Agro industrial waste: alternative sources of substrates for the production of lettuce seedlings

The agro industrial sector produces large amounts of waste which often are not properly disposed. The objective of this study was to evaluate the potential use of burnt rice husks and sugarcane bagasse as a substrate for the production of iceberg lettuce seedlings. The study was conducted in the city of Frederico Westphalen, RS, in 2015. The experimental design was completely randomized and consisted of six treatments and four replications with 100 plants / replication. The treatments were composed of organic waste, a commercial substrate, and mixtures of these components resulting in the following treatments: T1 = 100% commercial substrate (SC); T2 = 100% burnt rice husks (CA); T3 = 100% sugarcane bagasse (BC); T4 = 25% CA + 75% BC; T5 = 50% CA+ 50% BC and T6= 75% CA + 25% BC. Responses were evaluated for germination, emergence speed index, dry weight of the shoot and root system. From the results it can be concluded that the best performance of the seedlings was found in the commercial substrate; however, costs can be reduced with the use of burnt rice husks, even though the chemical characteristics may influence the development of the seedlings. The use of sugarcane bagasse resulted in low levels of seedling development, this was likely related to the physical characteristics of these mixtures and the possible presence of allelopathic substances.