Slow delivery of a nitrification inhibitor (dicyandiamide) to soil using a biodegradable hydrogel of chitosan

Minet, E.P. and O'Carroll, C. and Rooney, A. Denise and Breslin, Carmel B. and McCarthy, C.P. and Gallagher, L. and Richards, K.G. (2013) Slow delivery of a nitrification inhibitor (dicyandiamide) to soil using a biodegradable hydrogel of chitosan. Chemosphere, 93 (11). pp. 2854-2858. ISSN 0045-6535

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Using chemical inhibitors to reduce soil nitrification decreases emissions of environmental damaging nitrate and nitrous oxide and improves nitrogen use efficiency in agricultural systems. The efficacy of nitrification inhibitors such as dicyandiamide (DCD) is limited in soil due to biodegradation. This study investigated if the persistence of DCD could be sustained in soil by slow release from a chitosan hydrogel. DCD was encapsulated in glyoxal-crosslinked chitosan beads where excess glyoxal was (i) partly removed (C beads) or (ii) allowed to dry (CG beads). The beads were tested in water and in soil. The beads contained two fractions of DCD: one which was quickly released in water, and one which was not. A large DCD fraction within C beads was readily available: 84% of total DCD bead content was released after 9 h immersion in water, while between 74% and 98% was released after 7 d in soil under low to high moisture conditions. A lower percentage of encapsulated DCD was readily released from CG beads: 19% after 9 h in water, and 33% after 7 d in soil under high rainfall conditions. Kinetic analysis indicated that the release in water occurred by quasi-Fickian diffusion. The results also suggest that DCD release was controlled by bead erosion and the leaching of glyoxal derivatives, predominantly a glyoxal-DCD adduct whose release was positively correlated with that of DCD (R2 = 0.99, p ⩽ 0.0001). Therefore, novel chitosan/glyoxal composite beads show a promising slow-release potential in soil for agrochemicals like DCD.

Item Type: Article
Keywords: Chitosan; Hydrogel; Dicyandiamide; Slow release; Nitrification inhibitor; Nitrogen loss;
Academic Unit: Faculty of Science and Engineering > Chemistry
Item ID: 7718
Identification Number: 10.1016/j.chemosphere.2013.08.043
Depositing User: Dr. Carmel Breslin
Date Deposited: 11 Jan 2017 14:33
Journal or Publication Title: Chemosphere
Publisher: Elsevier
Refereed: Yes
Funders: Department of Agriculture, Food and the Marine

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