Simulation model application to predict impact of climate change on potato productivity in Indonesia
Aplikasi model simulasi untuk prediksi dampak perubahan iklim terhadap produktivitas tanaman kentang (Solanum tuberosum L.) di Indonesia
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Potato is an important horticulture crop in Indonesia in terms of planted area more than 55.000 ha and its production 864.000 ton. The crop is commonly grown in upland areas above 800 m where runoff and erosion often cause environmental problem whereas the yield is relatively low due to various reasons. The crop growth depends on climatic variables particularly rainfall, solar radiation and temperature. Climate change, particularly temperature increase and rainfall decrease, is expected to adversely impact potato growth with the results of even lower yield of the crop compared to the current yield. In order to develop potato crop simulation model, field experiment at Pacet and Galudra (West Java Province) and Kerinci (Jambi Province) were conducted to derive parameters that are required for model building and validation. The experiments were conducted from December 2009 to September 2011. The model being constructed consists of (1) crop-development submodel, (2) crop-growth submodel, and (3) water-balance submodel. Model was calibrated using data collected from three field experiments. The application includes determining potential yield of potato crop under different climates, both under current condition and under different climate change scenarios. The model was also run at different planting dates to find the maximum yield from which optimum planting date was determined. Result showed that in general validation results using paired t-test suggest that model predictions are not significantly different (P > 0,05) with field measurements at Galudra and Kerinci for variables of periods of developmental phases, biomass of root, stem, leaf and tuber, leaf area index, and soil water content (Granola cultivar) and biomass of stem, tuber and soil water content (Atlantic cultivar). However, graphical test of the relationships between model predictions and field measurements have coefficients of determination (R2) higher than 0,80 for all of variables being tested. The simulation model of development, growth and waterbalance of potato crop could predict climate change impact on potato productivity in several potato production centers in Indonesia (Minahasa, Alahan Panjang, Pangalengan, Pasuruan, Wonosobo, and Deli Serdang). Predicted potato yields in the six potato production centers using three scenarios of increasing temperature and decreasing rainfall for the year 2020, 2050, and 2080 based on climate change projection in Indonesia for the future (SRES A1) were in the range of 13% – 31%, 25% – 47% and 37% – 63%, respectively. Potato production center in Pangalengan was predicted to experience the biggest decline in yield for all scenarios. Predicted yield of Atlantic variety was 25 ton ha-1, which was higher than Granola variety of 16 ton ha-1. Climate change adaptation options based on simulation of the model are: optimal planting time, use of superior potato varieties that have higher value of RUE, and select application of suitable potato varieties that are more tolerant to high temperatures.