Feeding the future – sustainable agriculture
This topic is sponsored by CSIRO Plant Industry and the bequest of J S Anderson, FAA.
With the population exceeding 6.7 billion and growing by over 6 million a month, the need to protect agricultural land and to increase food production has become critical. Does sustainable agriculture have the answers?
About 5000 years ago, large cities were flourishing in the flat plains of what is now southern Iraq. The cities were surrounded by thousands of hectares of crop land irrigated from the rivers. Farmers grew barley, wheat, flax, dates, apples, plums and grapes, and herded sheep and goats for meat and milk.
This early example of intensive agriculture proved unsustainable. By around 4000 years ago, desert had replace the fields and the cities had been abandoned. History records many such examples of agricultural communities flourishing and then failing, often because farming eroded the soil, exhausted the soil’s nutrients or caused a build-up of salt.
There were many fewer mouths to feed in those days; the global population was probably no more than a couple of hundred million. So if agriculture failed in one area, plenty of arable land remained available for development.
The world no longer has that luxury. The need to protect agricultural land and to increase food production has become critical. Around the world the concept of sustainable agriculture has been embraced to try to ensure that food supplies will continue to match demand.
What is meant by sustainability?
Meeting the needs of the present without compromising the ability of future generations to meet their own needs is the key principle behind the concept of sustainability. If natural resources such as soil, nutrients and water are used up at a rate faster than they are replenished, then the farming system is unsustainable. Sustainability is also dependent on maintaining a high level of biodiversity, especially in the soil and the surrounding environment.
But moving from broad definitions to practical prescriptions is, of course, far from easy. Farmers will adopt systems that maintain or enhance the natural resource base only if these also provide a living for themselves and their families. Therefore, economic and social issues, as well as the productivity of the land and the broader health of the environment, have to be considered when working towards sustainable agriculture.
Following extensive consultations with farmers and other expert groups, Australian government authorities have identified a set of key indicators of agricultural sustainability. Each indicator is accompanied by a set of measurable attributes that provide the basis for sustainability assessments.
|Long-term real net farm income||
|Natural resource condition||
|Off-site environmental impacts||
From Sustainable Agriculture: Assessing Australia's Recent Performance (1998). A report to the Standing Committee on Agriculture and Resource Management of the National Collaborative Project on Indicators for Sustainable Agriculture
The Australian scene
As a major agricultural exporter, Australia feeds not only its own population but also some 50 million people in other countries. The exports are vital to our economy and make an important contribution to the world’s food supply.
Farmers and scientists are working together to lift production and improve product quality, and also to overcome major threats to sustainability that have emerged over the years. A number of farmer-focused agricultural organisations have already been set up in Australia (eg, Birchip Cropping Group, Conservation Farmers Inc, Kondinin Group, and Mallee Sustainable Farming Project). These organisations collaborate with scientists who are involved in ongoing projects, conduct their own research, and keep farmers informed about research results. AusAID and the Australian Centre for International Agricultural Research also find that a collaborative approach to agricultural research is very effective in their overseas projects.
Some of the biggest threats to sustainable agriculture, and approaches to deal with them, are outlined below.
Loss of biodiversity
Australian farmers, like their colleagues in Asia and the Pacific, have come to realise the importance of a diversity of organisms in agricultural ecosystems. A productive soil is called a 'living' soil because of the enormous number and diversity of organisms that cycle nutrients through the soil, maintain its structure, and prevent outbreaks of pests and diseases.
Above ground, natural enemies and pollinators are essential for profitable and sustainable agriculture. Many modern agricultural practices (eg, monocultures, poor crop rotation, pesticides and heavy machinery) reduce biodiversity to low levels and trigger even greater adverse responses (eg, pesticide treadmills).
One sustainable approach to suppressing soil-borne pests and diseases in crops is biofumigation. This utilises toxic compounds produced by brassicas (eg, cabbages, turnips and mustard) to kill soil pathogens. Farmers can alternately plant a brassica crop with another crop (eg, wheat) to break the life cycle of soil pests and diseases, instead of using synthetic pesticides.
Groups are also attempting to restore biodiversity that has been lost. One Landcare group in New South Wales is using information from the Australian National Herbarium to determine what plants originally grew in the area as part of their native plant revegetation project.
