrounded by farmland (PLOS One, doi: 10.1371/journal.pone.0185809). Many bird species have also declined markedly, largely attributed to the use of pesticides and fertilisers in intensive agriculture (Proc. Natl. Acad Sci., 2023, doi: 10.1073/pnas.2216573120).
Mind the gap
By 2030, the European Commission aims for 25% of EU agricultural land to be certified organically farmed.
By 2030, the European Commission aims for 25% of EU agricultural land to be certified organically farmed. To get near such ambitious targets, however, organic must close the gap in terms of yields. By some measures, organic farming increases species richness by around 30% (J. Appl. Ecol.; doi: 10.1111/1365-2664.12219). But results are variable. A counterargument is that lower productivity will necessitate more land to produce food, potentially eating into non-agricultural land.
‘There has been scientific evidence for more biodiversity on organic farms. You also have lower yields, so there are upsides and downsides,’ says Ulrich Schmutz, an agroecologist at Coventry University, UK.
One key difference with organic farming is how nutrients, especially nitrogen, are applied. ‘It’s probably better known for its aversion to synthetic pesticides,’ says Morgan. ‘But to my mind, the defining feature is around nitrogen.’
Manure needn't necessarily be applied with bare hands.
Rather than synthetic nitrogen made by the energy intensive Haber-Bosch process, organic wastes such as manure are added to organic farms or nitrogen is naturally fixed by legumes. This has advantages such as slower release of nitrogen and promotion of a healthy soil microbiome. Organic agriculture also aims to harness beneficial insects, including pollinators such as bumblebees, predators such as wasps and decomposers such as beetles.
The divergence in yields is arguably greatest with cereals, with wheat thriving when fed plenty of nitrogen. The UK is a record beater for wheat yields, notes Nicola Cannon, an agronomist at the Royal Agricultural University in Gloucestershire, UK. ‘This is reliant on creating the correct canopy for maximum light interception, sufficient moisture to avoid stress and fungal disease, and reduced competition from weeds.’ Under long summer days of northern England, with enough nitrogen, yields can hit 9-10t/ha. Without fertiliser, at some sites this can be 2 or 3t/ha.
With the recent ban on neonicotinoids, oilseed rape has become a particularly challenging crop in the UK.
A Lincolnshire grower in 2022 harvested a record 17.96t/ha wheat crop, more than twice the UK average. In such productive locations, farmers can grow wheat, wheat, oilseed rape on repeat rotation. An organic grower, however, would require a sophisticated rotation of crops often over a seven-year cycle. Organic works fine for arable crops such as wheat, barley and oats, says Morgan, ‘but it depends on how much natural nitrogen you can build up’. This means planting nitrogen-fixing legumes such as clover and peas some years. ‘The organic manure system is very important for soil fertility,’ says Lukas Pfiffner, a scientist at the Research Institute of Organic Agriculture (FiBL) in Switzerland. ‘Organic farming focuses on the circulation of nutrients.’
Switzerland has many farms with animals and crops, says Pfiffner. But the UK has transitioned away from mixed farms, making organic agriculture tougher. ‘There’s not a huge coverage of organic arable in the UK,’ says Morgan. ‘It is perceived as difficult to do, and difficult to recoup any additional costs.’ Morgan also senses institutional resistance to organic agriculture in the UK from the Government down, and advocates more financial support for low-input farming.
Pest, disease pressures
The larvae of hoverflies and of lacewing are voracious predators of aphids (pictured).
EU legislation on organics works by listing allowed active ingredients. The number of agrochemicals permitted under EU legislation has declined dramatically in recent decades. But organic farming has always coped without synthetic compounds, relying instead on naturally occurring pesticides and living organisms.
In Switzerland, more than 380 active ingredients are approved for conventional farming, with only 100 allowed for organic, according to FiBL. The smaller arsenal can pose challenges. ‘There’s nothing impossible for organic, but some crops have a higher yield penalty and there can be difference challenges in terms of pests and diseases,’ says Morgan.
With the recent ban on neonicotinoids, oilseed rape has become a particularly challenging crop in the UK. ‘In some regions of Germany, it is virtually impossible to grow oilseed rape, but the organic sector would move towards trying sunflowers or hemp as oil crops,’ says Sabine Zikeli, Director of the centre for organic farming at the University of Hohenheim, Germany. In the UK, Scotland’s Rural College in Aberdeen advises that resistant varieties of oilseed rape and new organic flea beetle deterrents could make the crop more viable.
While organic growers use no synthetic pesticides, in the last two decades, increasing research effort has been directed into alternative crop protection methods. Biocontrol agents have become increasingly important, and they make up a substantial proportion of the EU allowed agents in organic agriculture. ‘There is a lot of demand [for biocontrol agents] but the regulatory procedure is difficult,’ says Zikeli. If pheromone traps developed for organic farming are also sold in conventional farming, such biocontrol agents become more attractive to commercialise, she adds.
There are other strategies too. Pfiffner at FiBL, Switzerland, has investigated how to defend apples without insecticides. ‘Apples and cherries are quite a challenge to grow organically,’ says Pfiffner. The quality and yield of organic tree fruit can be reduced by 10 to 25% due to insect and pest damage, yet consumers increasingly want to buy organic apples. The European project EcoOrchard tried out flower strips along the borders and alleys of apple orchards. The larvae of hoverflies and of lacewing are voracious predators of aphids, but the adults require specific pollens and nectars – provided by the flower strips – to make their home beside orchards (Agriculture, Ecosystems and Environment, 2019, 278, 43; doi: j.agee.2019.03.011). ‘We found a really good impact on Rosy apple aphids,’ says Pfiffner, a significant pest on apples. Netted cherry trees trials so far have not yielded such positive results, however.
