Pesticide reductions of 50% achievable in UK

Pesticide reductions of more than 50% could be achieved by redesigning crop rotations and employing new technologies in the UK, a group of scientists, advisers and farmers within the Endure project team found.

But the more radical rotations would have implications for profitability at both the farm and national level.

UK yields are among the highest in Europe, but pesticide use is intensive, so, with growing pressure on reducing pesticide use, the team looked at what scope there was for reducing use in a winter cereals cropping system while maintaining production and profitability.

Rotation was a key tool for interrupting pest build-up, as well as the use of crop protection technologies, but the severity of pest problems could be influenced by the cropping system, Andrew Ferguson, a Rothamsted Research research scientist who led the study told Farmers Weekly.

Arable rotations were dominated by cereals, with oilseed rape or pulses typical as break crops, he said. But continuous autumn sowing had led to increased problems from grassweeds and higher herbicide use, while fungicide use was high because of mild and moist winters encouraging septoria in wheat and the responsiveness of varieties to treatment.

The increasing size of farms and use of contractors had led to an increase in early drilling, he added. "September-drilled wheat crops are associated with high disease risk and can lead to grassweed problems, leading to more pesticide use."

The starting point for examining how pesticide use could be reduced within an arable cropping system was diversifying the rotation to include more spring cropping and a greater variety of crop types, which could help reduce problems with weeds and diseases, Mr Ferguson explained.

Seven four- and five-year rotations were examined with progressively smaller proportions of winter cropping. Fallow was included as an option in some rotations for tackling severe grassweed problems.

When compared with the most common rotation of two winter wheats and an oilseed rape crop, including more spring cropping and/or fallow could reduce annual pesticide use by as much as 30%, Mr Ferguson said.

A further 20% reduction on the least radical rotations could be achieved by using current technologies, such as more effective and timely use of pesticides according to need determined by economic thresholds, forecasting and decision support systems, ploughing before second cereals and spring cropping to help with weed management, and using resistant varieties.

Emerging and future technologies, such as GPS-controlled pesticide applications, using wide-row spacings in oilseed rape to allow targeted weeding and nutrient applications, and better resistant varieties, could reduce pesticides by 30% on top of the rotations.

Testing the new rotations in the DEXiPM performance tool designed by the Endure team found the newer rotations had a lower environmental impact, but a risk of not being economically viable, he admitted.

"Although there are more first wheats in some of the rotations, wheat production is likely to be significantly reduced in all the rotations, and it is doubtful if there would be a market for a large increase in bean production.

"The wide adoption of the proposed rotations would potential impacts on profitability and production at national and farm level.

"Policy makes need to be aware reducing pesticide use has consequences."

France goes extreme

A similar project undertaken in France looked at redesigning cropping systems in three French regions from the basis of starting with nil pesticide use.

The result was a 95% potential reduction in the use of pesticides in one system designed for the Burgundy region. The system used included two years of alfalfa within an eight-year period, and only two years of winter wheat.

Mechanical weed control, biological control and use of resistant varieties are also cornerstones of the strategy.

France has a stated political aim of reducing pesticide use by 50% by 2018.

Source: FWI