GPS Fertiliser Spreading

Groundspreaders of fertiliser now operate with in-vehicle, computerised, GPS-directed, 12-20m wide application paths to ensure optimum coverage of paddocks, with no overlaps or missed portions and to provide recorded, verified tracks for environmental audits. This is light years away from the first mechanised ground spreaders in the 1930’s when a Munro spreader hung on the back of the truck tray and delivered 4m swathes as long as fertiliser bags were manually opened and the contents fed into a hopper.

In the Masterton district there are examples of both the latest GPS technology (Smith Spreading) and the old Munro spreader (Garrity Bros) preserved as a working vintage machine. The NZ-developed GPS technology comes from TracMap of Mosgiel, Dunedin.

Over half the groundspreading trucks in New Zealand run the TracMap computerised guidance and mapping system, developed in Dunedin. TracMap also provides systems for agricultural spraying, viticulture and horticulture, pod irrigation, travelling irrigators, ag aviation and fleet tracking, which means a diversified business supports continued research and development. The first TracMap units were installed into trucks in 2006. TracMap founder Colin Brown, a farm adviser, sat down with groundspreader Grant Smith to find out what he required.

The units have to work in demanding conditions of corrosive fertiliser dust and heat. They are mounted inside the truck cab and provide constant feedback to the driver on the truck’s route, as a GPS boat unit does, showing where that truck has been within the paddock and farm. This avoids overlaps, missed areas and allows the truck driver to plan the optimum pattern for covering that paddock. TracMap claims 1m of accuracy on a pass-to-pass basis and 3m when returning to resume a job, which is more than adequate for most purposes. It can even deliver more accuracy at a greater cost.

The coverage pattern generated in the TracMap system can then be sent by computer and the web to Dunedin, overlaid on Google Earth and made available to the landowner and/or stored for future reference. If an aircraft is running a TracMap system, the pattern of prior coverage by the groundspreader can be fed into the aircraft unit so the pilot can see on the screen what areas have already been covered.

This means that trucks can do the easier country and leave the aircraft to do the rest, with no risks of overlaps or misses.

Among the other benefits for groundspreaders using TracMap are reduced foam markers, the ability to work into the night and to find the exact finishing spot for

resumption with another load the next day. The units are said to be easy to learn and use and they provide a quick calculation of the area covered at the end of the day.

TracMap records also contribute towards nutrient management plans, environmental and food safety audits and quality assurance programmes. This is called proof of placement, which puts the onus on the groundspreaders. The maps can also be used to claim Road User Charges refunds for trucks which are being driven off-road a large portion of their working life.

Grant and Heather Smith of Clareville, Wairarapa have a business with three spreading trucks – a MAN with tractor tyres, a Mercedes and an Isuzu. All three have the TracMap GPS units at a cost of about $7000 per unit. They also have Transpread on-board computers which set the floor chain speed, spinner speed and spreader door setting when provided with the required spreading rate, fertiliser density test and the swath width. All trucks are regularly tested for their actual spreading rates and the Transpread computers calibrated.

Different fertilisers have different spreading widths – 12m for RPR, 15-18m for good quality lime and 20m for superphosphate.

About 10 years ago Grant went on a fishing trip and saw a GPS unit being used in the boat and reckoned it could benefit his business. He got a friend to buy an Outback system from Canada at a cost of $10,000, versus about $19,000 in New Zealand. It worked well for five to six years, providing a camera card which Grant could take out of the unit, put in a computer and provide a printout to the farmer. That unit eventually failed but fortunately Colin Brown had taken up the challenge to produce the TracMap system for New Zealand requirements after consulting with Grant.

Grant installed the first TracMap system available in 2006.

Garrity Bros rural cartage business in Greytown (founded 1893) has one of the few remaining Munro Spreaders in operational condition, preserved as an historical curiosity. Rod Garrity gives demonstrations of how the Munro worked.

These spreaders were built in Winton Southland by the Munro engineers, who had close associations to Bert Munro of the World’s Fastest Indian fame. In 1937 Cecil Garrity bought a new six-cylinder Chevrolet truck and a new Munro Spreader, which was built to attach to the back of the trays of lorries, wagons, drays or trailers. It was invented and marketed as three machines in one – a mixer, a topdresser and a seed sower. The standard conveyor box width (spreading width) was 4m. The truck load was five tonnes in bags of fertiliser or seed. In operation, the bags had to be opened and their contents manually emptied into the hopper of the Munro while the driver slowly crawled around the paddock. The spreading rates could be altered with complicated cog-wheels and sprockets.