Agricultural use of three (sugar-beet) vinasse composts: effect on crops and chemical properties of a Cambisol soil in the Guadalquivir river valley (SW Spain)

Disposal of concentrated beet-vinasse, a high-density syrupy waste from the sugar industry, constituted an environmental problem. Vinasse can be recyc led as a fertiliser due to its high organic matter, N, and K contents. Howe ver, the direct application of vinasse is constrained by its high salinity (EC 250-300 dS m(-1); Na 28 g kg(-1)) and high density (1.3 g cm(-3)). Thes e problems can be overcome by co-composting the vinasse with other solid wa stes. A study was conducted in the Guadalquivir river valley, SW Spain, in Coria del Rio, Seville. Three mixtures of a concentrated depotassified vina sse and solid wastes were co-composted in static windrows. The composts obt ained were used in field experiments to study the effect of their applicati on as deep fertiliser on three crops: corn (Zea mays L.); sugar-beet (Beta vulgaris L.) and sunflower (Helianthus annuus L.). The effect on chemical p roperties of a Xerochrept (Cambisol) soil after 2 years of compost applicat ion and after a further year of residual effect was also studied. A treatme nt with traditional inorganic fertiliser (applied as deep fertilisation) an d an unamended soil (Control) were used for comparison purposes. Generally, the application of composts or inorganic fertiliser significantly increase d crop yield when compared with the Control treatment. At the end of the ex perimental period, soil oxidizable-C, total humic extract-C and humic acids -C contents significantly increased in soils treated with composts when com pared with Control and inorganic fertiliser treatments. Organic fertilisati on also increased the Kjeldahl-N content of the soil. A slight increase of soil salinity was observed both in the composts and in the inorganic fertil iser treatments. Nevertheless, this increase did not cause sodium hazard to the soil. Go-composting of vinasse with agricultural residues serves two o bjectives: disposal of wastes and recycling of waste components. Furthermor e, vinasse composts can be used as an alternative to mineral fertilisers. ( C) 2001 Elsevier Science B.V. All rights reserved.