Agriculture Reference
In-Depth Information
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Since 1991, FSU experienced droughts during different years, as iden-
tified by the AVHRR-based indices (figure 6.1, right panel) and affected
100-150 million acres of crops and rangeland, reducing the total FSU grain
production by 10-15% (20-30 million metric tons). Independent coun-
tries incurred up to 30% of grain losses. The worse economic problems
occurred when major drought affected both winter (mostly Ukraine and
southern Russia) and spring grain crops (eastern regions in 1991, 1996,
and 1998). These droughts were confirmed by climatological observations.
In these cases, crop yield anomalies showed strong correlation with vege-
tation health indices (Kogan, 1997, 2001).
A
rgentina
[83],
A
rgentina is the second largest exporter (next to the United States) of
co
rn and coarse grains, and the third largest exporter of wheat (FAO,
20
00). Droughts and dry spells are frequent and devastating in this country.
Si
nce 1985, Argentina experienced two major and several minor droughts.
By
all standards, the most damaging droughts occurred during 1988-89
and 1989-90 crop seasons (figure 6.2), when the country lost between
15 and 20% of the total grain production. The minor droughts were less
intensive and affected smaller areas, causing 5-10% reduction in crop
yields. These results were validated by the ground measurements of wheat
yield in Cordoba province (Seiler et al., 2000).
Line
——
0.4
——
Long
* PgEn
[83],
China
China produces grains and cotton, mostly for domestic consumption. From
time to time, China also imports small amounts of agricultural commodi-
ties. However, in 1994, China unexpectedly imported a huge volume of
cotton, exceeding by almost twofold the largest purchases since 1981.
These imports were preceded by a cotton yield reduction three years in
a row: 22% in 1992-93, 11% in 1993-94, and 7% in 1994-95. Our in-
vestigation indicated that this reduction can be attributed to unfavorable
growing conditions (vegetation stress) across the main cotton-growing ar-
eas (figure 6.3).
Of all three years, the most severe vegetation stress (both moisture and
th
ermal) occurred in 1992, which also showed the largest yield reduction.
So
me deterioration of vegetation conditions was also observed in 1994, but
th
e drought-related stress was partially offset by a almost normal summer
ra
infall. Unlike the other two drought years, the 1993 drought was due to
excessive moisture as revealed by the AVHRR-derived data.
C
onclusions
This chapter has described a drought monitoring technique based on the
estimation of green canopy stress from AVHRR-derived indices that char-
acterize vegetation health, moisture, and thermal conditions. The products
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