Farming can be looked at as a game of using every resource available, as efficiently and responsibly as possible, to provide maximum production from those resources.

The application of fertiliser has been used for decades, the benefits for soil and plant health are well known. If you are in the same boat as the majority of farmers, spending upwards of $50,000 a year on fertiliser, how can you maximise your investment?

It is common practice amongst rural contractors to operate under GPS guidance, however, many farmers do not spread in the same quantities as the average contractor. So, do the costs of investing in GPS guidance stack-up, and how much can it increase accuracy?

To better understand the cost savings, efficiency and gains, TracMap has run an experiment in conjunction with dairy farmer, Henry Bolt to gain better insight into the issue.


TracMap Area Manager, Gus Hewitt, rode shotgun with Henry Bolt, a Synlait supplier who has recently invested in GPS guidance systems from TracMap. The experiment was to spread multiple paddocks, with and without GPS guidance.


After 6 years of spreading his own fertiliser without using a GPS, Henry was able to spread with 20% higher accuracy with TracMap’s system.


For Henry, the lower accuracy rate results in under-spreading, so we can calculate the efficiency and value gained by maximising coverage.

With the total farm size at 200ha, an entire round of spreading would mean 196ha spread using a GPS and 156ha without. So what difference does the additional 40ha of applied product make?

Dairy NZ suggest that in spring you have an 80-100% chance of getting a 10:1 N response rate, and with Henry applying 50kg/ha of Nrich urea (46% N), that’s 23kg N/ha.

As a consequence, Henry will grow an additional 230kg DM/ha for the 40ha, producing 9,200kg DM in total.

Assuming 12.5kg DM = 1kg milk solids, that’s an additional 736kg of milk solids.

With a projected $6.50 payout, the total revenue generated for that additional 40ha is $4,784.

Henry is budgeted to repeat his urea applications six times throughout the year, so without including capital applications twice a year, Henry could make an additional $28,704 per year with the use of a GPS.


It is also common to find over-spreading when not using a GPS, and in fact, you may deliberately over-spread to avoid the losses mentioned above.

The issue with over-spreading is the increased chance of nutrient leaching, as well as a greatly reduced response from your fertiliser. Put simply, it is the law of diminishing returns combined with negative environmental impact. It’s not benefitting the next generation or the bottom line.

A 200ha farm, doing six rounds of urea a year at 50kg/ha will be spending over $35,000 on product annually. If we flip the results and look at an example where 20% over-spreading is occurring, then $7,000 worth of product is wasted, having both a reduced effect on growth and a negative effect on the environment.


The TracMap system is comprised of a cloud-based job management system called TracMap Online that works with TracMap’s in-cab or bike mounted GPS display units.

All spreading data is automatically sent back to TracMap Online, from here reports can be generated easily for compliance and future farm planning. Being able to view and track application brings visibility to your business and makes it easier to optimise your operations.

The TracMap system can also be used to effectively manage other daily tasks and staff activity on farm.

  • Simplify pasture, effluent and irrigation management
  • Plan, map and record k-line shifts and irrigation coverage
  • Accurate break feeding, helping your staff get it right every time
  • Optimise nutrient application for best soil health
  • GPS guidance maximises fertiliser coverage while reducing waste
  • Variable rate mapping, application and reports
  • Drop GPS location markers for areas needing remedial work
  • Easy job management and task allocation

TracMap have recently partnered with Farm IQ so, in the very near future, any data captured using TracMap’s system will be able to be imported into the Farm IQ platform for a fully comprehensive farm management tool.

Article written by TracMap Upper South Island Area Manager, Gus Hewitt.