Nutrients are essential for plant and plant root growth. However supplying too much nutrients can cause nutrient leaching or runoff from the land, resulting in adverse environmental effects, such as excess plant and/or algae growth in waterways.
The two most common nutrients are nitrogen and phosphorus. These can be dissolved (soluble), solid (insoluble), or found in organic matter.
Read more about this in the Nutrients Inputs Fact Sheet (60KB, pdf). Although this fact sheet refers to the Rotorua lakes the principles can be applied to any other waterway such as streams and rivers.
The nitrogen and phosphorus cycles are described below and illustrate the movement of these nutrients in a pastoral system.
The nitrogen cycle
Nitrogen is highly soluble when not taken up by plants and can leach through groundwater into waterways.
The phosphorus cycle
Phosphorus is attached to soil particles and therefore can move into a waterway through erosion.
Management of nitrogen and phosphorus
Nutrient release from land can be managed through best land management practices.
Some examples to manage nitrogen and phosphorus from entering waterways include:
• Prevent direct application of fertiliser to waterways
• Fence off waterways from stock
• Follow best practice to apply farm effluent
For an outline of efficient use of fertiliser on land and tips on the efficient use of nitrogen fertiliser read the Efficient Fertiliser Use Fact Sheet (102KB, pdf).
• Prevent direct application of phosphorus fertiliser to waterways
• Manage soil erosion (slips, slumps) to prevent soil entering waterways
• Control runoff from tracks, feed pads, races to prevent it entering waterways
• Avoid overgrazing and pugging especially close to waterways
• Fence off waterways and establish riparian vegetation or grass strips to filter nutrients from water entering the waterway.
Refer to the New Zealand Fertiliser Manufacturer's Research Association's Code of Practice for Fertiliser Use for further information about best management practice.
Additional information on nutrient management can be found on the Dairy NZ website
The following fact sheets provide more information on nutrient management and tools available to manage nutrients on land in the Bay of Plenty region.
Land Management factsheets (see 09 Runnoff Management on Pastures, 33 Riparian Management Plan)
Riparian Protection (348KB, pdf)
Lakes Fact Sheets (see 05 Riparian Protection - Benefits to the Rotorua lakes, 06 Wetlands)
Farm Dairy fact sheets