Zeolitic tuff containing an appreciable abundance of clinoptilolite was composted with animal waste to produce a dry friable non-odorous material that can easily be mixed with soil to produce an amended soil substrate. In earlier work it was found that leachate samples taken from organo-zeolitic treated substrates had nitrate concentrations an order of magnitude greater than those without the amendment. Comparative analysis of separate batches of organic-soil mixtures had shown that those containing zeolitic tuff had a very much higher concentrations of nitrate, in their leachate samples, than those containing only animal manure. Clinoptilolite has an ion-exchange property that is highly selective towards ammonium and it appears that the clinoptilolite component in adsorbing and ion-exchanging ammonia, as it is liberated from the decomposing animal waste, “buffers” its loss from volatilization and leaching. As a result, ammonium oxidizing micro-organisms are stimulated, which leads to enhanced nitrification and increasing ionic mobility of the substrate pore water. These functions allow plant growth to be stabilized on acid mine waste in such a way as to favour luxuriant growth on such sites, which normally are devoid of vegetation. The chemical analysis of plant leaf and stem tissue has identified trends in nutrient uptake and an attempt is made to understand the mechanisms responsible for this behaviour.