The Australian team's water saving idea won the day.

The Australian team's water saving idea won the day.

New Zealand's answer to going green was a fleet of fast, cheap minibuses. Korea's environmentally-friendly solution involved learning how to communicate with trees.

But in the end it was an Australian system designed to cut water use on farms that took top prize in a global contest for technology students keen on saving the planet.

The world finals of the Imagine Cup, run by Microsoft, drew more than 120 teams of high school and tertiary students from 61 countries to Paris.

Competitors, who had been selected after winning the local rounds of the competition in their home countries, had to use Microsoft technology to build technology which "enables a sustainable environment".

After four rounds of gruelling presentations in as many days, Australia's team was yesterday declared the overall winner in the competition's flagship software design category.

The software competition involves Dragon's Den-style presentations of the teams' concepts to panels of judges who grill competitors for evidence that their ideas solve real-world problems and have the potential to become commercially successful.

The Australian project, called Soak (Smart Operational Agriculture toolKit), is a prototype network of solar-powered sensors used to control water usage on a farm by measuring environmental aspects such as temperature and soil moisture levels.

If the technology has the commercial success the team is aiming for it will end up on rural supply store shelves and around the world. While farm environment sensor systems are already in use, a key element of the team's project is a focus on bringing the cost of sensors down to under A$100 ($126) through mass-production. They say they are in discussions with technology giant Hewlett-Packard which is interested in marketing the system.

New Zealand's four-member Imagine Cup team, from Canterbury University, failed to secure one of the 12 semifinalist slots in the software competition, but remain upbeat about the commercial potential for their project.

It is a program to control a fleet of "Taxibus" shuttles which the team's computer modelling shows would reduce transport-related carbon emissions significantly by making public transport faster and more convenient.

The Korean team's "Tree Talk" project - focused on improving arboreal health by monitoring "natural signs" emitted by trees - attracted early interest in the competition but missed out on a top six spot.

New Zealand team captain and Canterbury graduate Louis Sayers said while it was disappointing not to have made it further in the competition, the team had learned valuable business lessons and presentation skills during the challenge.