Best management practices for fertiliser application
Most agricultural fertiliser is spread by contract ground spreaders and aerial applicators following the applicable parts of the Code of Practice for the Placement of Fertiliser. Good communication between the contractor and farmer or land manager is essential for best value from fertiliser and to minimise environmental risks. The ideas listed below are also useful considerations for land managers who apply their own fertiliser.
- Express all application rates in kilograms per hectare (kg/ha); lime application may be stated in tonnes/ha. Be sure your spreading operator is absolutely clear about the desired fertiliser application rate.
- Give details of the application area. A map showing the location, boundaries and size of the area(s) to be treated is best. Pointing out easily identifiable ground features can help the contractor find the right paddock.
- Describe any hazards present, such as power lines, trees, silage pits or hidden steep slopes that may be dangerous to the operator. It is also important to highlight any ‘unusual’ activities that may be taking place on the farm – e.g. tree felling.
- Note any areas and features to be avoided, such as streams, lakes, ponds, wetlands and riparian strips. It is helpful to mark these on the map, rather than rely on verbal explanation. Areas of high nutrient status may not respond to the fertiliser being applied and should usually be avoided – e.g. stock camps.
- Note any conditions to be avoided. Avoid applying fertilisers, particularly those containing nitrogen, when soil moisture levels are high (at or near field capacity) to avoid the risk of nutrient moving laterally rather than being absorbed into the soil. There is a risk that fertiliser applied on slopes will be washed downhill if the soil surface is hard and dry and/or the vegetative cover is very short. Delay spreading fertiliser materials if the wind is strong enough to cause drift away from the target area or if the wind direction is towards nearby sensitive crops or dwellings.
- Consult the fertiliser supplier for information about hazards to livestock from direct intake of fertiliser. Avoid application on blocks where livestock are grazing.
- Specify the accuracy and evenness required. The usual measure for evenness of spread is the coefficient of variation (CV%), in which the lowest figure represents the most even spread. Spreader operators should be given a clear indication of the evenness (CV%) required for the job in hand.