A study by the University of Évora shows that a mixture of nuts and biochar can replace 20% of coconut fiber on vegetable substrates, maintaining lettuce productivity and reducing nitrates in leaves, according to the statement released today.
© Shuttestock
07/11/2026
by
Lusa
Um study of the University of Évora (UÉvora) shows that a mixture of nut shells and biochar can replace “20%” of coconut fiber of a vegetable substrate, maintaining the productivity of lettuce, has been published today.
In a statement, UÉvora adds that this study developed in the Experimental Heritage of Mitra also causes a reduction in “61%”, in the concentration of nitrates in lettuce leaves.
According to the document, a multidisciplinary team from UÉvora evaluated the potential of crushed nuts, a by-product of the agri-food industry, as a substrate component for greenhouse lettuce production.
“The study, published in the international scientific journal Horticulturee, brought together researchers from the areas of Agricultural Sciences and Chemistry and Biochemistry, involving the Mediterranean Institute for Agriculture, Environment and Development (MED) and the Institute for Global Changes and Sustainability (CHANGE), reads in the document.
In the test, different mixtures of coconut fiber, nuts and biochar were compared, a carbon-rich material obtained by chemical biomass term transformation.
“ Among the formulations studied, we highlighted the combination of 80% coconut fiber, 12% nuts and 8% biochar (in volume). This substrate has achieved a productivity of 7.1 kg of fresh lettuce per square metre, comparable to that recorded with the reference substrate, consisting exclusively of coconut fiber”, they explain.
The concentration of nitrates in the leaves, according to the study, “declined about 61%”, from “approximately 4,130 to 1,600 mg/kg” of fresh material.
“ There was also an increase in the content of anthocyanins, natural compounds of the family of flavonoids associated with antioxidant activity ", add.
Researchers also point out that the results show that the composition of substrates “can influence not only crop productivity” but also “important characteristics” of vegetable quality.
When exploring a new use for nutshells, researchers consider that the work contributes to the development of “solutions aligned with the principles of the circular economy” and to the “diversification of raw materials used in horticulture”, with the potential to reduce dependence on imported materials.
“ Research is a promising step towards the recovery of agro-industrial waste and the development of new technological solutions in horticulture, and it is necessary to continue studies to optimize formulations, watering management and its application in different crops and production conditions”, they add.