Quality of Spent Mushroom Compost Amended with Organic Material- Effect on Nutrient Content and Plant Growth

Abstract: Peat, as a non-renewable growing media, poses environmental concerns due to extraction and decomposition processes, leading to increased greenhouse gas emissions. Alternatives growing media with potential to replace or reduce the use of peat are of great need. The current thesis aims to assess the quality and potential of the composted material generated from industrial waste streams as a peat substitute and evaluate its impact on plant growth and the physical, chemical, and microbial properties of the substrate. Three different compost proportions were prepared using apple wastes, spent mushroom compost (SMC), and wood chips. These compost mixtures were combined with peat in three different treatments (A, B, C), with treatment D serving as the control (100% peat). Treatment A consisted of 70% peat and 30% compost mixture consists of 40% apple wastes, 20% SMC, and 40% wood chips. Treatment B consisted of 70% peat and 30% compost mixture consists of 25% apple wastes, 50% SMC, and 25% wood chips. Treatment C consisted of 70% peat and 30% compost mixture consists of 33% apple wastes, 33% SMC, and 33% wood chips). The compost mixtures were evaluated in pot experiment under controlled conditions in a greenhouse chamber using basil plants (Ocimum basilicum) as a model crop. The physical parameters, including bulk density (BD), compact density (CD), water holding capacity (WHC), and porosity, were measured. Chemical parameters including pH, electrical conductivity (EC), and nutrient contents were also analyzed. Microbial analysis was performed to determine the bacterial and fungal flora present in the compost before and after plant cultivation´. Physical and chemical parameters were also evaluated before and after plant cultivation. Biomass measurements were taken after five weeks of growth. Statistical analysis was conducted using one-way analysis of variance (ANOVA) to assess significant differences among the treatments. Initial assessment of the composts prior to plant cultivation revealed alkaline pH values and low electrical conductivity (EC), which are unfavourable for plant growth. Addition of compost to the peat effectively lowered the pH values and improved the EC, bringing them closer to optimal ranges for plant growth. The addition of compost reduced also bulk density and increased soil porosity. Microbial assessments showed abundant microorganisms in the compost materials, with an increased abundance of bacterial and fungal flora observed in compost-amended substrates. The addition of compost, particularly treatment C, enhanced the abundance of bacterial flora. Treatments A and B incorporating compost exhibited better plant growth parameters, including fresh and dry weight of leaves and roots. Overall, the findings support the use of compost amendments in peat-based substrates to create a favourable environment for plant growth, improve nutrient availability, and enhance soil microbial communities.