Articles
15N NATURAL ABUNDANCE OF BARLEY AND SPINACH FERTILIZED WITH LEGUME RESIDUES, COMPOST OR INORGANIC NITROGEN
Article number
938_36
Pages
277 – 282
Language
English
Abstract
Agencies for organic farming certification require the development of control techniques to control fertilisation management.
Natural 15N abundance, expressed as δ15N, is considered as an integrated descriptor of the N historical cycle of an agrosystem, thus isotopic techniques has been proposed to verify the organic or inorganic nature of N fertilizers applied to crops.
Therefore δ15N of organic and inorganic fertilizer should be consistently different, and plant 15N should reflect δ15N of fertilizers employed.
In this work, the δ15N of spinach (Spinacia oleracea L.) and barley (Hordeum vulgare) cultivated with three different types of fertilizers (inorganic fertilizer, composted sheep manure, and legume residues) at three N rates (low, medium and high) were compared in a pot trial performed in a greenhouse.
Results showed that with compost the δ15N was always higher than 5.5 in barley and than 8 in spinach.
However, with inorganic fertilizer or legume residues the δ15N was lower than 5 in barley and than 6 in spinach.
Besides this, δ15N increased strongly with the rate of compost applied, reaching values higher than 13.It could be concluded that isotopic techniques could be useful in verifying if barley or spinach have been fertilized with compost.
However, these techniques do not seem to differentiate between crops grown with inorganic fertilizers or with legume residues.
Therefore, its applicability to be used as control technique by agencies for organic farming certification is limited.
Natural 15N abundance, expressed as δ15N, is considered as an integrated descriptor of the N historical cycle of an agrosystem, thus isotopic techniques has been proposed to verify the organic or inorganic nature of N fertilizers applied to crops.
Therefore δ15N of organic and inorganic fertilizer should be consistently different, and plant 15N should reflect δ15N of fertilizers employed.
In this work, the δ15N of spinach (Spinacia oleracea L.) and barley (Hordeum vulgare) cultivated with three different types of fertilizers (inorganic fertilizer, composted sheep manure, and legume residues) at three N rates (low, medium and high) were compared in a pot trial performed in a greenhouse.
Results showed that with compost the δ15N was always higher than 5.5 in barley and than 8 in spinach.
However, with inorganic fertilizer or legume residues the δ15N was lower than 5 in barley and than 6 in spinach.
Besides this, δ15N increased strongly with the rate of compost applied, reaching values higher than 13.It could be concluded that isotopic techniques could be useful in verifying if barley or spinach have been fertilized with compost.
However, these techniques do not seem to differentiate between crops grown with inorganic fertilizers or with legume residues.
Therefore, its applicability to be used as control technique by agencies for organic farming certification is limited.
Authors
I. Irigoyen, J. Muro, B. Lasa, F. Storino, I. Domeño, I. Jauregui, M. Azpilikueta, P.M. Aparicio-Tejo
Keywords
δ15N, certification, legume residues, natural abundance, organic farming, compost
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