1 September 1995

Map making is put to test

"YIELD MAPS are not a solution – they just pose questions," says Peter Jurschik of Germanys Institute of Agricultural Engineering.

Involved in a project with Hydro Agri to find ways of utilising GPS systems to improve crop profitability, Mr Jurschik specialises in creating the necessary hardware.

"Yield mapping is just one use for GPS; there are now other ways we can use the system."

And it is the Hydro Agri nitrogen project – a project which sets out to place prescribed doses of nitrogen to specified areas of crop in respect of yield potential (see arable page 48) – that has brought to the fore some of the latest technology.

One of the most suitable ways of becoming aware of the low- and high-yielding areas of a field is, of course, through the use of yield maps. On Hydro Agris trials site at Golzow, east of Berlin, three systems have been used: Massey Ferguson, Claas and RDS.

"All three have their advantages," says Mr Jurschik. "The MF system has a good yield sensor, the Claas is very user friendly and the RDS can be removed and used on other farm machinery."

But knowing a fields high and low yielding areas is only a part of Hydro Agris requirements. Soil N content, soil type, soil moisture and plant population are also needed – and the relevant maps and field co-ordinates recorded to calculate nitrogen application rates and control the machinery applying it.

Soil sampling and its subsequent analysis, at the best of times, is an expensive and laborious task. For site-specific fertiliser application the samples need to be taken quite close to each other if a true picture is to be made.

The Institute of Agricultural Engineering has now developed a mechanised method of recording soil samples using the GPS system. It is a system based on a PC program called "Fieldnavigator", a program which is also claimed to be suitable for weed mapping and other in-field recording operations.

Once the co-ordinates of the field, the working direction and the sampling intervals have been entered, the driver of the sampling vehicle is directed to specific co-ordinates on a grid pattern by the on-board GPS system. Once analysed, the data is used to produce an "N" map, the information being used when calculating how much nitrogen should be applied to any given part of the field.

Adapted Amazone

Its one thing to know what rates of fertiliser to apply to specified areas of a field but another to achieve it. Mr Jurschiks team has adapted an Amazone ZA-M1 spreader which has twin discs and a spread width of 36m.

Fitted with a GPS system working in conjunction with an on-board computer loaded with the information to tell the spreader how much to apply and where, the driver just has to drive up and down the tramlines.

As different co-ordinates are reached, the outlets from the spreaders hopper are widened or narrowed by electric motors – the degree of change made in respect of the spreaders calibration. In operation variations in application from 35-112kg/ha were achieved.

"It is all starting to come together," says Mr Jurschik. "But there is still a lot of work to do – particularly where it comes to obtaining information about the soil. We desperately need to develop systems which reduce costs and labour input.

"Even so, the day is dawning when GPS systems will become an accepted, cost-effective part of successful arable production."