ISSN: 1659-2751

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Determining the Quality of Organic Fertilizers using Bioassays

Abstract

The quality of an organic fertilizer is determined by its nutritional content and by its ability to provide nutrients to a crop. The latter can be established in various ways, including bioassays. Bioassays measure the response of a crop, either in production or nutritional content, to the application of the organic fertilizer. The trials can be conducted both in field and in greenhouse and the results can be compared between the two. The bioassays in the greenhouse, although shorter in time, can be used as rapid indicators of the quality of an organic fertilizer. The quality of various organic fertilizers produced at EARTH University was evaluated with bioassays using corn (Zea mays L.) as the indicator crop. Six treatments were evaluated in a field experiment and in a greenhouse trial: bokashis from three farms, the Integrated Livestock Farm, the Integrated Organic Farm and the Agro-commercial Farm; two chemical fertilizers, 10-30-10 (N-P-K) and 10-30-10 + urea; and a control (no fertilizer added). The short, eight-week greenhouse trial was a good indicator of the quality of the organic fertilizers produced at EARTH, particularly for those organic fertilizers with a low C:N like those from the Integrated Organic Farm (C:N=18) and those with high C:N like those from the Agro-commercial Farm (C:N=40). However, the greenhouse trials did not have the precision necessary to determine the quality of organic fertilizers with intermediate C:N like those from the Integrated Livestock Farm (C:N=25).

Key words: Bioassays, bokashi, quality of organic fertilizers.

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