Potential of Producing Organic Lettuce Seedlings without Peat Using Agricultural and Agro-industrial Compost

Abstract

Peat is an unrenewable resource. The potential of using composts made from a mixture of agricultural and agro-industrial wastes as peat substitutes was evaluated in this study. Four compost piles (C1-C4) were constructed by mixing various wastes after estimating their properties. C1 was a 1:1:1.5 weight ratio mixture of filter mud, mushroom waste, and date-palm fronds, while C2-C4 were a 0.5:1 weight ratio mixture between either bagasse, cutting grassland, or date-palm fronds and cattle dung. After four months of decomposition, the compost’s physical, chemical, and biological properties were estimated in comparison to commercial compost (CC), peatmoss (PM), and their ideal ranges (IR) for seed germination and seedling growth. Composts had significant differences in physical and chemical properties. Some composts revealed property values within the IR. The principal component analysis (PCA) revealed that composts lack peat-like properties. Composts had a lower C/N ratio and organic matter, along with higher bulk density, electrical conductivity, and pH compared to PM. Cattle manure enhanced organic matter and carbon, total nitrogen and potassium, and ammonium levels and reduced ash levels in C2-C4, compared to filter mud in C1. The suitability of C1-C4, CC, and PM substrates for growing crisp lettuce 'Big Bell' seedlings was evaluated during the winters of 2018 and 2019 under plastic-house conditions. The substrates had significant effects on lettuce seedling traits. C2-C4 substrate seedlings’ vegetative shoots grew more rapidly than other substrate seedlings due to the increased length and diameter of their stem and leaf area. The PCA revealed that PM-substrate and C2-C4 substrates had similar effects on lettuce seedling growth traits. The proper mixing of agricultural and agro-industrial wastes based on their properties can produce compost with relatively suitable physical, chemical, and biological properties for lettuce seed germination and seedling growth. It will take more investigation to improve the C2-C4 compost’s properties by using certain techniques.