Examining the policy-practice gap: The divergence between regulation and reality in organic fertiliser allocation in pasture based systems

•Practical constraints on farms explain the policy-practice gap in nutrient management.•Farmer decision modelled as a function of field and farm characteristics.•Drivers of slurry management are slope, distance from yard, land use, soil type.•High soil P fields received slurry despite policy regulation. Slurry and animal manure generated from livestock production systems are typically recycled back to land to replace nutrients removed in products leaving the farm such as milk, meat and grass. Avoiding environmental losses of nutrients due to slurry spreading requires careful management, contingent on farmers following agronomic advice and policy regulation, yet, nutrient losses to water from agriculture continues to put a significant pressure on water quality. The objective of this study was to examine whether a policy-practice gap in slurry management exists on farms by identifying the factors that influence the decision to spread slurry, across the farm. To achieve this, a Heckman selection model was used to identify the drivers of slurry management using farm and field management records and soil information from commercial livestock farms combined with spatial datasets on landscape position. The main drivers influencing the decision to spread slurry were practical considerations relating to the structure and spatial arrangement of fields on the farm, such as proximity to farm yard, as well as landscape position. Field and landscape variables were also related such as slope, elevation, drainage capacity, soil type, presence of open ditches, and soil phosphorus (P) level. Fields with excessive soil P content had a high probability of receiving slurry in greater amounts, thus challenging the assumption that farmers use soil testing to guide slurry management, and identifying the main agri-environmental policy-practice gap and a need for better knowledge exchange in this area. Despite current policy, practical considerations override soil testing and these results showed that slurry management and allocation is rooted in the spatial arrangement of fields on the farm. The results indicated that farmer decisions are driven by factors that relate to the time, cost and labour involved in spreading slurry, indicating the need for water quality measures and policy to consider the practical constraints and considerations from the viewpoint of the farm.