Release Kinetics of Iron (Fe) from Soil and Growing Media Mixtures: An Incubation Study

An incubation study was conducted to examine the time dependent release of iron from the soil and growing media mixtures of Cocopeat (CP), Vermicompost (VC), Farm Yard Manure (FYM), Pressmud (PM), Vermiculite (VL), and Composted cocopeat (CCP) with various levels of ferrous sulfate (FeSO4) application for 60 days. Higher Fe release was recorded in the growing media comprising soil + composted cocopeat (1:1) followed by Cocopeat + Vermicompost + Press mud (1:1:1). Fitting of various kinetic equations for better understanding of iron release satisfactorily accounted (R-2, 0.867 to 0.998, at p <=.05) by the zero-order kinetic equation. Higher half-life time for Fe release (t(1/2)) as well as initial Fe concentration (q(0)) was noticed in Soil + Composted cocopeat and Cocopeat + Vermicompost + Pressmud. A significant negative correlation between pH, C/N ratio with Fe availability as well as higher organic carbon content prompted iron release. Based on the released amount of iron and principal component analysis with hierarchical clustering, Cocopeat + Vermicompost + Press mud (1:1:1) and Soil + Composted cocopeat (1:1) were grouped as best growing media mixtures. Higher initial Fe availability, release rate, and half-life time for iron release was observed in Soil + Composted cocopeat and Cocopeat + Vermicompost + Pressmud growing media which makes them more efficient as those can sustain the Fe supply for a longer period of time with higher availability to crops.