Friday, 14 July 2006 - 4:40 PM

Measurement of Fluxes in the Rootzone: Tools and their Uses.

Brent Clothier1, Steve Green1, Marijn Van der Velde2, Glendon W. Gee3, Carlo van den Dijssel1, Siva Sivakumaran1, and Markus Deurer1. (1) HortResearch, Tennent Drive, Palmerston North, New Zealand, (2) Univ of Louvain (Louvain-la-Neuve), Croix dus Sud 2, Louvain la Neuve, Belgium, (3) Battelle, 3200 Q Ave., Richland, WA 99354

The soil of the rootzone is the first filter for most of the water we use. The quality and quantity of our water resources are determined to a large extent by the way we use our soil and manage our lands. The ecosystem services and productive potential provided by our soils, mean that soil is invaluable in terms of natural capital. Yet we have limited understanding of the impact of soil use and land management on the transport and exchange processes that underpin these ecosystem services. This nescience is due, in large part, to our inability to monitor directly water and solute transport in the rootzone. New tools are, however, providing us with sharper vision of the state and fluxes of mass and energy in the rootzone. New devices, capable of direct, remote and continuous monitoring of soil water content, solute concentrations and fluxes, are giving us a better understanding of rootzone dynamics. Furthermore, new tools are being developed to provide independent measurements of the key parameters required for modelling the transport processes in the rootzone. Better monitoring and better measurements for model parameterisation will, in tandem, provide us with new understanding and improved prediction of fluxes in the rootzone. We present results from the use of our arrays of multiplexed TDR probes, which provide measures of the changing pattern of soil-water content, extensive in both time and space, under a variety of land-uses and weather patterns. This monitoring of the changing state of the soil's water content is complemented by use of buried fluxmeters, which provide a direct measurement of the unsaturated drainage of the soil solution, along with the capacity to measure the concentration of solutes in the leachate. We include measurements made under a field of squash pumpkins on a small coral atoll in the tropics of the Pacific, as well as monitoring under pasture, potatoes and kiwifruit in regions of New Zealand. We show how complementary use of disc permeameters to measure the soil's hydraulic properties, plus heat-pulse devices to measure sap-flow and the transpiration of plants, can combine to provide comprehensive measurements of the rootzone water and solute balances.

Furthermore, we outline the use of these measurements and parameterisations in a modelling scheme to realise longer-term risk assessments, at regional scales, of the sustainability of land-management practices.

Back to 3.5D Combating Global Soil & Land Degradation IV. Salinization, Sodification and Other Forms of Degradation in Agricultural and Native Ecosystems - Oral
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Back to The 18th World Congress of Soil Science (July 9-15, 2006)