Dynamics of iron under long-term application of chemical fertilizers and amendments on maize-wheat cropping sequence

Iron (Fe) is one of the essential micronutrient plays a crucial role in redox systems in cells and in various enzyme. The Fe-deficient plants have lower redox reaction and enzymatic activity. Intensive chemical fertilizer resulted in depletions of micronutrients especially Fe from the soil. To understand the dynamics of Fe under long-term fertilizer experiment the present study was initiated during 1972 at experimental farm of College of Agriculture CSK HPKV, Palampur in randomized block design with eleven treatments replicated thrice. The soil of the experimental area was silty loam, acidic in reaction and taxonomically classified as “Typic Hapludalfs.” Surface (0–20 cm) and subsurface (20–40 cm) soil samples collected after the harvest of maize (Kharif, 2008). The continuous use of chemical fertilizers and amendments for the last 36 years in maize-wheat system in an acid Alfisol brought out marked depletion in the pools of Fe as compared to buffer plots. All the pools of Fe were noticeably higher in farmyard manure (FYM) amended plots compared to zero-fertilized plots. Although, residual fraction was found to be the most dominant fraction but organically bound and exchangeable forms were found to play major role in the nutrient supply and crop productivity and nutrients’ uptake. Highest productivity of maize (2008) and wheat (2008–2009) was recorded under 100% nitrogen, phosphorus and potassium (NPK) + FYM treatment. FYM and lime treatments resulted in significantly higher uptake of all the nutrients by both the crops compared to other treatments. Organically bound fraction was found to have highest significant and positive correlation with yield and nutrient uptake of maize and wheat crops. Further, regression analysis studies too revealed that organic form was the most important pool contributing towards the variation in the above parameters. While, exchangeable and organically bound forms contributed significantly towards diethylene triamine pentaacetic acid (DTPA)-extractable Fe.