Iron release characteristics in groundnut growing red and black calcareous soils of Cuddalore district

The current study was assessed the nutrient release pattern of iron using different sources of iron fertilizer at various levels in groundnut-growing red and black calcareous soils of the Cuddalore district at regular sampling intervals. The study design was completely randomized block design with different levels of iron sulphate (FeSO4) at 25 and 50 kg ha-1, iron-enriched farmyard manure (Fe-EFYM) at 37.5 and 50 kg ha-1 and iron-ethylene diamine dihydroxy phenylacetic acid (Fe-EDDHA) at 1 and 5 kg ha-1 three replicates at different sampling intervals of incubation. The release pattern of iron was analyzed. The study revealed that the releasing rate of iron increased with the advancement of the incubation period up to 42 days and thereafter declined in both type of calcareous soil. The maximum release of iron was found with the application of 50 kg FeSO4 ha-1 as Fe- EFYM, which recorded mean values of 26.92 and 26.13 mg kg-1 on 42nd day in red and black calcareous soils, respectively. Application of Fe-EDDHA at 5 kg ha-1 recorded a gradual increase in DTPA iron availability from 7th day (17.35 mg kg-1 and 12.03 mg kg-1 in red and black calcareous soil, respectively) to 42nd day (21.49 mg kg-1 and 18.87 mg kg-1 in red and black calcareous soil respectively). Then it showed a steady decline in both calcareous soils. The results of the current study showed that the efficient usage of iron in both calcareous soils was greatly increased by the combined application of organic and inorganic fertilizers.