title: Agricultural potential of anaerobically digested industrial orange waste with and without aerobic post-treatment.
abstract: The potential of anaerobically digested orange waste with (AAD) and without (AD) aerobic post-treatment for use in agriculture was evaluated through chemical analyses, short-term phytotoxicity and long-term plant assays. Chemical analyses showed that AD contained ammonia and organic acids, and aerobic post-treatment did not significantly remove these phytotoxins. The N:P2O5:K2O ratio in AD was 1:0.26:0.96 and aerobic post-treatment did not change the composition in AAD except for K2O (1:0.26:1.24). Heavy metal contents in AD and AAD were more or less the same and were below the upper limit recommended for non-sewage sludge application on agricultural soils. Short-term phytotoxicity tests showed that seed germination and root elongation of Chinese cabbage and ryegrass were severely inhibited at digestate concentrations of 60-100%. Germination index values were well below the score of 50% required to indicate the phytotoxic-free nature of compost. Long-term plant assays showed that AD and AAD, when supplemented with a base fertilizer, resulted in higher plant growth, and fresh weight and dry matter production than AD without base fertilizer. The results thus indicate that aerobic post-treatment did not have any significant beneficial effect on reducing phytotoxicity, and AD could be used as such on agricultural soils, especially with high P.
authors.affiliation: Department of Biological and Environmental Science, P.O. Box 35, University of Jyväskylä, FI 40014, Finland.
authors.forename: Prasad
authors.initials: P
authors.lastname: Kaparaju
authors.forename: Jukka
authors.initials: J
authors.lastname: Rintala
authors.forename: Aimo
authors.initials: A
authors.lastname: Oikari
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001937:Brassica / Q000254:growth & development; D032084:Citrus sinensis / Q000737:chemistry* / Q000633:toxicity; D005308:Fertilizers / Q000032:analysis* / Q000633:toxicity; D007220:Industrial Waste / Q000032:analysis*; D008129:Lolium / Q000254:growth & development; D018675:Toxicity Tests
chemical_list: D005308:Fertilizers; D007220:Industrial Waste