Department of Agricultural Engineering, Faculty of Agricultural Technology, Gadjah Mada University, Yogyakarta-INDONESIA
Relationships among global climate indices (Southern Oscillation Index, SOI; sea surface temperature, SST), rainfall and rain-fed crop yields were investigated in highland areas of southern Indonesia. Rainfall data were collected during the rainy season (October–March) from 1981 to 2009 in Gunungkidul district, Yogyakarta Special Province, southern Java, an important area of rain-fed crop production. Rainfall was highest in the southern and western mountainous areas, especially near the coast, and SOI and SST Niño.West values were highly correlated with rainfall in those areas. Soybean and dryland paddy yields were highly correlated with the amount of rainfall in January, and the average SOI during June–September was highly correlated with maize yield during January–April.