Over The Horizon

"Heavy" Soil Physics in Japan

New Zealand soil physicists have been showing Japanese counterparts a new technique for analysing how water and chemicals move through soil.

"In Japan, and through-out the world, there is growing anxiety about the rising levels of nitrate being found in groundwater. The intensification of agriculture, and the burgeoning use of fertilisers and other chemicals such as pesticides, is leading to the degradation of ground and surface water resources," explains Dr Brent Clothier of HortResearch's Environment Group.

Soil physicists are trying to better understand the way in which water and chemicals, such as nitrates, move through various soils. Such an understanding would enable better man-agement strategies for maintaining good crop yields without compromising environmental quality, Clothier says.

Clothier has developed a field technique for testing such transportation, and his colleague Dr Steve Green has written a computer simulation which permits prediction of water and chemical leaching patterns.

In the field process, deuterium oxide or heavy water -- better known for its use in nuclear facilities -- is released from devices called disc permeameters. Use of heavy water allows the water being released to be distinguished from that already present in the soil.

The rate at which the heavy water is released indicates the capillary and transmission characteristics of the soil. The soil under the permeameters can be tested to see how far the deuterium penetrates.

Clothier and Green hope to use their Japanese tests and the simulation they have developed to produce land management strategies that will minimise contamination of groundwater by agricultural chemicals.