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Understanding Overseer maintenance fertiliser/nutrient recommendations

Helpdesk
  • Updated

The Overseer model creates maintenance nutrient recommendations as part of the functioning of the pasture model. 

The maintenance nutrient recommendations can be found in the Reports > Block Details report as below:

and a summary is also provided in the Reports > Compare Blocks report: 

When viewing this information, it is important to remember: 

  • Maintenance nutrient recommendations are ONLY provided for pasture blocks, not crop, fruit or fodder crop blocks.
  • There is no such thing as a "Maintenance Nitrogen" application, hence why the N box is always "NA".
  • The maintenance nutrient amount recommended, is the quantity of a nutrient which the model assesses is required to maintain soil test levels of that nutrient at their current level, given the farming activity being modelled on that block. 

  • Overseer is a "decision support tool" NOT a "decision making tool. Farmers and growers should work with a suitably qualified person to assess whether their soil nutrient levels are depleted, at target range or above target. Some guidance is available in the Fertiliser Association  "Fertiliser Use" booklets, available here . E.g. for dairy farms, the levels below are suggested: 



    Source: Fertiliser use on New Zealand Dairy Farms, Fertiliser Association of New Zealand https://www.fertiliser.org.nz/files/site/Dairy-Farms-booklet24(Digital).pdf Page 13

This means, that if a soil test is showing an Olsen P level of, say, 55, on a sedimentary soil. The maintenance recommendation from the model will be the amount of nutrient P required to maintain the soil P status at 55.
This may not be economically or environmentally desirable, and so farmers are recommended to consult with a suitably qualified advisor (e.g. your fertiliser rep or independent consultant) to decide on a suitable fertiliser strategy. 
 

If farmers do not already have a trusted advisor for fertiliser decision making, they may find the  Nutrient Management Adviser Certification Programme helpful, a list of qualified advisors can be found here.