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United States Department of Agriculture

Agricultural Research Service

Title: Compositions of Humic-Type Substances from Ascophyllum Nodosum and the Influences on Grass Growth of Seaweed Extracts and Other Organic Amendments

Authors
item Mcinerney, R - LIMERICK UNIV
item Hayes, Mhb - LIMERICK UNIV
item Clapp, Charles
item Cross, P - LIMERICK UNIV
item Pereira, P - LIMERICK UNIV

Submitted to: Proceedings of the Brazilian Socity of Humic Substances
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2004
Publication Date: July 25, 2004
Citation: Mcinerney, R.J., Hayes, M., Clapp, C.E., Cross, P., Pereira, P. 2004. Compositions of humic-type substances from ascophyllum nodosum and the influences on grass growth of seaweed extracts and other organic amendments. Proceedings of the Brazilian Socity of Humic Substances. p. 226-229.

Interpretive Summary: Larger applications of commercial seaweed extracts were found to be necessary to give noticeable improvement in grass growth in a shallow sandy loam soil in western Ireland. Seedling growth was inhibited when the same concentrations were used in sand culture. The sandy loam had sufficient colloidal components to sorb the phytotoxins that are released from the seaweed under the conditions used. Field trials have shown that rye grass growth was superior in the sandy loam amended with Ascophyllum nodosum after the alginate component was removed from the seaweed (compared with the extracts of fresh seaweed). This indicates that the alginate does not enhance rye grass growth on medium to heavy soils. The impact will be to provide a simpler and less costly method for supplying trace metals like iron to grass crops, while decreasing risk of possible pollution of over-application of nutrients on sandy soils.

Technical Abstract: Commercial products from the seaweed Ascophyllum nodosum in western Ireland were fractionated using standard IHSS procedures to determine their compositional properties. The fractions were analyzed by CPMAS 13C-NMR and FT-IR spectroscopy. The NMR spectra of the humic-type materials isolated from processed (alkaline extraction at temperatures ~ 120 oC) seaweed were significantly different from those of humic substances from soil, lignite, or water, and are more likely to represent browning reaction products. The FT-IR spectra (as did the NMR data) showed strong evidence for hydrocarbon structures, and similarities in the fingerprint region to plant derived products. The field growth trials strongly suggested that composted Ascophyllum nodosum gave significantly enhanced root growth of ryegrass (compared to the commercial seaweed products). The harsh procedures used in the isolation of the commercial product are likely to have inactivated the plant growth stimulants. Commercial humic acids from lignites gave grass growth that in some cases was superior to that for the commercial seaweed product. However, one of the seaweed products gave superior grass chlorophyll content, probably because it enhanced uptake of iron.

Last Modified: 12/17/2014
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