Table 4 Comparison of prediction yield between model prediction and BPS data in El-Nino years
Year Regency
2004 2005
2006 Model
BPS Error Model
BPS Error Model
BPS Error
tha tha
tha tha
tha tha
Bandung 4.8
5.1 6.4
4.3 5.1
15.2 4.0
5.2 23.4
Bogor 6.4
5.0 27.3
4.9 5.2
5.6 5.0
5.3 4.8
Bekasi 4.7
4.8 2.7
3.8 5.4
28.9 3.0
5.2 42.0
Ciamis 5.8
5.3 9.2
5.5 5.2
5.3 3.8
5.4 28.6
Cianjur 6.2
4.8 29.6
5.2 4.9
6.4 4.8
5.0 4.7
Garut 5.0
4.9 0.2
5.0 5.2
5.1 3.7
5.0 26.0
Indramayu 4.2
5.5 22.9
3.6 5.5
34.5 3.1
5.3 41.2
Karawang 4.4
5.4 18.1
3.5 5.2
32.6 2.8
5.4 49.3
Kuningan 5.5
5.0 10.8
4.8 5.2
8.5 4.7
5.3 12.9
Majalengka 4.6
5.3 12.6
4.2 5.5
23.9 4.1
5.4 24.8
Purwakarta 6.3
5.0 24.9
5.6 4.9
13.8 4.7
5.0 7.5
Subang 5.0
5.2 4.2
4.5 5.3
15.9 3.7
5.4 32.2
Sukabumi 6.1
4.8 27.7
4.6 4.8
3.5 4.7
5.0 6.4
Sumedang 5.5
5.0 9.0
4.8 5.2
7.8 4.8
5.3 9.3
Tasikmalaya 6.2
4.9 26.2
6.0 5.1
18.1 5.0
5.2 4.9
Cirebon 4.2
5.4 22.8
3.5 5.1
32.8 3.5
5.2 33.4
Average 5.3
5.1 15.9
4.7 5.2
16.1 4.1
5.2 22.0
Effect of extreme El-Nino event on rainfall was clearly seen in year 2006. It effect was significant for growth of rice crop. It caused result of model very low
compared by BPS data. Figure 11 showed comparison of monthly rainfall in year 2006 and 2008. It seen rainfall data dramatic dropped in July until November
2006. Continuity of water supply is important in the beginning stage of rice development. Low of rainfall over 2 month caused growth activity of paddy not
optimal that it decreased dry matter accumulation of rice crop.
Figure 11 Monthly rainfall in year 2006 and year 2008.
The table 5 shows the results of the model in La-Nina years 2006 2008. The highest error of prediction was found in Indramayu in year 2007 with 27.9
while the lowest error of prediction was found in Sukabumi at year 2008 with 1.4. The average error of prediction from 16 regencies in West Java in year
2007 was lower than that in 2008. In overall, the error prediction of the model in El-Nino was higher than La-Nina event, or it can be said the model was good at
predicting the yield in La-Nina events than that it El-Nino events. Table 5 Comparison of prediction yield between model prediction and BPS data
in La-Nina years
Year Regency
2007 2008
Model BPS
Error Model
BPS Error
tha tha
tha tha
Bandung 4.7
5.6 16.9
4.3 5.8
26.3 Bogor
5.8 5.4
7.2 5.5
5.8 4.1
Bekasi 4.8
5.4 10.8
4.5 5.5
19.4 Ciamis
5.7 5.8
1.6 5.6
6.0 6.3
Cianjur 5.7
5.0 13.6
5.4 5.3
1.6 Garut
5.1 5.2
1.5 4.4
5.5 20.2
Indramayu 4.1
5.7 27.9
4.2 5.6
25.4 Karawang
4.5 5.5
17.4 4.4
5.9 25.2
Kuningan 5.8
5.5 5.9
5.9 5.7
2.9 Majalengka
5.3 5.5
4.3 4.8
5.5 12.4
Purwakarta 5.8
5.4 7.5
5.8 5.3
11.0 Subang
5.1 5.5
7.2 4.9
5.8 14.7
Sukabumi 5.9
5.0 18.3
5.2 5.1
1.4 Sumedang
5.4 5.3
2.0 5.2
5.4 4.3
Tasikmalaya 6.1
5.3 14.6
5.8 6.0
2.5 Cirebon
4.5 5.8
22.1 4.7
5.7 18.5
Average 5.3
5.4 11.2
5.0 5.6
12.3
Scatter diagrams of El-Nino and La-Nina years between model results and BPS reports are shown in Figure 12. The underestimate values are bigger in La-Nina
than El-Nino years. In El-Nino events, the average of underestimate values is 28 in predicting the rice production of more than 800.000 ton. On the other hand, in
La-Nina years, the model almost predicts much bigger than the actual production from BPS except in predicted rice production over Bandung regency. Predict of
rice production in La-Nina events better than El-Nino events with r
2
0.8.
