Structural properties and dissolution behavior of new generation controlled release phosphate glass fertilizers

Abstract

In this work, different phosphate glasses in the Na2O-K2O-CaO-P2O5, Na2O-K2O-CaO-Al2O3-P2O5 and Na2O-K2O-CaO-Al2O3-SiO2-P2O5 systems are synthesized by conventional melt quenching technique and investigated in terms of physical, thermal, and structural properties along with long-term dissolution behavior in different solvent media, i.e., deionized water, and 2% citric acid solution simulating the neutral soil environment and pH value of the plant root zone. In addition, the effect of selected glasses (with and without microconstituent doping) on the growth of tomato plants are examined and their potential use as controlled release glass fertilizers is evaluated by linking their chemical durability behavior with structural changes in the glass network. Consequently, studied glass compositions - exhibiting long term (over 90 days) nutrient release during plant growth along with insignificant change in pH and no toxic compound release during dissolution process - are evaluated as promising controlled release fertilizers for tomato plants.