A sustainable management of the residues from biogas plants has to be considered due its potential use as plant fertilizer and soil conditioner. Our objective was to evaluate the biogas-digestate as a nutrient source for biomass production of three different plants: sida (Sida hermaphrodita -Malvaceae), maize (Zea mays L. -Poaceae) and alfalfa (Medicago sativa L. -Fabaceae). The used biogas-digestate was obtained after the anaerobic digestion of maize silage, as the major feedstock, and minor amounts of chicken manure. The treatments were established in five replicates including biogas-digestate, NPK fertilizer and a control. Pots were filled with the fertilized soils (biogas-digestate and NPK treatments) and control soil, and seedlings were transplanted and grown for 30 days under greenhouse conditions. Analysis of the shoot and root dry mass and nutrients content (C, N and P) of Sida hermaphrodita, Zea mays L. and Medicago sativa L. revealed similar values for both biogas-digestate and the NPK fertilizer applications, which were greater than the control, showing a positive fertilizing effect of the biogas-digestate for biomass production of the respective plants.

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