Production of Slow Release Fertilizer from Waste Materials

Abstract

This chapter aims to study the feasibility to produce slow release fertilizer from waste materials. Three waste materials i.e. leonardite, zeolite and rice straw were utilized. Four formulations of slow release fertilizer were prepared by using different compositions of leonardite, leonardite and zeolite, leonardite and rice straw and leonardite, zeolite and rice straw. The nutrient contents of each formulation were adjusted in order to relate to those of the N13:P13:K13 commercial slow release fertilizer by the addition of fertilizer materials. Bentonite was applied at 10 wt% to act as a binder. All four formulations of slow release fertilizer were coated with resin. Morphologies of the coated and uncoated formulation surfaces were revealed by scanning electron microscopy (SEM) and the N, P, K nutrients release contents were also determined. The results indicated that the uncoated formulations have the N, P, K release contents higher than the coated formulations and the commercial slow release fertilizer. The slow release fertilizer formulations without zeolite (sample 2) have N, P, K nutrient release contents slower than with zeolite (samples 1 and 3). However, the N, P, K nutrient release rates are still high comparing to the commercial slow release fertilizer. Moreover, the coated formulation has the nutrient release contents as well as the commercial slow release fertilizer especially for the formulation with zeolite (formulations 1 and 3). According to the morphologies revealed by Scanning Electron Microscopy, many pores were found on the uncoated formulations in contrast to the coated formulations and the commercial slow release fertilizer, which have smooth surfaces.