Healthy soil and sustainable growing

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European farming methods blamed for soil degradation
Reporter: Maria Taylor
First Published: 9/04/00
http://www.abc.net.au/landline/stories/s116302.htm

Soil degradation in Australia and across the globe is right at the top of
serious environmental problems.

It costs Australian farmers $2.5 billion a year in lost production and
nobody has even calculated off-farm costs such as salt-polluted rivers or
loss of bio-diversity or wildlife habitat.

"Scientists are documenting alarming levels of salinity, soil
acidification, wind and water erosion, soil structural decline and loss of
fertility, waterlogging, sodicity, non-wetting soils and so on," scientist
Anna Ridley said.

Most of these problems arise from the mismatch between Australian soils,
water balance and climate and the traditional European farming and grazing
methods.

Australia has achieved amazing agricultural success with methods that
worked well in Europe and North America. But along the way farmers ignored
the limitations of Australian soils and climate and didn't appreciate the
value of native ecosystems.

Dr Ridley said farmers are learning they may be paying a big price for the
vegetation clearance and other dramatic changes that have been made to the
landscape.

"After close to 200 years of farming in some areas and as little as 30
years in others, we are seeing a lot of warning signs that all is not well
with the soil and water that underpin our agricultural success," Dr Ridley
said.

"Researchers are making big advances with better crop varieties, more
efficient farming systems and genetic improvements.

"But these advances will be compromised in the next 50 to 100 years and
farmers won't be able to keep up production if the quality of soil keeps
declining," she said.

Australia's soil legacy

When it comes to soil, most Australian farmers and graziers were
handicapped from the start.

Almost all Australian soils are geologically old, infertile and underlain
by salt. The weather is hardly predictable and prone to droughts and
floods. Weather and soils, of course, determine what will grow.

Glancing back at the natural forces that shaped the Australian continent
over millions of years helps to understand the problems farmers are facing
today.

Some 15,000 years ago, in the glacial period, the northern hemisphere was
covered in ice and much of Australia was a sand-blown desert, two-thirds
covered in dunes. It was cold, windy and dry, with rainfall maybe half what
it is today.

Gradually, in the past 10,000 years, humans on the continent got used to an
environment recovering from that extremely dry and inhospitable stage.

Even today, 70 per cent of Australia is arid or semi-arid and soils in the
north, south and west tend to be shallow, often sandy and not very fertile.
Only 10 per cent of the land is cropped or under improved pasture. The
soils remain among the least fertile in the world.

The major agents for creating and renewing fertile soils are earth
movement, volcanic activity and ice sheets moving over the landscape -
grinding down rocks, depositing minerals and nutrients.

The Australian landmass for the most part hasn't experienced the big
soil-renewing processes for many millions of years.

We do have some alluvial floodplain soils and a small percentage of rich
basalt soils, the legacy of the most recent volcanoes, which were still
long ago.

But most Australian soils are even older than that, which is why they're so
weathered and relatively infertile. The continent's ecosystems were adapted
to the poor soils and also to Australia's extreme climate swings and
variable rainfall.

The shrubby ground cover, which is still being removed today, was holding
the soil in place through drought, wind and heavy rains.

Modern day farmers and researchers are now trying to learn from the way the
native vegetation has adapted to the environment.

Human impact

Our geological history also left a great store of salt in the soil, rocks
and water tables. Much of it was laid down by ancient inland seas. More
salt was blown onto the land from the surrounding oceans. Flat landscapes
and related poor drainage meant the salt accumulated in the ground.

Then, for most of the past 100 years, governments encouraged farmers and
settlers to clear away most of the native vegetation. Getting rid of the
bush was an attitude shared by most Australians, city and country alike.
Australia-wide, we're still clearing more trees and shrubs than we're
planting. This history set up a time bomb of environmental problems -
particularly in regard to salt.

"It was not well understood that Australian native trees and shrubs took up
enough rain water all year round to keep the underground salty water table
well below the root level. The water below ground and the vegetation above
ground were in balance," Dr Ridley explained.

Trees act like pumps, drawing moisture from deep in the soil. When trees in
the upper parts of the catchment are replaced by shallow-rooted pastures,
water leaches through the soil, dissolving salts and taking them down
slope, only to reappear again at the soil surface, often some kilometres
away.

With increased amounts of water draining from the catchment areas, water
tables in the valleys and plains below rise closer to the surface, bringing
salt with them.

