Assessing microbial population dynamics, enzyme activities and phosphorus availability indices during phospho‑compost production


1 School of Agricultural Sciences, Faculty of Agriculture and Natural Sciences, University of Mpumalanga, P/Bag X11283, Mbombela, 1200, South Africa

2 Department of Production, Soil Science and Agricultural Engineering, University of Limpopo, P/Bag X1107, Sovenga, South Africa

3 Food Security and Safety Niche Research Group, North-West University Mafikeng Campus, P/Bag X2046, Mmabatho, 2735, South Africa

4 Agricultural Research Council-Grain Crops Institute, P/Bag X1251, Potchefstroom, 2530, South Africa


Purpose This study assessed changes in bio-quality indices and plant available P released during aerobic–thermophilic cocomposting of different mix ratios of non-reactive ground phosphate rock (GPR) with poultry and cattle manures.
Methods Aerobic–thermophilic co-composting of different mix ratios (5:5, 8:2, 7:3 and 9:1) of non-reactive GPR with poultry and cattle manures was carried out. Compost piles without GPR addition were included as control. Compost samples were taken at mesophilic, thermophilic, cooling–stabilization and maturing phases for microbial counts, enzyme activities and P assessment.
Results Abundance of different microbial groups across the composting phases varied greatly (p0.05) indicating inhibition of the P forms. Quantitatively higher P was obtained from poultry manure-based phospho-compost and in the 8:2 mix ratio at compost maturity. Microbial diversity and enzyme activity exerted positive impact on P mineralization and availability from the non-reactive GPR signifying the beneficial effect of co-composting.
Conclusions Co-composting of P-rich non-reactive GPR with organic wastes containing variable chemical composition promotes microbial diversity during composting and increases plant available P content and compost fertilizer value.