THE USE OF SEAWEED ALONG THE COAST.

Otago Witness, Issue 3101, 20 August 1913, Page 14

THE USE OF SEAWEED ALONG THE COAST.

When seaweed can be obtained is sufficient quantity, it is an invariable manure for applying to cereal or root crops wherever the cartage does not raise its cost to a prohibitive limit. The long, flat strips or foliage in its green state decomposes rapidly on anything except very light land yielding chietly ammonia and potash salts. In the green state the percentage of potash varies from .8 to 1.5 per cent., and it has a nitrogen content of .3 to .8 per cent. It is ploughed into the land at the rate of 20 to 30 tons per acne, or used in the form of a compost with farmyard manure and earthy matters. It makes farmyard manure more rapidly effiective. On account of its potash it is a valuable manure for potatoes, but should be used in conjunction with superphosphate of basic slag. Potatoes do not want any excess of nitrogenous manure, because it renders them waxy and gives them a tendency to boil a bad colour, and makes them more susceptible to disease attack. On the Irish and Scotch coast seaweeds form the chief manure for potatoes, and excellent quality results from its use. In some localities after the wide leaves or foliage have been used for manuring the land, the “tangles” or heavier stems are kiln burned and maiv keted ns kelp for the extraction of the sulphuric acid they contain. The crofters make quite n business of dealing with the kelp. The wind and waves pile the tangles in huge glittering rolls along the beaches. These are stacked on the turf in great heaps on steitlis —i.c., foundations built of sea-rounded stones arranged to give ingress to air, and dried till the following spring. Along the edges of the drying greens they build burning pots or kilns—hollows lined with blue stones from the beach—about 2ft deep and sft in diameter. 'Hie ware and tangles arc usually burned together in these pits. A good bottom heat it secured, and new fuel is piled on so as to prevent a burst of flame. The whole seaweed is resolved into a pulpy mass of keln like grey crumbling earth mingled with black ashes and white quartz — thoroughly mixed together and piled to cool and harden. In this condition it is marketed. Spring and summer are the helpers’ seasons, and dry weather is required by anyone who has secured a good stack of tangles—rescued from the waves—or a big share in the “brook of ware” or mass of seaweed thrown up on the beach. When applied to the land the seaweed is carted away wholesale in its natural state, and ploughed in without any other treatment. It is difficult to estimate the money value of seaweed to the farmer. The Board of Agriculture, has issued a leaflet on the subject, and this gives the result of a series of analyses, which show that the wet weed as gathered lias an average composition of .5 ■nitrogen. 1.2 potash, and .9 phosphoric acid. The fertilising material in one ton would there fore cost about 18s or 19s in the form of a merchantable manure. No account is taken of the sodium, calcium, and magnesium salts, which would he beneficial, particularly in light soils, but the availability of its constituents would have to ho determined before a tentative valuation could he made. Experiments to test the manorial value of seaweed have been

made at 1< rondhjenes and in Great Britain, in the former seaweed proved fully as effective as farmyard manure for early potatoes as far as quantity was concerned, but retarded ripening somewhat. Superphosphate and seaweed proved better than farmyard manure and superphosphate. It is, however, on such gross-feeding crops as mangolds and the cabbage tribe that it would be expected to show its fullest effect. It decomposes very completely, and in doing so forms soluble substances which easily wash away. It should, therefore, not be allowed to rot in heaps by itself,, but put straight on to the land in its green state. If tfiat is not practicable it should be mixed with farmyard manure, which would absorb some of' the products of decomposition. Analysis shows that the seaweeds have not all equal value, as manure. Ihe long, broad Jeaf-like “ lammaria is richer than “ fucus,” the common black weed of the rocks. And that out or thrown up in the early part of ic yeai is richer than that obtained later m summer or autumn. A considerable amount of water is lost in drying in the a . nd . lf weed has not been washed bv lain in the meantime its manurial value would be increased four or five fold. Under wmtl, Cl^ nmSt or reS uM ton (>f ifc wtm]d bs £ , 5 ?■' £6 ~ , Ihe amount obtainable must at times be enormous, end it is v Ol thy of consideration whether it cannot be more widely utilised than it is at present by farmers conveniently situated close to the coastline.