Specials Environment

Posted December 1996

Crop forecasting: Outputs

Introduction | Inputs | Model | Outputs

THE OUTPUTS described below have different levels of "added value". The most synthetic of all is no doubt the crop yield map, an essential tool for decision making at the national level. Based on such maps, governments can calculated district and provincial yields and production, and decide whether food production is adequate. Necessary action can thus be taken in advance.

Crop yield map

A crop yield map is an extremely synthetic and useful product. Its simplicity hides the fact that complex analyses, and a very sizeable amount of data, have been used in its preparation. It clearly shows areas of high and low yields, and constitutes the basis for regional/provincial production estimates.

 View GIF image: 10K / 526x401 pixels

Crop condition map

Next to maps based on reports provided by field observers, NDVI is one of the tools that can be used to map out crop condition. The two maps below show the same area during two rather different years: a dry year (1984) and a wet year (1988). The difference is striking in northern Senegal and Niger.

Crop conditions, western Africa
September 1984 (top) and September 1988 (bottom)

 View GIF image: 24K / 456x316 pixels

Other indicators

There are many different monitoring indicators. Most of them rely on the comparison of some current value with average or "normal" conditions. The best known indicator of this type is rainfall departure from normal. Below, two examples are illustrated: departure of Cold Cloud Duration from the average of several recent years, and a synthetic image showing the difference in cereal yields in Niger between 1995 and 1996.

Cold Cloud Duration difference between July 1996 and the 1989-95 average, West Africa

 View GIF image: 16K / 600x329 pixels

Cereal yields in 1995 and 1996, and the difference of the two years (1996 minus 1995), Niger

 View GIF image: 12K / 515x401 pixels

That concludes our presentation. For further information on Agrometeorological Crop Forecasting, contact the FAO Agrometeorology Group (e-mail: agromet@fao.org).

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