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March 22, 2002
Near-normal amounts of winter precipitation have helped to ease the three-year drought in parts of Central Asia and improved prospects for 2002/03 winter grains. In western Uzbekistan, southern Turkmenistan, and southern Tajikistan -- three areas that have been particularly hard-hit by the persistent dryness -- beneficial precipitation has resulted in an early green-up of native grasslands. While improved vigor of natural vegetation does not guarantee subsequent favorable conditions for grain crops, mid-March moisture conditions are likely the best in three years in these chronically drought-affected regions.
Satellite imagery indicates that current conditions are relatively favorable for winter grains that have broken dormancy and resumed tillering. Most of the vegetation seen in the imagery is natural vegetation -- mainly grassland, not cultivated grain crops. (Note that vegetation in the satellite imagery is displayed as red, and brighter red indicates more vigorous vegetation.) Winter wheat, the dominant grain grown in Central Asia, will reach its peak "redness" in several weeks, when the crop advances to the flowering stage. April satellite imagery will provide a much better indicator of winter-wheat yield potential.
Vegetative vigor can also be expressed by a vegetative index (in this case a normalized-difference vegetation index, or NDVI) which is derived from the satellite imagery. A higher index indicates more vigorous growth. Recent NDVI images from Central Asia show the rapid green-up of the native vegetation in the past few weeks. (In the NDVI images, the color green indicates vegetative vigor.) A year-to-year comparison shows the sharp improvement in mid-February conditions in southern Turkmenistan. It should be re-emphasized that the imagery and vegetative-index products for February and March are driven largely by non-cultivated vegetation. The condition of this natural vegetation, however, provides an early-season indicator that beneficial winter precipitation has indeed improved prospects for 2002/03 winter grains.
For more information, contact Mark Lindeman
with the Production Estimates and Crop Assessment Division on
(202) 690-0143.
