A new study from Rothamsted Research highlights the environmental trade-offs of converting grassland into arable farmland, showing significant reductions in soil macronutrients and increased nutrient pollution.
Using long-term, field scale data from the Rothamsted North Wyke Farm Platform (a National Bioscience Research Infrastructure for the UK) in Devon, researchers compared three farming systems: permanent pasture, improved grassland comprising a grass/clover mix, and land converted from grass to arable cropping.
Dr Yafei Guo from Rothamsted commented: “Many studies examining the impacts of land use conversion rely on plot scale data, meaning that field scale data, more representative of real farm conditions, is rare. Equally, many studies only focus on single outcomes rather than examining multiple outcomes simultaneously. The North Wyke Farm Platform provides a heavily instrumented and unique platform to address these gaps.”
The study found that converting grassland to arable cropping caused immediate and substantial declines in soil quality. Soil organic matter dropped by 45%, while soil carbon and nitrogen both fell by 41%, and phosphorus declined by 61%.
These changes indicate rapid depletion of key macronutrients essential for long-term soil fertility.
At the same time, pollution emissions to water increased. After conversion, concentrations of nitrogen species and carbon in runoff increased significantly, with nitrogen species losses rising by 200–300 times.
The research also examined carbon dioxide exchange between the farmed land and the atmosphere. While all systems showed seasonal variations, permanent pasture consistently acted as a stronger carbon sink than the other systems and the differences among the three systems were not statistically significant.
In comparison with the arable conversion treatment, grass-based systems maintained more stable soil conditions and nutrient levels. Permanent pasture, in particular, retained higher levels of soil carbon, nitrogen, and phosphorus, and showed more consistent emissions to water.
Professor Adie Collins, Science Director at Rothamsted Research added: “These findings highlight the need to carefully balance food production with the protection of our natural resources, and the environmental risks associated with converting grassland to arable production to feed a growing global population.”
