Iron and nitrogen interactions in groundnut nutrition

A pot experiment was conducted to estimate the levels of iron (Fe) needed to correct Fe-deficiency chlorosis in groundnut grown in an alkaline soil and to study Fe x nitrogen (N) interactions in soil and plant and their associated effects on growth and yield. Four levels of Fe (0, 2.5, 10, and 25 mg Fe kg(-1) soil as Fe-EDDHA) and two levels of N (0 and 100 mg N kg(-1) soil as NH4NO3) were applied factorially in a completely randomized block design. Higher rates of 10 and 25 mg Fe kg(-1) caused a significant reduction in leaf area and aerial biomass accumulation irrespective of N treatment. The Fe x N interaction was significant for all of these parameters. Specific leaf area increased at higher levels of Fe application. Higher Fe levels induced symptoms suggestive of manganese (Mn) deficiency. This diagnosis was supported by decreasing concentration of Mn in leaf blades with increasing Fe levels. By contrast concentrations of most other elements in leaf blades increased with increasing levels of Fe application, suggestive of plant growth but not uptake of other elements being reduced by Mn deficiency.