African farmers who use weather forecasts based on El Ni�o data are likely to see an increase in crop yields, according to a new study.

Researchers ran workshops in four Zimbabwean villages to inform farmers of the forecasts. Those that used the information to choose when and what to plant saw greater yields of crops such as maize.

Details are released in the US journal Proceedings of the National Academy of Sciences. At the begining of their study in September 2000, the researchers, from Boston University in the US and the University of Zimbabwe in Harare, found a fair degree of scepticism among farmers about the value of weather forecasts.

During a series of workshops, they attempted to stimulate awareness of the potential benefits of using forecasts, and discussion on how farming practices could be changed to cope with abnormally wet or dry seasons. Coming into the 2002/2003 season, the scientists predicted a lower than average rainfall because of a mild El Niño event; and broadly, this proved to be correct.

The following season, the prediction was for a return to normal, which again turned out to be largely accurate. Just over half of the farmers - 57% - reported that they changed decisions on when and what to plant because of the forecasts, either planting at different times or choosing different varieties.