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Nitrogen budget for drystock farmers

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  5. Nitrogen budget for drystock farmers

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%.
  Total N inputs
kg N/ha/yr
 

Total N inputs

 = 

Outputs

1. Wool
Multiply the amount of wool sold (kg/ha) by 0.165 to give you the amount of N/ha/yr in wool.
  N in wool
kg N/ha/yr
Wool sold kg/ha x 0.165 = 

2. Stock
Some drystock farmers will be aware of their stock units while others prefer to keep track of liveweights as a measure of stock sold off the farm. Choose the measure that best suits your situation.

Either
Multipy the amount of stock sold (SU/ha) by two to give you the amount of N/ha/yr you lose in animals.
  N in animals
kg N/ha/yr

Stock sold SU/ha x 2		 = 

Or
Multiply your liveweight (kg/ha) sold by 0.03 to give you the amount of N/ha/yr going off the farm in meat.
  N in animals
kg N/ha/yr
Total kilograms of liveweight sold kg/ha x 0.03 = 
  Total N outputs
kg N/ha/yr
 

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 - that is, the amount of nitrogen left in your system after your product leaves the farm.
 

Farm N surplus

 = 
The higher your farm N 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 N surplus.
  Low leaching potential
(ground water N below the drinking water standard)		 Medium leaching potential
(ground water N on or just above the drinking water standard)		 High leaching potential
(ground water N above the drinking water standard)
Farm N Surplus Less than 90 Around 115 Above 140

Find out about reducing the effects of nitrogen leaching.