Grasslands managed for dairy and meat production represent a major land use across most regions of the world. As global demand for food products continues to rise, grassland is increasingly being converted to arable land. However, such conversion represents a significant land use change that can result in a suite of unintended consequences. Against this background, we examined three agricultural systems on the Rothamsted Research North Wyke Farm Platform. The systems studied were: a Permanent pasture monoculture, a High sugar grass that was converted to arable cropping, and a mixed sward of the same High sugar grass with white clover. Following conversion, the magnitude of carbon dioxide exchange in the High sugar grass converted to arable system was reduced relative to pre-conversion conditions. However, these differences were not statistically significant, reflecting substantial temporal variability in carbon dioxide fluxes. This land use change also resulted in a significant immediate 45% decrease in soil organic matter, a 41% decrease in soil carbon, a 41% decline in soil nitrogen, and a 61% reduction in soil phosphorus. In addition, flow-weighted inorganic nitrogen concentrations in combined surface and subsurface runoff significantly increased after conversion, while flow-weighted concentrations of carbon also significantly increased after conversion. The Permanent pasture monoculture exhibited a greater overall carbon dioxide sink capacity compared to the High sugar grass with white clover mixed sward. Both grass-based systems maintained relatively stable and higher concentrations of soil organic matter and nutrient concentrations (carbon, nitrogen, phosphorus) compared with the arable conversion. Runoff from these grassland systems also showed stable nitrogen concentrations. Overall, our findings highlight the environmental risks associated with converting grass to arable land and underscore the importance of land use management strategies that prioritize the preservation of grasslands and manage the risks of unintended consequences. • Environmental consequences of land conversion investigated using the world’s most instrumented farm. • Ploughing conversion of high-sugar grassland to arable reduced the carbon dioxide sink compared with pre-conversion. • Conversion immediately reduced soil carbon by 45%, nitrogen by 41%, and phosphorus by 61%. • Conversion also increased nitrogen losses to water.
Guo et al. (Wed,) studied this question.