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Fertilising Fields from Outer Space

New Zealand farmers will have help from outer space in fertilising their crops, with the development of a satellite-based system to evaluate fertiliser effectiveness and field conditions.

A team of agricultural experts is evaluating software packages that use pinpoint satellite navigation to produce soil, fertility or yield maps of a field. With this information, a farmer can accurately calculate fertiliser requirements for various parts of the field rather than having a blanket application over the entire paddock.

John Austin, a Te Awamutu maize grower and agricultural contractor, is heading the TBG-funded research. Austin estimates the system has the potential to save up to 20% in fertiliser costs.

"In the Middle Ages a farmer walked each furrow with a hoe and had intimate knowledge of the field's health," says Austin. "It is hard to have that same intimate knowledge in today's mechanised farming environment, so we are utilising technology to give the modern farmer that insight."

The system will track the progress of a combine at harvesting through GPS satellite navigation, recording the yield in 5x5 metre grids across the field. It will then produce a map of the field showing variation in crop yield. Using that information, the farmer can test the soil in the low yield areas and compare the results to high yield sites to discover the reason for the difference.

In tests on seven fields, wide variations in soil fertility have been discovered, even though the whole field has received the same amount of fertiliser. Some areas had too much potassium, whilst others had very little.

Soil fertility and yield response data can be fed into a lap-top computer in the tractor, and used to govern the fertiliser application. This reduces wastage and the potential for leaching, while optimising fertiliser use. Agri-chemical application can also be managed in the same way.