Lucy, 18, said all four were "very excited" to be chosen for the week-long tour of science institutes which winds up with an awards ceremony at Government House in Wellington.
"It's the culmination of months of hard work. It'll be a wonderful opportunity for us to make connections for our future careers and meet people in the industry," she said.
Georgia, 17, said winning almost one in four seats on the tour reflected well on the school and its support for science students.
Thirty-two students around the country were nominated for Realise the Dream on the strength of their regional science fair projects. They were narrowed down to 17 by a rigorous application process which included interviews and self-made video clips.
All four Kerikeri projects touch on the highly topical issues of water quality and farming practices. Jason, 17, also won a place on last year's tour; Alex, 13, is the youngest Kerikeri High student ever chosen.
Head of biology Julie Harrisson put the students' success down to the depth of science at the school and how well they prepared and conducted themselves in the interview.
The Realise the Dream road trip is organised by the Royal Society of New Zealand to reward and celebrate students who have completed outstanding science research or technology development.
Participants will visit Fisher & Paykel Healthcare, the Liggins Institute, the Photon Factory at Auckland University, Huntly Power Station, DairyNZ, Niwa and Fraser Engineering. Team building activities include climbing Auckland Harbour Bridge.
The top students will win scholarships and trips to science events in Italy, Taiwan and the US.
The winning projects...
Alex Edwards, Year 9
Alex wants clean rivers for swimming and a clean Bay of Islands for spearfishing, so she conducted a range of tests over a two-year period to find out what determines water quality. She measured suspended solids and water clarity to calculate which rivers contribute the most sediment to the Bay. She explained her results by examining the substrate, topography, vegetation and land use along each river. She has worked closely with local councils and farmer land use groups.
Lucy Ellingham, Year 13
Lucy investigated the effect of phosphate levels on plant growth. Her experiments examined the effect of phosphate on freshwater aquatic plants and established the "danger zone" where plant growth accelerates rapidly. She then examined two farms to see if different management techniques influenced runoff, and whether calcium carbonate, a component of agricultural lime, could be used to reduce phosphate pollution. Her findings could have a significant impact on New Zealand's dairy industry.
Georgia Putt, Year 13
Georgia's project was inspired by a particularly unpleasant algal bloom in an irrigation lake near her home two years ago. By testing water and algae from seven Northland lakes she identified the effect of population density on the rate of algal growth. She then investigated the effect of nitrate concentrations and considered three methods for reducing algal blooms - planting willows, bulrush islands and adding zinc powder. She found willows and floating islands reduced nitrate levels and algae density.
Jason Leaming, Year 13
The growth of dairy farming and the move towards keeping cows on stand-off pads has seen big increases in two waste streams - wood fibre scraped off the pads and cow effluent. Combining these waste streams allows farmers to recycle nutrients into the soil. Jason's investigation explored vermicomposting (using worms to create compost) as a tool for managing waste from stand-off pads.
