Effect of iron and manganese interaction on paddy yield and iron and manganese nutrition in silicon-treated and untreated soils

To study the interaction effects of Fe and Mn in Si-treated and untreated soils, we conducted an experiment in the glass house of the Department of Soil Science and Water Management, H. P. Agricultural University, Palampur, India, with paddy (RT-42) as a test crop. We applied manganese as MnSO4·7H2O at rates of 0, 25, and 50 mg kg and Fe as FeSO4·2H2O at rates of 0, 25, and 50 mg kg. Silicon was added as Na2SiO3·5H2O at rates of 0 and 200 mg kg. Applied Mn, 25 mg kg, increased the grain and straw yield over control and 50 mg kg Mn decreased the yields over 25 mg kg Mn, when soil was not treated with Si. When soil was treated with Si, 50 mg kg added Mn did not produce any effect on paddy yield. When Fe was applied, however, 50 mg kg Mn in Si-treated soil increased the paddy yield even over 25 mg kg Mn. In Si-untreated soil, this level of Mn did not show any effect on yield. The grain and straw yields were higher with Si-treated soil than with Si-untreated soil. The concentration and uptake of Fe and Mn decreased with the application of Mn and Fe, respectively. The conentration of Fe and Mn and the uptake of Fe in the paddy were higher with Si-untreated soil than with Si-treated soil. The uptake of Mn was not affeted by Si additions.When more Fe and Mn were applied, the respective retention of Fe and Mn by root was decreased and their translocation to shoot was increased. When more Mn or Si was added, however, more Fe was retained by root and less was translocated to shoot; when more Fe or Si was added, more Mn was retained by root and less was translocated to shoot.The respective absorption of Mn and Fe in paddy was 0.85 and 0.51 mg pot up to tillering, 7.27 and 4.85 mg pot between tillering and flowering, and 4.20 and 2.52 mg pot between flowering and maturity. At maturity, 9.65 and 5.82 mg pot of Mn and Fe taken up were retained by straw and 2.77 and 1.76 mg pot were translocated to grain. The distribution of Mn in grain and straw increased with applied Mn and decreased with applied Fe. When more Si was added, more Mn was translocated to grain and less was retained by straw. When more Mn or Si was applied, however, less Fe was translocated to grain; when more Fe was applied, more Fe was translocated to grain.