Agriculture Reference
In-Depth Information
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yield varied from 10% to 14% with an average of about 12% (Heryanto
et al., 2002).
Using the Southern Oscillation Index Another approach to estimate the
crop production in the coming season is the Southern Oscillation Index
(SOI) data (Meinke and Hammer, 1997; Rahadiyan, 2002). A prelimi-
nary study indicated that the variation in national rice production could
be explained partly by the SOI for April. The use of the April SOI was
motivated by the evidence that after April the cumulative drought area
increased rapidly, especially during El Niño years. Negative anomalies in
rice production occurred mostly for El Niño years, while positive anomalies
occurred for La Nina years.
[338
Using Crop's Physical Appearance Drought severity is determined based
on the proportion of the dry leaves in rice fields. If only the tip of the leaf
gets dry, it is called slightly affected ( Ringan ); if one-quarter of the leaf is
dry, it is called moderately affected ( Sedang ); if one-quarter to two-thirds
of the leaf is dry, it is called heavily affected ( Berat ); and if all of the leaf is
dry, it is called completely damaged ( Puso ). These drought symptoms are
monitored every two weeks by the pest and disease observers at subdistrict
levels. The data are sent to the district and then to the province and finally
to the Directorate of Plant Protection. The Directorate of Plant Protection
analyzes the data and provides a drought distribution map.
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Drought Vulnerability Map The Directorate of Plant Protection has de-
veloped a map showing drought vulnerability in a district. Vulnerability is
determined using frequency, intensity, and size of area affected by drought
(Alimoeso et al., 2002). The analysis suggested that most of the vulnera-
ble districts are located in West Java province, South Sumatra/Lampung,
and South Sulawesi (figure 26.2). These three provinces are the main rice-
growing areas of Indonesia. Among the three, West Java is the largest rice-
producing province in the country. Any drought in West Java could have
a significant influence on national rice production and food security. In
West Java, districts considered to be very prone to drought are Indramayu,
Bekasi, Sukabumi, Tasikmalaya, Bandung, and Cirebon. Loss of rice pro-
duction in these districts increased significantly during El Niño years (figure
26.3) and could go up to 500,000 tons (Alimoeso et al., 2002).
From historical data, it was shown that, in general, the area affected by
drought increased significantly during El Niño years (figure 26.4). How-
ever, from national production statistics, the impact of El Niño, apart from
1982, is not distinct, except for rice (figure 26.5). This condition appears
due to a number of reasons (Suryana and Nurmalina, 2000; Meinke and
Boer, 2002): (1) the statistics are based on calendar years rather than on
El Niño years, (2) not all regions of the nation are affected by drought
simultaneously, (3) shortage of water may force a farmer to switch from
rice to secondary crops, (4) restricted water supply may reduce the area
[338
 
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