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

F R Kutu,O A Dada,T J Mokase,O H J Rhode

doi:10.1007/s40093-018-0231-9

Abstract

PurposeThis study assessed changes in bio-quality indices and plant available P released during aerobic–thermophilic co-composting of different mix ratios of non-reactive ground phosphate rock (GPR) with poultry and cattle manures.MethodsAerobic–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.ResultsAbundance of different microbial groups across the composting phases varied greatly (p < 0.001) mostly dominated by fungi that was generally more in the cattle than poultry manure-based phospho-composts. Fungi and actinomycetes counts in the composts were positively correlated with alkaline phosphatase and β-glucosidase. A strong inter-correlation between β-glucosidase and alkaline phosphatase (r = 1.000, p < 0.001) was observed, suggesting that both enzymes possess same origin. Alkaline phosphatase and β-glucosidase contents in the phospho-composts showed negative correlation with water soluble P (r = − 0.65, p < 0.001), and Bray P1 and Fe–P contents (r = − 0.15, p > 0.05) 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.ConclusionsCo-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.

Highlights

With urbanization and rapid increase in human population which was recently projected to hit 11.2 billion in 2100 (UNDESA 2015), greater improvements in waste management strategies are needed to deal with the rising volume of global wastes generation
Available statistics suggest that the amount of solid waste generation and its composition vary greatly across countries; with greater amount in highly developed and wealthy countries including those with high population density (UNEP 2011)
Bacterial count was highest at the maturing phase while fungi and actinomycete counts were highest during the mesophilic and cooling phase, Table 1 Microbial counts and the concentration of measured enzyme activities in the phospho-compost samples

Summary

Introduction

With urbanization and rapid increase in human population which was recently projected to hit 11.2 billion in 2100 (UNDESA 2015), greater improvements in waste management strategies are needed to deal with the rising volume of global wastes generation. Available statistics suggest that the amount of solid waste generation and its composition vary greatly across countries; with greater amount in highly developed and wealthy countries including those with high population density (UNEP 2011). Composting is one of the crucial management strategies often used for the safe disposal of the prodigious amount of wastes that are continuously generated globally through anthropogenic. The importance of composting as a waste management option encompasses multiple benefits such as greening of wastes, environmental friendliness and its potential to guarantee safe and sustainable future (UNEP 2011). Aside providing carbon for soil organisms, it serves as cost-saving potential bio-fertilizer source and the supply of valuable nutrients for plant use (Chatterjee et al 2013; Manderson 2014)

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Conclusion