Publication (Media): MINIMISING NUTRIENT LOSS WOULD PROTECT RIVERS AND FARMS

Publication Type:	Media Release
Publication Name:	MINIMISING NUTRIENT LOSS WOULD PROTECT RIVERS AND FARMS

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Raisin, Greg and Markwort, Karen (1995) MINIMISING NUTRIENT LOSS WOULD PROTECT RIVERS AND FARMS - Aug 7 1995, CRCFE, Canberra - Media Release.

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August 7, 1995

CRCFE

MINIMISING NUTRIENT LOSS WOULD PROTECT RIVERS AND FARMS

The development of techniques to minimise the loss of nutrients from agricultural lands would be of great benefit to farmers as well as the environment, wetlands researcher, Greg Raisin, said at a Pasture and Grasslands Conference, held in Albury recently.

Mr Raisin, a Scientific Officer from the Cooperative Research Centre for Freshwater Ecology based in Albury, pointed out that the challenge was to retain nutrients on farms where they could be used to promote agricultural productivity and to prevent them from entering waterways where they might stimulate algal blooms.

A lot of the nutrients lost from rural lands eventually find their way into rivers. The Murray Darling Basin Commission has estimated that between 25 and 75 percent of nutrients entering the Murray Darling system come from diffuse sources such as agricultural lands, forested lands and urban areas.

Toxic algal blooms are just one visible symptom of excess nutrients being washed into waterways.

Single point sources of pollution such as sewage treatment works used to be the focus of nutrient control efforts, Mr Raisin said. While they were of major importance in the effort to control water pollution, they were not the only problem.

“It is now generally accepted that we have to look at managing nutrients from much wider areas,” he said.

Mr Raisin has been studying the quantity and quality of water flowing out of mole drains and comparing it to surface water runoff from the surrounding catchment.

Mole drainage is a technique recently employed in Australia to drain excess water from the soil profile. Farmers have used the mole drains very successfully to reclaim boggy lands for agricultural production. The drains are constructed using a floating mole plough system which is pulled through the clay subsoil when it is soft and malleable, creating a small tunnel with vertical cracks through the soil profile to the surface.

The mole drainage water quality study began in December 1992 and was funded by the Land and Water Resources Research and Development Corporation (LWRRDC) who were interested in finding out the extent to which this technique may increase the amount of nutrient and salt leaving rural catchments and entering waterways.

The study was conducted at two mole drain sites on properties in the Kiewa Valley and another at the Rutherglen Research Institute. The Institute is developing mole drainage techniques in order to help farmers alleviate poor drainage and to maximise pasture yields from their land.

The downside is that as water moves through the soil profile it picks up nutrient such as nitrogen and phosphorus. The mole drain provides an avenue for the nutrient to move out of the area. Mr Raisin said that there was no point solving one problem and creating another down stream.

Mr Raisin has measured the volume of water from the mole drains and the catchment using v-notch weirs. The flow has been recorded every 15 minutes with data loggers. Water samples were collected by automatic water samplers which were activated during storms. The amount or load (kg) of nutrient and salt leaving the mole drain and the surrounding catchment was determined over a range of storms between 1993 and 1994.

Preliminary results have indicated that the nutrient load leaving the mole drains in the Kiewa Valley are higher, in most cases, than that from the surrounding catchment, particularly for nitrogen. However, this trend was reversed during heavy rainfalls which generated high-runoff. In these cases, the surrounding catchment released greater loads of nitrogen and phosphorus than the mole drains.

There were two confounding factors with regard to the mole-drained areas.

“The mole-drained areas received higher nitrogen inputs from improved clover growth and fertiliser, and cow stocking, than the rest of the catchment,” he said. “Presumably, the concentrations of nitrogen in the soil in these drained areas would also be higher.

“These drained areas also receive nutrients and flow from springs which are fed by the rest of the catchment.”

Further research needs to be conducted to find ways of reducing the loss of nutrient via mole drainage so that this technique can be used to maximise production while minimising downstream problems.

Media contact...Greg Raisin...(060) 43 1002
Karen Markwort...(06) 201 5369

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