HR: 1330h
AN: H43B-06    [Abstracts]
TI: Measuring and Modeling Solute Transport in the Rootzone: Protecting the Receiving Water Environments of the Coral Atolls of Tonga
AU: * Clothier, B E
EM: bclothier@hortresearch.co.nz
AF: HortResearch, Tennent Drive, Palmerston North, New Zealand
AU: van der Velde, M
EM: vandervelde@geru.ucl.ac.be
AF: Universite catholique de Louvain-la-neuve, Croix du Sud 2 BP2, Louvain-la-neuve, Belgium
AU: Green, S R
EM: sgreen@hortresearch.co.nz
AF: HortResearch, Tennent Drive, Palmerston North, New Zealand
AU: Gee, G W
EM: glendon.gee@pnl.gov
AF: Battelle Pacific Northwest, PO Box 999, Richland, WA 99352 United States
AU: Manu, V
EM: mafsoils@kalianet.to
AF: Ministry of Agriculture & Fishing, Vaini Research Station, Nuku'alofa, Tonga
AU: Menoniti, V
EM: mafsoils@kalianet.to
AF: Ministry of Agriculture & Fishing, Vaini Research Station, Nuku'alofa, Tonga
AU: Vanclooster, M
EM: vanclooster@geru.ucl.ac.be
AF: Universite catholique de Louvain-la-neuve, Croix du Sud 2 BP2, Louvain-la-neuve, Belgium
AB: Intensification of agriculture on the raised coral atolls of the Tongan archipelago, notably through squash-pumpkin production, has lead to increased use of agrichemicals. Agrichemicals, both fertilisers and pesticides, pose a risk to these fragile environments. Sustainable land-management practices are needed for small-island developing states. On Tongatapu, solutes leaving the rootzone of the squash can rapidly find their way to the underlying freshwater lenses. These lenses are hydraulically linked to the internal lagoon, and the fringing reefs. We have used buried, non-suction fluxmeters to monitor both the quantity and quality of drainage leaving the rootzone of squash. Fertiliser is traditionally applied at planting. During establishment of the squash in 2003, some 350 mm of rain fell, with 70 % of this leaving the rootzone of this permeable soil as drainage. The concentration of nitrate-N in the drainage water was measured at around 50 mg-N/L. All of the initial fertiliser dressing had been lost, along with N mineralised from the plowed-in grass. Pesticides are needed in humid tropical environments to control weeds, pests and diseases. These chemicals can leach though the rootzone to contaminate receiving waters. We modeled the transport and fate of the presticides used in squash production, and we developed a Decision Support Tool (DST). Our DST can be used to select the best pesticides for local conditions, to tailor practices for minimising leaching losses below the rootzone, and to avoid the build-up of residues in the soil. This project, funded by the European Union and NZAID, took a multi-disciplinary approach through measurement and modeling protocols. Our DST enabled us to engage the wider community and stakeholders. There has been increased awareness of the impacts and risks associated with productive land management in the fragile hydrological environments of this small-island developing state.
UR: http://www.croppro.alterra.nl
DE: 1818 Evapotranspiration
DE: 1829 Groundwater hydrology
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1899 General or miscellaneous
SC: Hydrology [H]
MN: 2005 Joint Assembly