Prospecção de substratos alternativos com Chlorella sp. como bioestimulante para produção de mudas de tomateiro

Abstract

The preparation and development of tomato seedlings generally rely on commercial substrates, which, despite their effectiveness, have high costs that compromise the farmer's yield. To reduce these costs while maintaining production quality, the adoption of alternative substrates has proven to be a viable solution. These substrates are not only sustainable, aligning with agroecological principles, but also utilize agricultural waste to ensure seedling health, provided they exhibit the necessary physical, biological, and chemical properties for plant development. Given the absence of a universally valid formulation for all species, it is essential to evaluate different compositions that fit the materials available in the growing regions. Bio-stimulants, which usually derive from the decomposition of animal waste and vegetable scraps, are essential components that promote plant growth. In recent years, microalgae have been recognized as promising in the biostimulant market, acting as growth promoters by synthesizing compounds such as phytohormones, vitamins, terpenoids, flavonoids, fatty acids, and polysaccharides, which demonstrate beneficial effects on the emergence, development, and productivity of crops. This study aims to validate an alternative substrate with the application of microalgae, evaluating the initial development of tomato plants (Solanum lycopersicum L.) in different substrates, which include Napier grass, coconut fiber, bovine manure, and horticultural compost, with and without the addition of freeze-dried biomass of the microalga Chlorella sp., using a concentration of 5g/kg per substrate through soil soaking. The results indicated that the treatment with the commercial substrate, which included the application of Chlorella sp., showed the best performances in various metrics: the highest percentage of emergence, seedling height, dry mass of the aerial part, dry mass of the root, and stem diameter. These data highlight the bio-stimulant potential of the microalga under experimental conditions for tomato cultivation. In contrast, the alternative substrates showed compromised performance, mainly due to the alkaline pH, suggesting the need for adjustments in formulations to optimize seedling development.