This worksheet has been developed by the Waikato Farm Environment Award Trust, with funding from the Ministry of Agriculture and Forestry (MAF) Sustainable Farming Fund. Waikato Regional Council and Dexcel also contributed to the project.
Inputs
1. Fertiliser
Divide your fertiliser nitrogen rating (%N) by 100 and then multiply by your rate of application:
(For example, urea is 46 percent N, while DAP is 18 percent N.)
%N
x kg/ha/yr
100
2. Clover nitrogen (N) fixation
Choose the clover nitrogen (N) fixation corresponding to the clover content on your farm.
% average annual clover content
Very Low 5%
Low 5-10%
Medium 15-20%
High 25%
Very High 35%
Clover N Fixed kg/ha/yr
35
70
120
180
250
Note: In productive pasture without fertiliser N, clover content is normally about 15-20%.
3. Effluent nitrogen (N) input
Select the figure corresponding to your production.
Milksolids/ha
600
800
1000
1200
1400
1600
Effluent N input kg/ha/yr
14
20
26
28
34
40
Note: This assumes that effluent is applied to the whole farm. In reality, your effluent block will be receiving a concentrated loading of nutrients from across the farm.
Total N inputs
Outputs
1. Milk production
Milksolids/ha
x 0.068
Total N outputs
Note: Bought in feed and feed sold off the farm are additional inputs and outputs that could be included in a full nutrient budget.
Farm nitrogen surplus
This gives your total farm surplus of nitrogen (N) - that is, the amount of nitrogen left in your system after your product leaves the farm as milk.
Farm nitrogen surplus
The higher your farm nitrogen surplus the greater the potential amount of nitrogen leaching from your paddocks into drainage and ground water, reducing water quality. Use the table below to assess the nitrogen leaching potential on your farm, depending on your farm nitrogen surplus.
Low leaching potential (ground water nitrogen below the drinking water standard)
Medium leaching potential (ground water nitrogen on or just above the drinking water standard)
High leaching potential (ground water nitrogen above the drinking water standard)
