Standardizing the Quality of Composts Using Stability and Maturity Indices: The Use of Sawdust and Rice Husks as Compost Feed Stocks

Many organic materials found in urban areas of sub-Saharan Africa have not been exploited for the development of feedstock specific quality standards of compost especially for use as soilless media. The objective of this study was to determine feedstock specific quality standard of compost using referenced stability and maturity indices and establish a simple model for predicting compost maturity based on different feedstock. Two sawdust feedstocks from Daniellia oliveri sawdust (single sawdust) and Daniellia oliveri + Chrysophylum albidum sawdust (mixed sawdust) including one rice husk feedstock were composted individually with poultry manure in three volumetric ratios of 2:1, 3:1 and 4:1. The 2:1 Daniellia oliveri sawdust compost achieved acceptable values for stability and maturity parameter at 8th week, and had the highest nitrogen (N) level (2.46%) and lowest carbon to nitrogen (C:N) ratio (15). In terms of associative relationships for single species sawdust compost, total nitrogen (TN) accounted for 93% of the variation in the C:N content of the compost. In the mixed species sawdust compost, TN explained 87% of the variation in the C:N. Total nitrogen only explained 77% of the variation in the C:N content of the rice husk compost. The study established an empirical relationship between TN and compost maturity and concluded that using stability and maturity indices and their relationships established in this study as standard, compost of higher quality could be obtained within the shortest possible time irrespective of the feedstock used.