Organic farming is not all about insects, but also about trying to improve soils, says Barbara Thürig, a plant pathologist at FiBL. Adding organic fertiliser such as manure can activate and feed soil microbes, which appears to reduce soil diseases. However, it is difficult to predict which treatments work best – something Thürig and colleagues are addressing in field trials of composts made, stored and aged differently. ‘It seems if you use woody material as compost then you promote Trichoderma or other fungi that can be suppressive against diseases such as Rhizoctonia,’ says Thürig.
Rhizoctonia is a fungal disease that inflicts damping-off in seedlings, root and stem rot and cankers on stems. Younger composts were found to contain more bacteria and better suited to deter other plant diseases. FiBL researchers aim to make recommendations on compost applications for farmers faced with specific soil-borne crop diseases.
Meanwhile, one major bugbear for organic vines and trees is fungal diseases. ‘Without any kind of fungicide, you wouldn’t harvest anything from vines.’ says Zikeli. ‘Perennial crops are much more difficult to manage when it comes to diseases. There’s no way to rotate, limited options for mixed cropping and so on.’
Vineyards, for example, are often heavily dependent on copper-based fungicides to protect against powdery mildew. Historically up to 50kg/ha of copper was applied on conventional vines, whereas European regulation now restricts this to 4kg/ha, and some northern European countries do not allow copper for some crops due to concerns about build-up of copper levels in soil and its potential to harm soil life.
‘The advantage of copper is that it is very cheap and effective against a broad range of pathogens,’ says Thürig. It sticks to leaf surfaces and preparations release copper ions quite slowly, another useful property.
‘The advantage of copper is that it is very cheap and effective against a broad range of pathogens.’
Barbara Thürig, FiBL
Most copper is used in conventional farming, however, organic farming also relies even more heavily on copper which is seen as contentious. There’s no silver bullet, says Schmutz, who has studied alternatives to copper fungicides. He advises more crop rotation, wider spacing or pruning to allow more light in orchards. Schmutz led a research project that recently recommended that the EU reduce copper applications further, from 4kg/ha to 2 kg/ha. Copper is used especially in Europe for vines and olives, followed by almonds (Agronomy, 2022, 12(3), 673; doi: 10.3390/agronomy12030673). Potatoes also require fungicides to protect them from blight.
An optimal solution for reducing copper in viticulture is to grow resistant varieties, according to Thürig, but this faces consumer resistance. ‘We have alternative resistant varieties, bred by crossing with American vines, but many people want to buy wine made from traditional varieties like pinot noir,’ she says. Another possibility is to genetically engineer resistance to specific pests or diseases into crops, but the organic movement and its consumers are far from accepting gene editing. Nonetheless, traditional breeding can still greatly improve resistance in organic crops.
Not all organic crops are at a disadvantage, however. For horticultural crops – such as some root vegetables, lettuces, peas, beans – there is almost no yield difference, says Schmutz, who carries out research at the picturesque Ryton Organic Gardens, five miles southeast of Coventry, UK. Such crops often are quite labour intensive, but technologies such as automated hoeing and weeding machines, and even fruit picking robots, offer more efficient ways for organic farmers to operate.
Against the flow
Proponents of organic agriculture say one additional upside concerns water quality. Organic farming should reduce nitrate runoff into waterways, provided any organic fertiliser is correctly applied. ‘In organic arable and animal farming, usually the nitrogen per hectare with the system is lower, and that results in less groundwater contamination with nitrate,’ says Zikeli. Nitrate is an anion, which is highly mobile in soils and linked to negative health outcomes such as cancer.
‘There’s a greater awareness of excessive nutrient loading in our rivers, but it is often viewed as an issue of sewage pollution,’ says Morgan. ‘We really need to tackle nutrient overloading in rivers by addressing agriculture.’ Much of Europe already suffers from nitrogen and phosphorus pollution in waterways, but organic agriculture is rarely touted as a solution.
‘We have bred crops to be nitrogen junkies,’ says Peter Smith, a plant scientist at the University of Aberdeen in Scotland, meaning they are reliant on mineral fertilisers and were bred to grow in their presence. ‘If we put the same amount of effort into breeding crops that thrived on low external nitrogen inputs, and that were naturally more resistant to pests and disease, then the yield difference between organic and non-organic farming could be closed.’
Quantifying any harm from pesticides remains challenging. ‘Pesticide contamination in organic products is always lower than conventional ones, but very often their levels are below the safety threshold,’ says Zikeli. If no pesticides are used in an area, there will be far less pesticide residues in waterways or groundwater. One recent study using a global system for classifying hazards found that 55% of the active substances used in conventional agriculture contained health or environmental hazard statements, compared with 3% of active substances used in organic agriculture (Toxics; doi: 10.3390/toxics10120753). ‘The mixture of compounds being found in rivers could be problematic, but we don’t know much about [their health effects],’ says Pfiffner, who cites the Toxics study as a reason to reduce synthetic pesticides use whenever possible.
In the UK, Morgan is frustrated by how organic food is sold. Supermarkets position organic as premium, seeing an opportunity to charge more, which conveys the idea of organic as unaffordable and does not reflect the actual cost of production, he says. ‘We’re not getting the research innovation in organics that would enable it to grow at the speed it could.’ Proponents of lower input agriculture say also there is a need for public advisory systems for farmers to go organic in Europe.
‘Supermarkets position organic as premium, seeing an opportunity to charge more, which conveys the idea of organic as unaffordable and does not reflect the actual cost of production.’
Gareth Morgan, Soil Association
‘It is a bit paradoxical, because the organic movement started in the UK, yet there is quite a bit of institutional resistance to it in the UK,’ Morgan says. ‘On the continent, organic is just another way to farm, whereas in this country, it is regarded as somewhat eccentric, and as somewhat elitist on the consumer side.’
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