Produktivitas Tanaman Kedelai pada Kondisi Tahun Normal, El Nino dan La Nina (Studi Kasus: Kabupaten Grobogan)

Abstract

Climatic variability such as La Nina and El Nino affects soybean productivity. La Nina and El Nino events cause an increase and decrease in rainfall while rainfall is the primary main irrigation source for soybean cultivation in Grobogan Regency. This research was conducted to estimate soybean productivity during Normal, El Nino, and La Nina conditions in Grobogan Regency using the DSSAT simulation model. Based on the simulation that has been done, soybean productivity under normal conditions is higher than in other state's situations. Soybean productivity under normal conditions in 2014 was 2227 kg/ha, La Nina in 2010 was 2198 kg/ha, and soybean productivity during El Nino in 2015 was 2132 kg/ha. Soybean productivity during La Nina descreased by 1,3% and El Nino descresed by 4,3%. High rainfall during La Nina increases the availability of water in the soil. However, excessive rainfall causes water stress. Waterlogging causes soybean seeds to rot at the beginning of planting, thereby inhibiting soybean plant growth. Low rainfall due to the 2015 El Nino in several crop periods caused a water deficit in soybean cultivation. Deficiency can be seen from the ETp value, which is higher than the rainfall. Validation of simulation results in field is indicated by the coefficient of determination or R2 of 0.75, which means that model's simulation results have explained 75% of the results in the field. Other factors explain the rest.