Weather-wise farmers could improve their yields
Farmers in developing and tropical countries could benefit enormously from access to interpreted agrometeorological data and improved seasonal forecasts. An accurate idea of the rainfall already in the soil, as well as that confidently predicted, would allow them to plant the right crop at the right time. This was one of the messages of an International Workshop on Agrometeorology in the Twenty-first Century, held in February in Accra, Ghana. The workshop was the initiative of the World Meteorological Organization and was supported by FAO and 12 other organizations.
Agrometeorology has one basic aim - to help farmers optimally manage climatic resources - essentially that is sunshine and rainfall or water. Optimum water use means planting the right crop for the moisture available, so that the crop uses most of it and leaves very little for weeds, at the same time as minimizing soil erosion and fertilizer loss because of water run-off. Optimal use of sunshine is largely controlled by water availability.
In Mali, a national programme to give farmers the benefit of accurate weather monitoring was launched, with WMO and FAO support, under the AGRHYMET Programme in the early 1980s. By simply recording rainfall and using decision tables, extension workers are able to advise farmers on what to plant, when. Rice, for instance, is a thirsty crop that needs good rainfall - if a certain amount has not already arrived by a certain date, it is not the right crop that season. At the other end of the scale, sorghum is relatively drought-resistant.
"I've seen farmers plant rice and sorghum in the same field, which makes no sense," said René Gommes, FAO's Senior Agrometeorologist. "With access to accurate rainfall data and reliable seasonal forecasts, farmers could plant one crop or another with confidence."
Rainfall levels determine more than which crop should be planted, when. They affect how much mineral fertilizer should be used, because fertilized plants grow more and so need more water, and they affect pest and disease incidence. Timely, reliable information on past and future rainfall is therefore extremely valuable to farmers.
Seasonal forecasts - which are quite different from the daily weather forecasts most of us watch on the television - have become more reliable in recent years. Such forecasts are based on historical data, climatological data, observed weather patterns and teleconnections. The El Niño weather phenomenon - during which altered water temperatures in the Pacific Ocean affect weather around the globe - is the world's most famous teleconnection. (Go to An El Niño Primer) Experts are observing more and more of these, improving their ability to predict how a season will develop.
Several areas for priority action were identified at the International Workshop, including:
Unfortunately, climatological station networks are deteriorating fastest in the poorest countries where farmers stand to benefit most from the information they provide. There are two reasons for the decline of the networks. First, there is simply a lack of funds in cash-strapped economies with many other priorities. Second, in many cases meteorological services are being privatized and concentrated where there is money to be made. Following this logic, climatological stations now tend to be concentrated near airports or big cities. But this is no help to farmers. Accurate weather information is required even in deserts because it is essential for good seasonal forecasts, and for such things as desert locust monitoring and crop forecasting.
Learning from the past
The Accra meeting also discussed the value of traditional techniques for manipulating micro-climates. "In many cases, we are rediscovering the value of primitive technologies," said Gommes. "People are reluctant to use them now because they seem so primitive, but they can be very effective and very useful for small-scale farmers."
Several such techniques relate to capturing occult precipitation - that is, available moisture not brought to ground in rainfall. Methods include planting trees or hanging mosquito nets in foggy areas to catch moisture. Even brick constructions can be used for the same purpose. Mulching the soil with leaves or farm residues is another simple but effective technique serving to reduce soil moisture loss.
Water is an increasingly precious commodity and low-cost, simple water-harvesting and conservation technologies remain very valuable in the search for sustainable ways to increase agricultural production.
30 March 1999