FEATURE ARTICLE: LESSENING THE IMPACTS FROM AGRICULTURE
This article was contributed by the Australian Centre for International Agricultural Research (September 2007).
Industrialisation and modern technologies have increased production along with associated wastes, including greenhouse gases. One area where agriculture has benefited is improved fertilisers to further boost production.
The use of nitrogen-based fertilisers can produce the greenhouse gas nitrous oxide. Unused nitrogen mixes with oxygen to produce nitrous oxide. Like other greenhouse gases nitrous oxide occurs naturally, settling in the atmosphere where it absorbs some of the sun’s heat, facilitating life-sustaining temperatures.
Increasing levels of man-made greenhouse gases can accelerate the rate at which heat is absorbed, potentially increasing global temperatures. Should these increases occur at a rate faster than 0.1 degrees each decade, the possibility of changes to the Earth's climate becomes more probable.
As population rates increase more food needs to be produced, which places pressure on available arable lands. In China's west, where irrigated wheat and maize are grown, nitrogen fertilisers play an important role in ensuring high yields. Increasing yields is a government priority, necessary to feed the country’s growing population of 1.3 billion. With limited water supplies and no more arable land, fertiliser application has become the main input variable for crop production.
The result has been excess fertiliser application, with nitrate leaching into local waterways, and nitrogen combining with oxygen to produce nitrous oxide, which is emitted into the atmosphere.
Reducing nitrogen use without impacting on yields is a challenge for China, and other countries. The Australian Centre for International Agricultural Research (ACIAR), part of the Australian Government’s international aid program, conducts agricultural research projects that link Australian and developing-country scientists to pursue solutions to common problems.
One project is addressing the challenges of reducing both water and nitrogen inputs used in agricultural systems in the province of Shanxi in China. The research also has applications for nitrogen use in Australian agriculture, and elsewhere.
Project scientists have begun to quantify water and fertiliser inputs to determine appropriate levels to maintain current yields. Already modelling of these inputs, using a water and nitrogen management model developed through past ACIAR research, has determined that fertiliser application rates can be significantly reduced. This will help increase available income as less is spent on fertiliser, as well as reducing excess nitrogen that either leaches into soils as nitrate or oxidises to form nitrous oxide.
Working with local farmers, project scientists have also begun to develop an idea of the barriers to adopting water-saving techniques. These, together with economic parameters and nitrogen dynamics, have been incorporated into a conceptual model for water and nitrogen management. The modelling has demonstrated that water use, like nitrogen, can also be reduced without harming yield potential.
An Australian component of the project, co-funded through the Cooperative Research Centre for Greenhouse Accounting, the Australian Greenhouse Office and the Grains Research and Development Corporation, is developing an Australian water and nitrogen management model for local agricultural conditions. Applications of this model are also being developed for use in Mexico and legume-based agricultural systems in China. A hand-held agricultural support system prototype has been developed and is being tested for wheat cropping in Australia.
For more information visit the ACIAR website, last viewed September 2007, at <http://www.aciar.gov.au>.