Around 2.5 million hectares of Australia's agricultural lands are currently affected by dryland salinity. According to reports compiled by the National Land and Water Resources Audit in 2000, the annual costs associated with dryland salinity are estimated at about $600 million in Western Australia and $250 million in the Murray-Darling Basin.
Dryland salinity has always existed, but it became more obvious when native grassland and mallee vegetation were replaced with crop and pasture plants. These annual crops take up less rainwater, so more water is added to the underlying water table. The water table then rises, bringing salt to the surface.
What is needed for sustainability in these regions are farming systems that match the previous water use, thus halting the rise in the water table. A common answer is to plant trees in large numbers, but this is often incompatible with the key goals of maintaining food production and farm income, and trees on their own would not overcome dryland salinity.
Scientists in many organisations are investigating approaches that meet the sustainability criteria. One approach is to implement ‘agroforestry’ systems that combine tree growing with cropping and grazing. Another approach is to use perennial pasture plants such as lucerne, which use more water and extract it from deeper in the soil than annual pasture plants, in rotation with high value crop plants. Along with these approaches to sustainable management, sophisticated technology to monitor saline areas and computer packages to interpret the results will be vital to tailoring options to individual regions and farms. As with many environmental problems, there is not a single 'solution'. Answers will require a mix of options that will vary from farm to farm and from year to year.
Soil acidity also costs the rural economy hundreds of millions of dollars a year, and the area affected is much greater than that plagued by salinity (Box 1: Acid eats into farm incomes). Australia has more than 33 million hectares of farming land with acid soils, which cost the nation around a billion dollars in lost income every year. Estimates suggest that up to 90 million hectares of land in Australia have the potential to be affected by acidity (ie, have a pH of less than 6).
The biggest losses in agricultural production come when acidity increases to the point where toxic elements in the soil, particularly aluminium, are dissolved. Adding lime neutralises the acid, but farmers usually cannot afford to do this on large areas of land, unless they are growing a valuable, acid-sensitive crops such as canola; as the value of a farmer's produce is increased, lime becomes more affordable.
To promote sustainable management of affected areas, people are investigating land use approaches that can slow or reverse the acid build-up. These approaches will reduce the need for liming. Research groups are also working towards breeding crop and pasture varieties that grow well in acid soils.
Pests and weeds
The threat that pests can pose to sustainable agriculture has been illustrated vividly in Western Australia’s Ord River irrigation area. Cotton growing began there in the early 1960s and at first showed considerable promise. About ten years later the industry collapsed, beaten by caterpillar pests that had quickly become resistant to insecticides.
The development of effective integrated pest management (IPM) strategies prevented the same thing happening in cotton growing areas in the eastern States. An easy-to-use software package is now helping growers implement these strategies, which minimise insecticide spraying while maintaining yields. In recent years cotton varieties, genetically engineered for pest resistance, have also helped to reduce insecticide spraying.
Another IPM approach to controlling of pests is the use of petroleum oil sprays. These sprays act as pesticides by blocking the breathing tubes of insects and also reduce egg-laying on leaves. The sprays are used in low concentrations and are biodegradable.
Integrated pest and weed management, based on a detailed understanding of the ecology and biology of the target organisms, is now seen as the key to sustainable control. It can involve, for example, biological control, crop rotations, planting resistant or tolerant varieties, or using insect traps as well as sprays. Key goals include keeping pesticide and herbicide use to a minimum and only using chemicals that are environmentally benign.
The broad view
Sustainable agriculture is a simple concept that embraces a complex web of issues. Some of these are the state of the soil; water availability; choice of crop; stocking rates; needs for pesticides, herbicides and fertiliser; climate variability and protection of biodiversity. Then there is a range of economic issues (eg, markets and production costs).
Developments in information technology will play a key role in managing the complexity. For example, CSIRO researchers have developed farm management computer models under the GrazPlan program that simulate interactions between factors such as pasture growth, climate, nutrient cycling and farm costs and income. Users can explore future impacts of different farm management decisions to identify sustainable approaches.
To achieve sustainable agriculture we must deal both with issues involving environmental impacts and productivity of the land. Any program to successfully develop a system of sustainable agriculture must have farmer involvement at all stages of its development, and must look at a farming system as a whole, not just at individual elements. The farmer-focused agricultural organisations in Australia are working with researchers to develop farming systems that are both sustainable and profitable.
Page updated September 2009.