When the water evaporates or is used by plants, the salts remain, so the
level increases in the topsoil, and soil salinity is the result.

"With the trees gone, annual crops with shallow roots like wheat, barley
and pastures don't take up enough water to stop the salt-laden groundwater
from gradually rising towards the surface as more water enters the system,"
Dr Ridley said.

The result is dryland salinity which is now recognised as a major threat to
our soils and agriculture.

"Dryland Salinity threatens a fifth of our arable land (an area nearly
three times the size of Tasmania) and it can't be reversed easily," Dr
Ridley said.

Irrigated cropping adds even more water to this unbalanced system. Also,
the amount of water diverted for irrigation has put an end to any natural
river flushing of salts out to sea.

The most dramatic example is in the Murray Darling Basin, Australia's
farming heartland. The basin is estimated to store 100 billion tonnes of
salt.

Don Blackmore, Chief Executive of the Murray Darling Basin Commission, said
that by 2015, 100 per cent of our irrigated agriculture in Southern MDB
will have high water tables and will have to be managed with additional
investment from government and farmers.

Millions of tonnes of salt are washing into our river systems from both
dryland and irrigation salinity. One cost of management is already evident.

"What people may not realise is that we have $50-60 million salt
interception schemes along the Murray," Mr Blackmore said.

"We pump 1,100 tonnes of salt everyday away from River Murray to protect
Adelaide (and) that costs us $2 million a year in power," he said.

But none of this was even remotely imagined by Europeans when they started
grazing and farming here. They looked back to Europe and introduced methods
which were developed with deep fertile soils and regular seasons and which
had well served in old country for hundreds of years.

Examples of methods include planting short-lived annual cereals and
pastures; extensive ploughing, removal of most native vegetation and hard
hooved animals.

In the vast grain belt of Western Australia, where farmers run sheep and
produce wheat, barley and other crops, a hundred years of farming with
these methods has given rise to a huge salt problem and other land
degradation headaches. Most of the soils are sand and clay and need to be
treated carefully to grow crops.

But erosion and salinity aren't the only land degradation problems we've
developed in the last 200 years. The loss of bio-diversity is well
documented in Australia, and there are other serious problems which farming
methods are bringing to light - like soil acidity.

Soils are naturally acidic in many areas but a recent government report
said half the agricultural soils in NSW and one-third of Victoria's as well
as 1.5 million hectares in Western Australia are now strongly acidic. The
pastures and crops we grow have played a big role.

The question commonly asked is: why are our soils becoming more acidic?

It is due to growing legume-based pastures on these soils, cropping systems
that inefficiently use nitrogen, eventually leading to an accumulation of
nitrate.
The danger is that acidification can increase to the point that plants
won't grow.

Solutions

When it comes to fixing soil problems, a big question is how farmers and
the community in general can have the biggest impact. The answer is: it
depends.

Conservation farming methods, farm by farm, can stop erosion and soil
fertility loss. Soil acidity can also be handled farm by farm. Adding lime
or changing crops varieties can ease the problem. But when it comes to
salinity and the loss of bio-diversity you need a much broader approach to
be effective.

For starters, all the landholders in a catchment have to get involved. The
question is, can they do it alone.

Here is South Australia's Coorong, the farmers, supported by local
government , have a district-wide plan to address soil degradation. The
plan is backed by dollar incentives from national programs and also
benefits from publicly-funded soil and landcare experts.

The Corong surrounds the Murray river estuary along the coast. The plan
seeks to involve all 570 land-holders in a district covering almost a
million hectares.

There are many projects under way to combat salinity. This part of the
country has only 20 per cent of their native vegetation left due to various
problems besides salinity.

The Corong effort is one of many action plans being set up throughout the
Murray Darling Basin. It's a good model but it's operating on short-term
grant money and it needs to be repeated across the country. So there's
still the question -- how do we, as a society, not just the farmers, take
responsibility for the health of our soil and water?

It's not just the farmers who pay and its not a question of blame. We know
a lot more and have gone from a subsidy to take out trees to a subsidy to
plant trees in 20 years. The question of who pays is pivotal - the
challenge is to build up the program with the help from governments,
agencies and grants.

CONTACTS

    * Grains Research and Development Corporation
      02 6272 5525
    * CSIRO Land and Water
      08 333 6215

SITES

   1. GRDC
      An descriptive site on the all sections of our grain industry.
Information on research,recent press releases and links to our
grain-related sites.
   2. CSIRO Land and Water