Agriculture Reference
In-Depth Information
Drought is often accompanied by relatively high temperatures, which pro-
motes ET and affects photosynthetic kinetics, thus intensifying the effects
of drought and further reducing crop yields (Mir et al., 2012). Drought is
an inevitable feature of climate that occurs in virtually all climate regimes.
Although global figures for the trends in economic losses associated with
drought do not exist, an UNDP Bureau of Crisis Prevention and Recov-
ery (2004) indicates that annual losses associated with natural disasters
increased from US$75.5 billion in the 1960s to nearly US$660 billion in
the 1990s. Agricultural regions affected by drought can experience yield
loss up to 50% or more. Over 35% of the world's land surface is con-
sidered arid or semiarid, experiencing precipitation that is inadequate for
most agricultural uses. Over exploitation of natural resources has endan-
gered water resources, biodiversity and soil quality, more than 1.2 bil-
lion people in over 110 countries are already affected by the social and
environmental effects of the land degradation in dry lands, which leads to
declining biological and economic productivity worldwide (Pervez et al.,
2009). The threat of global warming may further increase the frequency
and severity of extreme climate events in the future. India is also one of the
countries, which have agriculture system challenged with climate change.
Vegetables are basically succulent in nature and generally consist of more
than 90% of water. Thus, water stress, mostly at critical period of growth
may drastically reduce productivity and quality of vegetables (Table 9.1).
Moisture stress during vegetative or early reproductive growth phase usu-
ally reduces yield by reducing the number of fruits/ seeds in vegetables,
while during flowering and fruit setting stage drought stress reduces fruit
quality, number of fruits, size of fruits and finally yield loss. Drought also
reduces seed number, viability, and vigor. Physiological processes mainly
responsible for plant growth and development are affected by water deficit
condition, and plant exhibit various defense mechanisms against drought
stress at the molecular, cellular and whole plant levels.
TABLE 9.1
Critical Stages of Drought Stress and its Impact on Vegetable Crops
Vegetable crops
Critical period for watering
Impact of water stress
Tomato
Early flowering, fruit set, and en-
largement
Flower shedding, lack of fer-
tilization, reduced fruit size,
fruit splitting, puffiness and
development of calcium defi-
cient disorder i.e. blossom end
rot (BER), poor seed viability
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