You can reduce P loss by carefully managing P in fertiliser and effluent as well as managing sediment and faecal matter losses.
Practical P loss tips
- ✔ Fence streams to exclude stock from waterways
- ✔ Use riparian planting as a buffer between paddocks, races and the water. The plants act as a filter, slowing down runoff and catching sediment and P. See the Riparian Planner Tool.
- ✔ Carefully select your paddocks, grazing routines and crops to minimise disrupting the soil and runoff to waterways, particularly during winter months. See Wintering cows on crops.
- ✔ Maintain races and direct water running off them away from waterways and into paddocks through the use of cut-offs. See Waterways.
- ✔ Control slips and hillside erosion to prevent losing valuable topsoil and P to waterways. See Erosion.
- ✔ Direct any effluent that collects on hard surfaces such as concreted races, bridges or culverts into your effluent system. See Effluent.
- ✔ Create greater effluent pond storage and defer irrigation to land
- ✔ Enlarge areas receiving dairy farm effluent
- ✔ Defer and/or apply effluent at low/variable rate
- ✔ Avoid applying farm dairy effluent to freely draining, stony soils under irrigation
- ✔ Test soil regularly and manage P fertiliser application to ensure Olsen P levels are within the optimum range; this minimises the amount of P leaving your farm in loss events. See P Fertiliser.
- ✔ Use good management practices to apply P fertiliser and effluent to ensure they do not run off to waterways.
Critical source areas
Managing Critical Source Areas (CSAs) is also important for reducing P loss. This concept ranks areas according to their potential to act as a P source and their potential to transport or lose P.
CSAs are those that have a high source and transport potential and can account for the majority of the P loss despite coming from a minority of the catchment’s area. They tend to be small, low-lying parts of farms such as gullies and swales where runoff accumulates in high concentration during rainfall events.
Steeper slopes and steeper stream banks are at greater risk of erosion and collapse, especially during high rainfall events and any activities that disturb soils or streambanks can cause losses of P. The cost-effectiveness of mitigations is on average greater when targeted to CSAs as opposed to untargeted implementation across catchments.
Adopting Good Farming Practice reduces the risk of P losses.
Good farming practice principles
Below are the areas and actions you can take to reduce P loss on your farm.