Agrochemical characterization, net N mineralization, and potential N leaching of composted olive-mill pomace currently produced in southern Spain

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Gomez-Munoz, B., Hatch, D. J., Bol, R. and Garcia-Ruiz, R. 2013. Agrochemical characterization, net N mineralization, and potential N leaching of composted olive-mill pomace currently produced in southern Spain. Journal of Plant Nutrition and Soil Science. 176 (5), pp. 655-664.

AuthorsGomez-Munoz, B., Hatch, D. J., Bol, R. and Garcia-Ruiz, R.
Abstract

In S Spain, the Andalusian olive oil industry generates annually 2.5-3.0 million tons of olive mill pomace, a by-product which is comprised of the residues from the two-phase oil-extraction process. The agricultural policies of the EU have led to widespread interest in recycling these agricultural by-products. Olive mill pomace might be evaluated as an organic fertilizer after composting, however, before wider use of composted olive mill pomace is advocated, characterization of the final product is needed. In this study, the physico-chemical characteristics, net N mineralization, and the potential for N leaching of 7 out of the 11 olive-mill-pomace composts currently produced in the Andalusian olive mills were investigated. Compost of olive mill pomace differed in the proportions of raw materials co-composted with the olive mill pomace, such as olive leaf material, manure, and straw. In all the composts tested, organic matter, total C and K were high with 60.5%, 30.7%, and 1.7% on average, respectively, whereas total P was low (0.4%) and with intermediate levels of N (1.5%). Compost pH (8.03), electrical conductivity (2.85 dS m(-1)), and germination index (65% on average) were adequate for agricultural use. Furthermore, principal component analyses revealed a clear relationship between the quality of the composts and the proportion of manure mixed with the raw materials. Net N mineralization was negative on average (-20 g IN g(-1)) after 1 y, but positive after 2 y of incubation with up to 94% of available N from the total N added and the short-term potential N leaching after compost application was negligible (less than 3.9% of added N) and much lower than the other N fertilizer with up to 80% added N leached. Overall, results of this study clearly show that these currently produced composts of olive mill pomace are suitable as soil improvers for agricultural purposes, but may not contribute significantly as a N fertilizer for up to 2 y after application.

KeywordsAgronomy; Plant Sciences; Soil Science
Year of Publication2013
JournalJournal of Plant Nutrition and Soil Science
Journal citation176 (5), pp. 655-664
Digital Object Identifier (DOI)doi:10.1002/jpln.201200421
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeDelivering Sustainable Systems (SS) [ISPG]
Processes and mechanisms of the interactions between grasslands and water
Soil and organic matter processes
Output statusPublished
PublisherWiley
Copyright licenseCC BY
ISSN1436-8730

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