Influence of diverse pasture species and reduced nitrogen inputs on soil health *

Pastoral farms rely on soils for the provision and regulation of a wide range of ecosystem services that benefit the farm and its surrounding environments. Maintaining services such as primary production and water purification and regulation is dependent on the chemical, physical, biological and organic condition or health of the soil. Increasing pasture diversity and reducing nitrogen (N) applications have been suggested as management options that could sustain or even improve the health of the soil. There has, however, been little research on the impacts of these practices on soil health to date.

We investigate how a change in pasture species diversity and reduction in N inputs impacts soil health on ten dairy farms in New Zealand (in Waikato, Canterbury and Otago). Four treatments were established on each farm. Prior to treatment establishment, soils across the ten farms had generally good health. Following the establishment of both simple and diverse pastures there was a decline in Olsen P, soil organic carbon (C), total N and potentially available N to below target levels. The declines reflect a loss or redistribution of nutrients during cultivation and pasture establishment. We detail how indicators of soil health have responded in the two years following treatment establishment and explore differences observed across soils and regions. We also investigate how additional measures of soil biology can improve our knowledge of the soil resource and discuss the potential for additional biological indicators.

Extending soil assessment from nutrient fertility to a broader consideration of soil health enriches the knowledge of land managers, fostering the potential for improved decision making on-farm. Better linkages between the health of the soil and its ability to provide ecosystem services are still required to ensure the total value of healthy soils is recognised in the context of the farm business and surrounding environments.

*Title in abstracts handbook: Soil health responses to changes in nitrogen inputs and pasture species diversity