Kiew, Ukraine
June 24, 2008
Estimated wheat yield based on
satellite-derived vegetative indices
The
USDA estimates Ukraine
wheat production for 2008/09 at 21.0 million tons, up 50 percent
from last year. The winter wheat crop has benefited from
excellent weather throughout the growing season and the
estimated yield of 3.09 tons per hectare is among the highest of
the past fifteen years. The current USDA yield estimate is based
chiefly on the analysis of satellite imagery: satellite-derived
vegetative indices such as the normalized-difference vegetation
index (NDVI) have proven to be a reasonably reliable indicator
of wheat yield in both Ukraine and the neighboring winter-wheat
region of southern Russia. Higher NDVI typically indicate
greater vegetative biomass or, in the case of cropland, higher
potential yield.
For winter wheat, the NDVI begins to increase after the crop
breaks dormancy and resumes vegetative growth in the early
spring, and reaches the maximum value when the plants reach the
flowering stage in mid- to late May. Methods for NDVI-based
yield analysis vary by region; in the case of Ukraine winter
wheat, the maximum NDVI provides the most reliable estimate of
potential yield.
Note that aggregate oblast-level NDVI typically continues to
increase even after winter wheat reaches its maximum value in
late May. This is due to the emergence and development of the
early spring grains (chiefly barley) and the summer crops (corn,
sunflowers, and sugar beets). The NDVI continues to build until
the summer crops reach their maximum values in July.
The vegetative indices for 2008/09 winter wheat indicate
excellent crop conditions and high potential yield throughout
the main production regions of central, southern, and eastern
Ukraine. The NDVI-based forecast for 2008/09 wheat yield was
determined by plotting historical yields against the
corresponding maximum NDVI for each oblast (the first-order
administrative territory, similar to a U.S. state). The
potential 2008 wheat yield for each oblast- was then estimated
based on regression analysis of the current-year NDVI.
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Eleven oblasts in eastern
and southern Ukraine account for nearly 70 percent of
the country's winter wheat production. These oblasts are
also marked by a reasonably high correlation between
NDVI and wheat yield. |
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(Click
on the map below to view NDVI graphs.) |
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Estimated wheat production was
calculated by applying the NDVI-derived yield to the
oblast-level sown area reported by the Ministry of Agriculture.
The total Ukraine wheat-production estimate of 21.0 million tons
includes 0.7 million tons of spring wheat.
The harvest of winter wheat (which accounts for about 95 percent
of total wheat area) typically begins in southern Ukraine in
late June or early July and is largely complete by early August.
Current USDA area and production estimates for grains and other
agricultural commodities are available on IPAD’s Agricultural
Production page, or at
PSD
Online. |
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