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Fine tuning improves water productivity

27 September 2004

Tuning crop varieties and agronomy to each other is a better approach to improving water-limited crop yields than focusing on ‘drought resistance’, according to CSIRO Plant Industry researcher Dr John Passioura, speaking at the 4th International Crop Science Congress in Brisbane today.

The Congress is held only once every four years and brings together over 1000 delegates from 65 countries to focus on the key issues for cropping systems that provide food, feed and fibre for the world.

“The notion of drought resistance has not proved to be very useful in improving the performance of globally important crops,” says John. “Seeking genes for drought resistance from desert plants is na´ve - certainly such plants can survive long periods without water, but with minimal growth. Genes for survival alone can’t improve yields.”

“A better concept is water productivity “, says John. “It is a quantifiable measure; grain per hectare per millimetre of water used, or transpired, by crops.”

The challenge of improving water productivity is in managing the crop or improving its genetic makeup so that:

  • It captures more of a scarce water supply for its own use (e.g. control weeds);
  • its leaves exchange transpired water for carbon dioxide more effectively in producing biomass (e.g. prevent leaf disease);
  • it converts more of its biomass into grain (e.g. get time of flowering right).

“We know the practical maximum is about 20 kg of grain per hectare per millimetre of water used by well-managed cereal crops. In much of the world there is a long way to go to get close to this figure because of stresses other than water – weeds, diseases, insects, poor nutrition and inhospitable soil. Overcoming these stresses is always the first step in increasing crop yields.”

“Once this step is taken, the fastest progress in improving yields will come from better agronomy and better genotypes explicitly tuned to each other so that the combination performs well in farmer’s fields.

“For example, rice and maize are much more sensitive to water stress than other cereal crops. This is mainly because the functioning of their floral structures is very sensitive to water stress at critical stages of development. There are good prospects for making these floral structures more resilient and the crop better adapted to the seasonal pattern of water supply.

“The focus should be one of resource economics, of water productivity, of most effectively using a scarce resource. There are no magic solutions in the offing that will enable large yields from scarce water.”

4ICSC would like to thank all its supporters including the following major sponsors:
AusAID, CSIRO, Pioneer Hi-Bred International and QDPI

More information:
Cathy Reade, Media Manager, 4th International Crop Science Congress
Mobile: 0413 575 934

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