Improving Physical Properties of Organo-Mineral Fertilizers: Substitution of Peat by Pig Slurry Composts

Abstract

Some granulated organo-mineral fertilizers (OMF) are made with peat and their utilization is expected to increase mostly because of their advantages over mineral fertilizers. However, peat is a non-renewable resource and could be replaced by sustainable organic materials such as stabilized composted pig slurry. The objectives of this study were to determine the changes of OMF physical properties when 1) substituting peat by composted pig slurry mixtures, 2) changing source of composted mixtures, and 3) increasing the level of organic material in the OMF. Thirty-four mixtures of compost, monoamonium phosphate (MAP), diammonium phosphate (DAP), and peat were granulated in OMF at different proportions. The increase of the compost proportion and the decrease of organic material input (30% vs. 60% of organic materials) improved most physical properties of OMF granule such as bulk and granule densities, total and granular porosities, water content, abrasion fragility, crushing strength, critical relative humidity, and water sorption from moist porous media. In addition, most compost types resulted in similar physical properties of OMF granules. Finding the appropriate organic matter content requires more research and the optimum OMF mixture should be chosen as a function of its combined physical, chemical, and plant response properties.