Assessment of the suitability of pineapple waste as feedstock for vermicomposting

Abstract

Declining soil fertility is a challenge to sustainable agricultural production in sub-Saharan Africa with a case of Uganda. However, the large volumes of agricultural waste generated from pineapples can be converted into soil conditioners through vermicomposting. by the use of earthworms. Several types of agricultural waste have been studied extensively as vermicompost feedstock, but little work exists on pineapple waste. The objective of this study was to investigate the suitability of pineapple waste for vermicomposting. To achieve this, an assessment of the physicochemical properties of fresh, pre-composted pineapple waste, and the resultant vermicompost, and determination of the optimal feeding rate and stocking density were performed.  The study revealed that pre-composting reduced the moisture content (28.8%), VOC (10.3%), and increased the pH (56.8%) which was helpful in waste stabilization as well as in the mass reduction of the waste. Vermicomposting after pre- composting increased the bulk density (92.3%), ash content (25.4%), pH (10%), EC (14.3%), total phosphorus (20.9%) and total potassium (28.4%) but decreased the moisture content (29.1%), VOC (11.8%), organic carbon (81.4%), total nitrogen (21.3%) and the C:N ratio (76.4%) of the pineapple waste hence giving a more stabilized and mineralized vermicompost. The study further revealed an optimal feeding rate of 2 kg feeds/kg worms and a stocking density of 1 kg worms/m² for complete nitrogen mineralization of the pineapple waste and 1 kg feeds/kg worms and 0.5 kg worms/m² for higher phosphorus concentrations. The degradation of the pineapple waste by earthworms demonstrated the practicability of vermicomposting as a simple and low-cost technology of converting pineapple waste into an effective nutrient rich soil amendment.