Green manure as a cleaner, sustainable strategy to enhance biomass and compounds of saw thistle (Sonchus oleraceus L.)

Abstract

The use of green manure (GM) represents a cleaner and sustainable approach to agricultural production. This practice can reduce the environmental and ecological impacts of sustainable agricultural development. Sow thistle (Sonchus oleraceus), is a non-conventional edible and medicinal plant that contains phenolic compounds and chicoric acid. The objective of this study was to evaluate the agronomic responses of S. oleraceus to varying doses of GM (Crotalaria juncea) in terms of photosynthetic pigment, phenolic compound, total flavone and flavonol content, and chicoric acid. The study was conducted in pots under field conditions over two growing seasons, using five treatments: no fertilization (control) and 30, 60, 90, and 120 t/ha of Crotalaria. Fifty days after crop, we evaluated leaf area, the leaves number, branches, stem diameter, and the dry weight of the stem, leaves, and roots, also, photosynthetic pigments, phenolic, flavonoids, and chicoric acid. Applying GM increased biomass growth in S. oleraceus. GM at 120 t/ha increased total dry weight by approximately 200% and 50% compared with the unfertilized control in the first and second growing seasons, respectively. Plants fertilized with GM showed higher levels of photosynthetic pigments. Regarding secondary metabolism, treatment without GM resulted in more significant accumulations of phenolic compounds, total flavonoids, and chicoric acid. These results emphasize the agronomic effectiveness of GM as a valuable and recommended agricultural practice for S. oleraceus. Some benefits of this technique are improved soil fertility. It is hoped that this study can contribute to reducing environmental impact without implying great costs for the producer.