Release kinetics of Zn from soil and growing media mixtures in a laboratory study

Abstract

Aim: To assess the zinc release from soils and various soilless growing media mixtures comprising different organic manures mixed at various proportions and to understand the kinetic behaviour of Zn release. Methodology: An incubation study was conducted to examine the time dependent release of zinc from soil and different growing media mixtures of Cocopeat (CP), Vermicompost (VC), Farm Yard Manure (FYM), Pressmud (PM), Vermiculite (VL) and Composted coco peat (CCP) by adding various levels of ZnSO4 (0, 12.5, 25, 37.5 and 50 kg ha-1) for 60 days. The Zn release at required time interval was quantified in soil and growing media mixtures. Results: Higher zinc release was recorded with growing media mixture of Cocopeat + Vermicompost + Pressmud (1:1:1) as compared to other mixtures. The release was linear up to 30 days and dropped at 45 days then increased. Fitting of various kinetic equations for better understanding of zinc release satisfactorily accounted (R2, 0.975 to 0.998, at p ≤0.05) by the zero order kinetic equation. Higher half-life time for Zn release (t1/2) was noticed with Soil + FYM and Cocopeat + Vermicompost + Pressmud mixtures, which confirmed their suitability. A significant negative correlation between pH, C:N ratio with Zn availability as well as linear decrease in organic carbon content prompted zinc release. Interpretation: Based on the amount of zinc released and grouping through principal component analysis with hierarchical clustering, a mixture of Cocopeat +Vermicompost +Pressmud at 1:1:1 was the best growing media mixture. Higher initial zinc availability and half-life time (t1/2) for zinc release makes it more efficient and best growing media mixture to sustain Zn supply to crops for a longer period of time.