Rice is the most important staple crop in the world, providing half the world's people with 80 percent of their diet. Thanks to the high-yielding varieties and improved farming methods of the Green Revolution, rice production grew quickly in the 1970s and 1980s, easily keeping up with population demand. But during the 1990s production began to slow. To address this concern and find ways to feed the growing population, FAO recently held a global Expert Consultation on Yield Gap and Productivity Decline in Rice Production.

"We'll need to increase current rice production from nearly 600 million tonnes annually to almost 800 million by the year 2025 if we want to keep up with population growth," says Mr Nguu Nguyen, Agricultural Officer in FAO's Crop and Grassland Service. "And to make sure the growth is sustainable, we'll need to do it using less land, labour, water and pesticides."

Experts first began to notice the decline in rice productivity in Thailand and India, and then confirmed it during long-term trials in the Philippines. Although no one can say with certainty exactly what led to the drop, it's probably due to a combination of factors, says Mr Nguyen. Intensive cropping may harm soil make-up. Irrigation, which encourages high yield, also can increase soil salinity. In some places, the scarcity of land and water impedes improved productivity. And as specially bred varieties reach their yield limit, there's simply much less room for improvement.

Part of the difficulty in explaining the decline stems from regional and cropping differences. For example, in many irrigated systems in Africa, the slowdown appears to be due to poor infrastructure and management, whereas in Asia prolonged soil wetness and nutrient depletion may be the culprits .

Experts at the consultation considered these downward trends worldwide and also noticed some anomalies. For instance, in the same period, Australia, Egypt and the United States managed to boost rice production, leading some to conclude that the negative trend wasn't inevitable.

In Egypt, for instance, a government-supported rice research programme helped raise production from 5.8 tonnes per hectare to 8.5 tonnes over ten years. Government policies facilitated rice production by increasing farmer participation, improving water and pest management and providing credit schemes.

Australia devised a 'rice check' system that helps farmers to identify which factors are causing slowdowns so they can respond with focussed actions.

Participants at the consultation agreed that improved research will help to clarify the trend and lead to a more effective response. They also devised some definitions and recommendations that will aid future research and policy.

To quantify how much improvement can be made in a given cultivation, the experts identified two measures of yield gap. Yield gap 1 is the difference between yield produced under ideal research conditions and that produced under an average farmer's conditions. Yield gap 2 compares the average yield of the top 10 percent of farmers in a location with the average yield of all farmers in that location. Participants outlined the causes of yield gap and guidelines on how to close it. They also proposed a check list, similar to the one developed in Australia, which included factors affecting rice yield, for example, seed quality, water management and crop protection from weeds, pests and disease.

Finally, they agreed on a series of recommendations for action at the national and global level:

• Increase farmer awareness about balanced fertilizer use.
• Warn about the dangers of overly intensive cropping.
• Support breeding programs to develop new varieties able to consistently produce high yields, even in the presence of abiotic and biotic stresses.
• Conduct fewer but more targeted and longer term research experiments.
• Monitor yield and productivity trends in select pilot sites with an emphasis on micro-level investigation including state seed farms and farmers' fields.
• Continue cross-country network research on yield and productivity trends in major rice-based cropping systems.