Characterization of Pozzolana from Tafila area and its potential use as soil amendment for plant growth

Volcanic tuff (VT) (Pozzolana) deposits are available in huge quantities in Tafila area. Al Hala Volcano (HV) is one of the biggest deposits for VT located in southern Jordan which was chosen in this study. Characterization of zeolitic tuff (ZT) minerals is the main goal of this study in addition to the agricultural application for possible usage as soil amendment and improvement. Field studies indicate that VT is highly altered to ZT due to percolating alkaline water. ZT is characterized by highly weathered, friable and range in color according to zeolitization process and chemical composition to many different colors. The three main ZT types are reddish (RZT), brownish (BZT) and grayish (GZT). Mineralogical studies indicate that VT is composed mainlyof three mineral compone nts: Volcanic glass (palagonit), primary rock forming minerals (idingsite and diobside) and secondary rock forming minerals (zeolites, calcite and clay minerals). The main zeolites minerals in HV are phillipsite and chabazite. The ZT from HV shows acceptable pH with high cation exchange capacity range from (189 meq/gm) for RZT to (136 meq/gm) for GZT. Geochemical studies indicate that ZT from HV has low Na2O% ranges between 0.34% - 1.44% with a high percentage of important oxides such as Ca, Mg, K, Mn, and Al. The type of Tafila Soil (TS) is silty clay texture which is considered as heavy soil as indicated by size fractionation analysis results. The ZT from HV is evaluated for agricultural applications by using RZT and GZT as soil amendments for planting tomatoes and pepper vegetables. The mixture with the ratio of 50:50 TS:RZT results shows increasing in terms of growth, yield and roots assemblages for both vegetables.