Nitrogen budget for dairy farmers

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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.

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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   Fertiliser N input
kg N/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
Clover N fixed
kg N/ha/yr
= 
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
Effluent N
kg N/ha/yr
= 
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
kg N/ha/yr
 

Total N inputs

 = 

Outputs

1. Milk production

 N in milk
kg N/ha/yr
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)
Farm N Surplus Less than 90 Around 115 Above 140

Find out about reducing the effects of nitrogen leaching.