Relative Growth Rate of Six Soybean Genotypes Under Iron Toxicity Condition

The objective of the research was to study relative growth rate of six soybean genotypes under iron toxicity condition. The design was factorial design, with two factors; arranged in completely randomized design with three replications. The first factor was Fe concentration, consisted of two levels, i.e. (1) 0 ppm Fe and (2) 375 ppm Fe where after 7 days the acidity was not maintain at pH 3.5. The second factor was genotype, consisted of 6 genotypes, i.e. two tolerant genotypes (MLGG 0799 and MLGG 0492), three susceptible genotypes (MLGG 0915, MLGG 0768 and MLGG 0169) and one check swampland tolerant-variety (Lawit). The results showed that genotypes of MLGG 0799 and MLGG 0768 had higher rhizosphere pH levels than other genotypes. MLGG 0492 had potency to self recovery better than other genotypes based on relative growth rate (RGR) of root dry weight, plant height and plant dry weight. MLGG 0492 may have different mechanism than others because this genotype remained to have higher RGR, although it was unable to increase the rhizosphere pH. Under control and Fe treatment conditions, Lawit had no significant difference of RGR of plant dry weight to other susceptible genotypes.