Impacts of long-term phosphorus and nitrogen fertiliser application on soil biology: a New Zealand perspective

Soil biology encompasses a vast diversity of organisms contributing to soil processes and functions that underpin the delivery of soil ecosystem services. We review the response of soil biology to long-term phosphorus (P) and nitrogen (N) fertiliser application, focusing on trials conducted at Winchmore and Ballantrae Research Stations under sheep grazing. Application of P and N fertiliser increases soil fertility and pasture production and can have impacts on soil biology. Higher earthworm abundance was associated with increasing P, but not N fertiliser application. Microbial biomass or respiration tended to increase with P application but decrease with N application. Both P and N fertiliser decreased fungal biomass. The few microbial functional groups studied also appear responsive to fertilisation. A decline in soil pH may have driven some of these changes and could have been mitigated with lime. Other factors, such as plant composition, may also be important to the soil biology but have received limited attention in these studies. There are currently few indicators that can be used on-farm to assess soil biology. We discuss these as well as measures that can be used in a research context to inform the impacts of fertiliser use on soil biology and its functioning.

Automated summary

Soil biology plays a crucial role in soil processes and functions, which are essential for the delivery of soil ecosystem services. This review focuses on the influence of long-term phosphorus and nitrogen fertiliser application on soil biology, based on grazing trials conducted at Winchmore and Ballantrae Research Stations. The application of phosphorus and nitrogen fertiliser enhances soil fertility and pasture production while also impacting soil biology. The response of soil organisms, such as earthworms and microbial biomass, varied with the type of fertiliser applied. Additionally, soil pH and plant composition may also play important roles in shaping soil biology, although more research is needed in these areas.