Physical Properties of Granular Organic-based Fertilisers, Part 1: Static Properties

Abstract

The need to recycle, dispose of and increase the value of organic wastes, combined with the knowledge that organic matter enhances plant–nutrient interactions, led to the development of granular organic-based fertilisers. The main objective of this research was to compare the physical properties of compound organic-based (COF) and bulk-blended organic-based fertilisers (BOF) with those of mineral fertilisers (MF). Standard and modified methods were used to measure their static properties. Compared with MF, COF had significantly lower bulk, granule, and particle densities and higher bulk and granule porosities and angles of repose. The variation in these static properties could be predicted in part with the N, P, K and organic matter contents as well as the particle size distribution. The organic matter content significantly influenced most physical properties. Bulk density, granule density, and the angle of repose decreased with increasing organic matter content while porosity and tensile strength increased with organic matter content. Bulk density and tensile strength were also significantly related to granule size distribution. The initial water content influenced density, porosity, tensile strength, and the angle of repose. Important relationships therefore exist between static physical properties, and these relationships can be used as partial predictors of other properties.