ABSTRACT
Iron toxicity is the main problem in using acid sulfate soils for growing rice, as it decreases its agronomic traits. The experiment aimed (1) to study the effects of Fe concentrations on some agronomic traits of 15 improved rice varieties and (2) to find varieties that are tolerant to iron toxicity in acid sulfate soils of tidal swampland. The experiment was conducted in the greenhouse of Indonesian Swampland Agricultural Research Institute, Banjarbaru, Indonesia, and made use of Factorial Randomized Completely Design with three replications. The first factor was 15 improved rice varieties, and the second was four Fe concentrations of acid sulfate soils (229.44; 236.34; 564.15, and 1277.50 mg kg-1 Fe). Furthermore, observation variables included plant growth (plant height, tiller number, root and straw dry weight), grain yield, harvest index, and iron toxicity symptoms. The results showed that an increase in Fe concentrations of acid sulfate soils led to a decrease in rice agronomic traits (maximum tiller number, plant height, dry weight of roots and straw, grain yield and harvest index), but an increase in iron toxicity symptoms. Varieties Inpara-1 and Inpara-2 revealed the smallest decrease in rice agronomic traits and exhibited the lightest iron toxicity symptoms, whereas IR64 showed the greatest decrease in the traits and the most severe symptoms. Inpara-1 and Inpara-2 were identified as the varieties tolerant to iron toxicity in the acid sulfate soils of tidal swampland.
