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Last week, researchers from University of California Davis published the results of the largest comparative study of no-till agriculture ever undertaken.

The researchers found that no-till – which is a key tenet of conservation agriculture, endorsed by the UN Food and Agriculture Organisation – can outperform conventional agriculture in drier conditions, due to improved moisture retention, but in wetter regions around the world shifts to no-till may result in yield penalties of up to 9 percent.

This led UC Davis Plant Science professor Chris Van Kessel to conclude that, "Broad implementation of conservation agriculture may not be warranted in all areas, particularly where residue retention and crop rotation practices are hard to implement."

However, at a presentation on 'The Potential of No-Till Agriculture for Arable Farmers' at Harper Adams University on Tuesday (04 November), visiting professor Dick Godwin presented the result of several months of analytical research which, supported by a number of farmers who have adopted the no-till method, demonstrates that the yield penalty may not be as great as previously suggested (especially in the drier areas of Southern and Eastern England), and that co-benefits of the approach may outweigh any small deficit.

No-till agriculture, by definition, is a method of farming in which soil is not tilled, seeds are drilled direct into the ground and weeds are controlled by other means. Worldwide, 150 million hectares are now farmed no-till and the area is increasing by around 10m ha per year.

Presenting the second research report commissioned by the Worshipful Company of Farmers, Prof Godwin noted that in the US and Australia no-till is almost the norm (covering 85-90 percent of Australia's arable land). He said that although min-till is gaining ground in the UK (it has been increasing in line with growing wheat yields over the past 30 years), no-till has been also been on the rise, though almost imperceptibly so.

Nevertheless, Prof Godwin maintained that his own research, supported by a study originally conducted in 1978 (and replicated in 1985 and 2012) showing that much of the UK, particularly South-East England and the East coast of Scotland, is suitable for no-till. Only in the wetter West of the island would serious impacts on yield be expected. Prof Godwin said that, by international standards, south and Eastern England are relatively dry areas. In fact, the Australian state of Victoria receives more annual rainfall than Eastern England, he claimed.  

According to the professor, the progression of climate change will drive the boundaries of the UK land area most suited to no-till further north and west.

Prof Godwin's research identified the potential of no-till to address environmental issues associated with current management methods, including reducing fuel use (which could be cut by 35-50 percent), fertiliser use (up to 50 percent reductions in P and K applications), water use, greenhouse gas emissions, improved carbon sequestration in soils and soil biodiversity.

In fact, research from the University of Nottingham, which compared soil cores taken from several tilled and no-tilled farms, revealed that (though nitrous oxide emissions were higher from no-till) on balance the management practice "Could play a significant part in reducing greenhouse gas emissions and climate change."

However, there are limiting factors that have hampered uptake of no-till in Britain.   

These include problems with weed control and germination in overly dry or sodden conditions; in the UK farmers may also struggle with problems caused by wetter and greener straw than their counterparts in US and parts of Australia. 

However, in line with observations made last week by UC Davis experts, who studied 5,000 paired observations of no-till and conventional systems all over the world, Prof Godwin's report for the Worshipful Company of Farmers found that when carried out in line with other sustainable practices no-till can yield real benefits. Practitioners who worked with Prof Godwin identified certain practices that can be especially useful, including effective crop rotation and Controlled Traffic Farming (in an experiment at Harper Adams no-till appeared to yield better than conventional on land that wasn't wheeled on).

Slugs

Pest control has the potential to be a major problem with no-till and was identified as a challenge which requires research attention in Prof Godwin's report. Slugs and snails in particular were a commonly reported problem in certain rotations, and in one case study slug pellet use went up 25 percent in a no-till rotation. However, as soil conditions improve, practitioners assured, worm numbers, soil structure and populations of other natural predators also rise, providing elements of sustainable and low-impact pest control.

Tony Reynolds, who has practiced no-till on his land in Lincolnshire and Leicestershire for over 12 years, said "Slugs and snails come with the territory." He noticed a build up of slugs in years two, three and four of his transition to no-till but assured that rebuilding soil health and keeping off the land eventually led to the return of beneficial creatures.

"We have slugs," he admitted. "But we also have creatures that eat them. Once the system gets going it takes care of itself [to an extent]."

Slugs seem to be a particular problem in oilseed rape. Expanding on the slug issue, Nick August – another no-till farmer who provided a case study – said, "All farmers are questioning the economic benefit of oilseed rape in their rotations, not just us no-tillers." He added that he is "Relieved methiocarb is gone, because it was a big killer of ground beetles," one of slugs' natural predators.

Tony Reynolds elaborated that, although there are still slugs on his land, there is more detritus in soils for them to feed on, meaning they do less damage to crops, whereas "In Sanitised farming there's nothing else. In that landscape if you plant a seed of course they'll go for the seed."

Furthermore, he said, there are more worms and beneficial insects. "Worms graze slug eggs, ground beetles graze on slug eggs."

Reynolds added that there are other benefits to allowing the soil to regenerate: "Because you don't disturb the soils, there are bees that nest in them and mouse holes. We have birds which are attracted by all the worms in our soil and these attract bigger birds that eat the smaller ones."

Black grass

Prof Godwin's report suggests that "A major risk to the adoption of no-till is management of grass weeds… this is a high research priority."

On Tuesday, Black grass proved to be a contentious issue. Prof Godwin's own research suggested that ploughing gave more effective black grass control (but that control in no-till varied widely depending on the date crops were sown). Though the professor suggested the best results were achieved by direct drilling after one year of ploughing, which buried weed seeds and ensured they remained buried, others contested this. Everyone seemed to agree that ensuring good drainage was a key factor in suppressing black grass.

Prof Godwin concluded that "Rotational cropping including the establishment of spring crops is part of the armoury of cultural control methods that need to be considered" to thwart black grass.

Tony Reynolds commented, "Classic agriculture is moving black grass from one end of the country to the other... leave it alone. If you don't disturb them, black grass seeds under the soil will rot. We have black grass, but it's what's dropping onto the ground and it’s easier to kill."

Even so, Prof Godwin suggested that more research should be carried out in a number of priority areas, including weed management and control of slugs and snails. Another key area is drill performance – even now, when no-till has taken off elsewhere, there is a lack of suitable machinery for UK conditions.

The no-till farmers who informed Prof Godwin's case studies agreed that external factors might drive more farmers towards less intensive management techniques such as no-till. Tony Reynolds said, "Classic agriculture involves pouring money and horsepower into getting on the land and ripping it up when you shouldn't be on it at all. We're now adding stuff that machinery has taken out."

"No till has half the diesel use compared to classic agriculture. When the price of diesel rises to £10/litre what will we do?" He concluded, "Soil is the be all and end all. If we destroy it we destroy ourselves."

Prof Godwin added, "Soil is a difficult resource to manage properly. We've done a lot to damage it over the last 50 years or so. [Now] we need to back off." He said that, in addition to the knowledge gaps identified around no-till, the lack of training for soil scientists is an issue of deep concern and more research sites and training programmes are desperately needed across the country.