Avaliação da qualidade e da fitotoxicidade de compostos orgânicos na produção de mudas de alface (Lactuca sativa)

Abstract

One of the main current environmental challenges in Brazil is the management of urban solid waste, most of which is organic solid waste. Given this scenario, it is essential to adopt measures to minimize and prevent the environmental impact caused by this waste. Composting has emerged as a promising solution, accelerating the decomposition of this waste, resulting in compost that can be used to nourish plants. This compost can act as a soil conditioner, enriching it with various nutrients, preventing erosion and serving as a substrate in horticulture, for example, bringing benefits to the environment and promoting economic and social development. The aim of this study was to assess the quality of the compost resulting from composting orange pomace and wood shavings, in retorts and beds, with different turning frequencies, comparing them with commercial substrates for growing lettuce. Analyses of pH, electrical conductivity, organic carbon and macronutrients were carried out, as well as phytotoxicity tests and an assessment of their influence on the germination and growth of lettuce seeds (Lactuca sativa) for seedling production in trays. To assess the phytotoxicity of the substrates, two germination index test methods were used for comparative purposes. The seedling production phase took place in a greenhouse, lasting 30 days and four replications, using Styrofoam trays with 128 cells as experimental blocks. At the end of the experiment, the seedlings were assessed for stability and resistance, as well as phytometric parameters and biomass. The phytotoxicity tests showed different results, but with the exception of the commercial Humusfertil® substrate, all the treatments tested were free of phytotoxins in both methods. The statistical analysis of the seedlings showed that the commercial Carolina Soil® substrate performed best in all the parameters analyzed. However, the other substrates showed similar results, suggesting their viability for growing lettuce. It can be concluded that the different composting methods and turning frequencies did not significantly influence the development of the seedlings. Although organic compost did not achieve similar results to commercial substrates, its use as a substrate complemented with mineral fertilizers can provide the essential nutrients for plant growth. This offers a viable solution for organic waste management, avoiding inappropriate disposal and promoting a sustainable treatment method.