Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Studies of Aspects of the Compositions of Humic-Type Substances from Seaweed and of the Influences of Seaweed Extracts on Grass Growth

item Clapp, Charles

Submitted to: International Humic Substances Society Conference
Publication Type: Proceedings
Publication Acceptance Date: July 21, 2002
Publication Date: July 21, 2002
Citation: Mcinerney, R.J., Cross, P., Clapp, C.E., Hayes, M. 2002. Studies of aspects of the compositions of humic-type substances from seaweed and of the influences of seaweed extracts on grass growth. International Humic Substances Society Conference. p. 327.

Interpretive Summary: Larger applications of the commercial seaweed extracts were found to be necessary to give noticeable improvement in grass growth in a shallow sandy loam soil. 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 good 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: Humic-type substances (HTS) from Ascophyllum nodosum, isolated in NaOH at elevated temperatures, were compared with humic fractions from soils and waters. The HTS from Ascophyllum nodosum were compositionally different from the naturally occurring humic acids (HAs) and fulvic acids (FAs). Studies of the effects of commercial seaweed extracts (from Kerry Algae Limited) on rye grass Lolium perenne grown in sand culture gave evidence for yields and quality of the grass under drought conditions. There were no differences in germination times (for rye grass seeds) between the control and the different concentrations of the commercial seaweed extracts used. No significant differences were observed in shoot length for all concentrations of extracts, even though shoot length was longer in the early stages of growth for the lower concentrations of the amended material. Chlorophyll content was greater in rye grass grown in sand amended with a commercial humate iron chelate compared to rye grass grown in sand amended with commercial seaweed extract mixed with humate iron chelate. The seaweed extract appeared to inhibit iron uptake from the humate chelate by the grass roots.

Last Modified: 4/22/2015